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2010 - 2011: Earth's most extreme weather since 1816?

Posted on 27 June 2011 by Jeff Masters

Every year extraordinary weather events rock the Earth. Records that have stood centuries are broken. Great floods, droughts, and storms affect millions of people, and truly exceptional weather events unprecedented in human history may occur. But the wild roller-coaster ride of incredible weather events during 2010, in my mind, makes that year the planet's most extraordinary year for extreme weather since reliable global upper-air data began in the late 1940s. Never in my 30 years as a meteorologist have I witnessed a year like 2010--the astonishing number of weather disasters and unprecedented wild swings in Earth's atmospheric circulation were like nothing I've seen. The pace of incredible extreme weather events in the U.S. over the past few months have kept me so busy that I've been unable to write-up a retrospective look at the weather events of 2010. But I've finally managed to finish, so fasten your seat belts for a tour through the top twenty most remarkable weather events of 2010. At the end, I'll reflect on what the wild weather events of 2010 and 2011 imply for our future.

Earth's hottest year on record
Unprecedented heat scorched the Earth's surface in 2010, tying 2005 for the warmest year since accurate records began in the late 1800s. Temperatures in Earth's lower atmosphere also tied for warmest year on record, according to independent satellite measurements. Earth's 2010 record warmth was unusual because it occurred during the deepest solar energy minimum since satellite measurements of the sun began in the 1970s. Unofficially, nineteen nations (plus the the U.K.'s Ascension Island) set all-time extreme heat records in 2010. This includes Asia's hottest reliably measured temperature of all-time, the remarkable 128.3°F (53.5°C) in Pakistan in May 2010. This measurement is also the hottest reliably recorded temperature anywhere on the planet except for in Death Valley, California. The countries that experienced all-time extreme highs in 2010 constituted over 20% of Earth's land surface area.


Figure 1. Climate Central and Weather Underground put together this graphic showing the nineteen nations (plus one UK territory, Ascension Island) that set new extreme heat records in 2010.

Most extreme winter Arctic atmospheric circulation on record; "Snowmageddon" results
The atmospheric circulation in the Arctic took on its most extreme configuration in 145 years of record keeping during the winter of 2009 - 2010. The Arctic is normally dominated by low pressure in winter, and a "Polar Vortex" of counter-clockwise circulating winds develops surrounding the North Pole. However, during the winter of 2009 - 2010, high pressure replaced low pressure over the Arctic, and the Polar Vortex weakened and even reversed at times, with a clockwise flow of air replacing the usual counter-clockwise flow of air. This unusual flow pattern allowed cold air to spill southwards and be replaced by warm air moving poleward. Like leaving the refrigerator door ajar, the Arctic "refrigerator" warmed, and cold Arctic air spilled out into "living room" where people live. A natural climate pattern called the North Atlantic Oscillation (NAO), and its close cousin, the Arctic Oscillation (AO) were responsible. Both of these patterns experienced their strongest-on-record negative phase, when measured as the pressure difference between the Icelandic Low and Azores High.

The extreme Arctic circulation caused a bizarre upside-down winter over North America--Canada had its warmest and driest winter on record, forcing snow to be trucked in for the Winter Olympics in Vancouver, but the U.S. had its coldest winter in 25 years. A series of remarkable snow storms pounded the Eastern U.S., with the "Snowmageddon" blizzard dumping more than two feet of snow on Baltimore and Philadelphia. Western Europe also experienced unusually cold and snowy conditions, with the UK recording its 8th coldest January. A highly extreme negative phase of the NAO and AO returned again during November 2010, and lasted into January 2011. Exceptionally cold and snowy conditions hit much of Western Europe and the Eastern U.S. again in the winter of 2010 - 2011. During these two extreme winters, New York City recorded three of its top-ten snowstorms since 1869, and Philadelphia recorded four of its top-ten snowstorms since 1884. During December 2010, the extreme Arctic circulation over Greenland created the strongest ridge of high pressure ever recorded at middle levels of the atmosphere, anywhere on the globe (since accurate records began in 1948.) New research suggests that major losses of Arctic sea ice could cause the Arctic circulation to behave so strangely, but this work is still speculative.


Figure 2. Digging out in Maryland after "Snowmageddon". Image credit: wunderphotographer chills.

Arctic sea ice: lowest volume on record, 3rd lowest extent
Sea ice in the Arctic reached its third lowest areal extent on record in September 2010. Compared to sea ice levels 30 years ago, 1/3 of the polar ice cap was missing--an area the size of the Mediterranean Sea. The Arctic has seen a steady loss of meters-thick, multi-year-old ice in recent years that has left thin, 1 - 2 year-old ice as the predominant ice type. As a result, sea ice volume in 2010 was the lowest on record. More than half of the polar icecap by volume--60%--was missing in September 2010, compared to the average from 1979 - 2010. All this melting allowed the Northwest Passage through the normally ice-choked waters of Canada to open up in 2010. The Northeast Passage along the coast of northern Russia also opened up, and this was the third consecutive year--and third time in recorded history--that both passages melted open. Two sailing expeditions--one Russian and one Norwegian--successfully navigated both the Northeast Passage and the Northwest Passage in 2010, the first time this feat has been accomplished. Mariners have been attempting to sail the Northwest Passage since 1497, and have failed to accomplish this feat without an icebreaker until the 2000s. In December 2010, Arctic sea ice fell to its lowest winter extent on record, the beginning of a 3-month streak of record lows. Canada's Hudson Bay did not freeze over until mid-January of 2011, the latest freeze-over date in recorded history.


Figure 3. The Arctic's minimum sea ice extent for 2010 was reached on September 21, and was the third lowest on record. Image credit: National Snow and Ice Data Center.

Record melting in Greenland, and a massive calving event
Greenland's climate in 2010 was marked by record-setting high air temperatures, the greatest ice loss by melting since accurate records began in 1958, the greatest mass loss of ocean-terminating glaciers on record, and the calving of a 100 square-mile ice island--the largest calving event in the Arctic since 1962. Many of these events were due to record warm water temperatures along the west coast of Greenland, which averaged 2.9°C (5.2°F) above average during October 2010, a remarkable 1.4°C above the previous record high water temperatures in 2003.


Figure 4. The 100 square-mile ice island that broke off the Petermann Glacier heads out of the Petermann Fjord in this 7-frame satellite animation. The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart. The images were taken by NASA's Aqua and Terra satellites.

Second most extreme shift from El Niño to La Niña
The year 2010 opened with a strong El Niño event and exceptionally warm ocean waters in the Eastern Pacific. However, El Niño rapidly waned in the spring, and a moderate to strong La Niña developed by the end of the year, strongly cooling these ocean waters. Since accurate records began in 1950, only 1973 has seen a more extreme swing from El Niño to La Niña. The strong El Niño and La Niña events contributed to many of the record flood events seen globally in 2010, and during the first half of 2011.


Figure 5. The departure of sea surface temperatures from average at the beginning of 2010 (top) and the end of 2010 (bottom) shows the remarkable transition from strong El Niño to strong La Niña conditions that occurred during the year. Image credit: NOAA/NESDIS.

Second worst coral bleaching year
Coral reefs took their 2nd-worst beating on record in 2010, thanks to record or near-record warm summer water temperatures over much of Earth's tropical oceans. The warm waters caused the most coral bleaching since 1998, when 16 percent of the world's reefs were killed off. "Clearly, we are on track for this to be the second worst (bleaching) on record," NOAA coral expert Mark Eakin in a 2010 interview. "All we're waiting on now is the body count." The summer 2010 coral bleaching episodes were worst in the Philippines and Southeast Asia, where El Niño warming of the tropical ocean waters during the first half of the year was significant. In Indonesia's Aceh province, 80% of the bleached corals died, and Malaysia closed several popular dive sites after nearly all the coral were damaged by bleaching. In some portions of the Caribbean, such as Venezuela and Panama, coral bleaching was the worst on record.


Figure 6. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

Wettest year over land
The year 2010 also set a new record for wettest year in Earth's recorded history over land areas. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. However, this record is not that significant, since it was due in large part to random variability of the jet stream weather patterns during 2010. The record wetness over land was counterbalanced by relatively dry conditions over the oceans.


Figure 7. Global departure of precipitation over land areas from average for 1900 - 2010. The year 2010 set a new record for wettest year over land areas in Earth's recorded history. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. Image credit: NOAA's National Climatic Data Center.

Amazon rainforest experiences its 2nd 100-year drought in 5 years
South America's Amazon rainforest experienced its second 100-year drought in five years during 2010, with the largest northern tributary of the Amazon River--the Rio Negro--dropping to thirteen feet (four meters) below its usual dry season level. This was its lowest level since record keeping began in 1902. The low water mark is all the more remarkable since the Rio Negro caused devastating flooding in 2009, when it hit an all-time record high, 53 ft (16 m) higher than the 2010 record low. The 2010 drought was similar in intensity and scope to the region's previous 100-year drought in 2005. Drought makes a regular appearance in the Amazon, with significant droughts occurring an average of once every twelve years. In the 20th century, these droughts typically occurred during El Niño years, when the unusually warm waters present along the Pacific coast of South America altered rainfall patterns. But the 2005 and 2010 droughts did not occur during El Niño conditions, and it is theorized that they were instead caused by record warm sea surface temperatures in the Atlantic.

We often hear about how important Arctic sea ice is for keeping Earth's climate cool, but a healthy Amazon is just as vital. Photosynthesis in the world's largest rainforest takes about 2 billion tons of carbon dioxide out of the air each year. However, in 2005, the drought reversed this process. The Amazon emitted 3 billion tons of CO2 to the atmosphere, causing a net 5 billion ton increase in CO2 to the atmosphere--roughly equivalent to 16 - 22% of the total CO2 emissions to the atmosphere from burning fossil fuels that year. The Amazon stores CO2 in its soils and biomass equivalent to about fifteen years of human-caused emissions, so a massive die-back of the forest could greatly accelerate global warming.


Figure 8. Hundreds of fires (red squares) generate thick smoke over a 1000 mile-wide region of the southern Amazon rain forest in this image taken by NASA's Aqua satellite on August 16, 2010. The Bolivian government declared a state of emergency in mid-August due to the out-of-control fires burning over much of the country. Image credit: NASA.

Global tropical cyclone activity lowest on record
The year 2010 was one of the strangest on record for tropical cyclones. Each year, the globe has about 92 tropical cyclones--called hurricanes in the Atlantic and Eastern Pacific, typhoons in the Western Pacific, and tropical cyclones in the Southern Hemisphere. But in 2010, we had just 68 of these storms--the fewest since the dawn of the satellite era in 1970. The previous record slowest year was 1977, when 69 tropical cyclones occurred world-wide. Both the Western Pacific and Eastern Pacific had their quietest seasons on record in 2010, but the Atlantic was hyperactive, recording its 3rd busiest season since record keeping began in 1851. The Southern Hemisphere had a slightly below average season. The Atlantic ordinarily accounts for just 13% of global cyclone activity, but accounted for 28% in 2010--the greatest proportion since accurate tropical cyclone records began in the 1970s.

A common theme of many recent publications on the future of tropical cyclones globally in a warming climate is that the total number of these storms will decrease, but the strongest storms will get stronger. For example, a 2010 review paper published in Nature Geosciences concluded that the strongest storms would increase in intensity by 2 - 11% by 2100, but the total number of storms would fall by 6 - 34%. It is interesting that 2010 saw the lowest number of global tropical cyclones on record, but an average number of very strong Category 4 and 5 storms (the 25-year average is 13 Category 4 and 5 storms, and 2010 had 14.) Fully 21% of 2010's tropical cyclones reached Category 4 or 5 strength, versus just 14% during the period 1983 - 2007. Most notably, in 2010 we had Super Typhoon Megi. Megi's sustained winds cranked up to a ferocious 190 mph and its central pressure bottomed out at 885 mb on October 16, making it the 8th most intense tropical cyclone in world history. Other notable storms in 2010 included the second strongest tropical cyclone on record in the Arabian Sea (Category 4 Cyclone Phet in June), and the strongest tropical cyclone ever to hit Myanmar/Burma (October's Tropical Cyclone Giri, an upper end Category 4 storm with 155 mph winds.)


Figure 9. Visible satellite image of Tropical Cyclone Phet on Thursday, June 3, 2010. Record heat over southern Asia in May helped heat up the Arabian Sea to 2°C above normal, and the exceptionally warm SSTs helped fuel Tropical Cyclone Phet into the second strongest tropical cyclone ever recorded in the Arabian Sea. Phet peaked at Category 4 strength with 145 mph winds, and killed 44 people and did $700 million in damage to Oman. Only Category 5 Cyclone Gonu of 2007 was a stronger Arabian Sea cyclone.

A hyperactive Atlantic hurricane season: 3rd busiest on record
Sea surface temperatures that were the hottest on record over the main development region for Atlantic hurricanes helped fuel an exceptionally active 2010 Atlantic hurricane season. The nineteen named storms were the third most since 1851; the twelve hurricanes of 2010 ranked second most. Three major hurricanes occurred in rare or unprecedented locations. Julia was the easternmost major hurricane on record, Karl was the southernmost major hurricane on record in the Gulf of Mexico, and Earl was the 4th strongest hurricane so far north. The formation of Tomas so far south and east so late in the season (October 29) was unprecedented in the historical record; no named storm had ever been present east of the Lesser Antilles (61.5°W) and south of 12°N latitude so late in the year. Tomas made the 2010 the 4th consecutive year with a November hurricane in the Atlantic--an occurrence unprecedented since records began in 1851.


Figure 10. Hurricane Earl as seen from the International Space Station on Thursday, September 2, 2010. Image credit: NASA astronaut Douglas Wheelock.

A rare tropical storm in the South Atlantic
A rare tropical storm formed in the South Atlantic off the coast of Brazil on March 10 - 11, and was named Tropical Storm Anita. Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004, one of only seven known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Anita of 2010 is probably the fourth strongest tropical/subtropical storm in the South Atlantic, behind Hurricane Catarina, an unnamed February 2006 storm that may have attained wind speeds of 65 mph, and a subtropical storm that brought heavy flooding to the coast of Uruguay in January 2009. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone.)


Figure 11. Visible satellite image of the Brazilian Tropical Storm Anita.

Strongest storm in Southwestern U.S. history
The most powerful low pressure system in 140 years of record keeping swept through the Southwest U.S. on January 20 - 21, 2010, bringing deadly flooding, tornadoes, hail, hurricane force winds, and blizzard conditions. The storm set all-time low pressure records over roughly 10 - 15% of the U.S.--southern Oregon, California, Nevada, Arizona, and Utah. Old records were broken by a wide margin in many locations, most notably in Los Angeles, where the old record of 29.25" set January 17, 1988, was shattered by .18" (6 mb). The record-setting low spawned an extremely intense cold front that swept through the Southwest. Winds ahead of the cold front hit sustained speeds of hurricane force--74 mph--at Apache Junction, 40 miles east of Phoenix, and wind gusts as high as 94 mph were recorded in Ajo, Arizona. High winds plunged visibility to zero in blowing dust on I-10 connecting Phoenix and Tucson, closing the Interstate.


Figure 12. Ominous clouds hover over Arizona's Superstition Mountains during Arizona's most powerful storm on record, on January 21, 2010. Image credit: wunderphotographer ChandlerMike.

Strongest non-coastal storm in U.S. history
A massive low pressure system intensified to record strength over northern Minnesota on October 26, 2010, resulting in the lowest barometric pressure readings ever recorded in the continental United States, except for from hurricanes and nor'easters affecting the Atlantic seaboard. The 955 mb sea level pressure reported from Bigfork, Minnesota beat the previous low pressure record of 958 mb set during the Great Ohio Blizzard of January 26, 1978. Both Minnesota and Wisconsin set all time low pressure readings during the October 26 storm, and International Falls beat their previous low pressure record by nearly one-half inch of mercury--a truly amazing anomaly. The massive storm spawned 67 tornadoes over a four-day period, and brought sustained winds of 68 mph to Lake Superior.


Figure 13. Visible satellite image of the October 26, 2010 superstorm taken at 5:32pm EDT. At the time, Bigfork, Minnesota was reporting the lowest pressure ever recorded in a U.S. non-coastal storm, 955 mb. Image credit: NASA/GSFC.

Weakest and latest-ending East Asian monsoon on record
The summer monsoon over China's South China Sea was the weakest and latest ending monsoon on record since detailed records began in 1951, according to the Beijing Climate Center. The monsoon did not end until late October, nearly a month later than usual. The abnormal monsoon helped lead to precipitation 30% - 80% below normal in Northern China and Mongolia, and 30 - 100% above average across a wide swath of Central China. Western China saw summer precipitation more than 200% above average, and torrential monsoon rains triggered catastrophic landslides that killed 2137 people and did $759 million in damage. Monsoon floods in China killed an additional 1911 people, affected 134 million, and did $18 billion in damage in 2010, according to the WHO Collaborating Centre for Research on the Epidemiology of Disasters (CRED). This was the 2nd most expensive flooding disaster in Chinese history, behind the $30 billion price tag of the 1998 floods that killed 3656 people. China had floods in 1915, 1931, and 1959 that killed 3 million, 3.7 million, and 2 million people, respectively, but no damage estimates are available for these floods.


Figure 14. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Image credit: Xinhua.

No monsoon depressions in India's Southwest Monsoon for 2nd time in 134 years
The Southwest Monsoon that affects India was fairly normal in 2010, bringing India rains within 2% of average. Much of the rain that falls in India from the monsoon typically comes from large regions of low pressure that form in the Bay of Bengal and move westwards over India. Typically, seven of these lows grow strong and well-organized enough to be labelled monsoon depressions, which are similar to but larger than tropical depressions. In 2010, no monsoon depressions formed--the only year besides 2002 (since 1877) that no monsoon depressions have been observed.

The Pakistani flood: most expensive natural disaster in Pakistan's history
A large monsoon low developed over the Bay of Bengal in late July and moved west towards Pakistan, creating a strong flow of moisture that helped trigger the deadly Pakistan floods of 2010. The floods were worsened by a persistent and unusually-far southwards dip in the jet stream, which brought cold air and rain-bearing low pressure systems over Pakistan. This unusual bend in the jet stream also helped bring Russia its record heat wave and drought. The Pakistani floods were the most expensive natural disaster in Pakistani history, killing 1985 people, affecting 20 million, and doing $9.5 billion in damage.


Figure 15. Local residents attempt to cross a washed-out road during the Pakistani flood catastrophe of 2010. Image credit: Pakistan Meteorology Department.

The Russian heat wave and drought: deadliest heat wave in human history
A scorching heat wave struck Moscow in late June 2010, and steadily increased in intensity through July as the jet stream remained "stuck" in an unusual loop that kept cool air and rain-bearing low pressure systems far north of the country. By July 14, the mercury hit 31°C (87°F) in Moscow, the first day of an incredible 33-day stretch with a maximum temperatures of 30°C (86°F) or higher. Moscow's old extreme heat record, 37°C (99°F) in 1920, was equaled or exceeded five times in a two-week period from July 26 - August 6 2010, including an incredible 38.2°C (101°F) on July 29. Over a thousand Russians seeking to escape the heat drowned in swimming accidents, and thousands more died from the heat and from inhaling smoke and toxic fumes from massive wild fires. The associated drought cut Russia's wheat crop by 40%, cost the nation $15 billion, and led to a ban on grain exports. The grain export ban, in combination with bad weather elsewhere in the globe during 2010 - 2011, caused a sharp spike in world food prices that helped trigger civil unrest across much of northern Africa and the Middle East in 2011. At least 55,000 people died due to the heat wave, making it the deadliest heat wave in human history. A 2011 NOAA study concluded that "while a contribution to the heat wave from climate change could not be entirely ruled out, if it was present, it played a much smaller role than naturally occurring meteorological processes in explaining this heat wave's intensity." However, they noted that the climate models used for the study showed a rapidly increasing risk of such heat waves in western Russia, from less than 1% per year in 2010, to 10% or more per year by 2100.


Figure 16. Smoke from wildfires burning to the southeast of Moscow on August 12, 2010. Northerly winds were keeping the smoke from blowing over the city. Image credit: NASA.

Record rains trigger Australia's most expensive natural disaster in history
Australia's most expensive natural disaster in history is now the Queensland flood of 2010 - 2011, with a price tag as high as $30 billion. At least 35 were killed. The Australian Bureau of Meteorology's annual summary reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." In 2010, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland has an area the size of Germany and France combined, and 3/4 of the region was declared a disaster zone.


Figure 17. The airport, the Bruce Highway, and large swaths of Rockhampton, Australia, went under water due to flooding from the Fitzroy River on January 9, 2011. The town of 75,000 was completely cut off by road and rail, and food, water and medicine had to be brought in by boat and helicopter. Image credit: NASA.

Heaviest rains on record trigger Colombia's worst flooding disaster in history
The 2010 rainy-season rains in Colombia were the heaviest in the 42 years since Colombia's weather service was created and began taking data. Floods and landslides killed 528, did $1 billion in damage, and left 2.2 million homeless, making it Colombia's most expensive, most widespread, and 2nd deadliest flooding disaster in history. Colombia's president Juan Manuel Santos said, "the tragedy the country is going through has no precedents in our history."


Figure 18. A daring rescue of two girls stranded in a taxi by flash flood waters Barranquilla, northern Colombia on August 14, 2010.

Tennessee's 1-in-1000 year flood kills 30, does $2.4 billion in damage
Tennessee's greatest disaster since the Civil War hit on May 1 - 2, 2010, when an epic deluge of rain brought by an "atmospheric river" of moisture dumped up to 17.73" of rain on the state. Nashville had its heaviest 1-day and 2-day rainfall amounts in its history, with a remarkable 7.25" on May 2, breaking the record for most rain in a single day. Only two days into the month, the May 1 - 2 rains made it the rainiest May in Nashville's history. The record rains sent the Cumberland River in downtown Nashville surging to 51.86', 12' over flood height, and the highest level the river has reached since a flood control project was completed in the early 1960s. At least four rivers in Tennessee reached their greatest flood heights on record. Most remarkable was the Duck River at Centreville, which crested at 47', a full 25 feet above flood stage, and ten feet higher than the previous record crest, achieved in 1948.


Figure 19. A portable classroom building from a nearby high school floats past submerged cars on I-24 near Nashville, TN on May 1, 2010. One person died in the flooding in this region of I-24. Roughly 200 - 250 vehicles got submerged on this section of I-24, according to wunderphotographer laughingjester, who was a tow truck operator called in to clear out the stranded vehicles.

When was the last time global weather was so extreme?
It is difficult to say whether the weather events of a particular year are more or less extreme globally than other years, since we have no objective global index that measures extremes. However, we do for the U.S.--NOAA's Climate Extremes Index (CEI), which looks at the percentage area of the contiguous U.S. experiencing top 10% or bottom 10% monthly maximum and minimum temperatures, monthly drought, and daily precipitation. The Climate Extremes Index rated 1998 as the most extreme year of the past century in the U.S. That year was also the warmest year since accurate records began in 1895, so it makes sense that the warmest year in Earth's recorded history--2010--was also probably one of the most extreme for both temperature and precipitation. Hot years tend to generate more wet and dry extremes than cold years. This occurs since there is more energy available to fuel the evaporation that drives heavy rains and snows, and to make droughts hotter and drier in places where storms are avoiding. Looking back through the 1800s, which was a very cool period, I can't find any years that had more exceptional global extremes in weather than 2010, until I reach 1816. That was the year of the devastating "Year Without a Summer"--caused by the massive climate-altering 1815 eruption of Indonesia's Mt. Tambora, the largest volcanic eruption since at least 536 A.D. It is quite possible that 2010 was the most extreme weather year globally since 1816.

Where will Earth's climate go from here?
The pace of extreme weather events has remained remarkably high during 2011, giving rise to the question--is the "Global Weirding" of 2010 and 2011 the new normal? Has human-caused climate change destabilized the climate, bringing these extreme, unprecedented weather events? Any one of the extreme weather events of 2010 or 2011 could have occurred naturally sometime during the past 1,000 years. But it is highly improbable that the remarkable extreme weather events of 2010 and 2011 could have all happened in such a short period of time without some powerful climate-altering force at work. The best science we have right now maintains that human-caused emissions of heat-trapping gases like CO2 are the most likely cause of such a climate-altering force.

Human-caused climate change has fundamentally altered the atmosphere by adding more heat and moisture. Observations confirm that global atmospheric water vapor has increased by about 4% since 1970, which is what theory says should have happened given the observed 0.5°C (0.9°F) warming of the planet's oceans during the same period. Shifts of this magnitude are capable of significantly affecting the path and strength of the jet stream, behavior of the planet's monsoons, and paths of rain and snow-bearing weather systems. For example, the average position of the jet stream retreated poleward 270 miles (435 km) during a 22-year period ending in 2001, in line with predictions from climate models. A naturally extreme year, when embedded in such a changed atmosphere, is capable of causing dramatic, unprecedented extremes like we observed during 2010 and 2011. That's the best theory I have to explain the extreme weather events of 2010 and 2011--natural extremes of El Niño, La Niña and other natural weather patterns combined with significant shifts in atmospheric circulation and the extra heat and atmospheric moisture due to human-caused climate change to create an extraordinary period of extreme weather. However, I don't believe that years like 2010 and 2011 will become the "new normal" in the coming decade. Many of the flood disasters in 2010 - 2011 were undoubtedly heavily influenced by the strong El Niño and La Niña events that occurred, and we're due for a few quiet years without a strong El Niño or La Niña. There's also the possibility that a major volcanic eruption in the tropics or a significant quiet period on the sun could help cool the climate for a few years, cutting down on heat and flooding extremes (though major eruptions tend to increase drought.) But the ever-increasing amounts of heat-trapping gases humans are emitting into the air puts tremendous pressure on the climate system to shift to a new, radically different, warmer state, and the extreme weather of 2010 - 2011 suggests that the transition is already well underway. A warmer planet has more energy to power stronger storms, hotter heat waves, more intense droughts, heavier flooding rains, and record glacier melt that will drive accelerating sea level rise. I expect that by 20 - 30 years from now, extreme weather years like we witnessed in 2010 will become the new normal.

Finally, I'll leave you with a quote from Dr. Ricky Rood's climate change blog, in his recent post,Changing the Conversation: Extreme Weather and Climate: "Given that greenhouse gases are well known to hold energy close to the Earth, those who deny a human-caused impact on weather need to pose a viable mechanism of how the Earth can hold in more energy and the weather not be changed. Think about it."

Reposted from Weather Underground by Dr Jeff Masters, Director of Meteorology.

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  1. DB @348, you got it exactly right. Let me thank you for the sterling job you and the other moderators do here on SkS. I would thank you far more often, except then I would be cluttering up quite a few threads with thanks, and multiplying your work by the need to remove all those posts.
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    Response:

    [DB] My pleasure, Tom.  I think I speak for the other moderators in that we would much rather step in and help in that fashion than those many times when we're forced to intervene & be the bad cop.  Your willingness to engage multiple parties in your usual patient manner is appreciated.

  2. Tom Curtis @ 348 I am not sure how you are calculating lapse rates from the graphs you have posted. Regardless that is not my point. I feel I am not communicating my idea very well with you and I fault myself for that. I was attempting to demonstrate my postition with the H-bomb situation in Post 337. "your argument is that the cold, more northerly air coming south has a reduced lapse rate, which will result in weaker CAPE, the fact that models predict a reduction in tropical lapse rates, but an increase in Arctic lapse rates runs directly counter to your main premise. In fact, to the extent that your argument has any validity, and with that knowledge of lapse rates, you should be predicting much stronger CAPE, and hence stronger and more frequent storms." My argument is not about the lapse rate of arctic air. It is about the actual temperature of this air and how it determines bouyancy of an air parcel. Current time the North pole air mass is at a certain temp aloft. From an article I linked to above, Continental polar air can have a temp of -40 C at 4000 meters. This cold air moves in during the winter and dominates the Midwest plains of the United States. As spring comes air is warming rapidly in the south slower in the north (especially if there is snow on the ground in the north). The air aloft warms much slower than the surface so it may not be at -40 C during spring (I don't have numbers) but it will still warm much slower than the ground. Say it is -30 C at 4000 meters. Now a strong low pressure systme pulls up a lot of the warm moist gulf air into this still cool air aloft. It is reasonable to expect a warm moist air parcel of 25 C moving into the area. Until it reaches the condensation level (maybe 1000 meters for this air) it will cool at the dry adiabatic of about -10 C/1000 feet. After the first 1000 meters the air has cooled to 15 C and start to condense. Now it cools at the moist adiabatic rate of around -6 C/1000 meters. It will cool 18 more C or be at -3 C when it reaches 4000 meters. The air aloft is still at -30 C. The parcel is considerably lighter than the surrounding air and continues to rise to the top of the troposphere, a powerful storm. You see it is not the lapse rate of the artic air that is so critical. It is its actual temperature profile in relation to the temp profile of air that will rise into it. If I am wrong in my thinking then you can criticize sources such as this. Book chapter about atmospheric stability. In this book here is a quote: "In addition to the seasonal effects directly caused by changes in solar radiation, there is also an important effect that is caused by the lag in heating and cooling of the atmosphere as a whole. The result is a predominance of cool air over warming land in the spring, and warm air over cooling surfaces in the fall. Thus, the steepest lapse rates frequently occur during the spring, whereas the strongest inversions occur during fall and early winter." So if I am wrong I guess it is the source I am using. I would like you to demonstrate how this thinking is flawed. Thanks. I am grateful you are taking the time to respond to my posts. I do learn alot from this interaction.
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    Response:

    [DB] Fixed link.

  3. Tom, I admire your patience. I am still following this and pulling my hair out-- kudos to you. Given that you are sincerely trying to get to the bottom of this. I'll engage you. Perhaps you can explain to Norman how it is possible to obtain a near adiabatic lapse rate to almost 500 mb above the southern great plains without a wiff of modified Arctic air in sight. Two hints: The Mexican plateau and strong diabatic heating. From Grünwald and Brooks (2011, Atmospheric Research): "This is a result of the generally lower values of CAPE in Europe (Brooks et al., 2003b). This is because the generators for high CAPE, which are high lapse rates in the mid-troposphere and high values of boundary-layer moisture, usually do not occur in Europe as often as in the US. The reason for this is the presence of the Rocky Mountains which high terrain accounts for the creation of high lapse rates and the presence of the Gulf of Mexico which is big and warm enough to provide abundant moisture on many days of the year." From Brooks et al. (2003, Atmospheric Research): "From an ingredients-based approach (Doswell et al., 1996) to severe thunderstorms, abundant lower-tropospheric moisture, steep mid-tropospheric lapse rates, and strong tropospheric wind shear are important. The central United States is in an ideal location for the juxtaposition of those ingredients with the high terrain of the Rocky Mountains providing a source for high lapse rate air and the Gulf of Mexico providing the moisture. Winds from the surface from over the Gulf (southerly) and from over the Rockies in the mid-troposphere results in strong shear at the same time it brings the thermodynamic ingredients together. Other regions near high terrain with moisture sources on their equatorward side (east of the Andes and south and east of the Himalayas) show up as well." From Brook s et al. (2007, Atmospheric Research): "High values of midtropospheric lapse rates are associated with air that is heated and dried over the elevated terrain of the southwestern US (Doswell et al., 1996), approximately 800 km to the west. Starting with 1 January, the atmosphere is dry (3.7 g kg−1) and relatively stable (6.3 K km−1).....During the spring and early summer, the lapse rates stay relatively constant, while the mixing ratio increases to over 13 g kg−1 by 1 July." Now as you can clearly see, the word Arctic did not appear once in those quotes. Tom your opponent is arguing a strawman. Also, in the future, so long as the surface warms as fast as the mid-levels, the lapse rates should remain largely the same for a given time of the year. I am not aware of any reason as to why the mid-or upper levels will warm faster than the surface over continental areas outside the tropics during the warm season. To wit, from a meta analysis conducted by Church: "But all current radiosonde datasets agree that globally, over the longer term (1958 to 2000) the surface and 850-300 hPa layers have warmed at comparable rates, but since 1979 the surface has warmed relative to the 850-300 hPa layer with the estimates ranging from 0.04 to 0.14 deg. K/decade for the various datasets (Angell, 2003)." [Source] Also from Church, "Despite the differences, there is general agreement among radiosonde products that the long-term record (1958 to 2001) shows little difference between surface and tropospheric warming rates, but the shorter records are more complex. The troposphere warmed with respect to the surface between 1958 and 1978, and cooled with respect to it thereafter during the satellite era." Note that the planet has warmed about +0.5 C during the satellite era without a decrease in lapse rates. Trapp et al. find that their is no marked changed in the lapse rates in their model simulations for the USA, consistent with the findings by Angell (2003). "The datasets also agree that the global warming of the surface and the troposphere were basically the same during 1958–2000, but that during 1979–2000 the global surface warmed more than the troposphere. The latter is significant based on the 54- station network." So in fact, it is expected that over land outside the tropics the surface should warm slightly faster than the mid troposphere. As stated by Dr. Gavin Schmidt from NASA: "The land-only ‘amplification’ factor was actually close to 0.95 (+/-0.07, 95% uncertainty in an individual simulation arising from fitting a linear trend), implying that you should be expecting that land surface temperatures to rise (slightly) faster than the satellite values." [Source]
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  4. Tom Curtis @ 348 Thank you for explaining the Trapp et al (2009) insignificant lapse rate increase. I don't know why they chose that height as significant. Supercell storms reach up to 20,000 meter (20 km) and can even go as high as 23 km. The lapse rate at the 3-5 km is not significant for severe thunderstorm ultimate CAPE value. Look at what happens above the 3-5 km level in your graph. Now the air is getting much warmer in the future. Oklahoma City has a latitude of 35.5 North (Tornado alley) and if you look at your graph, Oklahoma city would be under air that is much warmer. The stratosphere starts at around 200 millibar level. The really warm spot goes up to the stratosphere. This would make a really postive lapse rate depending upon how much the warming actually is (can be 3 to 14.6 which is a large range). Wouldn't this warmer layer of air suppress the upward motion of an air parcel?
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  5. Tom, As you probably know, given that you referred to 700-500 mb lapse rates, there is very good reason why severe thunderstorm researchers are interested in low-level buoyancy: "Research has shown that low-level CAPE and or corresponding lowlevel CIN may have relevance to tornado production. More CAPE in the lowest levels (and thus lower LCF heights) above the ground suggests stronger potential for large low level vertical accelerations and enhanced low-level mesocyclone intensification, and thus increasing likelihood of tornadoes in supercells......Simulations of storms with small CAPE (~ 800) squashed into the lowest 5 km indicate that pressure gradient forcing from rotation in mid levels is the primary force for accelerations below 500 mb. Above 500 mb, buoyancy forcing becomes more important (Wicker and Cantrell, 1994). Low-level buoyancy is also related to LCL/LFC heights (RFD characteristics)." [Source]
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  6. Tom, I do not know where you are getting your data, but as shown previously on this thread, the stongest storms are not increasing. Violent tornadoes decreased over the past half century. Even tropicla cyclines have not shown this. While I admit that my analsis may be incorrect, at least I am looking at the correct data.
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  7. Eric the Red @356, on rereading my previous post I found that I mistated my point. Where I wrote:
    " In this case the data is showing a clear trend to more tornadoes, but significant trend for the strongest categories of tornadoes. Other forms of storms also show a positive trend. In other words, both data and models agree."
    I hand intended to write:
    " In this case the data is showing a clear trend to more tornadoes, but a significant negative trend for the strongest categories of tornadoes. Other forms of storms also show a positive trend. In other words, both data and models agree."
    Evidently my thought got ahead of my typing and some words dropped out as sometimes happens. I apologize for any confusion, and ask that the moderators correct the original if convenient. For what it is worth, the data on the strongest tornadoes is problematic in the same way as the data for all tornadoes. Specifically, the Fujita scale classified tornadoes based on the damage that they did. With improved building standards, equivalently strong storms would cause less damage resulting in under reporting of strong storms in later years.
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  8. Tom, We agree on the problems associated with the tornado data, on both strongest and total. I see now that it was a simple typing error, so forgive me if my comment seemed overly harsh.
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  9. Tom Curtis and Eric the Red, This thread is about extreme weather. Statistically a 7 sigma standard deviation is extremely rare. From this earlier link on tornado count... Tornado count. I typed in all the data on an excel sheet to check on trends and averages. As I was entering the data I noticed the number 212 tornadoes in January 1999. It was so much above the numbers I had been enetering I decided to check out the standard deviation for this freak occurence. Using this calculator: Standard Deviation calculator. The average number of tornadoes in January from the data set was 18.31. The standard deviation ws 29.65. The 212 tornadoes in January 1999 would be 7 standard deviations from the average (sigma 7). This is a very rare occurence indeed. "σ Percentage within CI Percentage outside CI Fraction outside CI 0.674σ 50% 50% 1 / 2 1σ 68.2689492% 31.7310508% 1 / 3.1514872 1.645σ 90% 10% 1 / 10 1.960σ 95% 5% 1 / 20 2σ 95.4499736% 4.5500264% 1 / 21.977895 2.576σ 99% 1% 1 / 100 3σ 99.7300204% 0.2699796% 1 / 370.398 3.2906σ 99.9% 0.1% 1 / 1000 4σ 99.993666% 0.006334% 1 / 15,787 5σ 99.9999426697% 0.0000573303% 1 / 1,744,278 6σ 99.9999998027% 0.0000001973% 1 / 506,800,000 7σ 99.9999999997440% 0.0000000002560% 1 / 390,700,000,000" The point of this is that the nature of weather, a chaotic beast, does have these very unusual events. I am not sure linking a dozen or so extreme events in a year demonstrates that Global warming is destablaizing the climate in a bad way. What I am wondering is that if I look at other data about the weather or a long series of years I will continue to find these very extreme events popping up. Just a characteristic of weather and nothing more.
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  10. Tom Curtis, Here is some material for you to consider if you have the interest. Tornado formation along the lines Albatross posted above. "the Rocky Mountains help divert upper level winds across the Great Plains which helps set up outbreaks conditions when cold air aloft overrides the very warm moist air below" Quote from the link above. So where is this cold air aloft coming from that the Rocky Mountains are diverting? This one says exactly what I have claimed above. "Thunderstorms are convective storms. They need unstable air, a temperature profile with warm air near the ground and cold air aloft. Thunderstorms are more likely in the spring and summer than in the fall and winter. In spring and summer the sun warms the ground, which warms the air near the ground. Air near the ground is also warmed in the fall, but there is an important difference. In the spring the air aloft retains its winter cold; the air will be more unstable than in the fall when the air aloft retains its summer warmth." And then there is this one. "Where the air for Tornado Alley comes from The warm moist air, called tropical maritime air, is swept up from the Gulf of Mexico and the Caribbean Sea due to lack of mountain barriers. During the spring months the Earth begins to warm, which adds to the layer of warm moist air which is close to the ground. While this is occurring, cool dry air masses, called maritime polar, often sweep in from the north or northeast. The cool air is trapped by the Rocky Mountains and rides close to 10,000 feet above the warmer air below. Cool air over warm air is an unstable condition. The hot middle layer, coming from the west often acts as a “cap” on the low-level warm, moist air. Only the strongest areas of heating near the ground can penetrate the cap. But when they do, the bottled-up, low-level moist air feeds into the break from miles around. The shifting winds then twist theses updrafts forming supercell thunderstorms. A breaking cap, with the help of an upper level jetstream, can cause convection to grow explosively, with storms rapidly becoming severe and tornadic." Source for the above quoted material. This source claims that the cold air the Rocky Mountains deflect come from Maritime Polar air masses from the north or northeast. This writer is claiming the cold air that creates the highly unstable air comes from the poles. My point has been this. If the poles are warming faster than the tropics (about twice as fast according to IPCC studies), the polar air being the source of the cold air aloft that generates the tremendous storms and heavy rains, as the poles warm the source of cold air will be less and hence the severe storms will be less frequent overall. The counter is that the warm moist air increase will be more than enough to overcome the lack of wind shear (and my idea, cold air aloft). The tropics are expected to warm 2 C in the next 90 years. Would this warming provide so much more fuel to storms that it will overcome the other conditions that are working to lessen the storm severity? I think it would not. My empirical evidence for these claims is that the warmer wetter air of July and August are not sufficient to overcome the loss of cold air aloft to drive the severe storms that occur in the spring and early summer with air that is colder and has less moisture content than later summer air. More evidence against increases in flooding from Global warming. Missouri River. Graph of Missouri river flows. In the graph link above you can see that the Missouri river has the greatest average flow in May. June is close but it drops sharply in July and August. Months that have the warmest moistest air of the year in the United States. If the Trapp theory is correct, why are not July and August the months with the most severe storms and greatest rainfall. Obviously air with the most moisture content does not lead to an automatic increase in precipitation as some on this thread are certain would happen. Here is one for the Mississippi river. Mississipi River. Graph from above Mississippi articlel. If you look at this graph you will see that the greatest flow of the Mississippi occurs in April (melting snow and heavy rains). Look what happens in July and August. Here are some historic high Mississipi River flows: "1927 2,345,000 cfs 1973 2,261,000 cfs 1983 2,150,000 cfs 1945 2,123,000 cfs 1950 2,054,000 cfs 1979 2,005,000 cfs 1937 1,977,000 cfs 1975 1,927,000 cfs" 2011 Mississippi flood "The Flood of 2011 set new record stages at Vicksburg and Natchez and approached record levels at Greenville and Memphis.[30] Provisional estimates by the USGS indicate that the peak streamflow at Vicksburg, 2,340,000 cubic feet per second, exceeded the both the estimated peak streamflow of the Great Mississippi Flood of 1927, 2,278,000 cu ft/s (64,500 m3/s), and the measured peak streamflow of the 1937 flood, 2,080,000 cu ft/s (59,000 m3" Yes 2011 was the worst flood in 100 years but it is not exceptional or extreme compared to the other flood events of the past.
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  11. Eric the Red From an earlier post by Tom Curtis at 258 "As Norman correctly points out, humidity alone is not enough for a thunderstorm; but heat and humidity are both definite factors in the strength of thunderstorms. If you increase both, ceterus paribus you will increase the frequency and intensity of thunderstorms. As it happens, increased warming is also expected to increase Convective Available Potential Energy, another key factor (see maps in my 246." There is a lot of assumption that increasing heat and humidity will lead to more rain or more severe storms. Or this on from Albatross at 269 "So the short of it is that increasing the low-level moisture is likely to increase the chances for more intense/severe thunderstorms, and perhaps larger hail too. Work by Botzen et al. (2010) predicts that:" I did a little study of 3 cities in the United States. Kansas City, Miami and Birmingham to test what effect heat and humidity have on preciptiation. I used these resources for this study. Monthly temperature and precipitation data. Humidity levels of cities in study, using afternoon humidity when temp is highest. This nice little calculator. I made it easy and just used one atmosphere in all cases. Pressure does alter the calculation a bit but not enough to overcome some major observations. Convert relative humidity into specific humidity and enthalpy. Kansas City: S.H. specific humidity. Month High temp S.H.(g/m^3) enthalpy (j/gram) rain (mm) April 19 C 0.00790 39.3 83.1 May 24 0.0115 53.7 115.6 June 30 0.0164 72.8 120.1 July 32 0.0184 80.22 91.7 August 32 0.0187 80.97 91.9 Miami: S.H. specific humidity. Month High temp S.H.(g/m^3) enthalpy (j/gram) rain (mm) April 29 0.013 64.01 85.3 May 31 0.016 73.41 140.2 June 32 0.0193 82.57 216.9 July 33 0.0197 84.94 147.1 August 33 0.0204 86.64 219.2 September 32 0.0196 83.37 212.9 It seems Miami is the only city of the three that roughly follows the moisture/temperature equation in relation to moisture. But in July the preciptiation drops even though it has a higher energy and moiture content than June. Look at Birmingham Alabama. The month with very little moisture in the air and low energy has the most rainfall. Maybe cold air aloft has a lot more to do with precipitation than moisture and heat content of ground level air. Small study but it does show that heat content and moisture do not correlate well with preciptiation levels, but the combination of cold air aloft and moisture and heat below seem to be a good combination. My hypothesis would be that cold winters and springs with a warm gulf are the cause of severe weather and floods in the US. Miami may get much more rain than Kansas City, but the storms generally are not as intense and less likely to cause flooding.
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  12. Norman @361, this is ridiculous. You take monthly figures from three different cities which means your observations are not controlled for geographical or seasonal variables. You then draw conclusions about the relation of three other variables as though the uncontrolled variables are completely inconsequential. If you are serious about this sort of analysis, you should gain daily data from a large number of stations, preferably with global coverage. You should then sort each stations data into separate categories based on the state of the ENSO index (or equivalent). You should then do a second sort based on month of the year. You should then test the correlation to temperature, humidity and rainfall for each of these subgroups to test the hypothesis. If the subgroups have too few samples for statistical significance, you should determine an anomaly for each subgroup, scale anomalies for a common standard deviation and then combine the scaled anomaly data to perform the test. Albatross may have suggestions on other variables you should control for (NAO?, AMO?, PDO?, IOD?, direction of wind for each station?) or how to improve the method.
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  13. Tom Curtis # 362 If you have a long record of temperature and precipitation (maybe 100 years) what would geographical or seasonal variables matter? A long series of averages smooths the infomation and takes into account the variables you have listed (like ENSO,AMO,PDO etc). In any given year maybe Kansas City had a May with 2" rainfall and a July with 12" rainfall. But over a hundred years the trend is that May has more rain than July and then you start to look for a reason for this. What is the why? I do not need to gain daily station data or global data...my question is not of a global nature. The question is, is there evidence in the empirical data (100 year or more monthly avearges) that warmer wetter surface air will lead to more severe storms? I am questioning this point. What is more valuable then determining a correlation to temperature, humidity and rainfall from subgroups of data would be to find the mechanism that results in severe weather. You are correct that relatively warm moist air is a necessary ingredient. You need this fuel to power your storms. But you also need unstable air. You can have very moist warm air but if the air above is stable you will not create any storms. Case of point. Omaha Nebraska for the last week. A high pressure dominated the area and not a cloud in the sky. The air was very stable above. The surface air was hot and moist and after cold air moved in Omaha had some nice showers. Now the next question is what makes air unstable. I have posted many links on this mechanism. Unstable air is a situation where you have cooler denser air above warm moist air and an inversion or cap that prevents the warm air from rising into the cold air. Some trigger has to move the warm moist air into the cooler air aloft. (it is like a container of oxygen and hydrogen gas, it is an unstable mixture but can remain in that state indefinately until a trigger occurs such as a spark). You need the cold air aloft or you do not have unstable air. You can get weakly unstable air because of the differential heating between the earth's surface and air above. The property of air as an insulator is why the whole thing works. As spring stroms occur they send latent heat aloft warming that layer and mixing the unstable air making it more stable. The tendency is to make unstable air more stable. So as July and August roll around, the surface air is loaded with energy (heat and moisture) but the air aloft is much more stable and this warmer air will not generate the level of intense storms.
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  14. Tom Curtis, Here is some evidence for you to consider. Revisit a link I sent earlier if you choose. It is about cooling of air in Fairbanks Alaska. Look at figure 2 of article. If you care to look at figure 2 you can see the ground temp drops about 38 C but the air at 4500 meters only drops around 10 C. Air is a really good insulator so the cold air from polar fronts and winter will still remain aloft only slowly warming by non convective processes. Convective events will turn the air at a much faster rate bringing the cold air down to the surface and moving the warmer ground air aloft (spring stroms).
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  15. Norman - On the one hand, I have to compliment you for taking the time and effort to look into these issues. On the other hand, I have to seriously criticize you for continuing to choose single or several site data sets to discuss global averages. That is just not appropriate, and not informative. In fact, it is (regardless of what those individual sites tell you) cherry-picking, no matter what results you get. I would suggest a different tack for you - look up the global data from someone you might disagree with (look here, for example), see if there are issues or analyses of that data that you find statistically inappropriate, and if you wish then discuss those. But, please, stop selecting one to three spots in the USA only, and claiming that they mean anything compared to the global data. It's incorrect, statistically meaningless, and rather sad to watch. You've accounted for a significant percentage of the posts on this thread, and you have been consistently wrong. Worse, you don't seem to understand the criticisms raised. I would strongly suggest you step back and review what you know, and what you don't know, before posting here again.
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  16. Tom Curtis, Here is more evidence of my position. Rather than criticize my research into this (limited by time and access to material). Why not find empirical real world data that supports your view that warm moist air will lead to more severe weather events. Then it would be easier to understand the postition you feel is the correct one. There is a lot of data that does support my current view. Perhaps there is much that supports yours as well. Here is some: Graph of tornadoes in Texas and Oklahoma by month of occurence. Source of above graph link. Oklahoma City climate. I like this web site better than the previous one I was using. It list the rain event per month as well as other data, clouds, sunshine. Oklahoma has the most tornadoes in May, it also has the most rain in that month. But the air is much warmer and has more moisture in July and August yet that is not when the most severe storms occur or the frequency of rain events May is 10 July is 6 and August is 7 (measured at least a trace). If that warm July or August air would be present under May's upper unstable air profile, then I would agree that the moisture and warm air would produce the more severe storms. But I think if you do not take the stability of air into consideration in any argument about severe weather you would greatly miss what is going on. I think stability of air far outweighs moisture and air temp for the production of severe weather and I strongly believe the empirical data available shows this to be the case. A few post up I linked to Missouri river flows and the Mississippi. These are large river basins that cover numerous states. They give a strong indicator of when most the rain falls in these basins. Hint, it is not July or August. The two months with the warmest wettest air that contains the most potential energy. You should answer why doesn't July and August produce the most severe weather. Why do tornado numbers drop sharply in these months? From this source. Alabama Tornadoes. "In the State of Alabama, tornadoes occur most often in the months of March, April, and May." How does your perception of severe weather explain this? Graph of location of Tornadoes in US, check Oklahoma and Texas. Graph of hail location. Graph of monthly tornado frequency. Note it is not July or August, the months with the warmest and most moist air out of the year in the US. Sourc of the above graphs. Climate of Dallas area. Note the May rainfall vs the July rainfall amounts in Dallas Texas.
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  17. Tom Curtis, Since you believe my research to be "ridiculous", can you demonstrate empirical data to support your claims that moist warm air is the major ingredient in the formation of severe weather? More warm and moist air will lead to more intense severe weather in the future. You have a model prediction of this. What is the empirical data available currently that would convince someone that this model is a good and valid resource? Again, I am not saying that it would not. I am requesting empirical evidence to support the claim. Thanks.
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  18. Norman @363, I am not interested in debating the issue with you. Anyone who has followed this thread knows you are only interested in coming to the conclusion you started with. This is made perfectly plain in your 359 (among many other places). When looking for signs of recent increases in extreme weather you come across an extraordinary example, and immediately interpret it as proof that extraordinary examples of recent extreme weather are not evidence of increasing extreme weather. It certainly, to your mind, had nothing to do with the 2-4 degree anomaly in the US at that time. It turns out that through out the course of this debate, for you , nothing can be. Having said that, and for the benefit for anybody else following this thread, it is obvious that a number of factors contribute to weather phenomena. Taking one example, El Nino events lead to hot, dry conditions in Queensland, and that La Nina conditions lead to cold wet conditions. A study such as yours using Queensland data, which did not correlate for ENSO would conclude that specific humidity was negatively correlated with temperature, whereas the opposite is true. The true situation would show up if you sorted the data for ENSO index. Of course, a different pattern arises in New Zealand, so you need to sort for location. In Tasmania, in constrast, ENSO is relatively insignificant but the heaviest rainfall comes in the winter months because the prevailing westerlies shift north in Winter, and blow moist air across Tasmania, whereas in summer they blow mostly south of Tasmania. If you fail to sort for these regional differences in weather patterns, they will introduce a spurious signal into your data. If you use only a small number of stations in a regionally restricted area, they will dominate the signal.
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  19. Norman: What causes rain/tornadoes etc is the temperature differential. At least in the upper midwest of CONUS. To find extrordinary weather events, you have to stick to the changeing of the seasons. One a season has stabalized, the extraordinary events deminish. Climate slueths from NOAA have not as yet found a correlation with present conditions, frequency etc tied to climate change. This may change in the future, but for now it hasn't.
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  20. Norman @367, I do not believe that I have ever said that warm moist air is the major ingredient in the formation of severe weather. What I do say is that for most conditions, increasing temperature and moisture content will increase the risk of severe storms. In many locations, however, the factors that increase temperature will also alter other factors so that overall risk is reduced. Taking Queensland again, increased temperature may well increase the risk of cyclones all else being equal, but ENSO dominates temperature variation in Queensland, with El Nino's decreasing the risk of cyclones. Consequently global warming is expected to decrease the frequency of cyclones in Queensland, but to increase the risk that cyclones that do arrive will be category 4 or 5. (This is often misinterpreted, IMO. The decrease in expected frequency is sufficiently large that the absolute number of category 4 and 5 cyclones will also decrease, though their proportion will increase.) In contrast on the West Australian coast, global warming is expected to both increase the frequency and power of cyclones. Overall the effect will be an increase in extreme conditions. IN Queensland we will get fewer cyclones but more and longer droughts, and the floods and cyclones we do get will be bigger. In Western Australia they will get fewer droughts, but more and larger cyclones and floods (except in the South West corner which will get almost permanent drought conditions). You want evidence of this? Reread the thread. I have already provided copious evidence and seen it ignored on a variety of specious reasons. I see no reason to do so again.
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  21. Tom, I just wanted to say that I very much appreciate your efforts on this thread. Don't feel that they have been for naught, I am sure that your posts have resonated with those many reasonable, informed and truly skeptical people out there. At this point it really appear that the contrarian is interested in dragging out the "debate" and arguing. Fortunately, very early on already science and reason yet again won the day; this thread has run its course.
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  22. Tom Curtis # 370 "Norman @367, I do not believe that I have ever said that warm moist air is the major ingredient in the formation of severe weather." What you had said "From an earlier post by Tom Curtis at 258 "As Norman correctly points out, humidity alone is not enough for a thunderstorm; but heat and humidity are both definite factors in the strength of thunderstorms. If you increase both, ceterus paribus you will increase the frequency and intensity of thunderstorms. As it happens, increased warming is also expected to increase Convective Available Potential Energy, another key factor (see maps in my 246" That is where I misquoted you, sorry. You used the words "definate factors" and I switched that to "major ingredients" also you said "thunderstorms" and I changed that to "severe weather". My flaw. I stand corrected.
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  23. KR @ 365 "On the other hand, I have to seriously criticize you for continuing to choose single or several site data sets to discuss global averages." In the series of posts above, I was not attempting to discuss global averages. Tom Curtis made the statement: "As Norman correctly points out, humidity alone is not enough for a thunderstorm; but heat and humidity are both definite factors in the strength of thunderstorms. If you increase both, ceterus paribus you will increase the frequency and intensity of thunderstorms. As it happens, increased warming is also expected to increase Convective Available Potential Energy, another key factor (see maps in my 246." I was attempting to demonstrate his point "If you increase both, ceterus paribus you will increase the frequency and intensity of thunderstorms." was not the case. In my series of posts the point was to show Tom that only a threshold humidity and heat are needed to initiate severe thunderstorms. The rest of the equation is unstable air (cold heavy air mass on top of less dense warm air). The more unstable the air, higher temp gradient between surface warm air and cold air aloft, the greater is the chance for severe weather. If you get a strong wind shear you also increase the chance for tornadoes. I did agree with Tom that if, in the United States, you would be able to send the higher energy July or August air into the unstable air of May, you would indeed create more severe storms than what are currently taking place. Your claim: "You've accounted for a significant percentage of the posts on this thread, and you have been consistently wrong. Worse, you don't seem to understand the criticisms raised. I would strongly suggest you step back and review what you know, and what you don't know, before posting here again." It is easy to say I am consistently wrong. Can you show how any of my links are not correct? Can you demonstrate that the month of May does not produces the most severe storms in the US? From your link: "How does one counter the Dunning-Kruger effect, in others or in themselves? Dunning and Kruger propose that improving a person's skills helps them recognise the limitations of their abilities. If there's a question about an aspect of climate science, the first step should be to investigate and improve understanding of the science. Odds are climate scientists have investigated the same question in the peer-reviewed scientific literature." KR, I do believe I have been doing this. Thanks to the intelligent and knowledgable Tom Curtis, Albatross, Daniel Bailey, Dikran Marsupial and many others I have recognized many flaws in my understanding and holes in my knowledge base. I have been attempting to investigate and improve my understanding of the science. I try to find peer-reviewed material for my posts, avoid blogs. One of my main reasons for posting on a scientific web site like this one. I am seeking more than one person's opinion on the issue. I want good science. From your link: "If there's no direct answer, find the closest topic and post a comment asking for answers. There are many well informed regulars who would be happy to point you towards any relevant peer-reviewed papers." My question is this: Why would weather events get more extreme when Global warming is pushing the Earth towards and equilibrium state (poles warming about twice as fast as tropics). I have been linked to articles where a computer model predicts more severe weather much later in this century. There is no way for me to validate the model. All I can determine for sure is maybe it will happen. But it does not answer my question above. I have found many sources that explain severe weather is caused by unstable air mass. You need cold air to develop this condition. If the poles are warming twice as fast as the source of the warm, moist fuel, then why wouldn't the instability of the atmosphere decrease as the Globe warms? It would have less cold air available to create the unstable air that generates severe weather. You also said: "But, please, stop selecting one to three spots in the USA only, and claiming that they mean anything compared to the global data. It's incorrect, statistically meaningless, and rather sad to watch" I think you are not understanding what I am attempting. In order to demonstrate a physical mechanism you do not have to go to every spot on earth to prove the condition is global. I am demonstrating that a reserve of cold air is necessary for the formation of most severe thunderstorms (there are always exceptions). If the reserve of cold air is reduced then the number and intensity of thunderstorms will be reduced. I choose points in Oklahoma and Texas because these are the areas that produce the most severe thunderstorms not just locally but globally. I demonstrate that May has the most severe storms in those states (tornadoes, rain, hail). I demonstrate that without the cold air aloft the highly energetic and moist air of July and August do not produce near the number of severe storms or rain events. If you drop a ball in your house and have supporting documentation of gravity, do you need to come to my house and drop a ball to test the idea? If I can demonstrate that warming of air in Texas and Oklahoma will not lead to more severe storms (over a 100 year period for precipitation and at least 50 years for tornadoes), why would I need to extend the area? I am demonstrating a mechanism that is supported by the literature (I have linked to multiple sources which confirm the mechanisms needed to produce severe storms). If the mechanism is a valid one, it will work anywhere on the globe.
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  24. Tom Curtis @ 368 Side note: To Albatross, you stated this thread has run its course. So unless someone else wishes to discuss more I will end here and go to read the Ocean acidification series (more in my field). Just wanted to respond to you Tom. You say: "Norman @363, I am not interested in debating the issue with you. Anyone who has followed this thread knows you are only interested in coming to the conclusion you started with. This is made perfectly plain in your 359 (among many other places). When looking for signs of recent increases in extreme weather you come across an extraordinary example, and immediately interpret it as proof that extraordinary examples of recent extreme weather are not evidence of increasing extreme weather. It certainly, to your mind, had nothing to do with the 2-4 degree anomaly in the US at that time. It turns out that through out the course of this debate, for you , nothing can be." I would think if would have nothing to do with the 2-4 degree anomaly in the US in January 1999. Here is why. January 1999 anomaly map. (Sorry I am not posting the graphs directly, I attempted it once but found my skill at this lacking.) February 1999 greater heat anomaly than January. January 1999: 212 tornadoes February 1999: 22 tornadoes More: January 1998 had 47 documented tornadoes. January 2000 had 21 documented tornadoes. If you do check out each of the linked maps to tornado number you can see all these years had strong temperature anomalies in January. But January 1999 soars far above the others. You would really have to stretch something to prove a causal link between January temps and tornado count in the US. Final link Does this sound sort of simialr to the topic of this thread, just switch 2010 to 1999 and there could be a match. History repeats.
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  25. KR @ 365 Can't leave without this one. From your link to the peer-reviewed material on climate change. "There are no indications in this study of more intense storms in the future climate, either in the Tropics or extratropics, but rather a minor reduction in the number of weaker storms." There is significant changes to storm tracks. The thesis of this thread is "2010 - 2011: Earth's most extreme weather since 1816?" The peer reviewed article does not see an increase in the intenstity of storms, only a change in location of storms. No change in intensity of storms.
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  26. Norman @373, now that I understand that your analysis is explicitly related to the formation of supercells in the United States, I will modify my criticism from 262 and 268 above. Specifically, for that question, your sample points are sparse but can make a reasonable claim to be representative. However bundling data without regard to season and ENSO index still means your analysis is ineffective. If you really want to do citizen science on this, I have to commend you but don't imagine for a second that it is easy. In science you don't get to skip corners, and a proper study will involve multiple thousands of pieces of data, and very careful analysis. If you are not prepared to put that sort of work in, your analysis will inevitably be both shallow and flawed. What is more, it will be irrelevant because genuine climatologists and meteorologists have put in the real work, collecting tens (probably hundreds) of thousands of pieces of data, and analyzing it carefully in peer reviewed literature where any obvious and, most likely, any subtle flaw has been pounced upon by somebody with a passion for truth or to make a name for themselves. So in order to accept your conclusions from your analysis, we would have to turn our back on a great deal more data, subject to a far more rigorous analysis. Not that I am trying to discourage you from your three city analysis. I am a great fan of such analyses so long as their role is understood. That role is to learn, not to discover. By undertaking such an analysis you can more quickly gain an appreciation of the issues involved than by any other method (other than a good lecture). But you will only do so if you understand the true nature of expertise, which is knowledge of the obvious errors in a field, and how to avoid them. Think about it. You and I are not expert in meteorology. Ergo we are likely to make obvious blunders and not realize it. In contrast, genuine experts (like Albatross) will probably also make errors, but they will be subtle and interesting errors. That is, errors that are hard to avoid, and which you learn a great deal by uncovering. So the obvious attitude you and I should take is that when we disagree with the experts, we should first check rigorously why we are wrong. Not the experts, but we ourselves. Only after checking rigorously enough to become competent in the field ourselves, and after floating the idea with a few experts, a significant proportion of whom then agree with us, should we even begin to suspect that we are right. Even at that stage history shows that we are probably still making an error, but at least it will be an interesting and subtle error. Frankly, that has not been your attitude on this or any other thread on Skeptical Science. That is why Albatross is so frustrated. It is not that you keep on asking questions, a behavior which delights most experts. Its that you don't accept answers.
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  27. In other news, "During the first three weeks of July, 12 weather stations have recorded all-time daytime highs. But 93 weather stations have seen their all-time warmest nighttime temperatures." Meanwhile, the ongoing saga of Damorbel's refusal to accept the existence of the GHE continues . . .
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  28. ThinkProgress posted a US version of the annual disaster count chart: The global version appears here. Geophysical events such as earthquakes, tsunamis and volcanic eruptions show no pattern of increase. All the increase is due to meteorological, hydrological and climatological events which have all more than doubled. From an insurance point of view it certainly looks like the climate is changing.
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  29. muoncounter, excluding tsunamis which are rather rare, the effects of weather are dispersed unlike earthquakes and volcanoes. So volcanoes and earthquakes can stay the same and have the same number of "catastrophes". Weather, on the other hand, will cause an increasing number of "catastrophes" because their definition is based on dollar value. The dollar value of property in volcanic zones is not going to increase as much as nonvolcanic zones. And while earthquake zones may increase in dollar value, they have rigorous construction and zoning laws. That is not as true for flood zones, and likely not true at all for other types of storm zones. In short, weather can hit anywhere and cause more dollar damage to meet the catastrophe threshold whereas earthquakes and volcanoes can only occur where they have in the past. But that doesn't mean that such weather events are not increasing, just that some of the upward trend can be explained by population and wealth.
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  30. It's worse than I realized. The Munich Re data is based on a number of sources that contain reporting coverage increases, see http://www.ccap.org/docs/resources/345/302-03901_en.pdf particularly their insurance affiliates. It really means that the trend is skewed by the extent of insurance coverage along with the increases in population and insured value.
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  31. Eric#379: The point was to exclude earthquakes and volcanoes from the rising trend - because if they did not, skeptics would say 'it's earthquakes and volcanoes!' The worldwide count increased by a factor of approx 2 1/2 since 1980, population by a mere 50%. The 'insured value of the world,' whatever that means, has not made up the difference. It is only by looking at this display on its own that you can find some rationalization. That is what being a skeptic seems to mean these days - each individual data point must have something wrong with it and can be taken in isolation. However, taking all of the other evidence for climate change into account, this graphic is a straightforward answer to those who say 'it's not happening' and 'it's not bad.'
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  32. Muon, http://www.propertycasualty360.com/2010/08/25/increased-exposures-not-climate-change-responsible-for-higher-cat-losses Reply from Munich Re: http://www.propertycasualty360.com/2010/09/27/munich-re-2010-cats-cause-18b-in-insured-losses-likely-linked-to-climate-change
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  33. Eric#382: From your first source, The report ... analyzed 22 peer-reviewed disaster loss studies from the last 30 years, conducted by a variety of sources that included the United Nations, the Intergovernmental Panel on Climate Change (IPCC) and some insurers. The studies analyzed mostly looked into losses in developed countries, in particular the U.S. -- emphasis added Reports that look at only the US would of course be biased by property value. However, the graphs I posted show number of events, not value of loss. From the report of Global Climate Risk Index: - Bangladesh, Myanmar and Honduras were the countries most affected by extreme weather events from 1990 to 2009; - All of the ten most affected countries (1990-2009) were developing countries in the low-income or lower-middle income country group; - In total, more than 650,000 people died as a direct consequence from almost 14,000 extreme weather events, and losses of more than 2.1 trillion USD (in PPP) occurred from 1990 to 2009 These are just indicators of what is already happening. Go back to the original post for the underlying cause: Hot years tend to generate more wet and dry extremes than cold years. This occurs since there is more energy available to fuel the evaporation that drives heavy rains and snows, and to make droughts hotter and drier in places where storms are avoiding.
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  34. Muon, the number of events is dependent on the value (there is a threshold). I have looked in vain for the threshold, but Munich Re didn't publish their definition of "event" AFAICS.
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  35. Eric#384: From the GCRI report's 'methodology': Each country´s index score has been derived from a country's average ranking in all four analyses, according to the following weighting: death toll 1/6, deaths per inhabitants 1/3, absolute losses 1/6, losses per GDP 1/3. Fully 50% of this index is based on mortality and is thus independent of loss value threshold. It is, however, telling that we have to look to the insurance industry for these data. Are you simply rejecting the basic premise that extreme events are occurring more frequently? Quoting Masters: Never in my 30 years as a meteorologist have I witnessed a year like 2010--the astonishing number of weather disasters and unprecedented wild swings in Earth's atmospheric circulation were like nothing I've seen. Or that there is an obvious cause and effect? Again quoting the OP: ... in his recent post, Changing the Conversation: Extreme Weather and Climate: "Given that greenhouse gases are well known to hold energy close to the Earth, those who deny a human-caused impact on weather need to pose a viable mechanism of how the Earth can hold in more energy and the weather not be changed. Think about it."
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  36. Eric (skeptic) - (Two links regarding exposure changes versus climate changes) From your second link: '"Nevertheless," Munich Re said, "it would seem that the only plausible explanation for the rise in weather-related catastrophes is climate change."' Your link therefore contradicts what you were (apparently???) trying to assert with it. Exposure increases are part of the increased risk factors, as has been repeatedly discussed before here - but weather related insurance events are occurring faster than (for example) tectonic events, and while it may be early to make statistical conclusions about it, extreme weather events do appear to be increasing. (Incidentally, Eric, it would have been nice if you had included some descriptive text along with the links, as anyone not familiar with the discussion would have found that completely incomprehensible. See the Comments Policy.)
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  37. KR @386, I have been all over the Munich Re data and all its permutations with Norman, both on the Linking extreme weather and global warming thread, and earlier on this thread. We covered every permutation on the data and established that: 1) The increased number of climate related extreme events relative to geophysical extreme events survives when the events are filtered for magnitude. 2) The increased number of climate related extreme events also occurred in long, densely inhabited regions such as Germany. 3) That geophysical and climate related events are not significantly different in the way the likelihood of damage changes with increase population densities. 4) That Major events are not single thunderstorms (or the equivalent) but a single weather system, possibly containing multiple supercells and tens of tornadoes, something no more likely to be missed in 1950 than now. 5) That Major events are classified as events that cause deaths or a time variant level of property damage, where that level of property damage increases faster than GDP so that increased wealth is unlikely to have caused in increase of reporting. 6) Indeed, on the contrary, improved warnings and building standards have reduced deaths and property damage and so if so the rate of reporting is as likely to have declined as increased. The clear conclusion is that there has been an increase in climate related extreme events due to global warming, although it is not certain how large that increase is. Eric(skeptic) was active in both threads where this was discussed, so he knows this as well as does anyone else. The intriguing question is why is he recycling a dead issue?
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  38. Tom: Some of your assertions require a bit of question. You state in item 4 that storms with multiple tornados would not have been missed in 1950. The tech to observe said multiples was not here in 1950. On this whole issue I am going to have to go with NOAA climate slueths, who find that there is no discernable trend at this time.
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    Response:

    [DB] "I am going to have to go with NOAA climate slueths, who find that there is no discernable trend at this time"

    You'll need to furnish a supportive link for that claim, given the extensive corroborating evidence Tom has already provided in this thread.

  39. Eric (skeptic) - I have to agree with what Tom Curtis said. Why are you continuing to beat a dead horse? Extreme weather is increasing, and it's not just increases in reporting or population density.
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  40. Camburn @388, are you seriously suggesting that storm cells that span multiple states and which generate multiple tornadoes might just have not been noticed in 1950? Where Americans all blind and deaf in the 1950's that you wish to argue this as a credible possibility?
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  41. KR (389), I am waiting for a reply on what Munich Re's definition of "event" is. If I had more time I would keep looking myself. Secondly, Norman summed up the case for you in 373, namely that heat and humidity are necessary but not sufficient for some types of extreme events and an increase in heat and humidity on the whole does not mean there will be an increase in those types of extreme events. Those types include strong tornadoes, currently in a long term downtrend. Tom (387), is the event you defined there, the same as Munich Re's event shown in the chart in 378? If so, then I have the definition I asked for and withdraw my request.
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  42. Eric (skeptic) @391, a disaster is a single event causing loss of life, significant injury or significant damage. In 2010, an Earthquake in Indiana damaging three buildings and causing a few injuries was classified as an event by Munich Re. A Major Disaster is a disaster in which at least 100 people die, or in which approx (85 + 4 * (t - 1980)) million dollars damage is done, where t = the year of the event. Clearly a hazard on the scale of the first may have passed without notice in 1950, but a hazard meeting the definition of a major disaster would not. The property value index approximately matches that of an exponential growth rate of 3% per annum, so increased property values are unlikely to have caused significant "bracket creep". An "event" is so defined that, for example, the April 22-28 and the May 20-25 Tornado outbreaks in the US in 2011 are each classified as a single event. So did the 2011 Queensland floods with a flooded effected area larger than Texas and California combined. Given this we can safely say that major catastrophes would not pass notice in any era post WW2 in the US, yet Munich Re data show a trend line for major climate related events which doubles the number of events over the last 30 years. In the meantime geophysical events have only increased by 60% over the same period. Property value bracket creep would effect both types of disasters equally, so the difference is likely to be primarily the result of a 25% increased frequency of extreme weather events relative to geophysical events with a margin of error close to the magnitude of the increase (ie, the relative increase could have been 40%, or 10% for all we know). I have not seen actual error bars put on the figure, and I doubt they could be effectively calculated given the data available. But claiming zero increase is done in the face of the evidence - not based on it.
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  43. Tom, thank you. FTR, I do not claim zero increase. For example, extreme rainfall disasters should be increasing with AGW.
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  44. Eric (skeptic) - My objections to Norman's posts are primarily in (a) extremely limited geographic extent, as we can expect climate change to have considerable local variances (and at 4% of the surface, the US rates as 'local'), and (b) his continuing overly-simplistic take on weather interactions, despite input from various knowledgeable people. In regards to your event definition questions, I'll note that even the links you provided contain statements by Munich Re to the effect that while reporting has increased, the number of weather related events has increased faster than reporting or economic expansion alone can account for. So - according to the folks providing the data, this is not only an effect of population, economic valuation, or reporting levels. There is an increase in weather related events over and above those other causes. And, since you've been in the discussion from the beginning, you should know that! And yet - after almost 400 posts on this thread you continue to hunt for a reporting change or other data distortion that would account for the increased weather events they see. I consider that to be beating a dead horse. It's simply isn't going to get off the ground and trot away...
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  45. Eric#391: Doll and Sieber 2010 define 'extreme events' in a scientific manner, making no reference to financial loss. Many of the above disasters are caused be extreme weather events. The IPCC (2001) has defined an extreme weather event as an event that is rare within its statistical reference distribution at a particular place. Definitions of ‗rare‘ vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile. Their figure 5, disasters due to natural hazards in EEA member countries 1980-2009 is remarkably similar to the Munich Re graphics. the number of disasters in Europe has been showing an upward trend since 1980, largely due to the continuous increase of meteorological and hydrological events. KR#394 is correct; if you really believe that all the evidence of trends in extreme weather here is wrong, present some to substantiate your case.
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  46. A very nice analysis of just how extreme the current drought really is posted at John Nielsen-Gammon's blog. One can quickly see the mean rainfall pattern -- and the historic variation around the mean in this spaghetti display. I won't be a spoiler; you'll have to see how 2011 compares for yourself.
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  47. I am going to respond on this thread to a comment by Eric the Red on the Republican Candidates vs Climate Science thread. Eric the Red: Your suggestion "Since global warming theory tends to favor El Nino conditions, the occurrance of the strong La Nina runs counter-intuitive" is, to the best of my understanding, simply false. Climate change does not favour any one state of ENSO except insofar as it affects the Pacific ocean currents which drive ENSO. Do you have a cite to scientific literature supporting your claim?
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  48. Since global warming theory tends to favor El Nino conditions, the occurrance of the strong La Nina runs counter-intuitive.. Unless there is new publications I am unaware of, this statement is not correct. Please reference if you do. The effect of GW on ENSO as far as I know is very much unsettled science, with different models giving different results. Expansion of the Hadley cells could give more La Nina conditions (just a lot hotter than previous El Ninos). What does appear to be robust, is that amplitude of ENSO variation will increase.
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  49. scaddenp#398: "amplitude of ENSO variation will increase" Spot on. EtR is indeed all wet on this idea. As far back as 1999, Timmerman et al saw the potential for these changes: The tropical Pacific climate system is thus predicted to undergo strong changes if emissions of greenhouse gases continue to increase. The climatic effects will be threefold. First, the mean climate in the tropical Pacific region will change towards a state corresponding to present-day El Nino conditions. It is therefore likely that events typical of El Nino will also become more frequent. Second, a stronger interannual variability will be superimposed on the changes in the mean state, so year-to-year variations may become more extreme under enhanced greenhouse conditions. Third, the interannual variability will be more strongly skewed, with strong cold events (relative to the warmer mean state) becoming more frequent. -- emphasis added The key is that stronger variability is superimposed on the warming trend. I see a clear analogy with increasing the energy content of an already oscillating system. More energy = more amplitude in both directions.
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  50. Muon, Outside of the greater variabiity, does not your emphasis indicate that changes will favor El Nino conditions? At least that is what I am reading from the first point above. Or are you all wet on this first point? There is no general agreement on the stronger variability, although it is possible as Timmerman states.
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