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Climate Hustle

Linking Extreme Weather and Global Warming

Posted on 18 June 2011 by Anne-Marie Blackburn

Whenever there is an extreme weather event, such as a flood or drought, people ask whether that event was caused by global warming. Unfortunately, there is no straightforward answer to this question. Weather is highly variable and extreme weather events have always happened. Detecting trends takes time, particularly when observational records are rare or even missing in certain regions. An increase in extreme weather is expected with global warming because rising temperatures affect weather parameters in several ways. Changes in the frequency of extreme events coinciding with global warming have already been observed, and there is increasing evidence that some of these changes are caused by the impacts of human activities on the climate.

How global warming affects weather parameters

Rising temperatures can have several effects on the factors involved in weather. For example:

  • They increase the rate of evapotranspiration, which is the total evaporation of water from soil, plants and water bodies. This can have a direct effect on the fequency and intensity of droughts.
  • A warmer atmosphere can hold more water vapour. The atmosphere now holds 4% more water vapour than it did 40 years ago as a result of increasing temperatures. This increases the risk of extreme rainfall events.
  • Changes in sea-surface temperatures (SSTs) also have an effect by bringing about associated changes in atmospheric circulation and precipitation. This has been implicated in some droughts, particularly in the tropics.

These changes don't automatically generate extreme weather events but they change the odds that such events will take place. It is equivalent to the loading of dice, leading to one side being heavier, so that a certain outcome becomes more likely. In the context of global warming, this means that rising temperatures increase the odds of extreme events occurring.

Changes in extreme weather events are already being observed

In the US, the Global Changes Research Program published a report in 2009 entitled Global Climate Change Impacts in the US. The National Climate Change chapter reports the following findings for recent decades:

  • Heavy rainfall events have increased both in frequency and in intensity by 20%, and are the main cause behind the increase in overall precipitation in the US. The Northeast and Midwest have seen the greatest increase in such events.
  • The frequency of drought has increased in areas such as the Southeast and the West, and decreased in other areas. Rising temperatures make droughts more severe and/or widespread, and also lead to the earlier melting of snowpacks, which can exacerbate problems in vulnerable areas.
  • Atlantic hurricanes have increased both in power and frequency, coinciding with warming oceans that provide energy to these storms. In the Eastern Pacific, there have been fewer but stronger hurricanes recently. More research is needed to better understand the extent to which other factors, such as atmospheric stability and circulation, affect hurricane development.

Similarly, Australia has seen the odds of both heavy rainfalls and droughts increase, and similar patterns are being observed worldwide, coinciding with rising temperatures over the past 50 years.

In conclusion, although it isn't possible to state that global warming is causing a particular extreme event, it is wrong to say that global warming has no effect on the weather. Rising air and sea temperatures have a number of effects on the water cycle, and this increases the odds for more extreme weather events.

NOTE: this is the Basic rebuttal to "Extreme weather isn't caused by global warming"

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Comments 201 to 236 out of 236:

  1. michael, et. al.,

    warming weather will add more moisture to the air, hence more precipitation. This will lead to greater rainfall.

    Snowfall occurs when the temperature is below freezing. In scaddamp #194, a warmer winter will result in more precipitaion, but it will fall in the form of rain, not snow. In general, warmer winters yield less snow.

    The largest snowfall occur when the temperature is nearest freezing. Very little snow falls when temperatures are much below freezing. In places were the average temperature is below freezing, then an increase in temperature will result in greater snowfall. Hence, Fairbanks, AK would expect to receive more snowfall in a warming world as the average annual temperature is ~-3C. Most of the rest of the world would see diminished snowfall as the temperatures rise further above freezing.

    Overall, AGW predicts greater precipitation, but not snow.
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  2. #193, Camburn, you are correct. The Canadians started filling their reservoirs in April based on a completely worthless (for this situation) treaty. They hit about 4000 cfs in April (see
    http://www.minotdailynews.com/page/content.detail/id/553971/Souris-River-system-tested.html
    and then proceeded to try to achieve the treaty value, rather than keep the flow at a higher precautionary rate. They proceeded with the same reservoir filling two more times (late May, and amazingly, earlier this month).

    The results are dramatic, a human-created flood with 34400 (current rate) being sent across the border today, ten times the treaty limit. For the sorry results see http://waterdata.usgs.gov/nd/nwis/uv?cb_00060=on&format=gif_default.=90&site_no=05114000
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  3. Eric the Red wrote : "Overall, AGW predicts greater precipitation, but not snow."


    Precipitation is precipitation, whether it falls as rain or snow, and others here have already shown how snow can be more likely, depending on local or regional conditions.

    More information and links available from Jeff Masters :


    Another interesting result from the Changnon et al. (2006) paper of Figure 2 is the relationship between heavy snowstorms and the average winter temperature. For the contiguous U.S. between 1900 - 2001, the authors found that 61% - 80% of all heavy snowstorms of 6+ inches occurred during winters with above normal temperatures. In other words, the old adage, "it's too cold to snow", has some truth to it. The authors also found that 61% - 85% of all heavy snowstorms of 6+ inches occurred during winters that were wetter than average. The authors conclude, "a future with wetter and warmer winters, which is one outcome expected (National Assessment Synthesis Team 2001), will bring more heavy snowstorms of 6+ inches than in 1901 - 2000. The authors found that over the U.S. as a whole, there had been a slight but significant increase in heavy snowstorms of 6+ inches than in 1901 - 2000. So, there is evidence that the average climate of the U.S. over the past 100 years is colder than optimal for heavy snow events to occur. If the climate continues to warm, we should expect an increase in heavy snow events for a few decades, until the climate grows so warm that we pass the point where winter temperatures are at the optimum for heavy snow events. However, a study by Houston and Changnon (2009) on the most severe types of snowstorms--the "top ten" heaviest snows on record for each of 121 major U.S. cities--shows no upward or downward trend in the very heaviest snowstorms for the contiguous U.S. between 1948 - 2001.

    And Joe Romm :


    Research says big snow storms not inconsistent with — and may be ampliflied by — a warming planet
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  4. EricS and Camburn,

    While management of river flows and dams is obviously critical in these situations and sometimes bad decisions are made. Have either one of you paused to actually consider why we have all this water on the ground to manage in the first place? This cannot mostly or all be blamed on officials guys, the primary reason for this situation is that the Northern Great Plains have been receiving record-breaking rains at a time when the soils are saturated, dams are full and rivers swollen. But yes, let us ignore those very real and critical factors and take our anger and frustration out on officials. And both of you seem to be forgetting that rivers are breaking previous records on the order of metres. No, no, nothing unusual going on here at all.

    I have stated before that people in denial about AGW can and will be knee deep in water and still be claiming that 1) It is OK, this happens all the time, nothing unusual here, or 2) This is happening because of something else unrelated to AGW.

    With all that said, Camburn, keep safe.

    PS: Camburn earlier I gave you the Chagnon details to look up trends in thunderstorms and associated phenomena, but you seem to have used it to go on a very different tack.
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  5. JMurphy

    You are quite right about what constitutes "precipitation".
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  6. Camburn,

    A long time ago you stated in a discussion with me that:

    "I am most interested in Argentina/Brazil as weather patterns in that area directly affect my business."

    With you being a farmer in N. Dakota, how does rainfall in Argentina/Brazil directly affect your business?
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  7. My guess would be that is where his planting stock comes in from.
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  8. JMurphy,

    Of course, we in the North know that adage well.

    A few notes on your post. Heavier snowstorms occurred in wetter winters sounds self-evident, and has no relation to temperature.

    The Changnon study was restricted to heavy snowstorms. Their graph of snowstorms (which may or may not correlate with seasonal snowfall) shows that snowstorms were lowest in the three decades from 1920-1950, and highest in the 1910s, and 1960-1980. Roughly corresponding to the high and low temperature decades (the exception being the 1990s).

    The heaviest snowfall occur when the temperature hovers around freezing. Colder temperatures tend to result in lower snowfall totals. The report did not mention total seasonal snowfall.
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  9. Albatros@206:
    We are in a global ag market with 3 grains being the main ones traded. Soybeans/Corn and Wheat. Brazil is a major player in Soy/corn.....Agentina soy/wheat. The US is a major player in all of them.
    Rainfall affects production in Brazil/Arg just as it does in the USA. All of this affects the world markets prices.

    That is how it affects my business.
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  10. Thanks Camburn. Have you managed to sow your seeds yet?
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  11. I was simply explaining why one river was breaking the record by five feet. Minot had 6.22 inches of precip in May versus normal of 3.91 but Jan-Apr were all below normal. Their river record is fairly isolated except for the Missouri downstream from the Ft Peck dam which just started releasing extra water in early June. The flood control releases must be considered when comparing old records to new ones.
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  12. Albatross:
    I got in what I could get in. We had 3 inches of rain two days ago and are once again extremely wet.
    The long term forcast, which is fairly reliable as it is a result of La Nina is continued wet for another 6 weeks.
    Production in Canada, North Central US is going to be down in major crops. Not a good thing.
    The thread is about extreme events. While present conditions in my area are not what one would consider extreme, I will say that they are tiresome. We have a long term cycle of wet and dry. We have another 20 years of wet to live through, assuming the cycle is persistent.
    A good gauge of long term precip in the upper MidWest is Devils Lake. It was running out of the Tolna Coule in the 1860'-1870's. The trend changed and the lake was virtually a dry basin in the 30's and very small till the 90's. It is once again filling to the point that it was in during the 1860's-70's.
    Once again, not extreme but causing a lot of economic distress.
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  13. "Overall, AGW predicts greater precipitation, but not snow."

    "Colder temperatures tend to result in lower snowfall totals."


    So, Eric the Red, can you see the divergence between those two statements of yours ?
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  14. JMurphy,
    None whatsoever.

    Snowfall is greatest at temperatures nearest freezing. As you deviate from there, snowfall decreases (drier when colder, changing to rain when warmer). Since most of the planet is above freezing most of the year, warmer temperatures will create a greater divergence from freezing, hence less snow.
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  15. Camburn @ 212,

    You say "The trend changed and the lake was virtually a dry basin in the 30's and very small till the 90's. It is once again filling to the point that it was in during the 1860's-70's.
    Once again, not extreme but causing a lot of economic distress."


    No. According to this fact sheet, Devil's Lake is at its highest levels since at least 1865. In fact, it has only been higher than current levels three times in the last 4000 years. So recent levels, while not unprecedented, are certainly extreme.


    [Source]
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  16. Albatros:
    Devils lake has a natural outlet in the Tolna Coulee. It has filled with sediment and would be draining Devils Lake right now if cleaned out. North Dakota will be doing this in the near future.
    During the 1860's and 1870's, Devils Lake was flowing through the Tolna Coulee into the Sheyene River.
    It is about to do so again.

    A brief history of Devils Lake:

    A brief history of Devils Lake
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  17. Dang......I had read that our current wet pattern should be over in approx 40 years. Now in the link above geologists indicate another 100 years of this......offfffffffta.
    I hope the 40 year fellows were correct.
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  18. Eric the Red, you should look here for more about snow and the temperatures involved :


    ...it can snow even at incredibly cold temperatures as long as there is some source of moisture and some way to lift or cool the air.

    ...most heavy snowfalls occur with relatively warm air temperatures near the ground—typically -9 degrees Celsius (15 degrees Fahrenheit) or warmer...

    ...snow will not form if the ground temperature is 5 degrees Celsius (41 degrees Fahrenheit).

    Plenty of room for snow at warmer than normal winter temperatures as the globe warms, and during colder than normal temperatures during strongly negative Arctic oscillations.
    What could be causing all that, I wonder ?
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  19. Tom Curtis @ 199

    I do like your research abilities. You do seem a very intelligent person. I have to concede my tornado argument as too shallow to demonstrate the point I was attempting between hazard (tornado) and disaster (when humans are impacted by a hazard) and that the number of disasters may not correlate at all with the number of disaters.

    Another point to consider. If all conditions were held constant then a true link between a hazardous weather event and disaster could be proof of increasing bad weather events. I may be wrong with my reporting point but another one to consider is the population growth and also the possibility of human migration. Since disasters involve people, if this variable is increasing, it will cloud a true link between hazard and disaster.

    With your skills and research talent I still wonder if you can find better data than Munich Re to prove exterme weather events are becoming more frequent as the globe warms?

    Since Munich Re does have a potential for profit by showing increasing danger from weather related disasters, even if that is not the true case, it is not the most reliable source. No better than ExxonMobil funded research against AGW or Tobacco company research proving smoking is safe. How could Munich Re profit from generating the perception of more disasters when this may not be the case? They can sell more insurance policies to worried people and businesses and take in more money to invest. They can charge higher premium rates to cover the supposed increases that may never actually take place.

    This is why I can't trust them as a valid source for this discussion and hope you can provide better sources that would have no reason to bias the data.
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    Response:

    [DB] Norman, it is my understanding that entities like Munich Re exist to quantify risk and to evaluate the cost of enduring that risk.  Given that, their potential for profit is identifying those areas more likely to endure any increased risk of damage due to natural disasters brought on by the consequences of a warming world.

    Essentially, they engage in bets with other entities that those other entities won't suffer a loss and the other entities are betting that they will.  To that end, Munich Re has engaged in a fact-finding mission to help establish the "odds" of the bet.

    That they have made their research public is a testament to fairness: all parties have the same "scouting report".  Does that help enhance your understanding?

  20. Nothing with which to disagree.

    Very cold temperatures lead to very light snows, which are very crystallize in nature. Heavy wet snows will fall when the air is warmer. But as the temperature continues to warm, the snow changes to rain. The exact temperature will depend on ground, air, and upper atmospheric temperatures.
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  21. Norman @219, I disagree with you regarding Munich Re as a source. For the Tobacco industry, anti-smoking strategies and the perception that smoking was damaging to your health results in losses, regardless of the accuracy of those perceptions. Likewise the Fossil Fuel industries stand to lose due to Global Warming regardless. In contrast, Munich Re will lose if global warming is real, and they do nothing about it; but they will also lose if global warming is not real and they lift their rates while their competitors do not. Their best interest is served by keeping their rates as low as possible while still accruing enough capital to cover any additional losses due to global warming.

    So unlike the tobacco industry which had (and has) a straight forward financial interest in deception, and the fossil fuel industry who have a straight forward financial interest in deception so long as they can avoid damaging their brand, Munich Re appears to have a financial interest (in this case) in honest reporting.

    Further, the directors of Munich Re have a very direct personal interest in not making false statements in share holder reports. The direct interest, in addition to opening themselves to being sued if the shareholders make a loss as a result of the false statements, is that such statements attract jail terms for violating the law. Consequently, absent evidence to the contrary, information that makes it into an annual report can fairly be deemed to be reliable.

    This is what Munich Re had to say about global warming in its 2010 annual report:

    From the CEO:

    "it is part of our social responsibility as a Group, given one of the great challenges faced by humanity – climate change and its consequences. We cannot remain silent and must act on this issue when we are in a position to help develop or support solutions with our knowledge and influence. But there is also an answer that is “nearer to home”:
    What is looming in connection with climate change has direct implications for our core business.
    Weather-related natural catastrophes are on the increase, and the evidence is that this is partly due to climate change. The consequences of global warming, if left unchecked, could be so serious in the long term that in a few decades adequate insurance protection would no longer be conceivable for people and firms in some regions. in all likelihood, this scenario can only be prevented if the warming is restricted to the much-cited limit of two degrees."

    (My emphasis)

    So, in a document to which criminal penalties attach if he lies, the CEO of Munich Re says that weather related natural catastrophes are on the increase; and that if unchecked that will make insurance simply to expensive to be commerically viable.

    Reporting on the business evnironment:

    "Our business environment is one of increasing complexity, with an upward trend in major insurance-relevant events. We are seeing a disproportionate rise in insured losses in relation to economic activity, for which we believe climate change is partly responsible, in addition to an increase in values in exposed regions. As a result, new risk potentials and accumulation hazards are emerging."

    (My emphasis)

    Reporting on risks:

    "Climate change Whilst we are in a position to adequately assess the known risks in our portfolio on the basis of current knowledge, scientific research into climate change is complex and the political and regulatory environment in which we operate is developing dynamically, so that we must remain vigilant with regard to the identification and representation of new and emerging risks. We adopt a multidisciplinary approach, using and combining the pertinent experience and expertise of our scientists, specialist underwriters, lawyers, economists, sociologists and actuaries as appropriate for the risk situation.

    Climate change represents one of the greatest risks of change for the insurance industry. In Munich Re’s Corporate Climate Centre, we are developing a holistic strategic
    approach to analysing and assessing these risks. The findings are made available to all business areas and our asset-liability management function. However, changes in the physical environment and new regulations resulting from climate change also open up many business opportunities. Applying the knowledge we have accumulated over decades,
    we exploit these opportunities – for example, through new insurance products for renewable energy technologies."


    So, the data which I have referred you to is being prepared by Munich Re so that they can properly assess the risks, and no company has a financial interest in lying to itself.

    Given that the information being given to shareholders in official financial documents is the same as that being prepared in the various reports which I have been quoting, if less detailed, I ask you again, do you have any specific reason to think the directors of Munich Re have indulged in criminal activity, or are you just discounting the information because you find it inconvenient?
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  22. It is a bit amusing that we have here such faith in free enterprise in the reinsurance industry while demonstrating the ill effects of free enterprise in other industries. I think we can read between the lines above that profit comes through higher risk estimates. Here is an example of State Farm pulling out of the retail insurance business in Florida, only to return as a high-priced reinsurer based on risk estimates that turned out to be inflated http://www.heraldtribune.com/article/20101205/article/12051021 Some caveats: the article is one-sided and the hurricane risk assessments were overblown by almost everyone following the 2005 season.
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  23. Eric (skeptic) wrote : "It is a bit amusing that we have here such faith in free enterprise in the reinsurance industry while demonstrating the ill effects of free enterprise in other industries."


    Who is showing "such faith" ? All I can see are acknowledgements that "free enterprise" will always try to safeguard itself against legal action and barriers to its continuing business; while constantly trying to keep itself in business by identifying future risks and ways to profit from those risks. None of that mitigates against any "ill effects" that such an enterprise may bring by focussing on itself to the detriment of others.
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  24. The Munich Re report is neither an advocation for or against global warming. The report simple states that weather-related natural catastrophies are on the rise and evidence is that this is partly due to climate change. This is a very legalistic statement, which simply states what has occurred, and how someone else has attributed some blame. They then state that temperature increases should be kept below the much-cited two degrees to continue adequate insurance protection. Again, no claim either way.

    All these statements, and more, are "what if" scenarios, and that the insurance industry should position itself accordingly. While not exactly a scientific paper, insurance reports are based on real data, and risks are calcaulated based on past events and future probabilities.
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  25. Eric the Red @224, the Munich Re report states what has occurred, but it also states "... for which we believe climate change is partly responsible ..." and when stating how they assess the risk that say, "We adopt a multidisciplinary approach, using and combining the pertinent experience and expertise of our scientists, specialist underwriters, lawyers, economists, sociologists and actuaries as appropriate for the risk situation."

    Consequently, they do not say how somebody else attributed responsibility for the increase in extreme weather events, but how they attribute that responsibility. Further, it is based on that attribution that they consider the risk that extreme weather events becoming so frequent that insurance becomes impractical is real, and something they are spending share holders money now to prepare for.

    This probably says nothing more than that their scientists accept the scientific consensus on global warming, and absence access to peer reviewed studies by the scientists, that is neither here nor there. But they do not reflect "what if" scenarios nor attribute to others these beliefs. Rather they are, and are legally required to be, the considered views of the board of directors.

    Having said that, the only evidence of weight in their report and other documents is to the question of whether or not extreme weather events are on the increase. The answer is yes. Interestingly that is something predicted by the theory of AGW, and something not predicted by any opposing theory. Coupled with the evidence provided above about the effects of increased tropical pacific sea temperatures on the frequency of ENSO events, and the evidence of the increased frequency of tornadoes (though not the largest tornadoes), that should answer Norman's question.
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  26. To anyone interested,

    There have been several posts on the topic that warmer weather will increase snowfall amounts. I am doing a limited test of this conclusion to determine if it is a valid conclusion based upon availabel evidence.

    I am picking one location (Omaha, Nebraska) as the test spot. Based upon the theory it should not matter where the test spot is located as this principle should apply to all regions. The concept is that warmer temperatures will lead to greater winter snowfall because warm air can hold more moisture.

    My understanding of weather systems is of a different nature. It could be caused by Global Warming but at this time I have not been able to make such a connection. I have learned that heavy snow or rain (at least for the plains of the USA) are caused by very strong low pressure systems that move across the Nation from West to East motion. In the US, a low pressure spins counter-clockwise. On the east side the air will pull warm moist air from the Gulf of Mexico (still warm water even in winter) and at the same time pull frigid Canadian air down from the north on the west side of the pressure system. The stronger the low pressure system, the more moist air it will pull up and the colder air it will pull down. This action causes rain and snow as the cold air moves under the warm moist air lifting it to condensation levels...the heat of condensation causes further lifting of the air pulling in even more moist gulf air.

    Heavy rain and snow are the combination of two events. The stronger the low pressure the greater is the intensity of the rain or snow. But intensity alone are not the only variable in determination of heavy rain or snow. The speed at which a low moves across the country is very important. Case of point. In Omaha Nebraska on Saturday morning there was a heavy rain of over 2". The local meterologist described the cause of the heavy rain as the product of the storm system stalling over an area before moving again, dumping a large amount of rain in a particular area.


    Back to the snowfall research.

    Omaha, NE snowfall in 2009-2010 winter season was 47.6". Normal snow amounts for an Omaha winter are 27.1". That winter season had 20" above normal snowfall (is that an extreme event...it did cause many accidents and cost a lot of money to the city for plowing).

    Source for Omaha snow accumulations used for this study.

    Going to the GISS temp anomaly map for this winter period, this season was shown to be below normal for Omaha which received well above normal snowfall amounts.

    Note to Tom Curtis. I do realize this is a very limited research test and may not satisfy all scientific rigor. I am doing it primarily to test the idea which so many believe is a rigid truth.

    GISS temp anomaly for winter of 2009-2010.

    (If anyone is interested in this project, Omaha Nebraska is located around the center of the United Sates)

    Snow for the 2003-2004 winter season had 47.8 inches and the temp anomaly for Omaha was above normal.

    GISS temp anomaly for winter 2003-2004

    Now to try a low snowfall amount much below normal. The winter of 1980-1981 was 9.1" of snow accumulation, much below normal. Temp anomaly for this year was above average.

    GISS temp anomaly for winter 1980-1981.

    The two heaviest snowfall accumulations on the NOAA data page.

    1961-1962 51.6" of snow accumulation neutral temp anomaly
    1959-1960 56.7" of snow accumulation little colder than normal but not much.

    GISS temp anomaly for winter 1961-1962.

    GISS temp anomaly for winter 1959-1960.
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  27. The next thing to study is to plot all the winter snowfall accumulations for Omaha Nebraska vs Global warming to see if there is a correlation between higher snowfall and Global warming as some have speculated should occur.

    I am not sure how the connection is made that a 4% increase in Global humidity (still want to know how someone determines this as Global humidity is very far from constant, evaporation rates are not constant nor is rainfall) will result in much heavier snows or rainfall amounts that lead to much greater flooding. I do not see how the math adds up.

    A 4% increase in Omaha's snowfall accumulation would average out at an inch more of snow per season. Something hard to see in a record that can very by several inches from one year to the next.
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  28. I have a question about what appears to be a drastic rise in flooding events. Could this be explained as greater awareness because of better global media coverage? Not saying it is the case but is this a possibiltiy?

    As reference. The News media has extensive coverage of most flooding these days. It makes it appear flooding events are much more likely and worse today. Increasing in frequency.

    Here is a record of Mississipi floods. Flooding events do not seem that unusual for this large river.

    Mississipi river flood events.

    Maybe it is caused by selective perception. We hear about a river flooding and a communities that are devestated (like Minot, North Dakota or Hamburg, Iowa) so it appears that such disasters are greatly increasing in number and severity.

    Could if be a minuse of information gathering? Like in the case of identical twins that are separated while young. Psychologists showed amazing similarities in likes and dislikes even though they were raised in different environments. Is this selective perception. You have an extremely large sample size to choose from and if you only select some matches from a huge set of possibilites you can make it appear an amazing link.

    Likewise with flooding. People here make the link that Global warming is causing many more floods with greater intensity flooding.

    But here is where the selective perception may come in. Every year a few rivers will flood and be reported upon. What of all the numerous rivers that did not flood in that year?

    Examples...

    Rivers in Nebraska that could flood and cause a disaster.

    Note the large number of rivers in just this one state, each with the potential to devestate some community that might lie near one of them.

    Look at the number of major rivers in Europe. There are several more minor rivers anyone of which could cause a disaster if a very heavy localized rain would occur in that river's basin.

    List of major rivers in Europe, note even this is a good number.

    A better study than media reporting to influence our perception would be to create a large data pool of rivers (maybe a few thousand global rivers). Monitor yearly flooding for a period of time and note if there seems to be a steady and consistent increase in flooding events and their severity.
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  29. Norman - "I have a question about what appears to be a drastic rise in flooding events. Could this be explained as greater awareness because of better global media coverage? Not saying it is the case but is this a possibiltiy?

    Not likely, considering the vast scale of the flood events. Jeff Masters has summed up the last year or so in his post 2010 - 2011: Earth's most extreme weather since 1816?
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  30. Too cold to snow? Fairbanks, Alaska is located in the interior of Alaska. Here is the average climate for this location. You can see the average monthly temps (in F or C) and you can look down at the average snowfall. Fairbanks is a very cold place in winter yet seems to receive a lot of snow (69" annually)

    Fairbanks Alaska climate data.
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  31. Rob Painting @ 229

    I have read this Jeff Masters post and am currently looking into it.

    He does use choice words however to give a boost to his conclusions.

    Here is an example: "
    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."

    Extreme configuration and unusal event?

    Looks like The AO is highly variable and that looking at a historical graph does not look so "extreme". Yes a record breaker but not highly unusual.

    Graph of the AO.
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  32. Norman - "There have been several posts on the topic that warmer weather will increase snowfall amounts. I am doing a limited test of this conclusion to determine if it is a valid conclusion based upon available evidence.

    I am picking one location (Omaha, Nebraska) as the test spot."


    You're choosing a single location to identify a change in global frequency of occurrence? That is beyond bad science, Norman - it's completely unreasonable.

    Global data, such as the Munich Re data posted earlier, is indicative of changes. Single site reviews (given regional weather variability, which itself may be induced by global warming) is not. I could not accept that as useful data - regardless of the results.
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  33. KR,

    I totally agree with your one point concern. I would love to find a data source for the entire US to compare snow and temp to a larger region. The only information I can find on a larger scale is snow cover for North America. This will not help determine snow amount vs temperature debate as you can have large coverage but shallow depth. I need snow accumulation data. I could try different cities and build a region. The NOAA data does cover a larger area than Omaha. Lincoln and Norfolk are also part of the data set. Still a small region and like you point out, subject to local factors.
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  34. Norman

    I would suggest the data sets available here, here, or here, among others, as global precipitation information.

    I'll note that finding these records from NOAA and NASA took roughly 3 minutes of Google time.

    And as I said earlier, you have not justified any issues with the data from Munich Re, who accumulate extreme weather information as part of their normal business cycle:

    “It’s as if the weather machine had changed up a gear. Unless binding carbon reduction targets stay on the agenda, future generations will bear the consequences.”

    "...it would seem that the only plausible explanation for the rise in weather-related catastrophes is climate change"
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  35. KR @ 234

    I found your fisrt link very interesting and useful. The other two I am not sure how they will help in answering the question. Does Wamrer air in winter lead to heavier snowfalls. I am looking for data similar to the one I posted for Omaha Nebraska. I could then build a regional basis to see if the point brought up is actually evidence based or a guess on minunderstanding of what causes snow events in the US.

    Do you know how Munich Re uses available data to build their charts?

    In your link Munich Re: "There are at present insufficient data on many weather risks and regions to permit statistically backed assertions regarding the link with climate change. However, there is evidence that, as a result of warming, events associated with severe windstorms, such as thunderstorms, hail and cloudbursts, have become more frequent in parts of the USA, southwest Germany and other regions."

    Ok what evidence do they have that as a result of warming, there are more severe thunderstorms.

    They are like a "black box" to me. They get information and build graphs but I have no clue what is their data source. All the peer-reviewed material provided on this web page go to great lengths to explain how they collected their data. If they use a proxy they explain why they think it is valid and they give the data they are using.
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  36. Norman. Munich Re's prime source of information is their own records of claims against insured risks. Being a reinsurer they have a much wider base of information than an individual insurance company.

    When assessing risks related to floods, storms and like events they take account of known meteorological and other science relating to the areas in question.

    So they have a fairly comprehensive set of data available. Their own problem is that the information they are most comfortable with relates to insured risks. If there is information out there on events in areas where people don't insure, it doesn't get directly into their database where they can analyse how well events line up with actuarial assessments of risk at the time policies were negotiated.

    Their general advice about climate overall is an amalgam of climate science at large combined with their own oversight of how well risk assessment lines up with insured events. So they're pretty confident about their assessment of trends in flooding in Europe and USA, but far less directly knowledgeable about south Asia and Africa.

    Seeing as their claims records about European floods line up very well with what meteorology and climate science say, they're pretty comfortable relying on meteorological records and climate science alone for areas where they have less claims experience.
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  37. Continuing from here.

    Camburn: "no statistical verification of increased events of extreme weather."

    No? See Deo et al 2007, reporting a statistically significant increase in Australian heat waves:

    Of the 61 sites over the observation period, only one station showed statistically significant decrease in heat wave incidence since 1950. The increases in heat incidences were confined in eastern and South Australia with the magnitudes of increases varying across the continent. Large increases of about 0.415ºC yr-1 have occurred at Snowtown (SA) and 0.394ºC yr-1 at Dubbo (NSW), while most of the remaining stations in eastern Australia showed smaller increases which were statistically significant at 95% confidence interval.

    A hint here, a hint there; pretty soon you're talking about a trend. Do they get much snow in Snowtown these days?
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  38. Anne Marie,

    That 4% increase in water vapor in 40 yrs. can have a greater warming effect than doubling of CO2. Water vapor is the most abundant greenhouse gas, 30 times more H2O molecules than CO2 molecules in the atmosphere. In absolute molecular count, a 4% increase in H2O is greater than a 100% increase in CO2.

    Since the sensitivity of doubling CO2 is 2C to 4.5C, we should have seen a 2C increase in temp. in the last 40 yrs due to 4% increase in H2O. Why is earth not warming fast enough?
    0 0
    Moderator Response: [Dikran Marsupial] Welcome to Skeptical Science! There is an immense amount of reference material discussed here and it can be a bit difficult at first to find an answer to your questions. That's why we recommend that Newcomers, Start Here and then learn The Big Picture.

    I also recommend watching this video on why CO2 is the biggest climate control knob in Earth's history.

    Further general questions can usually be be answered by first using the Search function in the upper left of every Skeptical Science page to see if there is already a post on it (odds are, there is). If you still have questions, use the Search function located in the upper left of every page here at Skeptical Science and post your question on the most pertinent thread.

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  39. Dr. Doom

    The sensitivity to a doubling of CO2 is only 2-4.5C after including the effects of feedback mechanisms, such as the water vapour feedback to which you refer. The direct sensitivity to a doubling of CO2 is about 1C. This is also the equilibrium sensitivity, and is the temperature rise once the ocean temperatures have reached the new equilibrium, which takes a century or so. It isn't the instantaneous sensitivity.

    The Earth has warmed up by about the amount expected. However this is taking the discussion off-topic (extreme weather is the topic).
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  40. Nice headline over at Climate Progress today:
    Study Finds 80% Chance Russia’s 2010 July Heat Record Would Not Have Occurred Without Climate Warming

    "… the majority of monthly records like the Moscow heat wave must be considered due to the warming trend. In highly aggregated data with small variability compared to the trend, like the global-mean temperature, almost all recent records are due to climate warming"
    "For July temperature in Moscow, we estimate that the local warming trend has increased the number of records expected in the past decade fivefold, which implies an approximate 80% probability that the 2010 July heat record would not have occurred without climate warming."
    "Our statistical method does not consider the causes of climatic trends, but given the strong evidence that most of the warming of the past fifty years is anthropogenic, most of the recent extremes in monthly or annual temperature data would probably not have occurred without human influence on climate."
    Fun stuff, this global warming thingy.

    The study itself can be found here (H/T to Mark Harrigan).
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  41. Speaking of extreme weather, the sun's kickin' out some major whup-a** (for us NH aurora geeks):




    http://www.swpc.noaa.gov/pmap/gif/pmapN.gif
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  42. Link to images of the aurora from last nite taken locally:
    http://www.facebook.com/media/set/?set=a.290369907653519.75544.165862740104237&type=1
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  43. Wow!, those are some awesome shots there Yooper.
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  44. Very impressive shots Daniel, love those reds!
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  45. Re #240 (the new PNAS) study. I am so glad that someone did a proper attribution study, the results are quite sobering. Hard to fathom that July's in Moscow are warming at >5 C per century there, and that is summer when the anomalies tend to be smaller.

    Very interesting to read about how the GISS correction for the winter urban heat island is swamping the signal in the summer months.

    That paper deserves its own post IMHO.
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  46. Dallas Texas suffered $1.5-2 billion dollars of damage from a hail storm last week. This link to a Reuters article gives some detail. Apparently from 1990-2010 the total damage in the USA from severe weather (except hurricanes) was about $20 billion. This single storm was 10% of that. Doug Bostrom has some interesting links at Real Climate in the monthly thread look around comment 206. Dougs links include peer reviewed articles about the frequency of hail storms and global warming.
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