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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 101 to 150 out of 236:

  1. OK, with one caveat: where you say consistent, I would add but not exclusive.
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  2. 101, Eric the Red,

    Certainly I'd agree. I don't think anyone would try to claim or even for a moment think that climate change is the only factor that influences extreme weather events.

    I think it's so obvious that no one would argue that we've had extreme weather events before climate change.

    The problem at hand is in figuring out how much of today's and tomorrow's extreme events are attributable to climate change, and to try to predict which will worsen in strength or frequency.

    And doing so requires studying both climate and weather, and using critical thinking of the factors involved to try to unravel things and arrive at the truth (ah, the true fun in science!).
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  3. Sphaerica:
    "I think it's so obvious that no one would argue that we've had extreme weather events before climate change."

    We have always had climate change, so it is impossible to establish a cut off of when the climate all of a sudden became static.
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  4. 103, Camburn,
    We have always had climate change...

    This is a singularly false and overly simplistic statement, one which begs to ignore problems and science, rather than face them.

    Surely you have something more substantive and meaningful to offer the world than the modern equivalent of "if man had been meant to fly, God would have given him wings!"
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  5. Camburn @ 103... We all know that climate has changed in the past. No one ever contradicts this. If climate had changed little in the past then there would be little chance that we could change it today. The central issue is how we are changing climate today.



    [Source]

    When I see this diagram of the CO2 record then I become very concerned about the stage we are setting for ourselves.

    I also think there is a fundamental misunderstanding that goes on with regards to extreme weather events. What we're looking at today is likely the result of adding just 4% more moisture to the climate system. It's looking pretty clear that even this small amount is resulting in changes in extreme weather events. Not yet outside the realm of what has likely been experienced in the past 10,000 years... but getting there.

    The question becomes, if this is what we get from 4%, what will we be seeing when we've added 40% more moisture to the climate system? It's my understanding that this is the problem we face.

    Is that extreme climate (extreme relative to today) something never on this planet? Probably not. But probably unseen for many many millions of years. Certainly unseen by any species existing today. Certainly unseen by human civilization.
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  6. 103, Camburn,

    Just to clarify, because I know you are quite capable of missing my point... I do not deny that the climate has changed in the past, by very, very small degrees if by "we" you mean during the last thousand years of civilization, or by larger degrees if by "we" you mean during the existence of homo sapiens as a species, or by even larger degrees if by "we" you mean "the denizens of the planet," spanning back to the earliest creepy crawlies that grew in the oceans.

    What is categorically false are the unspoken implications of your statement that climate change is either impossible to predict (or in this case prevent), or that it is harmless (given the countless mass extinctions and dead civilizations that have resulted from past climate change).

    So when I say that your statement is singularly false and overly simplistic, this is what I mean.
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  7. Camburn @65,

    You need to actually read the literature provided to you. And you choose to miss the point of the Arctic paleo study.

    From Polyak et al. (2010):
    "Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations.

    The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorter-term (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities."



    From an interview with Polyak:
    "The paleo data we have so far is very scant, so we can’t know for sure when the Arctic was ice free in the summer last time. To be conservative, the closest candidate is the early Holocene (roughly ~10 kyr ago), when the insolation in the Arctic was high due to the beneficial orbital configuration; however, the more data I see, the stronger is my impression that there was not that little ice at that time. The next best (actually, better) candidate is the Last Interglacial, about 125kyr ago, again due to orbitally-driven high insolation: the ice was likely very low, but we can’t say whether it was completely ice free in summer or not. There are also a few other major interglacials, which may have had a similar picture, in particular Marine Isotopic Stage 11, about 450 kyr ago. In any case we are talking about very rare events controlled by a forcing very different from today. If none of those intervals was really ice free, then a million year assessment would be correct."

    From SkepticalScience,
    "In sum, although natural factors have always influenced the state of Arctic sea ice, research strongly suggests that today's decline is driven by the novel influence of anthropogenic CO2 we've added to the atmosphere and thus is unique in Earth's history."

    From the first line of the abstract in the paper you provided @65 regarding impacts of changes for one small portion of the Canadian Arctic (not the whole Arctic, or the globe). You insist on missing the point, and miss the point of relatively large amplitude local changes versus changes over much larger regions and/or global changes. I do not know how to communicate this fact to you. Maybe you should engage Polyak and argue with them? I do not suspect that doing so would go well for you though.
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  8. Camburn @20,

    "1. There is an 8-12 month lag time for the effects of La Nina and what precip and temp will do."

    and the very next post

    Camburn @21
    "The effects from the current La Nina cycle will prevail for another 4-6 months in the USA."

    Make up your mind. Now what do the experts say? From the very first paragraph of Trenberth et al. (2002):

    "Following an El Nino the global surface air temperature typically warms up by perhaps 0.1C with a lag of ~6 months [Newell and Weare, 1976; Pan and Oort, 1983; Jones, 1989; Wigley, 2000]. In an exceptional event such as the 1997–1998 El Nino the amount exceeds 0.2C. Christy and McNider [1994] and Angell [2000] show that the entire troposphere warms up with an overall lag of 5–6 months, but the lag is slightly less in the tropics and is greater at higher latitudes"

    Trenberth (2002) found lag of 3 months:
    "The lag of global mean temperatures behind N3.4 is 3 months, somewhat less than found in previous studies. In part, this probably relates mostly to the key ENSO index used...."

    From a WMO release on 23 May 2011:
    "However, climate conditions over the next 1 to 2 months may continue to be La Nina-like for some regions, because the atmospheric aspects of the event may decay more slowly than the cool tropical Pacific waters, particularly for this La Niña in which the atmospheric indicators have maintained considerably greater strength than the oceanic ones."

    Are you going to admit error, or do the leading scientists and WMO have that wrong too Camburn? Either that or you now need to argue your opinions with Polyak et al., Trenberth and the WMO.
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  9. Camburn @65,

    "The link you posted to river trends is really about worthless"
    I see, but a glib dismissal of the science is not convincing, not scientific and neither is referring us to an anonymous poster on another thread--science is not overturned that easily. Unbelievable that you unquestioningly and uncritically and unskeptically accept what Charlie A writes on the internet versus a paper published in a journal. Please stop this nonsense. From Min et al. (2011, Nature):

    "Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. These results are based on a comparison of observed and multi-model simulated changes in extreme precipitation over the latter half of the twentieth century analysed with an optimal fingerprinting technique. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming."

    The you make this truly bizarre, but telling, statement:
    "People are suggesting extreme events are a somewhat recent occurance? How about the floods of the Mississippi River in the 1920's? The recent floods did not break those records. Or the heat waves and fires in Russia when Tchaivosky was creating beautiful music."

    A beautiful strawman argument,and quite offensive to the informed reader. In fact, it is quite disingenuous. You continue to miss the point--your behaviour and reaction to scientific evidence that does not support your opinion is really starting to look like cognitive dissonance on your part. You just keep repeating the same mantra, over and over again-- that does not make your opinions correct.

    Please read my post @64 again. Also read the comment @68,and the posts @104 and @105.
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  10. Albatross:
    My cognitive abililty is quit good. I do not miss the point at all. I look at historical events verses recent events and can see no change in intensity nor pattern.

    What you call a strawman arguement happened. Both on the Mississippi and in Rusia during the time frame indicated.

    This thread is about AGW and extreme events. As of yet, which is readily admited by the authors of the papers posted is that their is not a correlation between the two.

    I can tell that you are totally missing the point over and over again.

    Charlie A posted from the Univiversity of Florida. I am sure their work is sound concerning hurricane intensity and quantity. It looks like you are dismissing this work because it does not agree with your perception.
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  11. Oh yes, I am sure the WMO knows more about La Nina and its affects on the US than NOAA does.

    (NOAA predicts that the affects of the La Nina will continue into Oct/Nov for my area).
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  12. Camburn... I think miss the entire point of, not only this conversation, but the entire issue of climate change. No one disputes that the planet has likely been about where we are right now during the Holocene optimum. The whole point is that natural forcing and feedbacks should have us on a gradual cooling trend in line with the past 6000 years. But we are seeing a rapid rise in temperature.

    The issue is not whether the planet has seen something like what we are currently seeing now. The whole issue is, if we continue changing the radiative balance of the atmosphere, what do we expect to happen? What kind of world are we bequeathing to our children and grandchildren?
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  13. Rob @112.

    Thanks for trying, but I'm sure your post will fall on deaf ears.

    I have tried to relay this point countless times...but they just keep repeating the same old tired mantra..."the climate has changed before, there have been extremes before, so ergo we do not have anything to be concerned about". Hmm, wonder how many people there were in the early Holocene? Hmm, ~10 billion of us expected later this century, many of them who are not free or have the ability to move as our predecessors could.

    As you can see from #111, they will not concede that they were wrong. What matter in their own back yard (if it fits their beliefs) will do just fine. ENSO teleconnects differently for different regions, and even differently for different parts of the USA. So we have no way of validating this claim. And yet another statement of fact with unsupported links. This is the NOAA/NWS/CP latest weekly assessment.

    Camburn claims that the recent La Nina will continue to affect his region until October or November. This is what the IRI have to say:

    "These observations indicate the presence of neutral ENSO conditions. Because the atmospheric component of the episode was so strong and long-lasting, however, some of the climate conditions associated with La Niña may continue to a mild degree through late June."

    And here is what CPC/NCEP has to say in their latest assessment:

    "Collectively, these oceanic and atmospheric anomalies reflect a transition to ENSO-neutral conditions, but with lingering La Niña-like atmospheric impacts, particularly in the global Tropics."

    Nothing about impacts lingering into the fall over the USA.

    So the WMO, IRI and NOAA (and affiliates CPC, NCEP, NWS) are all in general agreement, and nothing in that NOAA assessment about affects of the recent La Nina continuing into the fall.

    I think Mr. Camburn ought to send a very strongly worded letter to them arguing that they are wrong.
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  14. Camburn @110,

    "Charlie A posted from the Univiversity of Florida. I am sure their work is sound concerning hurricane intensity and quantity. It looks like you are dismissing this work because it does not agree with your perception.

    We are getting our wires crossed, my apologies. At #109, I was referring to Norman's comment @70 about the hydrological cycle, not to the ACE index.
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  15. Some have stated I am a "Cherry Picker" on posting historical weather events.

    I look at the history of each area that is considered a major deviation and look at some historical information on that area. I looked at the history of Pakistan floods and severe flooding is not so extreme as it seems to happen often enough.

    I would like someone to define what an "extreme" weather event is so research can progress to see if weather anomalies are really getting more extreme in a warming world. What would constitute an extreme rainfall amount? What is an extreme temperature?

    Name an extreme weather event that occured this year so I will not be blamed for cherry picking.
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    Response:

    [DB] "I looked at the history of Pakistan floods and severe flooding is not so extreme as it seems to happen often enough."

    Umm, you may want to try reading your posts before submitting them.  Because you're saying the record-setting floods of 2010 happen often enough...

    Actual analysis instead of the Eyecrometer is called for.

  16. Norman @115, because of the chaotic nature of weather, it is impossible to look at a single event and say this would not have happened, or not been as bad without global warming. So if you pick any single event, you are cherry picking. This is even true of the Russian Heatwave of 2010:



    The Russian heatwave of 2010 is literally unprecedented in history. There is no historical record of a heatwave in Russia as intense of that of 2010 (though there is one that was a few days longer). Immediately after the heatwave, there was a denier jumping onto every site he could and posting a list of literary references to Russian heat waves, that he claimed where comparable or worse. His game was given away by one of the quotes which actually quoted temperatures, around 5 degrees lower than the heat wave of 2010, and there is no reason to believe any of the others quoted where any worse. On the contrary, there is every reason to believe the Russian meteorological deparment (whose name I can't remember) who said that no equivalent heat wave was on record in the last one thousand years.

    That quote was the source of the often repeated claim that the Russian Heatwave was a one in one thousand year event. In fact, assuming a normal distribution (not a safe assumption) and relative to recorded July temperatures it was less than a 1 in 66,000 year event



    Not content with that, that well known "alarmist" Tamino calculated that using the known temperature distributions for Moscow, including those known to have been affected by global warming, the probability of the event was just 1 in 260 per annum. Without the recent warming trend due to global warming, it would have been around 1 in 1,000 per annum. (As an aside, it is predicted to become an annual event by the end of this century with global warming.)

    But I can't just pick the Russian Heatwave and say global warming. That would be cherry picking. Nor can I pick the Pakistani flood and say global warming. From memory the Pakistani Flood of 2010 was the second largest in extent, the largest in damage done, but relatively low in terms of lives lost (due to modern communications, transport and medicine) in the just over one hundred year record of Pakistani floods. Nor the much worse, but under reported 2010 China floods, nor the 2010 Indochina floods.

    Nor can I point to any one of the seventeen (plus?) national heatwaves in 2010.

    In Australia, I can't point to the three 1 in 1,000 year rainfall events that happened in three days in a 60 by 60 mile area, thus causing the Brisbane floods. Nor can I point to the record flood affected extent in Queensland that more than doubled the previous record. Nor can I point to that previous record, set in March 2010. Nor can I point to the 2011 Victorian floods which where the worst floods in Western Victoria "...far as [the Bureau of Meteorology's] records go in terms of the depth of water and the number of places affected". Nor indeed to the floods in the same area in September 2010.

    If I point to any one of these events, and the list is no where near exhaustive, I am cherry picking. But what I can do is point to the combination of them all. And then it becomes clear that both the number and intensity of extreme events is on the rise. And nor is it just a function of ENSO. La Nina conditions certainly contributed to the extensive flooding in Australia this year, but in March 2010 when Queenslands previous record for flood extent was set, there was a strong El Nino.



    Statistically, something unusual is happening with the weather. And in most cases there is an intuitive causal connection to global warming. Weather is complex, and chaotic, so the exact nature of the causal connection is in many cases still being thrashed out. But it would be shere folly to use that as an excuse to believe the statistical correlation between extreme weather events and increasing temperatures is a fluke.
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  17. Is there a definition of what counts as an extreme weather event?

    If so, is anyone plotting them over time to determine their frequency? I'd be keen to find more information on this topic.

    Tom curtis' @ 116 provides a good example of frequent exteme recent weather events but is there a reliable record of these over a statistically significant period of time?
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  18. DB,

    On the Pakistan flooding issue. This article is a brief history of flooding in that area. 12 major floods in 69 years seems to indicate that this area is prone to floods and large floods are not a rare event. Can you link other weather related disasters in some of the flood years. It is hard for me to get much global weather destruction of earlier days.

    Pakistan flooding recent history.

    Another article does suggest the possibility of warming but also gives another reason as why this flood was so devestating.

    Man interference may have made the flood worse.
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  19. Tom Curtis @ 116

    I must state I do like the depth of thought and intelligence you display in your posts. You really do provoke thought. Thanks.

    Here is one on the Russian Heat Wave of 2010. Most are commenting about the unprecedented heat wave but what about the unusual cold at the same time in Siberia. Moscow was about 5 C above normal but at the same time Siberia was 5 C below. Did that set some record cold for this region? No one mentions it so I don't know. I can't find a resource for normal or record temps for Siberia on the web (such as Intellicast or Accuweather).

    Russia Heat wave of 2010.
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  20. Tom Curtis @ 116

    I don't think including China's flooding will help convince anyone that Global warming is increasing extreme weather events. Yangtze River has flooded 1000 times in 2000 years. The Yellow river has a long history of tragic floods. I would need some really solid evidence that floods in China are getting worse.

    China's floods are most frequent events.
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  21. Tom Curtis @ 116

    I have already seen the information on the 17 Nations that had record high temps in 2010.

    I guess there are currently around 195 countries on Earth (does change around a bit). What I was looking for is the entire data set of the World's Countries record high and low temps and in what year they took place. I could not find such information so my research is uncertain at this time as to determine if this is significant or not. Maybe in the larger data set clusters of record high and low are the norm and not the exception but only a complete data set will answer this. If you know how to find one I would be thankful.
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  22. Stevo @117, the graph in my 116 shows an increase of between 50 and 100% in the number of extreme weather events from 1980 to 2008. That certainly seems statistically significant and over enough time to me.
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  23. Norman,

    The Pakistani floods are nothing out of the ordinary, as they occur roughly every decade. The Russian heat wave was certainly an anomaly, shattering the previous record which stood for over 70 years. Both of these events appeared to have been caused by the same blocking pattern.

    Many of the events in the graph in #116 are not cause by global warming, so a correlation is difficult.

    Many of the nations reporting record high temperatures in 2010 do not have consistent temperature records of more than 50 years, so that a comparison with earlier periods of the 20th century is impossible.
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  24. "Many of the events in the graph in #116 are not cause by global warming, so a correlation is difficult."
    Well we can rule out the "geophysical events". However, what makes you so sure other events are not caused by global warming? Because you can assign another proximate cause without considering ultimate causes?
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  25. Norman @119:



    First, the Moscow July average for 2010 was about 8 degrees C above average, not 5. It was literally off the scale for NOAA's chart. In contrast, the Siberian cold region was only 4 degrees below average (the circles do not touch, so the largest circles in that region are only the second largest on the scale).

    Second, for the Moscow heatwave, 17 cells are shown with a value of 5 degrees plus; while for Siberia only two cells show a - 4 degree anomaly. Around the fringes of the Moscow heatwave are another 12 cells with a plus 4 degree anomaly, so even the fringes of that event constitute a far more significant heatwave than the Siberian cooling.

    Third, as is fairly obvious, the Siberian cold snap is in fact part of the same weather pattern which caused the Moscow heat wave. Because of the anti-cyclonic pattern of NH weather systems, if one part is bringing hot air up from the south, than at a different latitude, the same weather system will be bringing colder air down from the north. Consequently whether a weather system is considered as bringing heat or cold overall should depend on the overall intensity of the system. In this case there is no question.

    Finally, if just picking the Moscow heatwave and saying ergo global warming is cherry picking, which it is; then just picking the Siberian cold snap and saying ergo not global warming is also cherry picking. In 2010 there were four or five record breaking heat waves, most covering multiple nations. There were was one record breaking cold snap covering just one nation, and another very intense cold snap in part of Antarctica (and an intense heatwave in another part, though not as strong).
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  26. Tom Curtis - (116) another great comment! Thank you for your contributions - I am really enjoying them.
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  27. Tom curtis @122
    My apologies. I didn't read the graph correctly.
    That graph is exactly what I was asking for. Thankyou.
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  28. Norman @118, the claim that humans contributed (other than by global warming) is a standard denier response to any flood. Immediately after the Brisbane floods of 2011 a skeptic of my acquaintance made that claim as a knee jerk response regarding Brisbane. In fact what humans had done to make the Brisbane floods worse was, they had built two major flood mitigation dams in the headwaters of the Brisbane river, the large of them designed to be able to safely abate 1 in 500 year floods; they had dredged the river to allow a freer flow of water; they had removed several small rocky islands, and broadened the channel at key locations for the same purpose; and they had removed the bar at the mouth of the river which in the past had acted as a natural dam to flood waters, greatly increasing flood heights in the city. But, not knowing anything about that, and not, in fact, knowing anything about the geography of Brisbane this skeptics reflex response was to immediately blame human activity.

    In Pakistan the situation is not so clear cut. First, in Pakistan there has been a number of major river works, including the installation of barrages to mitigate floods. On the other hand, the river had been allowed to silt up a little, and some forest hills had been heavily cleared for timber. So, human activity may or may have not been a net help, and certainly could have done more to mitigate the flood.

    What is certain is that these factors pale compared to the nature of the precipitation that caused the flood. When you have record breaking rainfall - in one city smashing the previous daily record by nearly 50% - the story of the flood is not how much silt was in the river. When the rain falls near the arid western frontier rather than in the typical wooded eastern mountains, the story of the flood is not deforestation.

    In this case the reason for the flood is very well known. It is a combination of the the blocking pattern that caused the simultaneous Russian heat wave, and record breaking sea surface temperatures in the Northern Indian Ocean. What humans did, or did not do may have influenced the depth of the flood by an inch or so - but the flood was caused by whatever caused that blocking pattern, and whatever caused the record breaking sea surface temperatures.

    Record breaking Sea Surface Temperatures. Global Warming. Hmmm! What possible connection could there be?
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  29. Norman @120, the 2010 Chinese floods were not record breaking, but neither where they run of the mill. The displaced over 15 million people, and a 240 million people where affected by them.

    The problem here seems to be that you do not appreciate how global warming must impact in a chaotic system. Put simply the fact that the mean global surface temperature is 0.6 degrees warmer than it was a century ago impacts on every weather system. As the regional expression of that temperature increase is part of the initial conditions for every weather system on Earth, every weather system is a consequence of global warming. Note that this is a trivially true fact - it follows from the definition of "chaotic"; and it is also uninteresting. But not remembering it means you will hopelessly miss frame any search for the effects of global warming on extreme weather events.

    What is interesting is that for every weather system we currently experience, many, similar weather systems would be experienced on some other day, or some other year, or at some other hour; or possibly at the same day or hour but coming from a slightly different direction if the Earth was 0.6 degrees cooler. But they may not have occurred at the same frequency.

    Now it is true that for some weather systems we can look at them and see a direct reason why global warming makes them more frequent. For others, however, we can only say why global warming would make them more frequent with no hope of making any particular connection for any particular storm or flood or drought. Technically this is true even for the extraordinary events such as the Russian Heatwave, or the Brisbane floods. But it is true of all the other events as well. Therefore it is only by looking at changes of frequency that we can truly detect the signal of global warming.

    Because the extra 0.6 degrees is a factor in the genesis of every weather system, and because equivalent events in most cases would have happened in a cooler Earth, you don't show global warming was not a factor by saying that some other equivalent storm happened in the past. You can only show that global warming does not increase the frequency of extreme events by showing there has been no increase in the frequency of those events.

    Which brings us again to the third graph in my 116. Ignore the red events, which are geophysical and not impacted significantly by any plausible mechanism of global warming. (There is a slight connection between soil humidity and risk of earth quake, so I can't say no connection.) But all of the other events are events that can be impacted by global warming. Now if you ask which of them was caused by global warming, the answer is all of them. There is no other logically coherent answer. So ask instead the relevant and informative question, does the frequency of the extreme events increase with increasing temperature?

    The answer is plainly, yes! Not only does it increase with the overall trend in global temperatures over the period, but there is even a partial correlation with the temperature variations of individual years.
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  30. Anyone wanting to look into record high and low temperatures could start at Maximiliano Herrera's site, although it might take further searching to actually find the dates for each country.
    However, national and continental records, with dates, can be found on one of his Wikipedia pages, showing that most of the records have been set in the last 50 years - and most of those since the 80s.
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  31. Tom Curtis @ 129

    I did look at the third graph and went to the web site it came from. This chart does show an increase in frequency of catastropic events related to weather but I can't find supporting documentation to interpret the information. What do they mean by catostrophic, how do they define the events, what are they looking at. It looks like an insurance company put this out so is it dollar value related?

    If I have more information on what the graph means it could be a strong point in showing an increase in frequency of extreme events.
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  32. More information (from Oxfam) on 'extreme weather events', going back to 1980 :

    There is a statistically significant increase in all disasters, and this trend is driven mainly by a rising number of floods in all regions and by more storm events in Asia and the Americas. Changes in population do not fully explain the rising number of floods, nor can the trend be entirely attributed to changes in how disasters are recorded. It was not possible to directly analyse the effect of climate change on disaster trends; however, there is insufficient evidence to exclude the possibility that climate change is increasing hazards and hence trends in reported disasters. This effect is unlikely to be very large, because the magnitude of climate change over the past 20-30 years is relatively small when compared with (for example) the growth in the world’s population over that time.
    Trends in the number of reported natural disasters
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  33. Tom @116,

    I have to agree with Actually Thoughtful @126. Great post, sad that its contents and message are lost on some.
    0 0
  34. JMurphy and Tom Curtis,

    The Munch Re have their 2010 report available online. You can download it here. From the report:

    "We need look no further than this past year for evidence showing that climate change is real and continuing. The year 2010 sets the trend towards ever warmer years and an ever decreasing ice cover in the Arctic Ocean. Globally it was one of the warmest years since records began 130 years ago. The ice cover during the annual minimum in September was the third-lowest, reaching an absolute minimum for the month of June. Data collected by Munich Re also show that (after 2007) 2010 brought the second highest number of loss related weather catastrophes since 1980, when our data series began."
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  35. It is a small point, but part of the rise in insurance claims is a trend (in the US at least) for increased population densities where climate change driven disaster is likely (and, per Tom Curtis, that is everywhere), specifically the forest urban boundary in the West/Southwest, along rivers, and along shorelines.

    However, this trend is minor compared to the impact of increased energy and moisture in storms.

    I appreciated the idea that the lower differential in temperatures that global warming brings should translate to weaker storms, but the observable reality (see Tom Curtis at 116) actually indicates the opposite.
    0 0
  36. Tom Curtis

    Why does Munch Re have two very different graphs of weather related catastrophes?

    Here is another one that is much different in look than your 116 post graph.

    Another Munch Re graph.
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  37. JMurphy @ 130 and 132

    I have already looked at both the extreme temp links you posted. I still can't find temp records outside the US.

    Intellicast web site gives every major city in US historical temp data (record high and low and years they happened). Accuweather provides nice monthly anomaly graphs for any given city a few months worth. The anomaly graph has the normal high and low line along with the record high and low so one can see in a glance if temps look too high.

    Maybe Europe has nice web pages for temp extremes.

    I read through your link at 132. Here is the conclusion to the study.

    "There is a statistically significant increase in all disasters, and this trend is driven mainly by a rising number of floods in all regions and by more storm events in Asia and the Americas. Changes in population do not fully explain the rising number of floods, nor can the trend be entirely attributed to changes in how disasters are recorded. It was not possible to directly analyse the effect of climate change on disaster trends; however, there is insufficient evidence to exclude the possibility that climate change is increasing hazards and hence trends in reported disasters. This effect is unlikely to be very large, because the magnitude of climate change over the past 20-30 years is relatively small when compared with (for example) the growth in the world’s population over that time."

    Basically the Munch Re report can not be used to determine the frequency of extreme weather events (hazards). An EF5 tornado is only a hazard in a field with no people present. It is recorded as a disaster when it strikes a populated area. Disasters are increasing but not enough data is available to determine if hazards are increasing.
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  38. Tom Curtis @ 129

    You claim "The problem here seems to be that you do not appreciate how global warming must impact in a chaotic system. Put simply the fact that the mean global surface temperature is 0.6 degrees warmer than it was a century ago impacts on every weather system. As the regional expression of that temperature increase is part of the initial conditions for every weather system on Earth, every weather system is a consequence of global warming. Note that this is a trivially true fact - it follows from the definition of "chaotic"; and it is also uninteresting. But not remembering it means you will hopelessly miss frame any search for the effects of global warming on extreme weather events."

    Actually I would agree with your statement...

    Global Warming = Climate Change. I am not questioning this postition.

    Here is the leap I question. Global Warming = Climate Change = Increased Frequency of Extreme weather events.

    Note please. I am not stating in a "denier" mentality that Climate Change is not increasing the frequency of extreme weather events. I am stating I have not been presented enough valid empirical evidence that this is indeed the case. First of all, what is an extreme weather event. Who is doing the counting? Is this an opinion?

    To be a valid study and scientific topic a rigorous definition of an extreme weather event is needed for accounting purposes. A record high temp or cold would obviously be an extreme weather event along with record rainfall. These would be the easy ones to document and record for a tally sheet. But what of the others? What if the temp is only one degree lower than the record? How much above normal would be considered extreme?
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  39. Norman, looking at IPCC WG2, it would seem that IPCC largely agrees with you. At the time of publication, there were a number of indicators showing increase in extreme events, but it mostly noted that problems with record-keeping and global data sets make this a difficult exercise.
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  40. Tom Curtis or Albatross,

    Here is a NOAA article with the number of severe thunderstorms in USA a year.

    Number of severe thunderstorms in US a year.

    This article says there are around 100,000 thunderstorms in the US per year. Of those 100,000 about 10% are severe as explained by the criteria in the article. With such a large number of events per year it should be easy to see if the frequency is increasing, decreasing or staying the same over given time period (sufficient to prove if a warming planet is increasing the number of severe thunderstorms a year). With hurricanes the yearly number is fairly small and may be difficult to establish a noticeable trend but with the large number of severe thunderstorms a trend should show up much more clearly.

    Do either of you know of any study done to determine if the number is increasing (please Albatross no models or guesses...just actual countable numbers)
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  41. Norman @136, following the United Nations, certain technical terms are used to define potentially harmful events. These are defined by the International Federation of Surveyors as follows:

    "Hazards can be single, sequential or combined in their origin and effects. Each hazard is characterized by its location, intensity, frequency and probability (UN/ISDR 2004, p. 16) and might lead to a disaster.

    A disaster is defined as a serious disruption of the functioning of society, causing widespread human, material or environmental losses, which exceed the ability of an affected society to cope using only its own resources (EEA 2006). The extent of the disaster depends on both the intensity of the hazard event and the degree of vulnerability of the society. For example a powerful earthquake in an unpopulated area is not a disaster, while a weak earthquake which hits an urban area with buildings not constructed to withstand earthquakes, can cause great misery (GTZ 2001, p. 14).

    Due to this fact, hazard events are only classed as catastrophes when human beings or their property are affected. The term natural catastrophe is used when a natural event is so intense that people suffer and material assets are affected to a substantial degree and on a more or less large scale. A “great” natural catastrophe is defined by the United Nations as a natural catastrophe that distinctly exceeds the ability of an affected region to help itself and makes supra-regional or international assistance necessary (cited in Munich Re Group 2005, p. 12). Generally this is the case when there are thousands of fatalities, when hundreds of thousands of people are made homeless, or when economic losses – depending on the economic circumstances of the country concerned – and/or insured losses reach exceptional extents."

    (My highlighting)

    Munich Re explicitly refers to the UN definition in their discussion of Great Natural Catastrophe's from which the chart you link to is drawn.

    So, to make this clear, Natural Catastrophe's are hazardous natural events which adversely effect humans. They are on the increase as is shown in the chart in my 116. Indeed, that increase has continued, as newer versions of the chart show a continued rise in natural disasters with 2010 having the second highest number on record. It also shows a continued significant correlation with annual temperatures.

    Weather related natural disasters do not exactly correlate with weather related events because as the population increases, the probability that a weather event (hazard) will adversely effect a human increases. This increased probability is not a direct match to increasing population because most of the increase in population comes from an increase in density of population in already populated areas. Consequently for most natural hazards, the location in which they occur is almost as likely to result in harm to humans now as it was 50 years ago. There is, however, some increase in that smaller natural hazards are more likely to result in some harm now than would have been the case in the past.

    Counteracting that effect is the fact that improved building standards and awareness and warning of risks has reduced the risk of harm. The net effect is probably best indicated by the rise in geophysical events, which, because effectively unaffected by climate, is only a consequence of the sociological factors. The trend of increase in geophysical events shows an approximately 50% increase over the period 1980 to 2010. In contrast, the trend in meteorological events shows a 100% increase, and hydrological events shows a 200% increase. This has lead Munich Re to conclude that:

    "Yet it would seem that the growing number of weatherrelated catastrophes can only be explained by climate change, The view that weather extremes are more
    frequent and intense due to global warming is in keeping with current scientific findings as set out in the Fourth IPCC Assessment Report."


    In contrast to a plot of natural disasters, a plot of great natural disasters is a poor measure of the increase in natural hazards. This is partly because they are fewer in number, so that random factors of location can make a very great difference in the consequences of the natural hazard involved. A magnitude 9 earth quake in Antarctica would be an interesting geophysical event, and may not be more than a natural hazard. The same earthquake with a shallow epicentre under Los Angeles or San Francisco would be a very significant great natural catastrophe. Other factors effecting the risk of a great natural catastrophe include population density, relative preparedness, and the economic means of the society to handle the consequences of a natural catastrophe. The equivalent events in Australia and in Somalia may be a natural catastrophe in Australia and a great natural catastrophe in Somalia simply because Australia has, and Somalia does not have, the means to respond to the disaster.

    And finally, and probably redundantly by now, the graph that you link is of great natural catastrophes, which is why it shows so different a pattern.
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  42. Norman, is there a model which claims thunderstorms in those latitudes will increase? As far as I know, the expectations of a warming earth are increased precipitation in some regions, increased heatwaves, and increased drought in some regions. The detail of what events and at what confidence level (likely, very likely) are here.

    Temperature statistics on heatwaves, and river flood frequency are the most likely parameters to be available in a form reliable enough for study.
    0 0
  43. Norman:
    Here is a study on hydrology that only uses stations that have at least a 50 year history so that a trend can be detected.

    The results of the study show that there has been no increase in hydrological events verses the long term mean.

    http://itia.ntua.gr/getfile/1128/2/documents/2011EGU_DailyDischargeMaxima_Pres.pdf
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  44. And here is one on global storm days:
    "However, the global total number of storm days shows no trend and only an unexpected large amplitude fluctuation driven by El Niño-Southern Oscillation and PDO. The rising temperature of about 0.5°C in the tropics so far has not yet affected the global tropical storm days. "

    http://www.agu.org/journals/ABS/2010/2010GL042487.shtml
    0 0
  45. This is a good peace talking about tornados in the USA. Note from the graphs that precipable water is well within historical ranges as well as other items required to produce tornadoes.

    http://www.esrl.noaa.gov/psd/csi/events/2011/tornadoes/climatechange.html

    Just some papers for thought and I hope these help you in your search of knowledge.
    0 0
  46. camburn - all rather useless because they are not linked to what is actually predicted for those indicators and regions. The WG2 link to rivers reports on 195 rivers. It still didnt distinquish between places expected to dry versus those expected to get wetter.
    0 0
  47. Norman @140,

    "Do either of you know of any study done to determine if the number is increasing (please Albatross no models or guesses...just actual countable numbers) "

    Well, I'm affronted :) Stanley Chagnon is your man and Google is your friend.

    FWIW, I have an idea as to how we can objectively look at this, but it will use a model.
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  48. People should also look the annual U.S. Climate Extremes Index (CEI) (with Tropical Cyclone Indicator) for 1910-2010. Note the the downward decline in CEI from 1910 to 1970, and since then an upward trend. With greatest frequency of extreme events in the first decade of the 21st Century. And it is still early days in our stupid experiment.
    0 0
  49. Albatross @148, it is worthwhile using the controls to look at the extremes in one day precipitation as well.
    0 0
  50. Camburn @143, the study you reference suffers from several major disadvantages. This first that using annual discharge is a poor proxy for extreme weather events. Extreme weather events come in the form of both droughts and floods (among other things) which have opposite effects on river discharge. So, rather than use annual river discharge the study should have looked at change in the variability of monthly discharge; and changes in the maxima and minima of monthly discharges. Without doing so, the study is not even capable of being an adequate proxy for increased extreme events.

    Further, the study takes no account of potentially confounding factors. Fairly obviously increased evaporation due to rising temperatures will be a confounding factor, but no notice is taken of it. More crucially, increased water use by humans for personal, industrial or agricultural use is a major confounding factor. For one example of the studies ignoring this, one of the rivers analysed is the Thames. It is hardly plausible, however, that the growth in London's population (between 25 and 40% depending on the district in the last decade) has not increased the water usage from the Thames, and hence reduced discharge rates.
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