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Going to extremes

Filed under: — gavin @ 17 February 2011

There are two new papers in Nature this week that go right to the heart of the conversation about extreme events and their potential relationship to climate change. This is a complex issue, and one not well-suited to soundbite quotes and headlines, and so we’ll try and give a flavour of what the issues are and what new directions these new papers are pointing towards.

Let’s start with some very basic, but oft-confused points:

  • Not all extremes are the same. Discussions of ‘changes in extremes’ in general without specifying exactly what is being discussed are meaningless. A tornado is an extreme event, but one whose causes, sensitivity to change and impacts have nothing to do with those related to an ice storm, or a heat wave or cold air outbreak or a drought.
  • There is no theory or result that indicates that climate change increases extremes in general. This is a corollary of the previous statement – each kind of extreme needs to be looked at specifically – and often regionally as well.
  • Some extremes will become more common in future (and some less so). We will discuss the specifics below.
  • Attribution of extremes is hard. There are limited observational data to start with, insufficient testing of climate model simulations of extremes, and (so far) limited assessment of model projections.

The two new papers deal with the attribution of a single flood event (Pall et al), and the attribution of increased intensity of rainfall across the Northern Hemisphere (Min et al). While these issues are linked, they are quite distinct, and the two approaches are very different too.

The aim of the Pall et al paper was to examine a specific event – floods in the UK in Oct/Nov 2000. Normally, with a single event there isn’t enough information to do any attribution, but Pall et al set up a very large ensemble of runs starting from roughly the same initial conditions to see how often the flooding event occurred. Note that flooding was defined as more than just intense rainfall – the authors tracked runoff and streamflow as part of their modelled setup. Then they repeated the same experiments with pre-industrial conditions (less CO2 and cooler temperatures). If the amount of times a flooding event would occur increased in the present-day setup, you can estimate how much more likely the event would have been because of climate change. The results gave varying numbers but in nine out of ten cases the chance increased by more than 20%, and in two out of three cases by more than 90%. This kind of fractional attribution (if an event is 50% more likely with anthropogenic effects, that implies it is 33% attributable) has been applied also to the 2003 European heatwave, and will undoubtedly be applied more often in future. One neat and interesting feature of these experiments was that they used the set up to harness the power of the public’s idle screensaver time.

The second paper is a more standard detection and attribution study. By looking at the signatures of climate change in precipitation intensity and comparing that to the internal variability and the observation, the researchers conclude that the probability of intense precipitation on any given day has increased by 7 percent over the last 50 years – well outside the bounds of natural variability. This is a result that has been suggested before (i.e. in the IPCC report (Groisman et al, 2005), but this was the first proper attribution study (as far as I know). The signal seen in the data though, while coherent and similar to that seen in the models, was consistently larger, perhaps indicating the models are not sensitive enough, though the El Niño of 1997/8 may have had an outsize effect.

Both papers were submitted in March last year, prior to the 2010 floods in Pakistan, Australia, Brazil or the Philippines, and so did not deal with any of the data or issues associated with those floods. However, while questions of attribution come up whenever something weird happens to the weather, these papers demonstrate clearly that the instant pop-attributions we are always being asked for are just not very sensible. It takes an enormous amount of work to do these kinds of tests, and they just can’t be done instantly. As they are done more often though, we will develop a better sense for the kinds of events that we can say something about, and those we can’t.

178 Responses to “Going to extremes”

  1. 101
    Hank Roberts says:

    SM, okay, you point to stuff ten or more years old; I pointed to recent work; have you any thoughts about the current papers?

  2. 102
    Ray Ladbury says:

    Septic Matthew, How interesting that you seem to think a response that sticks to facts is trying to goad you.

    I agree that one can tell little from any single event–however extreme. However, when you start seeing more large events than expected and when the effect of those events begins to have global consequences (e.g. food insecurity), that’s a pretty good indication that something important has changed. We’re there.

  3. 103
    wili says:

    I have to mostly concur with ccpo.

    Meanwhile, I notice that people here continue to spend much time engaging with trolls and nitwits, while ignoring important posts, such at the one that (should have) directed the august posters here attentions to the recent study highlighted at climate progress on tundra destabilization.

    Maybe it’s just me, but if we have crossed crucial tipping points, I would kind of like to know it–just ’cause I prefer knowing the truth, especially from sites like this.

    Has the tundra and the ESAS (see N. Shakhova’s recent work) crossed a threshold that those mature enough to handle very hard truths should know about?

    (By the way, I completely trust wall street and everything that its Journal puts out–they’ve done ‘a heck of a job’ with the economy, and I think we should turn the care and nourishing of the livability of the entire planet over to them right away [/sarconol])

  4. 104
    ccpo says:

    Septic @ 98: Sorry, but this is completely incorrect. I have not gone back to look at it, but I’m certain both the high and low were probably related to the same phenomenon. Rather, the cut-off that created the heat wave probably prevented Moscow from participating in the cold wave. It was anomalous. Moreover, the concern about highs and lows is not abou any one, but about the preponderance of new highs to new lows being at about 2:1 as opposed to a more typical 1:1-ish.

    Further, your contention the US lows were not anything unusual is also largely incorrect. The lows went as far as Mexico and are related (known, but not proven) to the Arctic oscillation which is related to levels of sea ice and higher than usual Arctic temps.

    I can’t (yet) prove it, but we both know it’s so.


  5. 105

    #73: I think smoker lawsuits are workable analogies to the Pall case, although toxic exposure suits like #26 mentioned are better. Re:

    “The idea is to determine a FAR for AGW as might be done for smoking, say. But in the case of smoking you have data on a real population of smokers and non-smokers. You only have to make one not particularly heroic assumption, i.e. that the risks for the individual whose loved ones are bringing the law suit were typical of the population of smokers as a whole.”

    A lawsuit brought by a single smoker would be very similar to the hypothetical lawsuit brought over the flooding. We do have data on the real population of extreme events pre and post climate change, and the assumption that a particular smoker is “typical” could be challenged in court. Again, though, asbestos or other toxic exposure suits would be more appropriate analogies.

    Gavin suggests medical mapractice might also be a good example. Sounds plausible to me, although I don’t know the field.

  6. 106
    Eli Rabett says:

    IEHO, these papers alert us to be watchful, and are an interesting effort at postdiction of climate effects on a local level, but one should be cautious about accepting them at full face value yet.

    Signing on enthusiastically to the next hot thing immediately risks looking foolish the next day. But this is interesting. Other than that Eli’s read on the thing is a good try to determine what the unperturbed boundary values were for a local climatology and whether they have been exceeded when the climate is perturbed.

  7. 107
    Michael H Anderson says:

    The “livability of the entire planet” – I like that. Cf. the Devonian, 8 times pre-industrial CO2, life flourished like crazy.

    But I no more expect this post wil be accepted than my previous one drawing attention to Phil Jones’s admission of no warming in 15 years.

    [Response: This comment probably deserves to be just Boreholed, but I think it at least provides a useful occasion to remind people that in the Devonian nobody was trying to feed 9 billion humans with plants and animals that are largely adapted to the climate of the past few million years or less. Heck, there weren't even any mammals yet, for that matter, not much animal life on land. Seed plants had just barely gotten underway on land, and insects were just getting going. So I don't think that you can exactly conclude it would be harmless to go back to a Devonian climate in the next couple thousand years. --raypierre]

  8. 108
    Ron Taylor says:

    Michael, for crying out loud, everyone here knows that you have taken Phil Jones’ comment out of context and misrepresented his meaning. If you actually do not know what his meaning was, you will have to look it up, because I am not about to tell you. If you don’t do that, then you will simply continue to make a fool of yourself. Your choice.

  9. 109
    One Anonymous Bloke says:

    Michael #106. You are out of your depth. Tread water, listen, learn. Thrashing around like that will just induce a feeding frenzy.

  10. 110
    paul haynes says:

    thanks for the excellent clarification – the four bullet points are fundamental and I’ll be adding them to my teaching powerpoints!!

  11. 111
    Brian Dodge says:

    Speaking of life “flourishing” with AGW, the Humboldt Squid is doing nicely; hake, and the fishermen who catch them, not so much -

    “Coincident with the arrival of Dosidicus in 1997, the numbers of hake declined, then recovered after the squid observations dropped off, from 1999 through 2001. When Dosidicus returned in 2002, the numbers of hake dropped again and have remained very low (Fig. 3). Numbers of hake have been significantly lower during periods when Dosidicus was present (1997–1999 and 2003–2005; Mann–Whitney U test, U = 1,176, n = 196, two-tailed P = 0.000),”

    “‘There’s very strong evidence that the squid expansion had a huge impact on the hake fisheries,’ says Field, who helped organize a symposium on the animal in 2007. ‘It looks like they’re doing the same migration as hake, which concerns me.’”

    Then there’s the “flourishing” of mosquito populations -
    “Recent disease outbreaks are consistent with model projections that warmer, wetter conditions will lead to greater transmission potential at higher altitudes and elevations. Mosquito-borne diseases are now reported at higher elevations than in the past at sites in Asia, Central Africa, and Latin America (Epstein et al., 1998).”
    “In New York City, an encephalitis outbreak in summer 1999 claimed three lives… West Nile virus as being responsible for this outbreak…which had not been previously documented in the Western Hemisphere”

    “The results of the empirical estimation indicate that climate conditions have an increasingly significant impact on the probability of people being infected by dengue fever. ” Estimating the economic impacts of climate change on infectious diseases: a case study on dengue fever in Taiwan Wei-Chun Tseng, Chi-Chung Chen, Ching-Cheng Chang and Yu-Hsien Chu

    It’s not all AGW gloom and doom; take jellyfsh, for instance -
    “Two centuries worth of data shows that jellyfish populations naturally swell every 12 years, remain stable four or six years, and then subside.
    2008, however, will be the eighth consecutive year that medusae, as they are also known, will be present in massive numbers.
    The over-exploitation of ocean resources by man has helped create a near-perfect environment in which these most primitive of ocean creatures can multiply unchecked, scientists say.
    “When vertebrates, such as fish, disappear, then invertebrates — especially jellyfish — appear,” says [Ricardo] Aguilar [research director for Oceana, a international conservation organisation].
    The collapse of fish populations boost this process in two important ways, he added. When predators such as tuna, sharks, and turtles vanish, not only do fewer jellyfish get eaten, they have less competition for food.”

    “Researchers also don’t know why the giant jellyfish are becoming more regular visitors to Japan’s shores.
    In the early 1900s large numbers of the giants were reported only every 40 years or so.
    But in recent years the jellyfish have been appearing with alarming frequency: Japan experienced unusually large outbreaks almost every year between 2002 and 2007.”

    Probably just a coincidence that it correlates with global warming, right?

    Wrong. (And perhaps relevant to
    “In eleven species studied from subtropical, temperate and subarctic environments, warm temperatures were related to large population sizes;”
    “Because climate changes have complex ecosystem-level effects, the proximate causes of jellyfish increases are difficult to deduce. Therefore, the effects of temperature, salinity and prey on asexual production of new medusae from the benthic polyps of scyphomedusae and hydromedusae also are reviewed. Experiments on temperate species show greater and more rapid production of medusae at warmer temperatures.”
    Climate effects on formation of jellyfish and ctenophore blooms: a review Jennifer E. Purcell, Journal of the Marine Biological Association of the United Kingdom (2005)

    “Data obtained since 1958 from the continuous plankton recorder show an increasing occurrence of jellyfish in the central North Sea that is positively related to the North Atlantic Oscillation (NAO) and Atlantic inflow to the northern North Sea.”
    Climate-related increases in jellyfish frequency suggest a more gelatinous future for the North Sea Attrill, Martin J., Jade Wright, Martin Edwards,Limnol. Oceanogr., 52(1), 2007, 480-485 | DOI: 10.4319/lo.2007.52.1.0480

    “Complicating future predictions will be the possibility that, if climate change exceeds some critical threshold, some marine systems will switch to a new state that might not only be less favourable than the present one, but also prove impossible to reverse.”

    With a little more push from humans, the ocean ecosystems might return not to the Devonian, but even further; Richardson et al[1] note
    “The potentially durable switch to a jellyfish-dominated system is reminiscent of the ancient, rudimentary ecosystems of the Cambrian, and has convinced some authors [26,53] that human stressors are propelling marine ecosystems ‘way back to the future’”

    Gibbons, M.J. and Richardson, A.J. (2008) Patterns of pelagic cnidarian abundance in the North Atlantic. Hydrobiologia 616, 51–65, cited by the Heartland Institute as a rebuttal to Attrill, “showed that variations in jellyfish abundance over 50 years in the oceanic North Atlantic are temperature dependent, with more jellyfish occurring in warmer years.”
    Richardson et al., in [1] suggests(with his tongue firmly in his cheek, IMHO; maybe Idso and Monckton at Heartland should read rather than cherrypick?) –
    “One potentially appealing response is to harvest more jellyfish for human consumption. Jellyfish are important culturally as a gourmet food in Chinese banquets, and are the ultimate modern diet food [56].”
    Richardson’s reference 56, Jellyfish as food, Hsieh et al, point out that “…the carbohydrate content in jellyfish is negligible for calorie calculations (Table 1). The calculated caloric value for a normal serving (100 g) of RTU is less than 20 Kcal.”
    “Amino acid analysis shows that tryptophan, a limiting amino acid, is either not detectable or is found in small amounts in jellyfish tissue (Kimura et al., 1983). Thus, the nutritional quality of jellyfish protein quality is low” and is only ~5 g per 100g serving.

    Perhaps Lord Monckton, echoing another infamous member of the nobility, believes we should “let them eat jellyfish.”

    [1] The jellyfish joyride: causes, consequences and management responses to a more gelatinous future Anthony J. Richardson, Andrew Bakun, Graeme C. Hays and Mark J. Gibbons, Trends in Ecology and Evolution Vol.24 No.6

  12. 112
    Jeffrey Davis says:

    re: 110 and the spread of disease

    Dengue Fever is now showing up in Florida.

  13. 113
    Lynn Vincentnatnathan says:

    RE #79 & (Even when beneficial changes are downplayed, as is usually the case.)

    I have to admit that when I moved to the Lower Rio Grande Valley in 2002, I secretly felt a bit happy that GW had a silver lining, and embarrassed I felt good about it, bec of all the other very serious harms it causes (but continued my household mitigation measures nevertheless & even more — like going on GreenMountain wind energy). In our area you can’t grow things in summer — too hot — so fall-winter-spring is our growing season. Except rarely in some years we get a killing freeze for a day or so, usually end of Dec, Jan. So with GW, I reasoned, these freezes would become less frequent & maybe non-existent.

    Now some are saying they maybe become more frequent caused by negative arctic oscillations (see ). As happened this year (in Feb, & 2 hard freezes really doing in my plants) and last year (Dec 4, 2009), killing much of my vegetable garden. So much for the silver lining.

    And I’m really mad at those darned people profligately emitting their GHGs AND (the kicker) denying any culpability, like sons of Cain. Can’t you darned profligate GHG emitters give a person a break?

    I wonder how the Mexicans feel after losing over a $billion of their crops a few weeks ago to the same freeze? See

  14. 114
  15. 115
    JohnB says:

    I’d just like to add to #85 Glen Fergus. Despite its position today as an industrialised, modern nation Australia is quite young. The first European settlers arrived here some 12 years after the American War of Independence.

    By 1850 the national population was only 405,356 spread over an area the size of the USA. Due to this it will be hard to draw comparisons to modern times and trends. We might know that a mjor flood occurred in 1862, but there is no way to accurately define the full extent or area covered. All we can know is that it was about “this high” in “this place”.

    My own State, Queensland (where Yasi hit) doesn’t enter the records until 1859 with a population of 23,520. The bottom line is that there could have been 5 Cat 5 cyclones every year before then and we wouldn’t know anything about them.

    I’m sorry, but I think the Australian data is too short and sparse to draw many conclusions from. The only certain thing is that we always have been and always will be a “Land of drought and flooding rains”.

    I also agree with Glen that too little attention is being paid to the non cyclonic nature of the recent event.

  16. 116
    john byatt says:

    Brisbane floods , Toowoomba is on the great dividing range west of Brisbane
    where the inland tsunami event began

  17. 117
    crandles says:

    Minor Nitpick: The CPDN team tries to be careful to use “Non-Industrial” rather than “Pre-Industrial”. There are obvious differences: Pre-industrial does not have current solar forcing whereas non-industrial does have current solar forcings.

    So perhaps a change would be in order from:

    “Then they repeated the same experiments with pre-industrial conditions (less CO2 and cooler temperatures).”

    to something more like

    Then they repeated the same experiments with non-industrial conditions (pre-industrial anthropogenic forcings like CO2 so cooler temperatures but natural forcings like solar at current levels).

  18. 118
    Dan H. says:

    Many other locations experienced favorable growing conditions over the past 30 years also. This was mainly a result of higher low temperatures, resulting in fewer freezes and a longer growing season (in some places up to two weeks). Summer highs have changed very little over that timeframe, resulting in less parchment.
    Additionally, much of the Midwest and Plains have experienced an increase in rainfall further increasing crop yields. Areas in the Desert Southwest have been reporting more drought-like conditions, which may be affecting your area.
    Southern states (and Mexico) have experienced fewer freezes in recent years than in decades past. This resulted in farmers growing crops in region that are not ideal. If conditions return to those in the 1960s and 70s, then these farmers will experience many crop failures due to the cold weather.

  19. 119

    118, Dan H,

    And what’s your point? That climate change will be good, or that it just hasn’t slammed us yet quite as hard as we can expect it to?

    To answer those questions, visit this site: Climate Wizard

    Choose “precipitation” and “mid century” from the radio buttons and stick to the USA.

    Doesn’t look too bad, though, does it? A bit wetter up north, a bit drier in the south east.

    But wait… that’s just an annual average. What if (as is the case) there are severe drops in precipitation during the growing seasons, but increases after it’s too late (or during the winter, when it hardly matters)? Or dangerously useless increases for very short periods (meaning floods and crop damage instead of moisture patterns that feed crop growth)?

    Choose different measurement periods from the drop down menu (e.g. “June”) to see what I mean.

    Hint 1: local precipitation is not so much dependent on local temperatures as more complex patterns involving distant regions and factors, which are in turn affected on average by climate. Warmer temperatures at one locale do not necessarily mean drought, and vice versa.

    Most models project a serious water deficiency for the American south and south west with climate change. And in that realm, one or two horrible months could kill an entire season of crops, no matter what you are trying to grow, or what the annual average is.

    Hint 2: It is still very early in the climate change issue. You can’t point to anything now and say “see, it’s not so bad,” or “yeah, things are worse for them, but better for those other people over there.” It’s too early to tell for sure.

    You’re going to have to wait fifty years to see what your calm patience with the issue has done to everyone else’s future.

  20. 120
    Gerry Quinn says:

    Ray Ladbury @87

    Might I suggest that you sit down and estimate exactly how much energy an increase in temperature of 1 degree C represents for the atmosphere plus the first hundred meters or so of ocean. Now consider that this is an AVERAGE and that the distribution of energy is not uniform and is subject to fluctuations–as in any thermodynamic system. I would suggest that this increase is more than sufficient for any sort of extremes we are seeing.

    What nonsense. For a start, a difference of 1 degree in the relevant region is equivalent to an 0.3% increase in the average temperature of 290K or so. That’s if absolute temperatures meant anything in this context, which they don’t. Temperature differences are what count in terms of available energy. Now you might be able to make a case on the basis of specific temperature differences, or increased moisture content of warm air, or whatever. Even then, you will be hard-pressed to make any such simple argument for dramatic changes based on actual local values, which fluctuate greatly about the average.

  21. 121
    Gerry Quinn says:

    Secular Animist @94

    Gerry Quinn wrote: “On the face of it, one would not expect that an increase in greenhouse gases sufficient to increase the average temperature of the Earth by a degree or so would have a dramatic effect on ‘extreme events’ in general.”

    On the contrary. On the face of it, that’s exactly what one should expect, because it is what the climate models have been predicting, and it is now occurring just as predicted.

    Actually, the models do *not* predict dramatic changes from a degree or so of warming (and, for obvious reasons to do with the size of typical temperature fluctuations on a less than global scale, one would be have to be very suspicious of any model that did).

    That is one reason why the IPCC have selected 2 degrees of warming as a reasonable target. It’s not expected to do anything particularly terrible.

  22. 122
    Dan H. says:

    Your post seems to indicate that the desert southwest and western Texas received an increase in precipitation during the past 50 years. Changing to seasonal or monthly precipitation did not seem to have a large effect on the growing season. I was also surprised to find such a large area of the US witness a temperature decrease over the past 50 years, especially in the summer and fall months. In fact, it appears that the entire temperature increase occurred from January – April, and was restricted to the Northern Plains and Western States. This is probably why we witness such a large extension in the growing season.

  23. 123
    Hank Roberts says:

    > an 0.3% increase in the average temperature of 290K

    Your calculation ignores a significant change occurring at 273.15 K.
    Your percent increase needs to be calculated against that as the zero mark.

    You do too know what I’m talking about. Deal with it.

    [Response: % changes in temperature are simply meaningless. - gavin]

  24. 124
    David B. Benson says:

    Gerry Quinn @121 — The current ~0.7 K increase is already bad enough. A full 2 K is likely to be rather rugged on us all.

    Mark Lynas’s “Six Degrees”:

  25. 125
  26. 126
    John Pollack says:

    Gerry Quinn @ 120 and 121

    As a weather forecaster, I would expect some rather dramatic changes in extremes with a 1C rise in temperatures. This is especially relevant in the sub/tropics, and in more poleward locations that receive subtropical advection. That’s because this would also raise the dew points by about the same 1C. Considering energy partition at fairly typical tropical temperatures and RH (70% for a crude estimate) over 2/3 of the extra thermal energy goes into evaporating water. This latent energy is made available downstream by increasing the CAPE (convectively available potential energy), thus energizing thunderstorms, tropical systems, etc.

    Models are typically not gridded finely enough to resolve convective instability. That’s why an important task for warm season forecasting in the mid latitudes of the humid U.S. is evaluating the low level moisture, and the potential for instability. Even 1C extra dew point at, say, 850 mb is enough to cause a “loaded gun” barely capped airmass to blow in spectacular convection.

    Poleward transport of moisture and instability by narrow low level jets, another feature not well resolved by models, also results in many flooding episodes, as well as severe convection.

    Considering that the capacity of air to hold water vapor increases nearly exponentially with temperature, I think a 1C increase is truly a big deal, and will add substantial extra energy to some already strong systems, models or no.

  27. 127
    David B. Benson says:

    John Pollack @126 — Exceptionally clear. Thank you.

  28. 128
    John E. Pearson says:

    Amazon has two books entitled \Statistics of Extremes\.

    Gumbel’s 1957 Dover Book ($16.47 )


    Jan Beirlant, Yuri Goegebeur, Johan Segers, and Jozef Teugels ($108.44)

    I bought one with an extremal price.

  29. 129
    Gerry Quinn says:

    John Pollack @126
    Certainly water vapour content is the most plausible large effect of an increase in average temperature; as you indicate, evaporation and condensation are ways of transferring large amounts of free energy, some of which can presumably end up in a variety of weather events.

    Of course extra water vapour has other effects as well. For one thing it is the mechanism for amplification of the basic CO2 greenhouse effect. And assuming that the amount of rainfall is in some way responsive to the average water vapour content, presumably higher temperatures can drive an increased number of extreme rain events. On the other hand, more rain, on the face of it, should mean less drought, so it’s not all bad.

    However, when we talk about the effects of an extra degree, we need to remember the main point I was making. The temperature at the Earth’s surface varies very widely. The average annual temperature varies globally over a wide range, depending not just on latitude and altitude but on many other factors. And at every location the temperature also varies, in some places more than others. It varies between day and night, it varies between seasons, and it varies day to day, week to week, month to month, and even over years, in response to weather systems of various longevity. The longest term weather systems shade into climate, which itself varies, and not just due to anthropogenic causes.

    It varies everywhere by much more than one degree. Which means that on most days, it is sometimes 1 degree hotter than it is today. Do we quake in fear when the weather forecast says temperatures will rise by one degree next week?

    Short version: a change of one degree in average temperature is surely not going to move any region of the world into a novel climatic regime! I can readily believe that, for example, flooding events, heatwaves, or what have you might become a bit more likely in many places. But basically, these are going to be happening in places that might expect such events anyway.

    A small change in global average temperature may certainly have statistically significant global average results. And it may well interact with other processes to make climates evolve differently than they would have otherwise, for better or worse – or, almost certainly, for better AND worse. But I don’t find the prophecies of doom in the comments here (not referring to your post) remotely credible.

  30. 130
    Icarus says:

    Gilbert Compo very kindly emailed me the following, regarding the recent WSJ article about the Twentieth Century Reanalysis Project and trends in extreme weather:

    I wanted to let you know that our letter has appeared at
    Severe Weather Is Driven by Many Factors

    While we appreciate the opportunity to discuss our work, we found that the resulting opinion piece “The Weather Isn’t Getting Weirder” (Feb. 10) does not accurately reflect our views.

    As for the statement that the Twentieth Century Reanalysis Project, which is a synthesis of weather observations going back to 1871, shows “little evidence of an intensifying weather trend”: We did not look at weather specifically, but we did analyze three weather and climate-related patterns that drive weather, including the North Atlantic Oscillation. And while it is true that we did not see trends in the strength of these three patterns, severe weather is driven by many other factors.

    The lack of a trend in these patterns cannot be used to state that our work shows no trend in weather. Many researchers have found evidence of trends in storminess and extreme temperature and precipitation in other weather data over shorter periods.

    Finally, the article notes that the findings are “contrary to what models predict.” But models project forward, while our analysis looked back at historical observations. We see no conflict between the 100-year-projection of changes in weather extremes resulting from additional carbon dioxide and the fact that our look back at three indicators showed no historical trend.

    Thank you for this opportunity to clear up any inadvertent misunderstandings about our work, which can be found at:

    Gilbert P. Compo
    Research Scientist
    University of Colorado at Boulder

    Jeffrey S. Whitaker
    National Oceanic and Atmospheric Administration

    Prashant D. Sardeshmukh
    Senior Research Scientist
    University of Colorado at Boulder

  31. 131
    xavier says:

    I agree with the excellent post by Gerry (129) and was actually thinking something similar the other day. I was watching a TV bit about Stephen Hawking and the black hole information destruction controversy and wondered if this idea could (loosely) have any relevance to climate or specifically to the earth’s temperature history. Does our climate gobble up temperature information like a black hole? Much is being claimed about the alleged direct effects of a 0.5 degree temperature increase (last 30 years) on our climate system. The idea that there is some type of memory mechanism in the atmosphere that “remembers” minor long-term temperature trends is something that is taken for granted but never really proven. If this temperature “information” is not stored and it is obliterated daily, how could it possibly drive climate variations or create increases in “extreme events”? As Gerry said, how could minor long-term trends drive weather when they are completely and utterly obliterated by hourly, daily, seasonal, and dynamical temperature swings? The only ones that can and do remember or record minor long-term trends are us! (And some would claim we do a poor job at that) If we were talking about a clearly observed long-term temp trend of say 5 degrees or higher then it might be worth having this discussion. We just don’t have anything close to that! The air, ground, and even the oceans have no built in mechanism to be able to remember the slight long-term temp trends that some people are attributing to almost every negative event on the planet. This small signal is completely obliterated by much higher amplitude signals – plus there is nothing to filter or store it anyways! A few weeks ago here in Texas the highs were in the low 20′s and couple days later the highs were in the 70′s. 99.99999 percent of us and most of our ecosystem survived that crazy up swing in temperature. Why would we not be able to survive a 0.5 degree change over 30 years? Worry about this seems like extreme exaggeration. So are people claiming that climate instability is caused by the upward shift in temperature itself? Like claiming that there is some type of climate “inertia”? (Another poorly proven concept) Again, our planet can survive DAILY temp swings much greater then any claimed long-term trend without more instability being introduced. Some regions of the planet experience diurnal and seasonal changes that are vastly greater then other regions of the planet. Do these regions have vastly more unstable weather? That would be a good test for this theory, would it not? So can anyone here prove that there exists something like a memory mechanism in the atmosphere? Also, can anyone here prove that there is any type of climate inertia mechanism where the mere existence of long term trends cause “instability”?

    [Response: The number of mistaken assumptions in your text are legion. Who has claimed that the "we will not survive" 0.5 deg C rise in 30 years? This is a strawman. For comparison, the last ice age was only about 5 or 6 deg C colder than today, and that was effectively a different planet. The change by 2100 will be the same order of magnitude if we are unlucky - this is not some trivial change we are talking about. - gavin]

  32. 132

    GQ 129: Short version: a change of one degree in average temperature is surely not going to move any region of the world into a novel climatic regime!

    BPL: Wrong. We’re talking about the planet’s mean annual surface temperature. A 1 degree change in that is enough to move agricultural growing belts hundreds of miles. Want the math?

  33. 133
    Didactylos says:


    First mistake: the temperature increase is defined as the accumulation of “hourly, daily, seasonal, and dynamical temperature swings” over a suitably long period. It’s not the other way around.

    Second mistake: the planet has a very good memory. Some processes will accumulate weather data over a year, and record them. Tree rings, glacier terminations, and many others do this for local weather. Other mechanisms integrate weather data over wider areas, which brings us to -

    Third mistake: the ocean is the “memory” that drives the climate system. It is where most of the heat is stored. And the heat in the top layers of the ocean has been steadily increasing recently, for mindbogglingly obvious reasons.

    Fourth mistake – oh, I just don’t care any more. Think about it carefully, and write in actual paragraphs next time, and you may get a less dismissive response.

  34. 134
    John Pollack says:

    Gerry Quinn @ 129

    While I agree that a 1 degree temperature increase is not likely to lead to a planetary scale disaster, it can certainly worsen local disasters. Daily fluctuations are certainly large, but there are times when a degree can make a difference. For example, a 1 degree increment to our dew point last summer would certainly have made a difference, when the dew point was already a rarely-observed 27C. The same applies in general to convective systems fueled by latent heat energy.

    I am also not as sure as you that a 1 degree increment will not move any region of the world into a novel climate regime. Paleoclimatic evidence says that there really can be tipping points, e.g. the Younger Dryas.

  35. 135
    Dan H. says:

    Better check your math. Travelling North from Dallas, TX in order to Oklahoma City, Wichita, Topeka, Omaha, Sioux Falls, Aberdeen, and Fargo, all incrementally about 125 further north, the average temperature decrease between each is 1.7C. Therefore, all things being equal, a 1C increase would move agriculture about 75 miles north. However, things are not all equal, as the recent temperature increase was observed primarily in the coldest values; nighttime lows and winter. Hence, agriculture is more likely to expand northward rather than move.

    [Response: Agriculture is much more vulnerable to temperature/precip extremes than to changes in the mean, and so estimates of agricultural impact need to think much more about the how the peak daily temperatures will change for instance, than the annual mean. And the impact of that is decidedly non-linear. - gavin]

  36. 136
    Dan H. says:

    Of course Gavin,
    But since the peak temperatures have changed much less than the average, the agricultural impact would be much less. As I stated previously.

    [Response: Stating it doesn't make it so. You would need to actually look at the data and the projections. - gavin]

  37. 137

    Actually what laypersons & policy-makers should be focused on is not whether this flood or that hurricane can be attributed in part to CC. That’s water under the bridge & for scientists to debate & figure out.

    What we should be focused on is mitigating CC to avoid such events in the future, and here the science is stronger: CC is expected to increase the risk of floods, droughts, and higher hurricane intensity. That’s somewhat a more solid statement, and that’s what we should be trying to mitigate, not events that have already happened.

  38. 138
    Septic Matthew says:

    The two papers are behind a paywall, but the Supplemental Information for Lin et al is available here:

    The work is admirable and exemplary. From a skeptical perspective it should not be believed until it has been critiqued, debated and replicated, but the work was really carefully done and I hope it inspires others. It does cite the book by Coles, op cit.. You can read a thorough critique on a skeptical blog: but the critic is detailed but nihilistic (can be pronounced to rhyme with “denialistic”, but usually isn’t), that is the critic concludes that the paper is rubbish and ought not even to have been published. That’s an extreme (!) conclusion. Like the famous MBH98, it can be improved upon, but it’s pioneering.

  39. 139
    Hank Roberts says:

    Dan H. should also make the aquaintance of a farmer and a gardener sometime, or read something about phenology, and learn something about the temperature-and-timing requirements for various crops. That would change his mind. Google would like to befriend him. Various producers of fruits and vegetables would have opinions on the practicality of his advice so far.

    Just e.g.:

    Sustainable Orchard Management System For Intermountain Orchards …
    Temperature data generated by orchard weather stations will be … Fruit production in the intermountain west is besieged with problems. To cope with these problems ….
    Google: “sustainable orchard management”

  40. 140

    RE #135, there are studies coming in that show the increasing diurnal minimum temps (night temps) are now harming certain crops….and CC increases the average night temps faster than the day temps. The study also says that in the future the increaing day temps (above a certain point) are expected to harm crops.

    Welch, et al. “Rice Yields in Tropical/Subtropical Asia Exhibit Large but Opposing Sensitivities to Minimum and Maximum Temperatures.” PNAS 107(33):14562-14567.

    Then factor in extreme weather events (including perhaps more frequent negative arctic oscillations that freeze-kill crops in areas where it’s too hot to grow crops in summer), and we could be facing serious food shortages.

    And we can’t expect the Arctic region to become the bread-basket of the world….people who live there tell me the soil is very poor. And when you look at the area on a globe rather than a flat map, there’s not as much acreage as it seems.

    And then there’s the impact of CO2….more pest damage, and harm to crops, esp at much higher levels….harm to seafood (fish, corals, shellfish). See:

    -Högy, et al. 2009. “Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment.” Plant Biology 11: 60-69.
    -Oh & Richter. 2004. “Soil acidification induced by elevated atmospheric CO2″ Global Change Biology 10.11: 1936-1946.
    -Hunter, M. D. 2001. “Effects of Elevated Atmospheric Carbon Dioxide on Insect-Plant Interactions.” Agricultural and Forest Entomology 3: 153-159.
    -Munday, et al. 2010. “Replenishment of fish populations is threatened by ocean acidification.” PNAS 107(29):12930-12934.
    -Doney, et al. 2009. “Ocean Acidification: The Other CO2 Problem.” Ann Rev of Marine Sciences 1: 169-192.
    -Hoegh-Guldberg, et al. 2007. “Coral reefs under rapid climate change and ocean acidification.” Science 318: 1737-1742.

    Not to mention death by hydrogen sulfide, which is expected to increase:

    Krump, et al. 2005. “Massive Release of Hydrogen Sulfide to the Surface Ocean and Atmosphere During Intervals of Oceanic Anoxia.” Geology 33.5: 397-400.

  41. 141
    SecularAnimist says:

    Compare and contrast Dan H’s blithely sanguine comments with this new article by the “alarmists” at The Economist:

    A special report on feeding the world: No Easy Fix
    The Economist
    February 24 2011


    Global warming upsets the world’s water cycle, increases the burden of pests, desiccates soil and reduces yields …

    An increase of 2°C in global temperatures … could cause a 20% fall in wheat yields. This would exceed any possible gains from warming in areas currently too cold to grow crops and would also offset the benefits of rising carbon-dioxide concentrations …

    Climate change also affects the rhythm of the seasons. Winters arrive later or spring earlier. Rainy seasons become shorter, milder or more intense …

    In 2009 Oxfam, a British charity, asked thousands of farmers in a dozen countries what worried them most about climate change. Their biggest concern was not higher temperatures but disruptions to the natural cycle …

    When the International Food Policy Research Institute (IFPRI) tried to work out the impacts of climate change on the main cereal crops, almost all its results suggested that yields in 2050 are likely to be lower than they were in 2000, sometimes much lower. Almost half the forecasts showed yield reductions of 9-18% by 2050. One came up with a drop in rainfed-maize yields of 30%. The most vulnerable crop turned out to be wheat, with the largest losses forecast in developing countries. The Indo-Gangetic plain, home to a seventh of mankind and purveyor of a fifth of the world’s wheat, is likely to be especially hard hit.

    And by the way, the Economist article only addresses agricultural food supplies and does not even discuss the serious negative effects of AGW on oceanic food webs which are a major source of protein for human consumption.

  42. 142
    Dan H. says:

    You seem to be unaware of the increase in agricultural output during the past century. While much of that is undoubtedly due to technological advances, the climatic changes have also contributed. TO say that all crops have benfitted equally is simplistic. However, many crops here in the Midwest have benefitted from the longer growing season and higher rainfall.

    [Response: The monetary value of wheat, corn and soybeans in North Dakota and Minnesota in 2010 is more or less irrelevant to a general discussion of the effect of climate change on agriculture. Both production, and monetary value, vary widely with economic and other non-climatic factors.--Jim]

    One of this country’s staples is wheat production. Cehck out the Kansas wheat yield since 1979. Is it a coincidence that the highest yield was observed in 1998?

  43. 143
    flxible says:

    Climate change also affects the rhythm of the seasons. (…)

    Their biggest concern was not higher temperatures but disruptions to the natural cycle …

    In my area we’ve had a shift for years now that I’ve been refering to as “false spring” – it missed the usual mid Feb period [La Nina?], but I’m expecting it to show up in early March to fool many things to break dormancy too early and be subject to damage from late frost. The Feb warm periods have been resulting in tree fruit not getting enough winter chill-hours to produce fertile bloom, so light crops and/or trees that wind up throwing blooms in late summer or fall!!

    In addition for the last few years there’s been a mid summer period when we get a 1-5 day spell so hot that veggie blossom set ceases, and if it’s late enough it prevents any subsequent set having time to mature, particularly hard on the tomato crop which doesn’t like the warm overnight temps.

    DanH really does need to try growing his own food to cure his myopia – I suspect he may have the opportunity within a few years, if he wants to keep eating.

  44. 144
    Dan H. says:

    I do grow a lot of my own food. This past year I had a very poor apple crop, by a bumper pear yield. My beans, peppers, and squash all had excellent seasons. My peas were hampered by a spring hail storm which hit at the most inopportune time. I was harvesting broccoli into december – had to clear the snow off the plants first.
    I am appalled at all the people who think that agriculture is in serious trouble, when all the recent evidence points to the contrary. Speculation about future events when not based on real world data does not count as evidence Secular. Now if we were substantially cooling the plant, that would cause a large disruption.

  45. 145
    SecularAnimist says:

    Dan H wrote: “However, many crops here in the Midwest have benefitted from the longer growing season and higher rainfall.”

    Dan H follows that assertion with a link to an Ag Week article about 2010 record harvests in North Dakota and Minnesota.

    The article that Dan H cites says absolutely NOTHING about attributing those yields to “the longer growing season and higher rainfall”.

    On the contrary, the article quotes North Dakota Commissioner of Agriculture Doug Goehring who attributes the yields to “the type of seed genetics we are getting, the good research and breeding programs, and the better equipment we have”.

    The article also notes that “many parts of the United States have had bad growing years recently”.

  46. 146

    DanH, you ask “Is it a coincidence that the highest yield was observed in 1998?”

    Well, I don’t know, and nothing you’ve posted seems to say (though I might have missed something in the Kansas report.) Absent serious consideration of the question, it could indeed be coincidence. Pace Jethro Gibbs, they do happen.

    The only attributive statement I came across was in the North Dakota item. The quote was:

    “That just tells you something about the type of seed genetics we are getting, the good research and breeding programs, and the better equipment we have. The fact is we are doing a better job of managing the crop.”

    Nothing there about temps.

    Is there something out there that actually supports the claim that rising temps in the Midwest have benefitted farmers? ‘Cause there doesn’t seem to be much in the links pointed to.

  47. 147
    SecularAnimist says:

    Dan H wrote: “Speculation about future events when not based on real world data does not count as evidence Secular.”

    The drought in Russia which caused Russia to ban all wheat exports, and the ongoing drought in China, and the drought followed by flooding in Australia, are “real world data”.

    Skyrocketing global food prices driven by crop failures are “real world data”.

  48. 148
    Hank Roberts says:

    > Dan H
    > You seem to be unaware of the increase in agricultural output
    > during the past century.

    This is so unrelated to anything I posted that I wonder if you’re for real.
    Could you make a greater effort to pass your side of the Turing Test here?

  49. 149
    Pete Dunkelberg says:

    Papers to the people!
    Min et al 2011, Pall et al 2011

  50. 150
    Pete Dunkelberg says:

    Min etal – will this link written with blanks instead of %20s work better?

    How about just this:
    or Zwiers et al Nature 2011.pdf

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