Is Extreme Weather Linked to Global Warming?

By Keith Kloor | June 2, 2011 10:01 am

That’s the million dollar question Yale Environment 360 put to a nice cross-section of climate experts. The roster includes Kevin Trenberth, Judith Curry,  Kerry Emanuel, and Roger Pielke, Jr., among others.

To my mind, there are no surprising statements from any of the aforementioned contributors, if you are familiar with their previously stated positions. (Somebody should correct me if I’m wrong.) Still, it’s good to have these views collected in one place and in sum, they should be helpful to those trying to make sense of this complicated issue.

CATEGORIZED UNDER: climate change, climate science
  • Sashka

    When a scientist says “undoubtedly” (as Trenberth did) discussing such a complex and obviously unsettled (everyone else admits it) problem he is no longer a scientist. He is just a propagandist. Trenberth’ shamelessness is truly amazing.

    The last gentleman, William Hooke, begins with quite a bizarre and silly statement. The planet’s main business is to redistribute the heat from the equator to the poles. This is done by way of large scale meridional circulation (both in ocean and atmosphere). In the big picture the extreme weather events are just a footnote.

  • sharper00

    Are violent events linked to extreme political rhetoric?

    Could it ever be proven an attack committed by an individual or group of individuals was directly related to the public statements of another? Without such proven links is it possible to say such statements carry such risk or that actions taken in such an environment were likely influenced by it?

  • Dean

    The question asked of them was: “whether they think there is growing evidence that human-caused global warming is contributing to an increased incidence of extreme weather”

    However some of them turned it around: “a few such examples of extreme weather cannot, by definition, be used as evidence for, or against, climate change” (Watson) and “To suggest that particular extreme weather events are evidence of climate change is not just wrong, but wrongheaded” (Pielke).

    The difference is not trivial. Extreme weather events are, by definition, rare events, and as such will be the last or weakest phenomenon to accumulate statistics to add to the evidence for AGW.

    But to the degree that there is evidence of AGW from other areas, particularly phenology, then it is not unreasonable to believe that the process can contribute to some types of extreme events. The emphasis here is “contribute” and Trenberth latched onto this: “It is when global warming and natural variability come together that records are broken.” To me that once sentence cut through most of the crap. AGW is not causing extreme events, it is exacerbating them.

    Since both Pielke and Curry are believers in AGW in general, that they both continually turn this question around (in other forums as well) demonstrates some kind of barrier to addressing the issue.

    It’s also important to differentiate on types of extreme events. Evidence for a connection with floods is much stronger than hurricanes and especially tornadoes, and the latter have most of the attention in the US this year.

  • grypo

    “The substantial interest in attributing extreme weather events to global warming seems rooted in the perceived need for some sort of a disaster to drive public opinion and the political process in the direction of taking action on climate change.”

    This statement should be put in a time capsule.  It is the essence of human folly.

  • Dean


    75 years ago, somebody might have said something like “the substantial interest in predicting Nazi aggression seems rooted in the need to drive public opinion to prepare the country for war” and later “. . . to assist Great Britain in her hour of need, since we will be next”.

    People look back now and ask why we were so blind. Of course we were blinded by the economic circumstances of the Great Depression. But there was a very strong denialist movement re the Nazis that evaporated right after Pearl Harbor. You might not blame the average unemployed guy for not wanting to pay to get ready for what would become WWII. But what are we to say to the very organized political movement that prevented anything beyond Lend Lease until Pearl Harbor? There are certainly many differences, but some parallels as well.

    So people who believe we are facing a very serious situation are indeed pointing to repercussions that they see and/or expect. Of course if you believe that most of the scientists and all of the major academies are either in on a conspiracy to get grant funding, or just fooled by some kind of bias, it looks like folly. But it looked like folly to the America First Committee as well.

  • Marlowe Johnson


  • kdk33

    Trenberths theory seems to be that since there has been some (amount in hot dispute) GHG warming then that GHG warming is a part of all bad weather. 

    Trenberth will also agree, I’m sure, that GHG warming is a part of all good weather. 

  • Marlowe Johnson

    Your ability to be spectacularly wrong on such a consistent basis is impressive.  Keep it up!

  • kdk33


    Do I need to school you again on SLR data?

  • Marlowe Johnson

    schooled? well done once again sir (see #8 above)!

  • kdk33

    Shall we review.  I’m game if you are?

    Skip the insults, and let’s just review the data.  Whadya say?

  • Marlowe Johnson

    ok.  here’s you:

    “Point us to the data showing that sea level rise is accelerating.”

    Here’s me:
    “High quality measurements of (near)-global sea level have been made since late 1992 by satellite altimeters, in particular, TOPEX/Poseidon (launched August, 1992), Jason-1 (launched December, 2001) and Jason-2 (launched June, 2008). This data has shown a more-or-less steady increase in Global Mean Sea Level (GMSL) of around 3.2 ± 0.4 mm/year over that period. This is more than 50% larger than the average value over the 20th century. “

    Now comes the part where you say up is down, no look over here, it’s all part of a eco-kleptocrat conspiracy etc…

  • Roger Pielke Jr.


    Here is the question we were asked:

    “Do you think there is growing evidence that human-caused global warming is contributing to more extreme weather events worldwide, and on what do you base your conclusion? Please cite an example or two of recent extreme weather events that you think either affirm, or refute, the contention that anthropogenic global warming is increasing the frequency and intensity of extreme events.”

    So what you read were in fact direct responses to what was asked.

  • Dean


    Roger – I disagree, but all I can do is repeat what I said. Asking if global warming is affecting extreme weather (the question posed) is not the same as asking if extreme weather proves global warming (your response in your first paragraph).

    Also, when addressing statistics of extreme weather, you cherry pick the data that supports your point (“data on tornadoes, large-scale river floods (in unaltered river basins), and landfalling hurricanes”), while ignoring that which doesn’t (intense rainfalls, etc.). Generally speaking, the events you are willing to deal with are almost always such rare events that it could be at least many decades until any trend could be detected. Why don’t you address the trends in extreme rainfall events instead or other weather phenomena for which it is reasonable to look for trends rather than only focusing on those that it is almost impossible to do so with?

    It’s kind of like saying there is no trend in smoking causing cancer in 49 year-old male albinos who smoke and live in some small town which has one 49 year-old male albino who smokes. No trend! Joila, no proof!

    Anything to avoid a statistically-adequate sample.

  • Brandon Shollenberger

    I’m confused by Dean’s criticisms here.  Can someone point out what (if anything) I’m missing?  The eight experts were asked if there is growing evidence indicating (anthropogenic) global warming is causing more extreme weather events.  Pielke said there is no evidence of any increase, so the answer is no.  That seems like a straightforward response.

    The only difference I can see in Dean’s approach is instead of people saying it isn’t evidence “of global warming,” they should say it isn’t evidence “of global warming impacting extreme weather events.”  Is that really all there is to it, or am I just missing something?

  • kdk33


    Are you capable of having a rational conversation. 

    You’re data shows an SLR acceleration of .01 mm/yr2 that is statistically teased from pretty variable, not so super-reliable, tide gauge data.  The more accurate satllite data shows no acceleration, and in fact a mild deceleration in recent years. 

    I said, I’ll grant you the .01 mm/yr2 acceleration (even though I think it’s questionable).  Even then the predicted sea level rise for the next century is about 350 mm (3mm/yr today, 4mm/yr in 2100).  Last centuries rise was about 200 mm.  I don’t think 350mm is scary and doesn’t come close to justifying decarbonization.

    At that point I believe you referred to the elephant in the room: the break up of continental ice sheets.  I find the possiblity too remote to worry about.  I asked for any data suggesting this might actually happen in the next 100 years.

    And then you threw insults.

  • NewYorkJ

    To use an analogy I’ve seen:

    “Do you think the statistical casino advantage from a roulette wheel is contributing to more very profitable sessions (session defined as one hour of play on one table)?”

    Kevin Trenberth: Yes.

    Roger Pielke Jr: No, because linking results from any individual session is foolish.  Also, a recent review (of mostly my own research) says the data is a result of players putting more money on the table.  That said, the casino edge is real.

    Judith Curry: The interest in linking very profitable sessions to any alleged casino advantage is rooted in the perceived need to hype such sessions to drive political action against casinos, which is revealing of my heavy personal biases more than anything, so “no”.

    On climate change and weather extremes, RC had a recent post on this:

  • Roger Pielke Jr.

    Dean- I’ve been writing on extreme rainfall and climate change for about 15 years, it is discussed in The Climate Fix and it comes up often on my blog, e.g.,

    Not even 49 year-old non-smoking small town albinos are unaware of this 😉

  • Dean

    Roger – Almost every quote I see from you these issues addresses land-fall hurricanes, storm damages, etc, as in your quote in the post that is the subject of this blog. It’s nice to see the blog entry you link to above, but from my vantage point that is the exception.

    My central point was the disconnect between “is global warming contributing to extreme weather events” and “are extreme events proof of global warming.” Maybe Brandon S doesn’t see the difference, but it seems awfully clear to me. Is there more moisture in the air now than a few decades ago? Does moisture in the air impact weather events?

  • Brandon Shollenberger

    Dean, there is an obvious difference between those two statements.  However, there is also some overlap in them.  If extreme events can’t be used as evidence for global warming, that means there isn’t enough evidence to indicate global warming is impacting them.  That’s all people like Pielke were saying.

    Obviously CO2 emissions impact extreme weather.  They’d do so even if they didn’t cause global warming.  Changing the makeup of the atmosphere will impact all weather.  The question is what sort of changes will we cause and how strong will they be?  That’s a question we don’t know the answer to.  Part of the reason we don’t know the answer to it is because we can’t discern an anthropogenic signal in most weather.

  • grypo

    Why More Precipitation Does Not Necessarily Mean More Flood Damage
    Is Roger suggesting that the increase in precipitation is not going to equal loss of life and property due to changes in the hydrological cycle going into the future?  If so, there is a significant body of work that disagrees with a statement like that, while at the same time citing his work as a factor in past loss.  I’d like to hear him clear this up, as it sounds like he thinks just moving people will solve this problem.  People all over he globe are now at serious risk and it would take an amazing amount of hubris to put his work in the context of his blog post.

    As we add CO2, we will add heat, we will add moisture, we will change the hydrological cycle in ways we can’t predict.  That water has to go somewhere.  It’s happening as we twiddle.

  • Roger Pielke Jr.


    Thanks for your reply, while there is of course no need for you to read what I have written, I’d suggest that your characterizations of my views would likely be more accurate if you did so …

  • kdk33

    “As we add CO2, we will add heat, we will add moisture, we will change the hydrological cycle in ways we can’t predict”


    I think most skeptics would agree with your statement above.  I, personally think this is an accurate summary of our understanding. 

    What I don’t understand is how you can write this and yet be so absolutely certain that CO2 emissions are leading us to catastrophe.

  • grypo

    The only thing I’m absolutely certain of, is the risk of catastrophe, or whatever else you want to call it.  Certain of Risk.  If we use the science as a guide, there is no escaping that we are, in fact, gambling away the near future, and are pretty much ready to damn the far future to severe risk.  The odds are against us if we plan on business-as-usual emissions for another few decades.  Presently, catastrophe is local.  It depends on where you are looking from.

    But I have many other concerns that have to do with international politics, ethics, economics, etc.

  • kdk33

    From whence does this risk arise?

    From what, exactly, are we at risk and on what basis do you compare this risk to others, including the risk associated with decarbonization.

  • grypo

    “From whence does this risk arise?”

    The risk arises from the physical changes we are making to the energy balance of the planetary system.

    “From what, exactly, are we at risk and on what basis do you compare this risk to others, including the risk associated with decarbonization.”

    We are at risk in many areas, an acceleration of the hydrological cycle being the risk we are discussing currently.  By continuing gamble against the odds, we risk life, community, property, etc.  If we begin at a reasonable time, we can mitigate risk against decarbonization.  We have control of what adaption and mitigation policies we make, and then rescind, if they are not working.  The longer we wait, the less room for mistakes we have.  To understand that, means getting familiar with latent heat and carbon physics.  OTOH, We do not have that same control over how the planet reacts to business as usual emissions paths.  By doing nothing we risk our both the economy, as well as all the other risks we incur on the environment in which we rely on to live.

    This doesn’t even get into the ethics of climate change effecting the poorer nations and even the poor in richer nations more than those of influence over the policies we make.  It also does not get into international politics and each nation’s place as a steward over our shared resources, the ocean and atmosphere, and the resources we trade.

  • kdk33


    You seem to have a variety (and to me somewhat bewildering array) of concerns.  Can we focus on just one:  the acceleration of the hydrological cycle.  I assume this is something associated with warming, but could you explain for me what this is and how it threatens us humans.  Also, why should the current warming make this a threat; past warming has generally been benefecial for humans.

    I know you have other concerns, but if you can help me understnad this one I would appreciate that.

  • grypo
  • kdk33


    Thanks for the linke; and, can I say, you are much better at this than Marolowe.

    In this, my short reply, I would ask if you know where the compelling data referred to in the link, but never actually presented, can be found.  I would like to look at it.  (I assume it shows in increase in “heavy precipitation events” (storms?) during the last century, and perhaps the 10% increase in precipitation.)

  • kdk33

    Now, to don my rabid denier frock and address a few of Karl’s points (BTW, the introducer is Joe Friday.  For real?:

    1)  Karl claims the reduction in night/day temp range is due to evaporative cooling.  I don’t know how this can be.  If night temps have increased more than day temps then evaporative cooling will have increased more in the night.  I’ve always understood that GW affects night more than day because it only affects outgoing radiation, hence the affect is less pronounced in the day when there is also incoming radiation

    2)  He (and I’ve read this elsewhere, and I’m admittedly taking some liberties with Friday’s words here) seems to be suggesting that higher temps and water content mean more energy hence worse weather.  But this isn’t necessarily true; the atmosphere could come to equilibrium at a high temperature and high water content with enormous energy and there would be no weather at all.  It is non-equilibrium that causes weather – temperature, pressure, concentration differences.  Since GW raises cold temps more than hot, there is a perfectly reasonable case to be made that it will reduce these driving forces.

    3) Friday points to the 10% increase in precipitation as if it were a problem.  I call BS.  10% more rain would be welcome at virtually any location on earth.  (a week can’t go by without our kind host derailing our animated climate talk with something about water scarcity).

    4) An increase in “heavy precipitation events” (euphemism for storms, I assume)?  It is my undertanding that storms are not getting worse.  However, to demonstrate my open mind, I’m certainly willing to look st the data, which Karl claims is compelling.  Sadly, he doesn’t present any.

  • kdk33

    oops. At 3 that should be Karl, not Friday.  I just couldn’t get Joe Friday out of my mind.

    BTW, grpo, I assume all of these changes occured in past warming cycles and those were (until the advent of climate change science) considered beneficial. 

    Why is it different this time?

  • grypo

    Karl is, for the most part, the person at the NOAA that collects all the analyzed data from all the studies done.

    1)  Evaporation cooling changes at higher rate in day than at night in an increased greenhouse situation.  Remember these are anomalies from baseline pre-1950, not direct temperature readings.

    2)  First, equilibrium happens when energy coming in, equals energy coming out over long periods of time.  The warming doesn’t stop -1- because of latent ocean heat energy and -2- the carbon cycle.  The increased energy happens due to enhanced greenhouse, this causes initial warming and feed-backs, like we are discussing here.  The water vapor increase is caused by warming, of any kind.

    But this isn’t necessarily true; the atmosphere could come to equilibrium at a high temperature and high water content with enormous energy and there would be no weather at all.

    I don’t know what this means.  A new equilibrium would not equal no weather, just different weather from before, ie an entirely different climate.

    It is non-equilibrium that causes weather ““ temperature, pressure, concentration differences.

    It causes changes in climate, hence, you seem to be arguing that adjustment from one climate to another causes extremes, then once in equilibrium, extremes will stop.  This isn’t true.  The new climate with more energy will see more flooding and drought, as well as many other changes, not all equal regionally or seasonally.   This is also complicated by our emissions of aerosols and interaction with clouds which reduce the intensification of the cycle.  Unfortunately aerosols are shortlived, CO2 is not.   But either way, we are in for long period of of extreme weather because we will not be in equilibrium in our lifetime on current emissions paths.

    3)  Climate change will cause water scarcity, but this goes well beyond climate change (as KK blogs about).  I understand this seems counter intuitive to 10% more water (and this was about mid to high latitudes, drought happens closer the equator and Hadley cell regions which are growing), but you must think of the water cycle as a complete system.  You must think of how much of that water is deposited in a place that is usable for growing, how much can be captured for drinking, and how much just runs off into the ocean, or floods into cities where it is fouled.  You must also think in terms of seasons and regions.  Some places will get no water over long periods of time.  The increased hydrological cycle will make wet times in wet places, wetter, while making dry places, in dry time, dryer.  The immediate issues would be ocean surges reaching freshwater reservoirs.   Increase heat waves.  Hadley cell growth poleward.

    Why is it different this time?

    I’m not sure why you assume that climate change has been beneficial in the past.  There are numerous examples going back to the beginning of human history where is has been a complete disaster.  But we are much different species, dependent on things that will change drastically on our current course at ractes which we are certainly not accustomed to and it puts us in risk of severe loss of life, resource, and treasure.  Perhaps you can be more dispassionate than I at this prospect.

  • Michael Tobis

    “Why is it different this time?”

    I think this is the crucial question  that people fail to understand. The rate of change we are already seeing is very large compared to recent natural variability, but these are the delayed changes we had committed to decades ago. We are in a period of accelerating change, and will continue to be in such a period for the foreseeable future.

    This is largely because there is a delay in the system, and largely because carbon in the climate system is cumulative on human time scales. Unless we drastically reduce the amount we emit (not just keep it from increasing) the climate will be responding to an ever larger, ever longer peak in forcing. The Arctic sea ice is already in motion. The ice caps and the deep ocean are starting to feel the kick.

    One of the main things that people fail to understand is that we ain’t seen nothin’ yet. The changes in the pipeline are delayed, and the forcing they respond to are cumulative.

    Look at the spike in the CO2 curve, not the spike in the temperature curve, and you will find no precedent whatsoever.

  • Michael Tobis

    “1)  Karl claims the reduction in night/day temp range is due to evaporative cooling.  I don’t know how this can be.  If night temps have increased more than day temps then evaporative cooling will have increased more in the night.  I’ve always understood that GW affects night more than day because it only affects outgoing radiation, hence the affect is less pronounced in the day when there is also incoming radiation”

    Two thoughts: 1) Clauisius-Clapeyron is strongly nonlinear so evaporation into warmer air is MUCH more efficient (why do we get dew in the early morning?) 2) Moisture on the ground may absorb solar shortwave energy directly, or through contact with the ground. There isn’t any of that at night.

    2) “seems to be suggesting that higher temps and water content mean more energy hence worse weather.  But this isn’t necessarily true; the atmosphere could come to equilibrium at a high temperature and high water content with enormous energy and there would be no weather at all. ”

    Correct. More energy in the system does not tell us whether weather systems will be more active, never mind more beneficial. It does, of course, tell us that the energy will be distributed in different ways, causing climate to shift, and challenging infrastructure in various places. And we also have to note that the changes are expected to increase in both amplitude and rate.

    Even in practice, some places will see less energetic weather even as the local column energy increases. (This will appear as drought.) This argument that “more energy is bad” is a bit simplistic, because it seems to argue in favor of ice ages. But differing amounts of energy will cause the adjustment processes to change, and this will appear on the ground as wildly varying patterns of weather, challenging local adaptations both natural and artificial.

    3) Agree  a global 10% increase in precipitation is not itself a big deal from a human point of view except perhaps at the outflow of major rivers. The point is that this is a large change climatologically, and will be accompanied by many local disequilibria even if it were evenly distributed in time and space. But there’s no reason to expect that.

    4) Both theory and observations indicate a larger proportion of rainfall in severe events, possibly even a reduction in small events, globally. I’m not in a position to dig up refs at this time but I have seen them. Again, the issue is how these large and accelerating changes play out on the ground.

    The piece I wrote on this topic yesterday makes some relevant points.

    A ten percent increase in local rainfall and a two degree increase in local temperature is not that scary, perhaps, even if it happens everywhere. But that is the most benign conceivable outcome, and it turns out to be one that is not actually physically possible.

  • DeNihilist

    DR Tobis,

    Thank you for talking like a scientist in the above comment. In my personnal opinion, if more of your contributions to this saga where in the above tone, you would reach a lot more people, who like me, want to hear REASONED arguments, devoid of sarcasm, catastrophy, ad homs, etc.

    Your above comment made me pause and re-read it, and to really delve into what you said.

    Again thanks for the chance to “see” your side in a respectful and scientific way.


  • DeNihilist

    Keith, I really think that you should take this little discussion between Dr. Tobis, Grypo and KDK33 aqnd make it a post of its own as an example of what JOE sixcase is looking for.

    For me, this little segment has brought more enlightment about what the real arguments are about in regard to the GW saga, then all the posts from RC and WUWT.

    If the main players in this saga could try and discuss issues the way this bit on the hydro cycle is being discussed, I think that real progress would finally be available to all of us!

    Thanx for the blog Keith, it seems to be slowly bringing some of us together.

  • kdk33

    I’ve just a few moments to remove my honey-do jacket and don my rabid denier frock.  I want to reply to several of the topics, but for now will stick to one:  time constants.

    So, MT or Grypo (or anybody else)…

    It is my understanding that there was a temperature response following the Mount pinatubo eruption (and other volcanoes).  What was the time constant for that event?

    It is my understanding that El nino makes it hot and la nina makes it cold.  What is the time constant for those events?

    What is the time constant for CO2 induced warming?

    If these three are different, why?

  • Michael Tobis

    kdk33, for present purposes, consider the atmosphere as a system. It responds rather quickly to radiative forcing which includes: shortwave energy mostly from the sun,  and longwave energy from the earth, sea ice, land ice and upper ocean, as well as energy exchanges within the atmosphere. Holding the surface fixed and changing the radiative forcing leads to an equilibration time constant on the order of weeks.

    Of the boundary terms, the land surface temperature adjusts quickly, but the sea, sea ice, and land ice respond on decadal, multidecadal, and centennial time scales. Also the upper ocean interacts with the deep ocean on a longer time scale still. So in a volcanic eruption, you get the quick atmospheric response, but generally the dust settles and the atmosphere bounces back before the other systems “feel” the change. (More accurately, the cooling pulse of several months is smeared out in the slower responding systems which greatly attenuates them.) The “human volcano”, though, is persistent. So the slower systems are waking up and starting to respond.


  • kdk33


    Thanks for the reply on time constants; sounds reasonable to me.  Now, regarding the previous…

    1)  Good point, vapor pressure isn’t linear with temperature.  Never-the-less, this evaporative cooling argument is not the one I’ve heard (many times) before and you seem a bit unsure yourself.  Maybe it’s a combination of both; maybe we aren’t totally sure.  I’m leaving this one in the air for now.

    2) I’m not sure you have a coherent point here.  One the one hand you agree that more moisture & absolute energy doesn’t mean worse weather.  On the other hand you suggest it will bring change and then describe those changes as “wildly varying”, “increasing in amplitude and rate”.  I find no justification for this claim.  As I noted, if AGW acts to minimize temperature gradients, that argues against extreme weather.

    3) We agree?  Wow! (though you’re waffling there at the end).

    4)  I’ve yet to see this compelling data, but I’ll read your post (don’t tell any of my friends).

    Lastly, my takeaway from your final comment (and your previous #33) is that you are afraid of runaway, or unprecedented warming – 7 or 9 or 10 degress C.  I also find those number scary, but I think those outcomes are too remote to worry about (but, of course, I have an open mind).

    Might I suggest, that this isn’t what we’re told.  Rather, we’re told that warming, of any kind, any magnitude, will be bad.  Really bad.  Drier where it’s dry, wetter where it’s wet, plagues of locusts. 

    So, if the real fear is runaway warming, maybe we can focus on untangling that hypothesis and spend less time on silly scary stories and attribution claims.

    Thanks for your replies.

  • Nullius in Verba

    “The changes in the pipeline are delayed, and the forcing they respond to are cumulative.”
    Would you be able to expand on that? My understanding was that the climate response was supposed to consist of a quick initial response due to the effective annual-decadal heat capacity of the surface waters with a time constant on the order of 5 years or less, followed by a much slower response on the order of a century or more as the heat transferred to the deeper ocean. And that not much heat had yet entered the deep ocean sink, so if you (hypothetically) returned CO2 to pre-industrial levels instantaneously right now, the temperature would drop to normal (post-LIA?) in about 5-10 years.

    In the alternative case of CO2 ceasing to increase, but staying constant at a higher level, then the build up in the deeper ocean continues for a longer period, leading to a continued rise. I thought this was the “heat in the pipeline”.

    However, you say “but these are the delayed changes we had committed to decades ago”. This suggests you believe the fast response of the surface layers (what we’re seeing) has been delayed by decades – this doesn’t fit with the ~5-year response to forcing that I thought the models indicated. I had also understood that enhanced CO2 forcing only started to be really significant around the 1950s, (the pre-1950 warming being mostly natural post-LIA recovery,) which would mean that for much of the post-1950 warming to be attributed to CO2, a short time constant is indicated.

    Can you clarify? Thanks.

  • kdk33

    Now, to once again don my rabid denier frock…  The following is gleaned from Groisman et al ’03, the link provided by Grypo.  I’d gladly look at other data, and perhaps draw different conclusions.  Of course, everyone is free to challenge my assessment.

    1) Temperature increases in the US result from increases to minimum temps with little effect on maximums.  “a substantial increase in maximums… was only observed in spring”.  So, to the notion that evaporative cooling explains the decrease in night/day temperature ranges in the US: I call BS.

    2) Precipitation.  It was rainy early in the 20th century, drier in the middle, then a return to slightly above start at the end (the authors identify a 5% overall increase, with which I don’t quibble; it cannot be associated with warming).  Of the two driest decades, the 1930’s and 1950’s, one occurred while it was cooling, the other while it was warming.  Precipitation decreased while it was warming (until about 1940, I’m told) then increased slightly while it was cooling (until about 1970, I’m told).  So, to the notion that there is a warming associated increase in US precipitation:  I call BS.

    3) On extreme precipitation events.  There is no trend.  To the notion that there is a warming associated increase in extreme precipitation events in the US:  the authors call BS, so I don’t have to.

    4) On heavy and very heavy precipitation events.  There is no trend, but a spike in these events in the late 1990’s, and a return to normal thereafter (data ends in ’03).  (Yes, the authors identify a trend, but I submit it is dominated by the late “˜90’s spike) There is no trend during early-century warming or mid-century cooling.  To the notion that there is a warming associated increase in heavy or very heavy precipitation events in the US:  I call BS with a caveat.
    Caveat:  The late 90’s spike is interesting.  It could be the start of a trend or a step change, though the return to normal thereafter argues against this.  It could simply be a series of outliers ““ rare events aren’t normally distributed; they are bounded by zero on the low side and unbounded on the high side, so outliers will virtually always be high.  I admit this is an interesting feature, but the only way to know what it means is to wait and see (or find better data).
    5) On drought.  The trend, if any, is a decrease in severe drought.  To the notion that there is a warming associated increase in severe drought in the US: I call BS.
    I find something very disappointing in this paper.  The authors are desperate to show a relationship between precipitation-related measures (call them P) and temperature (call it T).  This could be expressed as P=f(T).  The data should be plotted accordingly: P versus T (they can even be offset in time, to account for “lags in the system”).  But it never is.  Why?  I’m eager to see this data plotted correctly, and perhaps I’ll draw different conclusions (because I am so open-minded).


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Collide-a-Scape is an archived Discover blog. Keep up with Keith's current work at

About Keith Kloor

Keith Kloor is a NYC-based journalist, and an adjunct professor of journalism at New York University. His work has appeared in Slate, Science, Discover, and the Washington Post magazine, among other outlets. From 2000 to 2008, he was a senior editor at Audubon Magazine. In 2008-2009, he was a Fellow at the University of Colorado’s Center for Environmental Journalism, in Boulder, where he studied how a changing environment (including climate change) influenced prehistoric societies in the U.S. Southwest. He covers a wide range of topics, from conservation biology and biotechnology to urban planning and archaeology.


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