Response From Dr. Desai On Wisconsin Temperature Trends

Marc Morano forwarded my post Lies, Damned Lies And Statistics to Dr. Desai at the University of Wisconsin. Below is his response.
————————————————————————————————-
From: Ankur Desai
Sent: Wednesday, April 13, 2011 12:54 PM
To: Marc Morano
Subject: Re: Your claims challenged on temp trend…Lies, Damned Lies And Statistics | Real Science
Marc,
I apologize for the delay in response, and perhaps my reply is old news by now, but I hope I can still have something useful to say.
As a caveat, allow me to first note that I answered the reporter’s questions using numbers provided by the Wisconsin Initiative on Climate Change Impacts (http://www.wicci.wisc.edu ) and produced by a detailed analysis of temperature station trends by graduate student Shawn Serbin (Forest and Wildlife Ecology) and Profs. Chris Kucharik (Agronomy Dept) and Dan Vimont (Atmospheric Science). My own research focuses more on understanding how ecosystems respond to climate variability (and vice versa) and I answered the reporter’s question since I happened to be around and as a climate scientist, am well versed in much of this research.
If you’d like I’d be happy to get you a copy of their paper – Serbin, S.P. and C.J. Kucharik, (2009). Spatio-temporal mapping of temperature and precipitation for the development of a multi-decadal climate dataset for Wisconsin. J. Applied Meteorology and Climatology, Vol. 48, 742-757.
So that’s not a cop-out, but just a note that while I support the claims made by WICCI based on my own understanding of temperature trends regionally and globally, that I did not directly produce this analysis and so would need more time to try replicating some of the trends reported in the blog. If you think that would be worthwhile, I could attempt to do so, but it will have to be in several weeks as the end of the semester tends to be a pretty busy time.
My short answer is that – yes indeed it is possible to “cherry-pick” trends and find time periods of a decade or two that stand in contrast to longer-term trends (and vice versa, trends greater than the long-term trend). Natural climate variability on the scale of a decade is well observed and even modeled reliably (in magnitude if not in exact timing given the random nature of much of how these variations are initiated) and reflects a variety of process such as changes in ocean mixing and atmospheric pressure patterns, even fluctuations in solar output. That said, models and observations agree that with continued forcing on the climate system (from any cause), trends become apparent once you average out past a couple of decades (i.e., over several cycles of natural internal variability). A recent paper ran a climate model, for example, over I think a thousand years with continually increased forcing (an unrealistic scenario, but more of a test of the model), and the model never goes more than a decade or so out with significant periods of no temperature increase or cooling.

Indeed, it is also true that the 1930s (Dust Bowl) was above normal, and possibly even similar in temperatures to today for Wisconsin. There is good evidence to support a anomaly in Pacific Ocean temperatures during that time period that shifted regions of high pressure, which was further exacerbated by the large-scale expansion of agriculture occurring at that time. I can send you a paper about that if you’re interested (Cook et al., 2009, Proc. Nat. Acad. Sci.). That said, as Pacific ocean waters cooled, the warm temperatures and dry conditions in the Great Plains receded.
Also, even with a warmer mean temperature, cold, even exceptionally cold seasons can occur. They just do so with lower probability. Gerry Meehl, a scientist at the National Center for Atmospheric Research, has shown quite nicely for example that the ratio of record highs set to record lows set has moved from 1:1 to about 2:1 over the past 50 years, even when correcting for the decrease in total number of highs and lows that would naturally occur with time and changes in number of stations. See: http://www2.ucar.edu/news/1036/record-high-temperatures-far-outpace-record-lows-across-us
Here’s an analogy that might make more sense (but one I just made up, so bear with me if it’s not perfect): Imagine a bathtub being filled with water. With time the level of water will rise. Now imagine we put a excited toddler (not a bad description of the climate system) on the other end who splashes about and causes waves to form back and forth. The level over any area of the tub goes up and down, but eventually goes up. The splashing also removes some of the water and over short time, may actually cause the water level to fall, but if the splashing is not inordinately violent and the spigot is open wide enough, the water level will rise. Certainly we can debate the ratio between the spigot and the splashing intensity!
The climate system is even more fascinating. There is some evidence that the exceptionally cold winters in the eastern U.S. this winter were triggered by a shift in the Atlantic pressure patterns caused by an unusually warm and open (less ice) Arctic. Indeed, while it was a cold winter (3-6 C below average winter) for many populated regions of the Northern Hemisphere (Europe and eastern North America), it was exceptionally warm further north (they were up to 21 C above average in northern Canada !).
Some sources for this last claim:
Our climate system never ceases to fascinate me and it’s nice, despite the regrettable rancor from many people (us scientists included) on the climate policy debate, that we have the resources and general interest from everyone to explore this system that sustains us!
So the short answer is that it is not trivial to define the averaging period (in time or space) for a trend. That said, once you get beyond 30-years, the trend becomes more about forcings (such as greenhouse gases or aerosols or solar variation) and less about internal variability.
As a final point, I should also note that in the short newspaper article, I did not ascribe a singular cause to the regional temperature trend in Wisconsin, but rather noted that it is quite similar to global trends; I believe above those trends for winter. I am perfectly willing to accept that the temperature trends in Wisconsin from 1950 are a mixture of local weather variability, land use change, changes in storm tracks as well as anthropogenic change, but the science is pretty strong that the global trends are mostly a response of increasing greenhouse gases (modulated by increasing aerosols) and so it doesn’t surprise me that those trends can be seen on smaller scales, too.
Now how these trends continue in the future, whether these trends are a cause for concern for humans or ecosystems, and whether mitigation policies would have an influence or are worth the cost are other worthwhile debates to have, but not the point of the specific question asked by the reporter or the issues brought up by the blog.
I hope this reply helps a bit and you are welcome to share it with others. I am happy to answer more questions (as long as you give me enough time 🙂 ). If you ever have specific questions especially related to issues around the carbon cycling, land ecosystem responses to climate variation, and how vegetation influences climate, please feel free to contact me.
Sincerely,
Ankur R Desai
Asst. Professor, Atmospheric & Oceanic Sciences Dept.
Faculty affiliate, Center for Climatic Research, Nelson Institute for Environmental Studies
University of Wisconsin – Madison
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19 Responses to Response From Dr. Desai On Wisconsin Temperature Trends

  1. stan says:

    He thinks the models are the truth. Sad.

  2. Joe friday says:

    What a crock of mush…. here’s a link from a Canadian newspaper that gives a different spin ….http://www.calgaryherald.com/technology/
    Getting+chilly/4592589/story.html

  3. Paul H says:

    He conveniently misses the point.

    While there may be a lot of sense in what he says, the criticism is that he (deliberately or not) used a set of clearly misleading statistics to promote a global warming agenda.

    An objective scientist would have said something like ” Temperatures are higher now than in the 70’s. However compared to temperatures earlier in the 20thC it is clear that the 70’s could be the exception. Furthermore, although there was a step up in the 80’s, temperatures have remained stable since and indeed may be dropping.

    We can theorise about the reasons for this trend, but really don’t understand them yet”

    Not difficult is it?

    The failure to say this and then to deliberately sidestep criticism suggests his objectivity is suspect.

  4. suyts says:

    Wow, that was an incredibly lengthy non-answer.
    So, now we’re going “beyond 30 years” for a trend, but not to the nearly 100 year flat-line? I’m glad he acknowledges that it is possible to “cherry-pick” trends.

    You see, the last ten years was like a kid playing in the bath-tub, so its ok to characterize the Wisconsin winters as warming even though it hasn’t over the last decade. Its getting darker because 20 hours ago the sun was diminishing from view and 12 hours ago I couldn’t see the sun altogether!! So, it must be getting darker! The sun rising was just a kid playing in a bath-tub and not part of the darkness trend.

    The tone and tenor of the response was nice enough though. It could be nice to have a vegetation expert around for some of the other ridiculous alarmist claims.

  5. Baa Humbug says:

    Desai correctly states that it is possible to cherry pick, then proceeds to cite a paper by Meehl et al accomplished cherry pickers.
    Desai calls himself a climate scientist, then repeats the meme that averaging past a couple of decades is enough to filter out natural variability such as solar cycles and ocean circulations. So there are no ocean cycles greater than a couple of decades, so we know enough about solar and planetary cycles to claim none are longer than a couple of decades? We can deduce from that that ice ages must come and go within a couple of decades. Milankovitch was an exaggerator.

    I am now convinced that we did smoke too much weed in the 60’s and 70’s. the students of the time who are the proffessors of today are lazy indeed.

  6. Al Gored says:

    What a clever weasel.

    “As a caveat, allow me to first note that I answered the reporter’s questions using numbers provided by the Wisconsin Initiative on Climate Change Impacts… ”

    In other words, “I was just parroting propaganda.” Give this man a job with the IPCC!

  7. PJB says:

    Certainly the poster child for climate-weaseling. It was only missing the key words; likely, seems, might etc. adroitly placed to negate the certitude of statements made. Indicative of someone that intends on keeping the grants flowing, regardless of what the results might show, before massaging.

  8. Andy Weiss says:

    It at least sounds like he was trying to be a gentleman, even if the science is dubious.

  9. omnologos says:

    There isn’t much of “gentlemanly” in Prof Desai’s response. He’s trying to keep the Moranos of this world at bay, burying them in irrelevant wordfalls. We have a word in Italian about it, it’s to be an Azzeccagarbugli, a Guess-disentangler, like a pettifogging lawyer that machine-guns witnesses, the judge and the jury with a large number of unimportant but grand-sounding quotes from past laws, or in Latin.

    The original point was very simple: Winters seem to be getting a whole lot warmer. Steven showed how that is not the case, according to NCDC, unless you only go back from now to three very cold winters in the late 1970s and no more.

    And so:

    Serbin, S.P. and C.J. Kucharik, (2009). Spatio-temporal mapping of temperature and precipitation: irrelevant. The abstract is here and there is not a pip about winter temperatures being on the increase (if there is, somebody should be fired at NCDC)

    trends become apparent once you average out past a couple of decades: irrelevant

    it is also true that the 1930s (Dust Bowl) was above normal: irrelevant

    even with a warmer mean temperature, cold, even exceptionally cold seasons can occur: irrelevant

    excited toddler: irrelevant

    And so on and so forth.

    once you get beyond 30-years, the trend becomes more about forcings: that is, given NCDC, forcings are averaging to zero change in winter temperatures in Wisconsin

    ——–

    Therefore the only logical reply to busy Prof Desai is to ask him a very short question: on what basis can anybody claim that in Wisconsin, winters seem to be getting a whole lot warmer? One doesn’t need to wait to the end of the semester to answer it.

    And without an answer, the rest of the interview is unfettered rubbish.

    • suyts says:

      I like the way you said it better than the way I tried.

      The fact is, winters in Wisconsin are not getting warmer. Neither is the earth in general. It hasn’t for almost 13 1/2 years. All blathering about a warming earth causing floods or droughts or anything else in the last few years simply denies reality. Any explanation about a warming earth = more snow is simply an utter falsehood.

      http://suyts.wordpress.com/2011/04/12/rss-going-negative/#more-38

  10. omnologos says:

    a comment of mine is in moderation (two links!) and there is a badly-closed italic markup. Oops!!

  11. Justa Joe says:

    Doc Desia should have said, he was just following orders.

  12. openmindedscientist says:

    All, please see (http://bellwether.metapress.com/content/a52767u506x4w629/?p=c9a8b10c7c0c4f1d82c3362b310112db&pi=0) for a description of the temperature and precipitation (arguably the most important) changes in Wisconsin from 1950 – 2006. You can also see (http://iopscience.iop.org/1748-9326/3/3/034003) which discuss the impacts on agriculture over this time period.

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