January 30, 2012

The Problem with Proxies

Filed under: Droughts, Precipitation

There is a new paper (in press in the journal Geophysical Research Letters) that presents a lesson that we all should keep in mind—results based on reconstructions of climate phenomena that are based on once or twice removed “proxy” indicators, may not be as reliable as they appear (or as they are presented) to be. If this brings hockey sticks and salacious emails to mind, you are not alone.

“Proxies” are putative indicators of climate for which there are no direct measurements. Tree rings, for example, are wider when the summer is wet and not too hot. The actual “explained variance” between them and, say, annual temperature is complex to derive and not all that high. The same is true for most other types of proxies (e.g., corals, ice cores, lake sediments, stalagmites, boreholes, etc.). Therefore, the uncertainties in using proxies to “reconstruct” some aspect of the climate are typically large (certainly larger than typically portrayed) and making (robust) conclusions from such analyses becomes a bit tricky. Such problems are among the reasons that many people jumped all over Michael Mann’s infamous “hockey stick” reconstruction of climate, which claims to accurately represent annual temperatures on a year-to-year basis back some 1000 years. Lesson: be very careful with proxy climate data.

Today’s example involves wildfire occurrence in the western U.S., and the climate patterns that may influence it.

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January 20, 2012

The Changing Influence of Time

Filed under: Climate Changes

Since anyone first heard of global warming, we have been told that a warmer world would result in higher moisture levels in the atmosphere, and intensification of the hydrological cycle, and any number of negative consequences could result (e.g., more floods, more intense storms). A warmer world would almost surely mean more evapotranspiration (ET) – hard to disagree on that front.

Well, in the real warmer world, it appears that things aren’t that straightforward (but what’s new about that!).

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January 17, 2012

A Response to Skeptical Science’s “Patrick Michaels: Serial Deleter of Inconvenient Data”

Filed under: Climate Politics

by Patrick Michaels

When the battle is being lost, there is a tendency to try to raise a level of distraction to shift the attention away from the desperate situation at hand. Such is the noise being raised concerning my presentation of the results from a recent series of scientific findings and observations—that lend further support to notion of modest climate change. The apocalyptics and the gloom-and-doom crowd are losing both the science battle and the policy war.

Dana Nuccitelli (aka dana1981) over at the website Skeptical Science has recently written a screed purporting that I delete “inconvenient” data in order to make my points. In fact, what I have done is to highlight the major findings of the studies I have commented on—findings that have indeed strengthened the case that global warming in this century will be in the lower end of the range of projections issued by the United Nations’ Intergovernmental Panel on Climate Change.

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January 10, 2012

Will Replicated Global Warming Science Make Mann Go Ape?

About 10 years ago, December 20, 2002 to be exact, we published a paper titled “Revised 21st century temperature projections” in the journal Climate Research. We concluded:

Temperature projections for the 21st century made in the Third Assessment Report (TAR) of the United Nations Intergovernmental Panel on Climate Change (IPCC) indicate a rise of 1.4 to 5.8°C for 1990–2100. However, several independent lines of evidence suggest that the projections at the upper end of this range are not well supported…. The constancy of these somewhat independent results encourages us to conclude that 21st century warming will be modest and near the low end of the IPCC TAR projections.

We examined several different avenues of determining the likely amount of global warming to come over the 21st century. One was an adjustment to climate models based on (then) new research appearing in the peer-reviewed journals that related to the strength of the carbon cycle feedbacks (less than previously determined), the warming effect of black carbon aerosols (greater than previously determined), and the magnitude of the climate sensitivity (lower than previous estimates). Another was an adjustment (downward) to the rate of the future build-up of atmospheric carbon dioxide that was guided by the character of the observed atmospheric CO2 increase (which had flattened out during the previous 25 years). And our third estimate of future warming was the most comprehensive, as it used the observed character of global temperature increase—an integrator of all processes acting upon it—to guide an adjustment to the temperature projections produced by a collection of climate models. All three avenues that we pursued led to somewhat similar estimates for the end-of- the-century temperature rise. Here is how we described our findings in paper’s Abstract:

Since the publication of the TAR, several findings have appeared in the scientific literature that challenge many of the assumptions that generated the TAR temperature range. Incorporating new findings on the radiative forcing of black carbon (BC) aerosols, the magnitude of the climate sensitivity, and the strength of the climate/carbon cycle feedbacks into a simple upwelling diffusion/energy balance model similar to the one that was used in the TAR, we find that the range of projected warming for the 1990–2100 period is reduced to 1.1–2.8°C. When we adjust the TAR emissions scenarios to include an atmospheric CO2 pathway that is based upon observed CO2 increases during the past 25 yr, we find a warming range of 1.5–2.6°C prior to the adjustments for the new findings. Factoring in these findings along with the adjusted CO2 pathway reduces the range to 1.0–1.6°C. And thirdly, a simple empirical adjustment to the average of a large family of models, based upon observed changes in temperature, yields a warming range of 1.3–3.0°C, with a central value of 1.9°C.

We thus concluded:

Our adjustments of the projected temperature trends for the 21st century all produce warming trends that cluster in the lower portion of the IPCC TAR range. Together, they result in a range of warming from 1990 to 2100 of 1.0 to 3.0°C, with a central value that averages 1.8°C across our analyses.

Little did we know at the time, but behind the scenes, our paper, the review process that resulted in its publication, the editor in charge of our submission, and the journal itself, were being derided by the sleazy crowd that revealed themselves in the notorious “Climategate” emails, first released in November, 2009. In fact, the publication of our paper was to serve as one of the central pillars that this goon squad used to attack on the integrity of the journal Climate Research and one of its editors, Chris de Freitas.

The initial complaint about our paper was raised back in 2003 shortly after its publication by Tom Wigley, of the US National Center for Atmospheric Research and University of Toronto’s L. D. Danny Harvey, who served as supposedly “anonymous” reviewers of the paper and who apparently had a less than favorable opinion about our work that they weren’t shy about spreading around. According to Australian climate scientist Barrie Pittock:

I heard second hand that Tom Wigley was very annoyed about a paper which gave very low projections of future warmings (I forget which paper, but it was in a recent issue [of Climate Research]) got through despite strong criticism from him as a reviewer.

So much for being anonymous.

The nature of Wigley and Harvey’s dissatisfaction was later made clear in a letter they sent to Chris de Freitas (the editor at Climate Research who oversaw our submission) and demanded to know the details of the review process that led to the publication of our paper over their recommendation for its rejection. Here is an excerpt from that letter:

Your decision that a paper judged totally unacceptable for publication should not require re-review is unprecedented in our experience. We therefore request that you forward to us copies of the authors responses to our criticisms, together with: (1) your reason for not sending these responses or the revised manuscript to us; (2) an explanation for your judgment that the revised paper should be published in the absence of our re-review; and (3) your reason for failing to follow accepted editorial procedures.

Wigley asked Harvey to distribute a copy of their letter of inquiry/complaint to a large number of individuals who were organizing some type of punitive action against Climate Research for publishing what they considered to be “bad” papers. Apparently, Dr. de Freitas responded to Wigley and Harvey’s demands with the following perfectly reasonable explanation:

The [Michaels et al. manuscript] was reviewed initially by five referees. … The other three referees, all reputable atmospheric scientists, agreed it should be published subject to minor revision. Even then I used a sixth person to help me decide. I took his advice and that of the three other referees and sent the [manuscript] back for revision. It was later accepted for publication. The refereeing process was more rigorous than usual.

This did little to appease to those wanting to discredit Climate Research (and prevent the publication of “skeptic” research) as evidenced by this email from Mike Mann to Tom Wigley and a long list of other influential climate scientists:

Dear Tom et al,

Thanks for comments–I see we’ve built up an impressive distribution list here!

Much like a server which has been compromised as a launching point for computer viruses, I fear that “Climate Research” has become a hopelessly compromised vehicle in the skeptics’ (can we find a better word?) disinformation campaign, and some of the discussion that I’ve seen (e.g. a potential threat of mass resignation among the legitimate members of the CR editorial board) seems, in my opinion, to have some potential merit.

This should be justified not on the basis of the publication of science we may not like of course, but based on the evidence (e.g. as provided by Tom and Danny Harvey and I’m sure there is much more) that a legitimate peer-review process has not been followed by at least one particular editor.

Mann went on to add “it was easy to make sure that the worst papers, perhaps including certain ones Tom refers to, didn’t see the light of the day at J. Climate.” This was because Mann was serving as an editor of the Journal of Climate and was indicating that he could control the content of accepted papers. But since Climate Research was beyond their direct control, it required a different route to content control. Thus pressure was brought to bear on the editors as well as on the publisher of the journal. And, they were willing to make things personal. For a more complete telling of the type and timeline of the pressure brought upon Chris de Freitas and Climate Research see this story put together from the Climategate emails by Anthony Watts over at Watts Up With That.

Now, let’s turn the wheels of time ahead 10 years, to January 10, 2012. Just published in the journal Geophysical Research Letters is a paper with this provocative title: “Improved constraints in 21st century warming derived using 160 years of temperature observations” by Nathan Gillett and colleagues from the Canadian Centre for Climate Modelling and Analysis of Environment Canada (not a group that anyone would confuse with the usual skeptics). An excerpt from the paper’s abstract provides the gist of the analysis:

Projections of 21st century warming may be derived by using regression-based methods to scale a model’s projected warming up or down according to whether it under- or over-predicts the response to anthropogenic forcings over the historical period. Here we apply such a method using near surface air temperature observations over the 1851–2010 period, historical simulations of the response to changing greenhouse gases, aerosols and natural forcings, and simulations of future climate change under the Representative Concentration Pathways from the second generation Canadian Earth System Model (CanESM2).

Or, to put it another way, Gillett et al. used the observed character of global temperature increase—an integrator of all processes acting upon it—to guide an adjustment to the temperature projections produced by a climate model. Sounds familiar!!

And what did they find? From the Abstract of Gillett et al.:

Our analysis also leads to a relatively low and tightly-constrained estimate of Transient Climate Response of 1.3–1.8°C, and relatively low projections of 21st-century warming under the Representative Concentration Pathways.

The Transient Climate Response is the temperature rise at the time of the doubling of the atmospheric CO2 concentration, which will most likely occur sometime in the latter decades of this century. Which means that results of Gillett et al. are in direct accordance with the results of Michaels et al. published 10 years prior and which played a central role in precipitating the wrath of the Climategate scientists upon us, Chris de Freitas and Climate Research.

Both the Gillett et al. (2012) and the Michaels et al. (2002) studies show that climate models are over-predicting the amount of warming that is a result of human changes to the constituents of the atmosphere, and that when they are constrained to conform to actual observations of the earth’s temperature progression, the models project much less future warming (Figure 1).


Figure 1. Dashed lines show the projected course of 21st century global temperature rise as projected by the latest version (CanESM2) of the Canadian coupled ocean‐atmosphere climate model for three different future emission scenarios (RCPs). Colored bars represent the range of model projections when constrained by past 160 years of observations. All uncertainty ranges are 5–95%. (figure adapted from Gillet et al., 2012: note the original figure included additional data not relevant to this discussion).

And a final word of advice to whoever was the editor at GRL that was responsible for overseeing the Gillett et al. publication—watch your back.

References:

Gillett, N.P., et al., 2012. Improved constraints on 21st-century warming derived using 160 years of temperature observations. Geophysical Research Letters, 39, L01704, doi:10.1029/2011GL050226.

Michaels, P.J., et al., 2002. Revised 21st century temperature projections. Climate Research, 23, 1-9.

[01/11/12: This post has been updated to correct the spelling of Gillett.]




January 3, 2012

Antarctic Temperature Trends

Filed under: Antarctic, Climate Changes, Polar

Almost exactly two three years ago, a prominent paper became a media darling as it, according to the alarmist website Real Climate “appeared to reverse the ‘Antarctic cooling’ meme that has been a staple of disinformation efforts for a while now.”

The Nature paper, by Eric Steig and colleagues, made the cover on the January 22, 2009 issue.


Figure 1. Cover of January 22, 2009 issue of Nature magazine (left) showing the map of temperature trends across Antarctica as determined by the analysis of Steig et al. (right).

Despite Real Climate’s predictable take on the situation, many long-time students of Antarctic climate change (including usn’s here at WCR) yawned. It has been known for decades that there is a net warming in Antarctic surface temperature that began during the International Geophysical Year in 1957. However, what is also well known, is that the vast majority of the observed warming in Antarctica took place from the late 1950s through the early 1970s and that since then—during a period going on 40 years now—there has been very little net temperature change over Antarctica taken as a whole.

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