BRATTLEBORO — Sometimes I wonder about myself. I'm 58 years old, and I've certainly had people peeved at me. But I'm not sure I've ever made anyone seriously, existentially PO'd at me.
Maybe it's time.
Since reading “Decoding the warmist agenda,” by Les Kozaczek [The Commons, July 9] I've been torn between my usual aversion to conflict and my temptation to offer a rebuttal.
To do so, after all, might reveal me as an actual, published researcher in the history of the Earth's climate and currently a teacher of the subject and possibly (gasps of horror, please) an intellectual.
Nonetheless, I found the abovementioned piece so ill-informed and so full of gratuitous vitriol that I can't resist responding.
I'll try to shed more light than heat on the subject of global warming, climate change, or whatever catchy phrase one prefers. This will include as many specific references as I can fit, so the reader can judge the original information independently.
Since I don't have space to adequately address all of Mr. Kozaczek's assertions, I'll focus on those areas closest to my personal expertise:
1. Is there credible, or even compelling, evidence that the Earth's climate is getting warmer?
2. If so, why is human-produced carbon dioxide identified as at least a major cause?
3. With all that contradictory information out there, how does one decide what to trust?
4. How does science address this sort of an issue?
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Is the world warming? According to a recent analysis by NASA, 2009 was barely behind 2005 as the warmest year on record; also in a virtual tie were 1998, 2002, 2003, 2006, and 2007. That same analysis concluded that 2009 was the warmest on record in the southern hemisphere.
Direct measurements go back only about 150 years for most locations, which admittedly is a sliver of the geologic record. I think that's pretty important, especially since natural changes in the Earth's orbit should have had the climate cooling for the last several thousand years.
Mr. Kozaczek is correct that there's been a marked increase in the carbon-dioxide (CO2) concentration in the atmosphere since the start of the Industrial Revolution, around 1750. Ice cores (vertical cylinders recovered by coring into the glaciers and ice sheets) from Antarctica show that, before then, the CO2 concentration had never exceeded 300 parts per million (ppm) over the last 800,000 years.
Since the first direct measurements of atmospheric CO2 were made in 1958, that value has risen from about 318 ppm to just over 390 ppm. That's about a 22-percent increase in less than 60 years and a 26-percent increase over the highest values measured before 1750.
Now, CO2 isn't the only greenhouse gas so that doesn't mean the overall warming should be 26 percent, but other greenhouse gases like methane and nitrogen oxides have also increased markedly in the last 260 years.
By contrast, our best evidence is that the sun's output has increased since 1700 from approximately 1,365 Watts per meter squared (W/m²) to 1,366 W/m² (Brittanica.com; also IPCC Fourth Assessment, fig. 2.17). Yes, that's less than 0.1 percent. It is extremely difficult to figure a way for such a small increase in solar output to measurably warm our climate.
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Now, let's consider sources.
Mr. Kozaczek is clearly unimpressed by the Intergovernmental Panel on Climate Change (IPCC). I have my own misgivings about large, bureaucratized organizations. And the IPCC is certainly a convenient whipping boy for skeptics.
It is not, however, the be-all and end-all of source material on global warming. The IPCC, as stated on its website, does no original research; it is instead a clearinghouse and a public face. The real data that demonstrate global warming come from thousands of research papers over the past many decades by thousands of research scientists from around the world.
In fact, the first calculation that more CO2 in the atmosphere should mean a warmer climate was published in 1896. And as a grad student, I was introduced to the topic in the winter of 1979, over a decade before the IPCC came into existence in December 1989.
The “conundrum” of a possible pause in global warming cited by Mr. Kozaczek also gives me an opening to discuss some basic rules on data analysis.
It's absolutely true that not every year has been warmer than the last, according to either atmospheric or oceanic readings. No one that I know of expects that.
Our climate system involves a number of phenomena like El Niño which alter the climate balance for a year or two, and others with less catchy names like the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). These can cause short-term warming or cooling that can obscure the overall trend.
Such variations make it essential to distinguish between the “signal” and the “noise.” These terms will make sense to anyone who's ever tuned an analog radio. The transmission that you're trying to listen to is the signal. The static due to interference or distance or being slightly off the frequency is the noise.
We use the same ideas when assessing trends. It's essential to focus on the signal and not be distracted by the noise. We need to pay attention only to trends long enough to remove the effect of phenomena like the PDO and the AMO.
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I've spent a good deal of time examining the literature to decide just how short a time period I'd be willing to trust. I come out with a minimum of 25 to 30 years. This would include the period from 1975 to 2009 examined by Dr. Phil Jones of the University of East Anglia, but not the period from 1995 to 2009. It's simply too short, and thus too subject to error caused by noise.
By the way, a glance at a BBC interview with Dr. Jones on Feb. 13 will show him saying, “I'm 100 percent confident that the climate has warmed.” He also states, “Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods,” when discussing the period from 1995 to 2009.
This is a fundamental principle of data analysis. We can only accept a conclusion if it passes rigorous, statistical tests. Does the period since 1995 show that the climate isn't warming, or merely that we can't be statistically sure that it is?
As I read Dr. Jones' interview, his conclusion sure seems to be the latter one. This also means that, however hideously hot I've found this summer so far, I can't cite that by itself as evidence of climatic warming any more than a skeptic can legitimately claim that a cold spell of a few months or even a few years in one region proves it isn't happening.
It is true that until the 1970s, many climate researchers thought our climate should be cooling. This was due in part to those orbital changes I mentioned earlier.
Records from ice cores started to be widely studied around the mid-1970s; these allowed the first measurements of atmospheric CO2 for centuries and millennia in the past. These new studies were revolutionary. They measured modern CO2 concentrations way above the natural cycles and going even higher.
In short, they were a dominant reason why we began to think the Earth might actually be warming due to man's releasing of huge quantities of CO2 into the atmosphere.
Note the irony here: Many skeptics of global warming accuse us of waffling because we no longer think the climate might be cooling, and then call us “true believers” when we now stick to our guns.
Pretty neat, huh? We're wishy-washy when we change our minds and acting on “blind faith” when we don't. But that's exactly how science is supposed to work.
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I'm not claiming all scientists are saints. They're not. But my experience is that science is far better at unraveling the mysteries of the physical world than any other angle of attack. That includes the output of talk-show hosts and advocacy groups, on whichever end of whichever political or environmental spectrum.
Since I view any such information as suspicious, I have included none in this piece. Even where I cited the IPCC, I included a corroborating source.
As a scientist, then, I should be ready to change my mind about any scientific subject, in the face of strong evidence that I should. I try my best to meet that standard. On the whole, my experience is that my colleagues do, too.
I hope that I'd have the integrity to change my mind if I saw real evidence that global warming was not happening, or that man was not the primary cause. To date, however, I have not seen that evidence.