Some of you may have heard about the “ICCC-6″ conference, sponsored by the so-called “Heartland Institute,” that will take place this Thursday and part of Friday in Washington D.C. It’s the best-known meeting of those who call themselves “skeptics” about global warming.
I suspect they’re not really skeptics at all. Why do I think that, you wonder? Can we talk?.
I’ve often discussed Arctic sea ice, and specifically mentioned that it’s one of the strongest evidences of global warming. All by itself it’s not absolute proof, but as evidence goes it’s strong. Very strong. It’s also an excellent litmus test to separate real skeptics from fake ones.
When I heard that the next incarnation of the Heartland Institute’s anti-climate conference was about to take place, I wondered — are they really skeptical? I decided to apply the aforementioned litmus test by finding out what their last major report (the most recent one I found was from 2009) had to say about Arctic sea ice. The report is titled Climate Change Reconsidered: The 2009 Report of the Nongovernmental International Panel on Climate Change; in brief it’s the NIPCC report. The Heartland Institute will gladly sell you a paper copy for a mere $123.00 — but if you must see it, I suggest you “Click the image to download the full text in PDF format” and get it for free.
Chapter 4 is “Observations: Glaciers, Sea Ice, Precipitation, and Sea Level.” Section 4.2 is “Sea Ice.” They finally get to the litmus-test subject in subsection 4.2.2, “Arctic.”
The first sentence emphasizes uncertainty in general, albeit innocuously enough:
Arctic climate is incredibly complex, varying simultaneously on a number of different timescales for a number of different reasons (Venegas and Mysak, 2000).
The second sentence shows their true colors:
Against this backdrop of multiple causation and timeframe variability, it is difficult to identify a change in either the extent or thickness of Arctic sea ice that could be attributed to the increase in temperature that has been predicted to result from the burning of fossil fuels.
That settles it. The authors of this report are fake skeptics.
It’s not difficult. It’s easy — so easy a child could do it — to identify a change in either the extent or thickness of Arctic sea ice that could be attributed to the temperature increase in the Arctic. Seriously. Read this. And this. And this and this and this and this.
After you do, you might still be skeptical about global warming — it’s possible. But unless you say, “OK, Arctic sea ice is damn powerful evidence but what about this other thing?” you’re not a skeptic. At least, not a real one. If you want to dispute other things maybe we can talk — but those who claim that what’s happened to sea ice in the Arctic is not strong evidence of global warming, are not skeptics. They’re in denial.
Identifying a change in Arctic sea ice extent that can be attributed to temperature is as easy as looking at this graph:
But the NIPCC report staunchly refuses to consider the graph of sea ice extent or show it to their readers. Think about that. The whole point of subsection 4.2.2 is to discuss Arctic sea ice extent and thickness, but at no point does the NIPCC report show a graph of either.
What then do they say about Arctic sea ice? They begin with this:
Johannessen et al. (1999) analyzed Arctic sea ice extent over the period 1978-1998 and found it to have decreased by about 14 percent. This finding led them to suggest that “the balance of evidence,” as small as it then was, indicates “an ice cover in transition,” and that “if this apparent transformation continues, it may lead to a markedly different ice regime in the Arctic,” as was also suggested by Vinnikov et al. (1999).
Reading Johannessen et al.’s assessment of the situation, one is left with the impression that a relatively consistent and persistent reduction in the area of Arctic sea ice is in progress. However, and according to their own data, that assessment is highly debatable and possibly false. In viewing their plots of sea ice area, for example, it is readily evident that the decline in this parameter did not occur smoothly over the 20-year period of study. In fact, essentially all of the drop it experienced occurred abruptly over a single period of not more than three years (87/88-90/91) and possibly only one year (89/90-90/91). Furthermore, it could be argued from their data that from 1990/91 onward, sea ice area in the Arctic may have actually increased.
I can’t help but wonder why the NIPCC report published in 2009 starts its essay on Arctic sea ice with Johannessen et al. 1999 (Satellite evidence for an Arctic sea ice cover in transformation, Science, 286, 1937-1939). A lot happened in the intervening 10 years.
Here’s the graph of both wintertime multi-year sea ice area, and ice thickness, from Johannessen et al. 1999 (diamonds are ice thickness, squares are ice area):
I digitized this graph to get their wintertime multi-year ice area estimates:
I’ve added a trend line estimated by linear regression, which confirms the claim by Johannessen et al. that these data indicate decrease at a rate of 31 thousand km^2 per year. More to the point: the result is statistically significant. Strongly so. It’s not just due to noise, to random fluctuations from year to year. It’s a real trend.
If we estimate the trend using linear regression for the later period mentioned by the NIPCC report, it seems to be going in the other direction:
Problem is, the trend using just this small subset of data (a mere 8 years) is not statistically significant. Not even close. It’s just a false impression created by the noise, the random fluctuations from year to year. It’s a fake trend.
Johannessen et al. reported a decline in Arctic sea ice based on a real trend estimated by statistical analysis of all the available data. The NIPCC report disputes that by suggesting a fake trend, based on no analysis at all other than “viewing their plots” and “it could be argued,” using only the last 8 years of data. What a coincidence that they chose a very low value as their starting point. Come to think of it, not a coincidence at all.
A lot has happened in the intervening 10 years. Johannessen et al. point out that wintertime multi-year ice closely follows the minimum overall ice area during the preceding summer. This is clear by plotting their estimates of wintertime multi-year ice, offset by 1.3 million km^2, alongside the summer minimum ice area:
If we estimate the trend in summer minimum Arctic ice area for the time period studied in Johannessen et al. we get a decline which is statistically significant — a real trend:
If we estimate the trend for just the 8 years used by the NIPCC report we get an incline which is not statistically significant — a fake trend:
Which trend gives a better indication of what was to follow? That’s easy to answer — just add the data up to the present:
The decline was real. The incline was fake.
The NIPCC report doesn’t show the actual data. It doesn’t consider data up to the present. Instead it suggests a fake trend based on 8 years of data using a cherry-picked starting point, to imply that the decline of Arctic sea ice isn’t real. I conclude that it’s the “skepticism” of the authors of the NIPCC report that isn’t real. It’s fake.