Last summer we examined some first-class misinformation about global warming from the “Heartland Institute,” namely their NIPCC report. We showed that their fake take on Arctic sea ice revealed that they’re not real skeptics, they’re fake skeptics.



There’s an update to that report (full version here), in which they’ve modified their discussion of the state of Arctic sea ice. Mostly they’ve eliminated it. Except for some vague generalities which don’t amount to a hill of beans, the closest they come to discussing northern hemisphere sea ice is to talk about ice conditions in Hudson Bay and on the Great Lakes — which together constitute a tiny fraction of ice-covered waters in the northern hemisphere. But Arctic sea ice is one of the most important, and most obvious, evidences of climate change, so why would you issue a 416-page report on the state of the climate but say almost nothing, and certainly nothing substantive, about Arctic sea ice?

It surprised me (and it takes a lot for the “Heartland Institute” to surprise me) how blatantly they misrepresented the changes in Great Lakes ice cover. They only reference one paper (Wang et al. 2010, Severe ice cover on Great Lakes during winter 2008-2009, EOS, Transactions, American Geophysical Union 91: 41–42), which discusses factors influencing the extensive ice cover during the 2008-2009 season. These factors include ENSO (el Nino southern oscillation) and AO (Arctic oscillation), and they demonstrate interesting facets of the interplay of these teleconnections with the year-to-year ice cover fluctuations. It’s worth noting that although the 2008-2009 season witnessed extensive ice cover, its maximum value was not the greatest on record (since the 1972-1973 season), only 5th-largest.

The paper only briefly mentions the trend in Great Lakes ice cover, saying



Previous studies show that Great Lakes ice cover had a significant downward trend,about -1% per year, for the period between the onset of winter in 1972 and the end of winter in 2001. Nevertheless, during the entire period of the winters of 1972-1973 to 2008-2009 (Figure Ib), the downward trend disappears or even reverses. This indicates that (I) natural variability dominates Great Lakes ice cover and (2) the trend is only useful for the period studied.



Their figure 1b shows annual maximum ice cover (filled circles), annual average ice cover (open circles), and winter-season average surface air temperature (red open squares):

The NIPCC report gives a modified version of their figure

It further draws this conclusion:



Wang et al. conclude from their study that “natural variability dominates Great Lakes ice cover,” and that any trend in the data — of which there are some of a few years and one that is lengthier — “is only useful for the period studied.” Given this finding, there is no reason to attribute any change in the annual average ice area of the North American Great Lakes to anthropogenic global warming.



How should one evaluate this argument? Unfortunately it’s work to do so — but fortunately, it’s simple. There’s a single method which exposes the misdirection in almost every case of fake claims by fake skeptics, namely: look at the actual evidence. In detail.

Be sure to read as much of the scientific research as you can — don’t limit yourself to the sources they give. Be sure to study the data yourself — don’t take their word for anything. Perhaps most important, don’t limit yourself to looking only at what they show you — be especially careful of fake skeptics turning the spotlight on a time span that’s too brief or an area that’s too small. If you use these safeguards, the truth of the matter will usually become clear. It’s work — but it works.

Step 1: study more of the scientific research than they refer to. We could, for instance, examine more recent work from the same authors: Wang et al. 2012, Temporal and spatial variability of Great Lakes ice cover, 1973-2010, Journal of Climate 25(4):1318-1329, doi:10.1175/2011JCLI4066.1. There’s a nice powerpoint presentation which summarizes this research. It shows trends in ice cover for all the Great Lakes (including Lake St. Claire) separately and combined:

Note that there are sizeable trends, and the change in total Great Lakes ice over the years has been one of significant decline.

Why, you might wonder, is there such a strong declining trend in Great Lakes ice cover? Wang et al. answer that very question, thus:

That kinda says it all.

Step 2: study the data yourself. There’s quite a bit available from Environment Canada. They provide two principal measures, the maximum ice cover for each winter season, and the “Total Accumulated ice Cover” or “TAC,” which combines not only how much area is covered but for how long as well. Analyzing the data shows that all the trends identified in Wang et al. (2012) are statistically significant. Here, for instance, is the trend in TAC for the Great Lakes:

Here’s the trend in seasonal maximum ice cover:

Here are both trends on one graph:

Not only are both trends statistically significant for the Great Lakes as a whole, they are so for all five Great Lakes individually. Study the data yourself, the result is clear: there is a strong, statistically significant decline in ice cover on the Great Lakes. All of ’em.

Step 3: look at more than they show you, and be especially wary of time spans that are too brief and areas that are too small. It’s obvious that the NIPCC report has done exactly that, because Hudson Bay and the Great Lakes combined are only a small fraction of the area covered by sea ice in the northern hemisphere.

Earlier, I asked “why would you issue a 416-page report on the state of the climate but say almost nothing, and certainly nothing substantive, about Arctic sea ice? Maybe it’s because of the graph they didn’t show:

When it comes to Arctic sea ice, we should note what the NIPCC report did not do. They didn’t survey the scientific literature to give a fair report of the state of current research. They didn’t present an array of data, or even present data for the Arctic overall, in order to give a realistic portrayal of the situation.

We should also note what they did do. They surveyed the scientific literature for the express purpose of finding a few quotes which they could use to discredit global warming science. Yet in spite of how easy it always is to execute this tactic, it’s surprising how little they managed to find.