How would we expect global warming to affect the world’s amount of snow cover?
The naive way — the simpleton’s way — would be to say that higher temperature must mean less snow, all the time, everywhere. Senator James Inhofe (R-OK) made himself a laughingstock on the senate floor when he showed us all that it was the “Jim Inhofe way.” It looks to me like it’s also the “Tony Heller way.”
The smart way is to recognize that higher temperature has two primary effects. First, whatever snow does fall will tend to melt sooner. Of course there will still be fluctuations on top of any trend present, but the trend from earlier melting would mean reduced snow cover, particularly during the melting seasons, spring and summer.
Second, higher temperature means the air can hold more water vapor; it’s basic physics (the Clausius-Clapeyron equation). That would mean that when it does snow, we could get more — after all, snow comes from water vapor in the air. So the trend might be for more snow cover, particularly during the snowfall accumulation seasons, autumn and winter.
One wonders: what do we observe?
The Rutgers University Global Snow Lab provides data on snow cover in the northern hemisphere (which has most of the world’s snow cover, having most of the world’s land). During autumn and winter, snow cover has expanded:
Actually, the wintertime snow cover expansion isn’t “statistically significant.” What looks like an increasing trend might just be a false impression from random fluctuations. Even the autumn expansion doesn’t quite meet the “95% confidence” standard — it too could just be random fluctuations, although there’s a good chance the upward trend is real. In either case, both autumn and winter snow cover are perfectly in line with what’s expected in a warming world.
For spring and summer, statistical significance of the trends is not in doubt:
In both seasons the amount of snow cover is declining, and that’s not just an appearance due to random fluctuations, it’s a real observed phenomenon. The summertime average snow cover is now only half what it used to be! Also, the rate at which snow cover is declining in spring/summer, is quite a bit more than the rate at which it’s increasing in autumn/winter:
It turns out that for all four seasons of the year, the changes we’ve observed in snow cover are just what we would have expected in a warming world.
If, that is, you’re smart about it. If you’d rather be the simpleton, you could use the Tony Heller way; he recently treated us to quite a snow job.
He points out that “Autumn snow cover has been steadily increasing for 40 years, and was second highest on record this year,” and shows us a graph to prove it (data and graph from Rutgers):
He goes on to tell us that “Winter snow cover is also increasing, with nine of the last ten years above average.” But only 6 of the last 10 years have had above average winter snow cover in the northern hemisphere. The reason he says 9 of 10 is revealed by the graph he shows, which isn’t for the northern hemisphere (like his first graph), it’s for North America only. Why switch? Maybe … so he could give the impression he wanted?
Heller’s coup de grace, however, is to imply that any claim of reduced snow cover is some sort of plot by “highly paid government experts”
“Meanwhile, our top highly paid government experts say that snow cover is decreasing, especially since 1980.”
He seems especially insistent on highlighting the “especially since 1980” part.
First of all, snow cover has decreased, if you consider the whole year, not just autumn and winter:
Second of all, it’s bizarre that Heller’s “evidence” of claims about snow cover from the “highly paid government experts” is this from the IPCC:
It talks about snow and ice, and it’s the ice part that gives us the “especially since 1980” comment. But Tony Heller doesn’t seem to get that … is that more of the simpleton’s way?
My opinion: the fact that Tony Heller did a “show and tell” on snow cover in autumn and winter but said nothing about the more extensive (and statistically significant) decline in spring and summer, the fact that he implies heavier snow cover in autumn/winter is somehow a “problem” for global warming science, and especially his offhand comment referring to the scientists who talk about it as “highly paid government experts,” indicates that he’s more interested in doing a “hatchet job” on climate science than understanding how the world is changing. Just my opinion.
But maybe he can tell me … where do I get one of those jobs as a “highly paid government expert”?
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