It may be the hottest year ever, or part of a suite of same, or some such. But it’s noteworthy that April 2020 saw the 2nd-largest drop in satellite-measured temperature we’ve seen in the 497 months that we have satellite records. As Anthony Watts reports, the usual duo of Roy Spencer and John Christy who originally figured out how to generate a surface temperature data set from satellite records keep us posted on developments. Even when they aren’t hugely polemically useful. The idea is to look at the data and develop theories based on it rather than look at the theories and develop data based on them. And the sudden change in temperature definitively proves … nothing in particular except that the situation is complicated, because this spring still looks like part of a gradual and inconsistent warming trend driven by a complex mix of factors that might be reversing unless it’s not. Dang.
Sometimes it’s hard to form much of a theory. For instance, Spencer and Christy report that the linear warming trend since 1979 nudged up slightly, to +0.14 C/decade. But it’s not really statistically significant. The temperature drop seems to be due to the fading footprint of aerosols from last year’s Australian fires, and April 2020 was the warmest since a volcanically-induced warming in 1993. But in the continental United States it’s the coolest since 1998 and below the seasonal average. Elsewhere, it was warmer than average in the Caribbean, Eastern Antarctica and western Australia, as well as and particularly so in central Russia. But cooler in other places including western Russia and also central Canada.
There’s no “gotcha” here. Just a complex picture that requires interpretation and investigation. Sadly, science is like that.
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