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SYFY WIRE Bad Astronomy

Yeah, About That Global Warming Hiatus…

By Phil Plait

It’s been a rough week for climate change deniers.

First, a paper came out basically destroying claims by a group of deniers that climate models “ran hot”, that is, always overestimated the amount the world is warming. It turns out the claim was fundamentally flawed in numerous ways, which isn’t terribly surprising. You can read all about it at that link.

But the bigger news is that a new paper has been published showing that the global warming “hiatus” or “pause” or whatever you want to call it doesn’t exist.

I’ve been leaning this way more and more over time. The original claim (touted mostly by the usual suspects) was that global surface temperatures had flattened since 1998, and therefore warming had stopped. Right away there are several problems with that claim; the biggest being that 1998 was an unusually warm year, so starting your measurements there is unfair (that’s called cherry-picking and is a big no-no). Another is that the average temperature of the planet goes up and down all the time, so you can’t just look at a few years and claim there’s a trend. A third is that using surface temperatures is misleading, since a lot of the heat goes into the deep ocean.

The new paper goes further than that. Applying some corrections to surface temperature measurements known to be a bit biased (more on that in a sec), they find that when you look at the warming that occurred from 1950 – 1999 you get 0.113° C warming per decade. When you look at 2000 – 2014, the warming is 0.116°C per decade, which is virtually indistinguishable from the earlier trend.

In other words, looking over the long run, warming hasn’t slowed at all.

Even more, playing devil’s advocate, the scientists tried to force their data to show them a hiatus; they redid the calculations starting in 1998, as so many deniers have done. The result? The warming from 1998 – 2014 is 0.106° C per decade. It’s still there.

The corrections they applied have to do with the way sea surface temperatures were taken; the method has changed over time, and that introduces biases into the data. The good thing though is that new methods, new understanding of the nature of data measurement, allow scientists to go back and re-examine older data and apply corrections to it. You can get more of the details at Hot Whopper, Real Climate, and at Greg Laden’s blog. Climatologist Michael Mann has a nuanced view of this he’s written as well.

I expect the deniers — as usual — will be blowing a lot of hot air about this, but the science is becoming ever more clear. Global warming is real, and it hasn’t stopped. People who claim otherwise are trying to sell you something… and you really, really shouldn’t be buying it.

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