Global Warming: How Far to 1.5°C?

There’s been a lot of talk recently about limiting global warming to 1.5°C, mainly focused on two things: 1) how important it is, and 2) how difficult it will be. This raises an important question: how far have we come already, and how much farther until we reach the 1.5°C limit?

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The Global Warming Signal

Many things affect global temperature, and the three best-known other than greenhouse-gases those are the el Niño southern oscillation (ENSO), atmospheric aerosols from volcanic eruptions, and variations in the sun. We can use historical data to estimate how strongly those factors affect global temperature. I’ve done so in the past, and by requests here’s an updated version which includes recent data.

Trump’s Plan to Handle Climate Change

From the U.K. Guardian, here.

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Global Warming: 1.5°C or less?

One of the most valuable posts I’ve seen recently at RealClimate is this one about the new IPCC Special Report on 1.5°C. The report has a lot to say that’s crucially important. The RealClimate report deals with only a bit of it; its genuine importance is spreading the word about the new report itself.

Multiple Testing

Suppose I showed you a close-up, on a live video feed, of where my shot at a target landed. The video is zoomed in on the target’s bulls-eye, and lo and behold, right there is my shot. No doubt about it: bulls-eye. I brag about what a good shot I am, and you’re impressed.

Then my cat gets on the table and accidentally zooms the camera view out to show the entire target (a cat? maybe not an accident). Now you can see that I took about 300 shots, they landed all over the place (some even missed the target completely), and one of them hit the bulls-eye. My guess: you would no longer be so impressed. You might even think my original camera view was misleading.

That, in essence, is how people still buy and sell the misleading claim that there was a “pause/hiatus/slowdown” in global surface temperature during the early 2000s. Some, I’d even venture to say most, do it without knowing what they’re doing. Some who have done it but have been told why it’s a problem, persist in doing it still. The former I’d call an honest mistake; the latter I’d call not just misleading, but deliberate deception.

Bhutan

Arctic Sea Ice for Suckers: Ron Clutz shows how to Hide the Decline

His method? A favorite climate denier trick: the one called “cherry-picking.”