so relieved!

[ljgeoff]

There's a new article in The Guardian quoting a study published this month in Nature. The author of the study is quoted as saying:

But uncertainty about how hot things will get also stems from the inability of scientists to nail down a very simple question: By how much will Earth’s average surface temperature go up if the amount of CO2 in the atmosphere is doubled?

That “known unknown” is called equilibrium climate sensitivity, and for the last 25 years the UN’s Intergovernmental Panel on Climate Change – the ultimate authority on climate science – has settled on a range of 1.5C to 4.5C (2.7 to 8.1 degrees Fahrenheit).

Cox and colleagues, using a new methodology, have come up with a far narrower range: 2.2C to 3.4C, with a best estimate of 2.8C.

Such a relief to know that we won't see anything above 4.5C!

Well, except for tipping points. The study excludes any extra warming from tipping points:

One wild card not taken into consideration by the new model is the possibility of rapid shifts in climate brought on by the planet itself. “There is indeed evidence that the climate system can undergo abrupt changes or ‘tipping points’,” Cox said.

The collapse of the gulf stream, the thawing of carbon-rich permafrost, or the melting of ice sheets on Greenland and Antarctica – any of these could quickly change the equation, and not in the Earth’s favour.

Oh, and the fact that around the middle of that range, at about 3C, we lose modern agriculture. There's that.