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CO2-induced global greening and cooling

08 Feb 2023 | Science Notes

Yes, cooling. A bit at least. A new study in Nature Communication (h/t NoTricksZone) adds to the evidence that additional CO2 in the air is driving an explosion of greening around the world. Based on satellite measurements over the period 2001-2018 the authors found that, as is generally held, the world has been getting more green. But then they decided to look at what the extra greening meant for local temperatures and found something very interesting. For about 70 percent of the world, they found that more green meant lower temperatures. Yes, plants cool things off. And while it’s not enough to reverse the overall warming trend entirely, in places like China and India where local land use policies have been focused on enhancing forest cover and irrigated agriculture, it has offset 20 to 40 percent of the temperature increase. Might be something worth putting into a climate model.

The authors found that the additional greening had a variety of local effects on temperature, some positive and some negative. The overall balance depended on location and regional land characteristics. For regions below 50 degrees latitude the net effect was negative, meaning more greening implied less warming. For the world as a whole, they attribute a cooling effect of -0.02 degrees C per decade to greening which is only enough to counteract about 5 percent of the warming taking place on land. In northern countries like Canada greening didn’t lead to any net cooling. But, as mentioned, in China the greening counteracted 20 percent of the warming and in India it countered 40 percent. Which is good to know since China and India have made it clear they plan to keep building their coal-fired power plant capacity to develop their economies, which means they will be contributing more and more of that lovely CO2 plant food to the air for their own landscapes as well as our own to benefit from. And also because we’re constantly told warming will clobber poorer countries hardest and most of them are already in the warmer parts of the planet.

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