In a surprising new study, scientists say they’ve pinned down the climate factor most strongly tied to variations in terrestrial carbon storage — that is, the ability of plants and other features of the Earth’s surface to take up carbon, thus preventing it from going into the atmosphere. They’re arguing that the biggest driver is tropical nighttime temperatures, which are expected to warm at a faster rate than average temperatures otherwise will.

As these temperatures rise, the researchers say, they could begin to seriously interfere with forests’ ability to store carbon, even helping tip the scales one day in the future so that our global forests turn into a net source of greenhouse gas emissions — leaking carbon into the atmosphere rather than sucking it out, and thus exacerbating global climate change.

The amount of carbon taken up by land ecosystems “bounces around from year to year, largely due to the climate bouncing around,” said the paper’s lead author, William Anderegg, an assistant professor of biology at the University of Utah and an assistant research scholar at Princeton University. It can be affected by annual fluctuations in environmental factors, such as temperature and precipitation, which can cause plants or soil to take up more or less carbon in a given year.

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Anderegg said he and his colleagues were interested in the “big unknowns” when it comes to carbon uptake — that is, what factors influence carbon uptake versus carbon release in land systems, such as forests. So they designed a study, which was published Monday in Proceedings of the National Academy of Sciences, to test four hypotheses on the factors that might be most important.

The first three factors — tropical mean temperature, tropical precipitation and both temperature and precipitation in semi-arid regions of the Earth — had already been well-established in the scientific community as important drivers of the global carbon cycle. These regions of the world — and tropical regions in particular — have been shown to be disproportionately important when it comes to the total amount of carbon poured into or sucked out of the atmosphere.

The fourth hypothesis — tropical nighttime temperatures — was a much newer idea in the scientific community, Anderegg said. The idea rose out of the some local studies in Costa Rica that had implicated night temperatures as an important influence on how much carbon is taken up by land ecosystems in that region.

The researchers used datasets on climate and carbon uptake by vegetation — largely compiled from satellite data — to test the four hypotheses and see which one seemed to have the biggest influence on variations in carbon uptake worldwide. And while all the factors played a role, they found that tropical nighttime temperatures, out of the four, was the most important.

That hypothesis “hadn’t been tested at the global scale,” said Anderegg. “So it was surprising to us that that was the one that always rose to the top in our statistical analysis.”

The reason for its importance is likely tied to a metabolic process called respiration, in which plants convert sugar into energy and release carbon dioxide in the process. It’s basically the opposite of photosynthesis, which takes up carbon dioxide and uses it to make sugar. In very simple terms, higher levels of photosynthesis can drive stronger carbon uptake, and higher levels of respiration can drive higher levels of carbon release in plants.

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Since photosynthesis requires sunlight and mainly occurs during the day, respiration is the dominant process happening at night. And in higher temperatures, the process speeds up in many plants, Anderegg said.

“The idea here is that on warm nights, plants — and other parts of the ecosystem as well, potentially — are consuming and using up more of their sugars and losing that carbon to the atmosphere more than they do on cooler nights,” Anderegg said.

Rising night time temperatures in the tropics cause trees and other flora to release CO2 which exacerbates global warming.

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From now on I will only give NEGATIVE feedback

So F#ck you