Tuesday, July 31, 2018

Uh-oh! Fires burning bright

Having driven yesterday adjacent to the Yosemite fire zone, I came away with a question.

I have no difficulty believing that California's extreme wildfire seasons are a consequence of, and exacerbated by, global climate change. (As are many fires elsewhere.) If year after year is very dry and very hot, there's a lot to burn in the forests. And so it has been. This sort of intuitive awareness of climate changing is not controversial, even among Republicans.

But is all this burning we're experiencing in itself a contributor to increasing CO2 levels? Are we caught in a dire climate feedback loop?

Chris Mooney is a responsible climate journalist and he answered this a couple of years ago.

Just as growing plant life pulls carbon out of the atmosphere through the process of photosynthesis, so decomposing — or burning — plant life releases it back again. In the meantime, the carbon is stored in the plant, or in the case of forests, the trees.

In a climate in which wildfires are a steady, regular occurrence — but don’t change much in intensity or number from year to year — they will still release carbon, but the regrowth of forests and other plant life will also pull much of it back in again. “If climate and fire regimes equilibrate, then fire-induced atmospheric CO2 emissions are balanced by uptake from surviving vegetation or via regeneration,” noted a major 2009 study on the relationship between fires and the climate system.

But in a climate where there’s a change to the size, number, or intensity of wildfires, it’s possible that forests could burn and release carbon considerably faster than regrowth allows it to be replaced. Fire “has a substantial positive feedback on the climate system,” the 2009 study concluded.

As California works through public policy to reduce our CO2 emissions from controllable human activities, our warming ecosystem may increasingly be outrunning our efforts. This makes it all the more important to do what humans can do to reduce CO2.

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