Feedbacks are key elements in climate science. They can be ‘negative’, such as the so-called blackbody radiation effect: the warmer the Earth, the more infrared radiation is sent back into space. But they are mostly ‘positive’ – in the sense that they reinforce the original condition – like the ravaging fires burning at unthinkable latitudes, during the record-hot summer that just went.
Down here on Earth, the limited visual perspective of human beings makes a few of them believe the planet is flat and many others think the climate isn’t changing much. However, up on board the International Space Station anyone can see how in peril (and round) our world really is. ‘In the last six years I have seen authentic changes,’ said astronaut Luca Parmitano in July. ‘I have seen deserts move forward and glaciers melt.’ A few days later, he might have seen smoke from fires in Siberia and in Alaska blanketing an area bigger than Europe. As I write, in late August, the Amazon is ablaze at a scale never seen from satellites before.
All these events are igniting positive feedbacks. In the Arctic, the naturally occurring fires open up land which, deprived of the tree cover, will get warmer in the future, thus melting permafrost, which will release more methane and carbon dioxide, which will warm the atmosphere and encourage more fires. This may push the planetary ecosystem close to the edge of a tipping point – a point of no return.
In the Amazon, thousands of human-induced combustions are paving the way to disaster: not only do they release vast amounts of carbon from trees and soil, which will heat up the climate more, but they also deprive the tropical forest of the moisture that makes the next rainfall. The worry is that one day, with a further increase in deforestation, there won’t be enough trees cycling water through the Amazon. It would be a tipping point for the whole of South America. And for the world.
The interaction of multiple feedback effects is what really turns climate science into an intricate web of unknown outcomes. But the disappearance of forest cover, albeit the scariest, is only one of them. It is blazingly clear we shouldn’t, both literally and metaphorically, be playing with fire.
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