Extreme Weather and Climate Change Are Stuck in a Vicious Cycle

It seems like every other week, a scientist is warning us that global climate change is going to lead to more extreme weather events. (Maybe we should listen?) But this week, we have scientists warning us that the whole thing is one vicious cycle, with extreme weather events causing additional climate change.

It's kind of a chicken-and-the-egg scenario, except what came first was probably pumping tons and tons of pollution into the atmosphere.

The idea makes sense if you think about it: Climate change has been linked to more and stronger hurricanes, drought (and forest fires), heat waves, and in some cases, heavy rains. For the bulk of industrialized human history, plants have been kind enough to absorb lots of our carbon emissions—up to 30 percent of all emissions. But plants have a hard time dealing with drought, hurricanes, and forest fires.

It's a phenomenon first observed in 2003, when Europe's heat wave killed as many as 70,000 people. In the aftermath of that heat wave, researchers noticed that the whole carbon cycle was thrown out of whack, as the soil hardened and plants died. Markus Reichstein, director of the Max Planck Institute for Biogeochemistry in Germany and author of a paper published today in Nature on the subject, said that the effect could be more important than you'd think.

Using satellite readings taken from 1982 through 2011, his team measured how much carbon dioxide was absorbed by plants for photosynthesis in a certain area both before and after major weather events. In a model in which Earth doesn't experience any extreme weather events (an admittedly unrealistic model), Reichstein found that Earth's vegetation would absorb 11 billion additional tons of carbon than in one that had extremes.

The effect is "by no means negligible," Reichstein said. "As extreme climate events reduce the amount of carbon that the terrestrial ecosystems absorb and the carbon dioxide in the atmosphere therefore continues to increase, more extreme weather could result. It would be a self-reinforcing effect."

As you might expect, drought is the most devastating extreme event for the carbon cycle, as it actively kills plants and cuts the amount of carbon absorbed by forests and plains. Reichstein's research looked mainly at less extreme-extreme events—the ones we've actually seen over the past hundred years, such as the 2003 drought. But one of colleagues, Michael Bahn, said the effect is only going to get worse as megastorms could become more frequent.

"We should also take account of events which so far have only happened once in 1,000 or even 10,000 years, because they are likely to become much more frequent towards the end of this century," he said.

Hurricanes, of course, dump tons of steel, trash, wood, and sometimes nuclear waste into the oceans. That doesn't necessarily directly affect climate change, but a recent study did suggest that air pollution may have actually cut the number of hurricanes in the Atlantic Ocean over the last century.

According to that paper, man-made aerosol pollution may have brightened clouds, helping to reflect light back into space, which would lead to reduced ocean surface temperatures and, therefore, fewer hurricanes during the pollution-heavy 1970s and 1980s. Under that model, clean air laws may have actually led to more hurricanes in the last two decades. Turns out nothing's ever simple when dealing with massive, worldwide systems.