The California drought is by all measures "exceptional." But humans have made it even more so. A new scientific study offers definitive evidence that anthropogenic climate change has amplified the drought out West, making it 15 to 20 per cent worse than it would have been otherwise.
Picture: A dry grassland and oak landscape of the Coastal Mountain Range, one of the areas hardest hit by the current drought, via Dominick McPeake
"This would be a drought no matter what," climate scientist and lead study author A. Park Williams of Columbia University told The New York Times. "It would be a fairly bad drought no matter what. But it's definitely made worse by global warming."
Analysing nearly every possible combination of data on temperature, rainfall, windspeed, and other drought-contributing factors, a paper published this week in Geophysical Research Letters comes to a sobering conclusion: though the drought that's gripped California since 2012 would have happened with or without human intervention, carbon emissions have given it a nasty edge. We've made the drought worse.
On average, the state of California has warmed by about 2 degrees Fahrenheit since the late 19th century. This is widely believed to be the result of anthropogenic climate change. Now, two degrees may not sound like much, but even a slight uptick in the air temperature can mean a lot more water getting pulled out of the soil. Indeed, Williams' calculations show that the air over California today can absorb roughly 8.5 trillion gallons more water in a typical year than it could have in the 19th century. More water in the air means less in the ground and less available for plants. This, in turn, means crop failures, dustbowls, fires, and all the other symptoms of exceptional drought we've become so eerily familiar with.
The fact that warm weather can amplify droughts is pretty much common sense. But it helps to have the human connection spelled out in a detailed scientific study. Humans are warming the planet, and that's making a terrible drought — one that's touched millions of lives — even worse. This gives climate-concerned politicians like Jerry Brown — who has repeatedly cited human emissions and global warming as factors contributing the drought — additional ammo to wield against rivals who seem determined to ignore and deny the existence of anthropogenic climate change until the End of Days.
My hope is that we're finally nearing the tipping point at which these warnings become too deafening to ignore. Just take a quick trip back over headlines this past summer. Massive fires raging across some of the wettest ecosystems in the world. Record-smashing heat waves in the Middle East and India. A monster El Niño brewing in the Pacific. To top it all off, the hottest month in recorded history.
It was time to pull our heads out of the sand ten years ago. It's definitely high time now.