In the normal course of the world, seasonal shifts in weather can cause crops to fail, water to rise and roads to ice over. But on top of that naturally chaotic system, anthropogenic climate change is creating hazardous conditions that pose similar—sometimes heightened—dangers. It's tricky to know, though, which events fall into which category—was that storm just an unusually bad one or the sign of things to come?
The relatively new scientific field of “extreme event attribution” seeks to separate routine (if unfortunate) weather from weather that can be chalked up to climate change. In a new report published by the American Meteorological Society, independent teams of scientists examined a swath of 2013's big natural disasters with an eye to figuring out how climate change may have contributed to the storms. Climate Central has a breakdown of the extreme events studied in the report, detailing which were tied to climate change and which were not.
Some of the events that the researchers tied to climate change—heat waves in Australia, South Korea, Japan, China and across Europe, and drought in New Zealand—make intuitive sense. Others, like the heavy rains that caused widespread flooding in northern India, fit when you consider the fact that India's rains are strongly guided by the seasonal monsoon, and the monsoon is already thought to be affected by climate change.
But some natural disasters that one would think would be attributable to climate change didn't seem to hold up under the scientists' scrutiny—most notably, the ongoing and record-setting California drought. At best, the drought's connection to climate change is up in the air, with some scientists saying there is a connection and others saying there is not.
In a certain theoretical sense, all weather is now being guided by our greenhouse gas emissions. Global warming is raising the energy in the air and the sea, and as an interconnected system any changes affect the formation of storms, drought and other extreme events. But in a more practical way, some extreme events owe their strength more to climate change than others—some heat waves are just heat waves, while others burn so hot or last so long that scientists think they would have been extremely unlikely, if not impossible, without the warming of climate change.
As Smart News has written before, “[t]here’s never an all-or-nothing relationship between climate change and a particular extreme event. But what event attribution allows us to say is how much more likely a particular weather event was or how much stronger it ended up being because of shifts caused by climate change.”
While not everything that seems like climate change necessarily is, a lot of nasty weather events are. The longer humans keep pushing the system, the more chances climate change will have to show its ugly side.