Severe Weather Events and Climate Change

What can we know about the connection between severe weather events and climate change? It turns out that scientists are increasingly able to draw very clear connections between individual weather events and climate change. This is important because while it makes sense to say that people shouldn’t be cheaply conflating weather and climate change like Rush Limbaugh does every time it snows in D.C. in January, in communicating the importance of fighting climate change, we do have to be able to craft compelling popular narratives connecting the actual events people are experiencing at a given time to global climate change. That is absolutely necessary if people are ever going to care about this issue enough to do anything at all. That’s why these findings are promising:

Scientists are now able to assess, in some cases within days, whether and how much the risk of such an extreme weather event has changed compared to the past — that is, before heat-trapping greenhouse gases altered our climate. This knowledge will help communities make decisions appropriate for today’s risks. These can include storm surge risk maps that reflect sea-level rise, better water management to reduce the effects of longer and more intense droughts, and improved floodplain management in increasingly flood-prone areas.

Climate change brings with it many existential threats — rising seas, acidifying oceans, species extinction. But the most immediate threats result from the changing risks of extreme weather. Our perception of these risks has been almost entirely based on the past. That’s how insurance companies have assessed our premiums. But if weather risks change, and events that used to have a 1-in-500 chance of happening in any given year now have a 1-in-50 chance, insurance premiums will rise or insurance itself might become unavailable.

Here’s an example that underscores the predictive power of extreme event attribution: A recently published study in the journal Nature Climate Change analyzed record-breaking rains in Britain that flooded thousands of homes and businesses and caused more than $700 million in damage in the winter of 2013-14. Scientists found that such an event had become about 40 percent more likely. As a result, roughly 1,000 more properties are now at risk of flooding, with potential damage of about $40 million.

Climate change is, of course, never the only player in a so-called natural disaster. Many other natural and human factors are at play. Countless communities are vulnerable because of limited resources and poor infrastructure. Certain classes of extreme events will be relatively straightforward to dissect and attribute (heat waves, heavy rains, certain types of drought) while others are at the far edge of what science can now understand (tornadoes, wildfires and the frequency and intensity of hurricanes).

Heat waves, for example, are expected to become more common, intense and longer because of the increase in heat-trapping gases in the atmosphere. One recent study found that an extreme heat wave last May in Australia was made 23 times more likely because of climate change. When the numbers get that big, it’s fair to say that some episodes of extreme heat would have been virtually impossible (but never absolutely impossible) without climate change.