Did climate change cause today’s awful weather?

Whenever there’s a heat wave or drought or hurricane, people often ask whether global warming is “to blame” for the bad weather.

It’s a tricky question. Storms and heat waves and droughts happen all the time. Global warming is expected to make certain weather events — like heat waves — more frequent. But it can be difficult to tie an individual weather event to warming.

One oft-used analogy is to baseball players and steroids. Baseball players can hit home runs without steroids. But they can hit more home runs, on average, after taking steroids. So it’s safe to say that steroid use will lead to more home runs. But it’s harder to prove that a specific home run was caused by steroids. (Would he have hit this home run if he never took steroids? Who knows?)

That said, climate scientists have been finding ways to link some extreme weather events to global warming. One study in the Proceedings of the National Academy of Sciences, for instance, found that a deadly 2010 heat wave in Moscow would have been very, very unlikely to occur in the absence of global warming. Studies like this are still fairly rare and often disputed, but they do exist.

Alternatively, you could say that global warming can make certain weather events worse. For example: it’s very hard to say whether an individual hurricane was “caused” by global warming. But sea-level rise can exacerbate the storm surges and flooding from the floods that do happen.