Droughts have long been known to place pressure on agriculture and water supplies, but they can also lead to increased carbon dioxide emissions.

This can happen when power-hungry states use electricity from fossil fuels to replace hydropower, an energy source crippled by the lack of water.

A new study from Stanford University researchers finds that from 2001 to 2015, drought-induced emissions accounted for about 10 percent of annual carbon dioxide pollution in California, Idaho, Oregon, and Washington.

While many states...