Extreme weather seems to make the headlines almost every week, as disasters increasingly strike out of season, break records, and hit places they never have before.

Decades of scientific research has proven that human-caused climate change is making some disasters more dangerous and more frequent. The burning of fossil fuels like oil, gas, and coal releases carbon dioxide into the Earth’s atmosphere, where it traps heat, warms the planet, and alters the conditions in which extreme weather forms. These changes are happening more rapidly than at any time in the last 800,000 years, according to climate records.

Below, we break down what experts know — and what they don’t — about the connections between climate change and flooding.