 It affects wind patterns. It affects the amount of sun we're getting. It affects the temperature of cooling water for a nuclear power plant. And it also affects the amount of hydropower that we can access. In recent years, droughts have caused hydroelectric dams in the US and China to falter. And so overall, this is why it is so important that we have a mix of different technologies in the system. To keep the lights on, says Lott, without having to burn more fossil fuels. I'm Daniel Ackerman for Marketplace.