Solar panels fight global warming by producing electricity that keeps us from burning greenhouse gas-producing fossil fuels. They also shade Earth from the sun. This extra shade should fight climate change, too—less solar radiation means a cooler Earth, right? It's not quite that simple, scientists report online today in Nature Climate Change. It turns out solar panels can actually make some locales hotter. The researchers simulated an idealized scenario: an Earth with deserts and urban areas completely covered in solar panels. (Because weather depends on so many factors, the group had to model an extreme scenario to confirm the changes they observed were actually due to solar panels.) The simulation showed that the extra shade first cools the covered area, but that temperature decrease changes local weather patterns. About 50 years after installing the panels, India and eastern Australia, for example, get warmer because of less rainfall, and the northwestern United States gets warmer because of wind pattern changes. The benefits of solar panels still outweigh their drawbacks, though. Realistic large-scale solar panel coverage could cause less than half a degree of local warming, far less than the several degrees in global temperature rise predicted over the next century if we keep burning fossil fuels. But the study shows that massive solar panel installments shouldn’t be the only fossil fuel alternative, the authors say.