Lightning in the Arctic used to be so vanishingly rare that people could go their whole lives without seeing a flash. But as the region warms rapidly, it may become more common—with effects that could reach outside the Arctic.

One recent study projects that the occurrence of lightning in the Arctic could double by the end of the century. Another study suggests that the number of Arctic flashes may have tripled within the last decade alone—though some researchers question that result.

Increased lightning is a worrying sign of today’s rapidly accelerating climate change, scientists say, but they’re also concerned for the future: More lightning could set off a cascade of ecological shifts that could release huge Arctic reserves of carbon into the