A study published Monday finds that the way clouds cover the Earth may already be changing because of climate change, Nell Greenfieldboyce reports for NPR. The study, which used satellite data to track patterns in clouds over two decades, found that clouds in the mid-latitudes shifted towards the poles during the 20-year period.

While these changes were predicted by many climate models of global warming, but the results are still startling. Said Joel Norris, lead researcher and climate scientist at the University of California, San Diego, “”I guess what was surprising is that a lot of times we think of climate change as something that’s going to occur in the future. This is happening right now. It’s happened during my lifetime — it was a bit startling.”

Norris tells NPR that these cloud shifts are probably primarily due to two influences — human-produced global warming, and the recovery from the cooling effect of two volcanic eruptions during that time frame.