Each fall in the Arctic, the sun sets until spring, plunging the region into total darkness. During these cold months, sea ice usually forms quickly. But this November, during a period when temperatures surged as much as 35 degrees above normal in a massive region, a 19,000-square mile chunk of ice–roughly the size of the entire country of Israel–disappeared.

Today, temperatures at the North Pole are predicted to be between roughly 21 degrees and 32 degrees Fahrenheit, or as much as 50 degrees hotter than normal at some points during the day.

A new analysis from researchers working with World Weather Attribution used a combination of computer modeling and observational data to see if the Arctic heat wave over the last two months is connected with climate change and not solely an extreme, but natural, temperature increase brought on by El Niño or some other phenomenon. Their unsurprising conclusion: Definitely climate change.

“What I found was that without climate change this event would be extremely unlikely to occur, and climate change has made it a lot more likely,” says Andrew King, a researcher from the University of Melbourne who led one part of the analysis.

A century ago, the probability of a heat wave of this size happening would have been so low that the researchers couldn’t precisely estimate it, saying only that the chances would have been less than 0.1% a year.

The North Pole is warming faster than any other part of the world. As temperatures warm, that has direct effects on Arctic wildlife. If rain falls and freezes on snow in the fall, reindeer may not be able to eat fodder under the snow for the whole winter (one event like this in 2013 killed 61,000 reindeer). If other food sources–like as phytoplankton, the base of the food chain in the ocean–are available at the wrong time, that can affect an entire ecosystem. Melting ice shrinks also habitat for animals like polar bears.

Some scientists believe that Arctic heat may also impact weather patterns in places like the lower 48 states or Europe, making extreme cold events more likely as Arctic air moves south. As white ice and snow disappears in the Arctic–reflecting less sunlight–that can also speed up global warming.