You ask: When will polar bears become extinct?

You ask: When will polar bears become extinct?

“You ask“Is a series of Columbia Climate School experts who solve readers’ questions about science and sustainability. The following questions were submitted by one of our members Instagram Followers, response from Robert Newton, A senior research scientist at the Lamont-Dougherty Earth Observatory.

Q: At the rate of global warming, how quickly will polar bears become extinct?

Robert Newton studies Arctic climate change at Columbia University’s Lamont-Dougherty Earth Observatory.

A: No one is sure whether the polar bear will become extinct. Whether this will happen depends on changes in the Arctic sea ice, which is an important habitat for polar bears. Main food source: Seal. Sea ice is very dependent on what happens to carbon dioxide emissions, and we don’t know what happens there. We have forecasts based on various emission scenarios, but as Yogi Berra said, it is difficult to predict the future before it happens.

Our team is in one Recent studies, Using model operations and basic physics, if we continue to emit carbon dioxide into the atmosphere at historical rates, then At some point in this century, The summer sea ice will almost completely disappear in the Arctic-millions of square kilometers of sea ice disappear. This is a problem for polar bears because their food source, seals, depend on sea ice. They need corrugated and ridged ice, where they can find corners, crevices and small caves to overwinter and give birth to their cubs. These ice scenes came from the accumulation of ice and were compacted within a few years. If the ice melts every summer and new ones appear every winter, the winter ice will be thinner-only about 1 to 1.5 meters thick-and flat. This does not provide a decent habitat for seals. It is also not a good habitat for polar bears to inhabit and give birth to cubs.

Some polar bear populations can actually nest and be born on land. But even these populations need thick corrugated sea ice platforms to hunt seals. If the seals are not in the nest and you have no cubs in the spring, then the polar bears will lose their main source of food.

At some point later in this century, if things continue as usual, the winter ice will also disappear. We don’t know when it will be. These models have different views on the exact temperature at which this will happen. But our best estimate is at the end of the 21st century. At that time, it was hard to imagine a large number of polar bears surviving.

There is evidence in DNA that some polar bears may mate with brown bears. Therefore, it is possible for polar bears to evolve by abandoning ice, moving back to the forest, and mating with brown bears. But once ice does not exist, polar bears will certainly cease to exist as polar bears. They are not suitable for hunting on land. They blend beautifully on the sea ice; they stand out in the forest like crazy. They are excellent swimmers, suitable for hunting marine mammals. If they have to forage and hunt in the tundra or forest areas on land, there is no reason to think they will survive.

So, to answer your question, my best guess is that polar bears may become extinct between 2050 and 2100.

In other words, all the models we run and our understanding of the physics of ice growth and ice melting indicate that sea ice will follow the atmospheric temperature very closely. With the warming of northern latitudes, sea ice is rapidly disappearing, but if we manage to control greenhouse gas emissions and reduce carbon dioxide in the atmosphere, sea ice will soon recover.

This is one of our findings-if people can stabilize the global average temperature at about 2 degrees Celsius, then in the foreseeable future, a considerable amount of summer ice will continue to exist, while winter ice will continue to exist, and it may be a polar bear Provide enough ice for many years. If at some future date, humans can capture carbon dioxide from the atmosphere and isolate it underground to reduce global temperature, then there is good reason to believe that the ice layer will return to the global average air temperature drop within a few years. So, in this sense, the future of the species is really in our hands.