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Carbon dioxide is a greenhouse gas in the Earth's atmosphere that traps the sun's heat. The amount of carbon dioxide in the air has risen steadily since the nineteenth century and is now at it's highest levels in 800,000 years. As a result, global temperatures are also rising: 2020 was one of the hottest years on record. But the planet is not warming evenly. The polar regions are heating up five times faster than anywhere else on Earth.
As a result, polar habitats are changing dramatically. Snow covers the Arctic for fewer days each decade, and the glaciers over Greenland and Antarctica are melting away. Sea ice is changing, too, getting thinner and covering less ocean. Polar bears depend on Arctic summer sea ice for hunting and traveling, but within a few decades, there might be none left.
Changes in climate and habitat have other consequences for polar animals. Some adaptions that supported survival are becoming unhelpful or even harmful. For example, blubber keeps marine mammals warm in cold water (see page 13). As temperatures continue to rise, the same blubber could cause those animals to overheat. When days get longer, ptarmigan turn brown for camouflage when the snow melts (see page 20). If warmer spring temperatures melt snow before the days lengthen, birds that are still white will be more visible to predators. As climate chance continues, these and other polar species may find it harder to persist.
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L.E. Carmichael (Polar: Wildlife at the Ends of the Earth)