Over the past 30 years, the Arctic has warmed at roughly twice the rate as the entire globe, a phenomenon known as Arctic amplification. Most scientists agree that this rapid warming is a signal of human-caused climate change.

Arctic amplification is not the only evidence of rapid climate change in the Arctic. The floating sea ice cover of the Arctic Ocean is shrinking, especially during summer. Snow cover over land in the Arctic has decreased, notably in spring, and glaciers in Alaska, Greenland, and northern Canada are retreating. In addition, frozen ground in the Arctic, known as permafrost, is warming and in many areas thawing. Scientists first started to see evidence of changes in Arctic climate in the 1980s. Since then, the changes have become much more pronounced.

Changes in the Arctic climate are important because the Arctic acts as a refrigerator for the rest of the world—it helps cool the planet. So changes in the Arctic climate could affect the climate in the rest of the world. Changes in the Arctic have effects that cascade through the food chain, from phytoplankton to marine mammals such as seals, walrus, whales, and polar bears.

Climate feedbacks

Researchers say that the changes in the Arctic are worrisome, because they could lead to feedback effects that lead to further warming. For instance, when the white sea ice melts in summer, areas of dark open water are exposed which can absorb more heat from the sun. That extra heat then helps melt even more ice. The loss of sea ice is known to be one of the drivers of Arctic amplification. Permafrost may also be involved in feedbacks. As permafrost thaws, plants and animals that were frozen in the ground begin to decay. When they decay, they release carbon dioxide and methane back to the atmosphere that can contribute to further warming. The changing vegetation of the Arctic also affects the brightness of the surface, which then influences warming. As the Arctic atmosphere warms, it can hold more water vapor, which is an important greenhouse gas.

Scientists have already seen evidence that positive feedbacks are occurring in the Arctic. Predicting the Arctic climate is difficult. Some of the changes in the Arctic could also be involved in feedback effects, or effects that reduce the amount of warming. For example, if warm temperatures make the Arctic growing season longer, more plants can survive and take up more carbon from the air. However, most evidence suggests that the positive feedback effects that hasten warming outweigh the negative feedbacks. According to NOAA's Arctic Report Card for 2019, permafrost thaw throughout the Arctic may be releasing an estimated 300 to 600 million tons of net carbon per year to Earth's atmosphere.

Scientists are studying the many factors that influence Arctic climate to help figure out how feedbacks work and what will happen in the future. Researchers are also investigating how the changes in the Arctic climate will affect climate in other parts of the world. Scientists study data collected by satellites and at ground stations and also used use sophisticated computer models.

This map shows trends in mean surface air temperature over the period 1960 to 2019. Notice that the Arctic is red, indicating that the trend over this 60-year period is for an increase in air temperature of nearly 4° C (76° F) across much of the Arctic, which is larger than for other parts of the globe. The graph shows linear trends over the period by latitude. —Credit: NASA GISS

Last updated: 4 May 2020