Global warming is occurring. We know this through scientific observations and our understanding of atmospheric physics and chemistry. We understand that human activities associated with burning fossil fuels is a primary forcing function. While global warming is occurring, observations indicate that rate of warming varies by region.
The Arctic and Antarctic are geographic opposites, and not just because they sit on opposite ends of the globe. The land-sea arrangements are different. Antarctica is a continent surrounded by water; the Arctic is basically a water body surrounded by land.
Observations show that the Arctic is warming faster than Antarctica. The Antarctica continent is very high (about 7,500 feet) and thus much colder to begin with so the snow and ice on the land are not melting as fast as the snow and sea ice in the Arctic.
The ice thickness on Antarctica averages about 1.4 miles. The brightness of this ice sheet reflects solar energy out to space, which limits regional warming in summer. The Antarctic peninsula, which juts further north into the Southern Ocean, warmed faster than any other terrestrial environment in the Southern Hemisphere during the latter half of the 20th century.
Observations indicate that the Arctic is the fastest warming region on the globe, a phenomenon called Arctic amplification. Summer sea ice in the Arctic has been shrinking more than 10 percent per decade over the past 40 years. As sea ice melts, solar energy is not reflected to space and helps warm the region. The accelerated Arctic warming influences the weather around the Northern Hemisphere by changing the temperature contrast between middle and high latitudes. Such influences are being studied intensively at present.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
