A Common-Sense Measure of Climate Change
In dozens of studies, including some done here at the Geophysical Institute, scientists have concluded that the planet is getting warmer, and the species performing the studies carries much of the blame. But why believe in global warming if we can't feel it?
Longtime residents of Alaska and Siberia may already be able to feel global warming, according to James Hansen, a researcher at the NASA Goddard Institute for Space Studies in New York. Hansen and his colleagues have developed a "common-sense climate index," to locate areas on the globe where climate change is large enough to be obvious to mailmen, secretaries, and other people who don't study global change for a living.
Using global weather records, Hansen based the index on conditions familiar to non-scientists--the number of hot days and the number of days with intense rainfall. Scientists believe a warmer planet will feature more hot days and more wet days. Dry areas will get hotter, and warmer temperatures in wet areas will increase evaporation, which will increase rain and snowfall. The result will be an increase of heavy storms and floods on one extreme and more droughts and forest fires on the other.
To create the index, Hansen and his coworkers used weather records from 1951 to 1997. They chose that period because most middle-aged adults grew up in those years and would be conscious of climate change if it was obvious.
Alaska and Siberia are two regions on the globe that have shown a significant shift in climate from 1951 to 1997. According to Hansen's index, people who have lived in Alaska since the 1950s should have noticed that a majority of summers seem hotter than normal in the Interior Alaska or that a majority of years seem wetter in Southeast.
Hansen hopes his index, available on the Internet at http://www.giss.nasa.gov , will allow people to compare one season's weather trend to another. For example, Anchorage, Barrow, Nome, Juneau, and Fairbanks experienced warmer-than-average temperatures in February, March and April, 1998, according to the Alaska Climate Research Center.
Is this global warming? The answer is probably no; it could be due to El Nino or natural climate variability, but by using the index, people can check to see if Alaska's spring was really unusual. Hansen and his colleagues have not updated the index to include Alaska's spring, but he said during a recent interview that March and April looked unusually warm at first glance.
Hansen said it is natural for climate to have short-term changes, such as a cold spring one year followed by a warm spring the next year, but it's also possible that Alaskans may have noticed a long-term change, where warmer springs are occurring more frequently than they did in decades past. If there is an enduring climate change that may be noticeable to Alaskans now, then much of the rest of the world may begin to notice the change during the next decade.
Hansen wants to test his hypothesis. Since Alaska is the first place where the climate index is approaching a significant level (where global warming should be becoming evident to people who have been here awhile), this gives him a chance to see how the index works.
For this reason, Hansen is interested in hearing from longtime Alaskans who have an opinion. Gunter Weller, director for the Center for Global Change and Arctic Systems Research at the University of Alaska, said that Alaskans are probably more sensitive to the winter, rather than the summer, climate. He notes that many longtime Alaskans say the winters are considerably warmer now than before, a fact supported by meteorological observations.
Are the seasons noticeably warmer than they were in the 1950s and 1960s? Are the rainstorms and snowstorms noticeably more intense? If you would like to offer your thoughts, write to me at the Geophysical Institute, P.O. Box 757320, Fairbanks, AK, 99775, call me at (907) 474-7468, or send an email: nrozell@gi.alaska.edu .
