University Of Texas Austin Biologist Develops New Evidence For Global Warming

According to scientists with the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research, temperature and precipitation records collected for the past century point to a slight increase in warmer weather throughout the world, accompanied by an increase in both the number and the severity of extreme weather events.

The scientists documented that rising temperatures and extreme weather also are having an impact on population, behavior, distribution and even the physical appearance of a wide variety of animals and plants in the wild. Dr. David R. Easterling, scientific director of NOAA's National Climatic Data Center in Asheville, N.C., is lead author on the paper.

Parmesan said the paper is especially significant because it coordinates data collected through the years on climate change with basic research on wildlife and with recent trends in wildlife attributed to climate change.

Scientists have plenty of evidence that extreme weather events can cause everything from bleaching of coral reefs and smaller beak size in some species of birds to changes in mating behavior of African elephants. Parmesan said the increasingly rapid extinction rate of species around the globe make it critical "to understand the specific impacts of climate change on those trends."

Parmesan said that, over many decades, a series of extreme weather events is believed to underlie a gradual range shift in the Edith's Checkerspot (Euphydryas Editha), a butterfly named for the checked patterns on its black, orange and cream-colored wings. This butterfly, found in the western part of North America, has moved northward and to higher altitudes over the past 100 years. Parmesan linked extreme weather events to the permanent disappearance of entire local populations of the colorful insects.

Parmesan said when reviewing research by other biologists, what really surprised her was that "every time (a Checkerspot) population went extinct, it was connected with an extreme climate year. The l976-77 California drought caused a lot of local population extinctions, and 20 years later they were still extinct." Due to the l983 El Nino, the snow never melted in some areas of Northern California's Gold Lake and the butterflies never emerged, she said.

Extreme weather events, from hurricanes to blizzards, are nothing new. But in the past, populations of animals were larger. When, for example, they shifted territory in response to a drought, they didn't run into farmland or urban areas. "Especially when you are talking about an endangered species that already is restricted to a very small habitat, one severe weather event can wipe out an entire species," Parmesan said.

Weather records reviewed for the study document an increase in the average global temperature of about 0.6 degrees centigrade since the beginning of the 20th century and a decrease in the number of days each year below freezing. Climate researchers have been looking for a link between the changes and increasing greenhouse gases from human activities. While some uncertainty remains, the evidence of such a link, especially in the past few decades, is growing stronger. Parmesan said a one or two-degree increase in global temperature in the next century doesn't sound like very much, but the increase "makes local extreme weather events even more extreme. In a particular year, the maximum high temperature in the summer could be 10 degrees hotter, and precipitation increasingly is coming down as floods," Parmesan said. "This is something that is happening now."