Nature Ignores Science on Greenland Ice Shelf
A feature article, Rising Tide, in the March 11 issue of Nature claims that global warming is melting Greenlands ice so rapidly that the whole ice sheet may melt and cause sea levels to rise significantly. However, as the Greening Earth Societys World Climate Alert (http://www.co2andclimate.org/wca/2004/wca_14d.html) points out, the Nature article is at variance with published scientific research, which finds that Greenland warmed rapidly in the 1920s without causing disastrous melting of the ice sheet, but has been in a cooling trend since 1940.
The most recent of a number of research articles that contradict Nature is Global Warming and the Greenland Ice Sheet, by P. Chylek, J. E. Box, and G. Lesins, which appears in the March issue of Climate Change. The articles abstract says, Since 1940, however, the Greenland coastal stations data have undergone predominantly a cooling trend. At the summit of the Greenland ice sheet, the summer average temperature has decreased at the rate of 2.2C per decade since the beginning of the measurements in 1987. This suggests that the Greenland ice sheet and coastal regions are not following the current global warming trend.
The authors found the most pronounced warming in the 1920s when the average annual surface air temperature rose between 2C and 4C in less than 10 yearsat a time when the change in anthropogenic production of greenhouse gases was well below the current level.
World Climate Alert points out, A 1C warming of the coastal stations would cause an increase in the melt area of 73,000 square kilometers, as Chylek et al. note. Given the 1C to nearly 2C cooling found in the coastal stations, Chyleks team makes this conservative statement, The results are inconclusive for the ice sheet as a whole, owing to the large uncertainties when balancing very large, difficult to measure, offsetting quantities. They add, Even the direction in which the mass of the Greenland ice sheet is currently changing is in dispute. In other words, anyone who claims Greenland is melting wont find a lot of support in the scientific literature.
NASA Finds Global Climate Models Overestimate Warming
A NASA press release dated March 16 contains interesting news for those who have disputed the strength of positive water vapor feedback effects in global climate models.
The release states, A NASA-funded study found some climate models might be overestimating the amount of water vapor entering the atmosphere as the Earth warms. Since water vapor is the most important heat-trapping greenhouse gas in our atmosphere, some climate forecasts may be overestimating future temperature increases.
Ken Minschwaner, a physicist at the New Mexico Institute of Mining and Technology, Socorro, N.M., and Andrew Dessler, a researcher with the University of Maryland, College Park, and NASA’s Goddard Space Flight Center, Greenbelt, Md., did the study. It is in the March 15 issue of the American Meteorological Society’s Journal of Climate. The researchers used data on water vapor in the upper troposphere (10-14 km or 6-9 miles altitude) from NASA’s Upper Atmosphere Research Satellite (UARS).
Their work verified water vapor is increasing in the atmosphere as the surface warms. They found the increases in water vapor were not as high as many climate-forecasting computer models have assumed. Our study confirms the existence of a positive water vapor feedback in the atmosphere, but it may be weaker than we expected, Minschwaner said.
In most computer models relative humidity tends to remain fixed at current levels. Models that include water vapor feedback with constant relative humidity predict the Earth’s surface will warm nearly twice as much over the next 100 years as models that contain no water vapor feedback.
Using the UARS data to actually quantify both specific humidity and relative humidity, the researchers found, while water vapor does increase with temperature in the upper troposphere, the feedback effect is not as strong as models have predicted. The increases in water vapor with warmer temperatures are not large enough to maintain a constant relative humidity, Minschwaner said. These new findings will be useful for testing and improving global climate models.