A great deal of recent media attention has been focused on the possible connection between global warming and extreme weather events. In fact, the 1995 UN science report stated that "overall, there is no evidence that extreme weather events, or climate variability, has increased, in a global sense, through the 20th Century." (Section 3.5.4, pg. 173.)
Hurricanes and Tornadoes
Although some people have argued that hurricanes are becoming stronger and more frequent and that droughts and floods are becoming more common, recent work by scientists worldwide dispute this hypothesis. Observational data show that the frequency of both hurricanes and violent tornadoes have not increased in recent decades. Sound theoretical arguments have been advanced that indicate even if global warming does occur, the frequency and aerial extent of hurricanes are not likely to increase. (Macdonald, Norman J., and Sobel, Joseph P., Changing Weather? Facts and Fallacies about Climate Change and Weather Extremes, Accu- Weather, Inc., 1995, page 3.)
There is basically no trend of any sort in the number of hurricanes experienced in any of the four regions [central Atlantic, east coast of the U.S., Gulf of Mexico, and Caribbean Sea, for the period 1947 to 1987] with respect to variations in temperature. (S.B. Idso, R.C. Balling, Jr., and R.S. Cerveny, "Carbon Dioxide and Hurricanes: Implications of Northern Hemispheric warming for Atlantic/Caribbean storms," Meteorology and Atmospheric Physics, Vol. 42 (1990), p. 261.
Heat Waves
The 1995 UN science report found that there was no evidence of an increase in extreme maximum temperatures across the United States. (IPCC Climate Change 1995, Working Group 1, section 3.5.3.4.)
Drought
Recent droughts in the Southwest and the excessive rainfall in the East are related to certain unusual features of the jet stream. There is substantial evidence that variations in the jet stream and associated drought conditions over the Southwest were due in part to abnormally cold sea temperatures over the central and eastern equatorial Pacific. (Dole, Randall M., NOAA Environmental Research Laboratories, Climate Diagnostic Center.)
Sea-Level Rise
"Initial estimates by the Environmental Protection Agency projected that a doubling of atmospheric carbon dioxide would cause sea level rises to rise by between 80 and 120 inches. By 1990 these estimates had been reduced by 75%. In 1996 a United States science advisory panel predicted a rise of only 15 to 22 inches by 2100 -- still based on shaky assumptions."
"Data from the warming of 1900-1940 show a drop in sea levels, while the subsequent cooler period shows a sea level rise. This effect is even more pronounced in comparisons of sea-level changes with sea-surface temperatures in the tropics, where most of the oceans’ evaporation occurs."
"These findings support the hypothesis that ice accumulation in the polar regions may have a greater impact on sea levels than do the melting of glaciers and the thermal expansion of ocean water. Support for this view also comes from concurrent but as yet incomplete measurements of ice accumulation at certain locations in Greenland and the Antarctic." Fred Singer, professor emeritus on environmental sciences, University of Virginia, "The Sky Isn’t Falling, and the Ocean Isn’t Rising."
While sea levels have always fluctuated throughout history, increases in global average temperatures have the potential to impact sea levels in three ways. Water expands in volume as its temperature increases above current levels, and this "thermal expansion" is the primary driver of predictions of rising sea levels. In addition, any melting of the polar ice caps could augment the sea level rise. Offsetting thes factors, higher average temperature could result in an increase in precipitation. This could have the effect of removing water from the sea through evaporation, and depositing the water via increased snowfall in polar regions, resulting in a buildup of water stored as accumulated snow and ice away from the sea. Current estimates are that sea levels have risen five to ten inches over the past 100 years, with the UN’s scientific panel on climate change predicting in 1995 a 20 inch increase over the next 100 years. This prediction compares to their 1990 estimate of a 26 inch increase over 100 years. Models which assign more importance to the precipitation effect predict smaller sea level changes and some models even show a sea level decrease.
Agriculture
"Global changes in temperature and precipitation patterns during the next century are not likely to imperil food production for the world as a whole." (U.S. Department of Agriculture Economic Research Service, June 1995.)
"The effects of the increasing atmospheric level of CO2 on photosynthetic capacity for the enhancement of food production and the output of rangelands and forests, appear far more important than any detectable change in climate." Sylvan H. Wittwer, "The Global Environment: It's Good for Food Production," 1997.
Health
"Fewer than 50 years ago malaria was endemic in many mid-latitude countries of the temperate zones and occasionally reached as far north as the Arctic Circle. The Netherlands, which last time we checked was a tad north of the tropical rain forests, wasn't declared malaria-free until 1970." Dr. Paul Reiter, Global Warming and Mosquito-borne Disease in the U.S., The Lancet, 1996. "Singapore, which is located just 2 degrees from the equator, reported no deaths from malaria in 1994. Malaysia, just next door, suffers from endemic malaria and dengue fever. The difference is not the climate, but the wealth of the two areas." Thomas Gale Moore, WHO Cares!, World Climate Report.
"Simple steps, such as screens on windows, the elimination of standing water, and suburbanization (which reduced population density and thus the risk of transmission) were largely responsible for eliminating mosquito-borne diseases. As evidence, we previously reported on a 1995 dengue pandemic that infected a Mexican state that borders Texas. Reynosa, Mexico reported 2,361 cases; the entire state of Texas reported eight cases. The only reasonable explanation for the difference is living standards. Where people enjoy good sanitation and public education, have the knowledge and the willingness to manage fresh water around households, implement programs to control mosquitoes, and employ screens and air-conditioning, these mosquito-borne diseases cannot spread. If the climate does warm, these factors will remain." Thomas Gale Moore, "The Big Scare", World Climate Report, December 30, 1996.
"Evidence for the importance of context can be found in the historic extent of malaria. Between 1780 and 1840 virtually all people living in Ontario, as far north as Ottawa, suffered from a disease ... now recognized as being benign tertian Malaria … Few climatologists would argue that there has been significant regional cooling in Ontario since 1840, so why did the incidence of malaria change from being almost universal to afflicting fewer than one patient per decade? Today, Ontario continues to host three species of anopheline mosquitoes capable of transmitting malaria. However, the large swamps in the south of the province have been drained, other surface waters are well managed, and disease surveillance leads to rapid isolation of patients and severance of the parasite-host cycle essential to further transmission of the disease. It is clear that public health measures, case management, and land use play a [more] significant role in determination of the prevalence of malaria than climate." Hadi Dowlatabadi, "Assessing the Health Impacts of Climate Change," Degrees of Change Newsletter, Global Change Integrated Assessment Program, Carnegie Mellon, September, 1996.
No comments:
Post a Comment