Global Warming Impacts

By JOE GROSSMAN, UPI Science News

April 4 (UPI) -- Offical reports from both the United Nations and the United States conclude that there will be significant global warming in the century ahead.

The United Nations Intergovernmental Panel on Climate Change projects a potential range of 2.5 to 10.4 degrees F (1.4 to 5.8 degrees C) global average temperature increase by 2100, under a variety of scenarios.

A Congressionally-mandated report, the U.S. Assessment of the Potential Consequences of Climate Variability and Change, concludes that humanity's contribution to global warming will increase in coming years and that the impacts will affect every person. The report projects a 5.9 degrees Fahrenheit (3.3 degrees Centigrade) average temperature increase in the U.S. during the next 100 years, if no steps are taken to reduce worldwide emissions of greenhouse gases.

The exact outcome will be determined largely by how much carbon-based fuels, such as gasoline, coal and natural gas continue to be used, as well as energy demand and technologies employed.

Global temperature is rising due to increasing levels of greenhouse gases which trap heat from the sun in the earth's atmosphere. The gases, mainly carbon dioxide, come mostly from burning carbon-rich fuels. Worldwide global warming may impact crop production, food costs, ocean chemistry and productivity, patterns of rainfall, water availability, numerous plant and animal species, human health, human migration patterns and ocean levels.

Temperature increases will particularly impact agriculture. Hardest hit will be food growing regions in the tropics, affecting much of Asia and Africa. Additional heat causes reduced crop yields and key crops there, such as rice, corn (maize), sorghum and millet are already near their heat-related biological stress limit.

A 3.6 degrees Fahrenheit temperature increase in tropical regions results in about a 5 to 15 percent decrease in crop production, according to Martin Parry, director of the Jackson Environment Institute at the University of East Anglia in England. Many studies of a 3.6 to 5.4 degrees Fahrenheit temperature increase show a 15 to 25 percent crop decrease, said Parry, who specializes in impacts of climate change on agriculture.

"Above a 3.6 to 5.4 degrees Fahrenheit increase in global warming all regions of the world show a decrease in major staples," Parry, an IPCC author, told United Press International.

William Easterling, professor of geography and earth systems science at Pennsylvania State University, told UPI that with a 5.4 degrees Fahrenheit increase in climate, corn yields are projected to drop 18 percent and rice to decease 15 percent.

At increases more than 3.6 degrees Fahrenheit (2 degrees Celsius), economists involved with the IPCC predict increased food prices that will put many products out of the reach of hundreds of millions of people. As the planet heats up there will be more evaporation, reduced soil moisture and, ironically, increased rainfall. Shorter periods of more intense rain can also reduce crop yields as well as increase flooding.

Kathleen Miller, who studies water availability at the National Center for Atmospheric Research, told UPI there is a general consensus that Rocky Mountain snow will melt earlier, causing increased flooding in the spring and reduced water availability later in the year. Some economic projections for decreased rainfall, a potential regional scenario, show water infrastructure costs in the U.S. increasing by $100 billion a year, Miller said.

Numerous species of plants and animals will be affected according to the IPCC report and the U.S. Assessment of the Potential Consequences of Climate Variability and Change. Increases in the average global temperature of even less than 1.8 degrees Fahrenheit (1 degree Celsius) "may cause irreversible damage to some systems and species including possible global, regional or local loss," the IPCC states. Forty-four regional studies, involving more than 400 species of plants and animals, support the IPCC conclusion.

"Look at the temperatures in the last 20 years. Look at the distributions of organisms and the biology. You have a link between the changes in these organisms and the anthropogenic forcing (human-caused global warming)," James McCarthy, director of the Harvard Museum of Comparative Zoology and co-chair of the IPCC impact report, told UPI.
In the last 50 years, the upper 300 meters (328 yards) of the world's oceans has warmed 0.56 degree Fahrenheit, with a total ocean increase of 0.1 degree Fahrenheit, according to an article in the journal Science.

Warming oceans are rising due to melting of ice and the thermal expansion of water. Many inhabited islands are being slowly submerged and some temperature-sensitive corral reefs are dying. A 50-year study of the California Current showed a 70 percent decrease in plankton occurring as the upper hundred meters warmed about 1.8 degrees Fahrenheit, affecting the local food chain.

John McGowan, an author of the California Current study at the Scripps Institute of Oceanography, told UPI, "It's hard to say if the effect is occurring elsewhere, due to lack of data."

Ken Johnson, who studies ocean chemistry and productivity at the Monterey Bay Aquarium Research Institute, told UPI, "Fisheries in general are sort of collapsing around the world. . . . Is it overfishing? Is it environmental change? I don't think anybody can give you a definitive answer."

In humanity's diet, seafood provides 5 percent of the total protein and 20 percent of total protein from animals, according to data from the National Oceanic and Atmospheric Administration. Human health is also affected by climate change and will be impacted, according to the U.S. Assessment and the IPCC. Heat related illness, drowning from floods, air pollution from smog, and infectious diseases will all increase with global warming.

Jonathan Patz, who is director at Johns Hopkins School of Public Health of a program dealing with the health effects of global and environmental change, told UPI, "Environmental refugees and major population displacement could be a tremendous issue around the world." Patz, who worked on the U.S. Assessment and the IPCC report, gave examples of recent childhood diarrhea outbreaks and hantavirus epidemics related to regional climate changes.

Duane J. Gubler, director of the division of vector-borne infectious diseases at the Centers for Disease Control and Prevention, and also an author on the IPCC report and the U.S. Assessment, told UPI, "The most import issue with regard to human health is that the effects of global climate change, whatever they are, can be mitigated by developing and implementing good public health infrastructure and prevention strategies."

While the extent of climate change will be determined largely by how much CO2 is emitted worldwide from burning carbon-based fuels, impacts in specific countries will depend on what responses are developed, a factor often dictated by a nation's wealth.