Global Climate Change

Global climate change is happening—here and now. It is no longer a theory,
but something that can be measured—and responded to.

The Greenhouse Effect

The greenhouse effect is a natural process that keeps the Earth about 33 degrees Centigrade warmer than it would be without the presence of greenhouse gasses in the atmosphere. These gasses– water vapor, carbon dioxide, methane, and nitrous oxide are the most important– trap infrared radiation reflected off the Earth by the sun’s rays, warming the lower atmosphere (troposphere) and the planet’s surface. Without the greenhouse effect, the earth would be a very different place. The oceans would be frozen solid, and human life as we know it would not exist.

Greenhouse Gasses and Climate Change

Over the last 200 years, however, the levels of these greenhouse gasses in the atmosphere (especially carbon dioxide) have risen markedly. Greenhouse gasses reached their highest recorded levels in the 1990s, according to the third report from the Intergovernmental Panel on Climate Change (IPCC). Carbon dioxide accounts for 55 percent of the greenhouse effect. Atmospheric carbon dioxide levels are now at around 376 parts per million, compared to a pre-

Click here for full-screen graphic

Click here for full-screen graphic

Industrial Revolution level of about 280 parts per million. Most of this increase is due to human activities, including the burning of fossil fuels, rice cultivation, and deforestation. This increase has led to what is called the "enhanced Greenhouse Effect." This enhanced effect is responsible for the current episode of global climate change. As the amount of greenhouse gasses in the atmosphere has increased, the global average temperature has risen. The 1990s were the warmest decade since records have been kept (starting in 1861); 1998 was the warmest year. The 12-month period from June 2001 to May 2002 was the second warmest on record.

The third IPCC report projects a global average surface temperature rise of between 1.4 and 5.8 degrees centigrade (approximately 2 to 10 degrees Fahrenheit) over the next 100 years. "The projected rate of warming," according to the IPCC, "is very likely to be without precedent during at least the last 10,000 years." Sea level could rise from .08 to 0.88 meters (about 3 to 35 inches) in the same period. This rate of climate change would cause significant global impacts both ecologically and societally.

Some of the changes that took place during the 20th century due to climate change, according to the IPCC 2001 report:

The Larsen B ice sheet in Antarctica has been breaking up in response to higher temperatures. MODIS image courtesy of NASA's Terra satellite, supplied by Ted Scambos, National Snow and Ice Data Center, University of Colorado, Boulder.

While some species undoubtedly would not be able to adapt and cope with higher temperatures, others would thrive in the new climate, crowding out other species. Evidence of this shift already has been found at Rocky Mountain National Park. A World Wildlife Fund study there found an increase in exotic plants at higher elevations recently, while timberline spruce trees, normally stunted, now are growing at an abnormally high rate.

Global climate changes will affect human beings as well. The 2001 IPCC study estimated that 80 million people will be displaced from coastal lowlands and islands within the next 100 years due to a global-warming-induced rise in sea level.

The Kyoto Protocol

The Kyoto Protocol, an international treaty that seeks to limit greenhouse gas emissions to 1990s levels, was signed by 160 nations in 1997. The treaty required ratification by 55 countries before it can take effect. Russia’s recent ratification of the treaty means that it will be in force early in 2005.

Under the Bush administration, the United States has refused to take part in the Kyoto Protocol, and has spurned further negotiations. The administration objected to what it felt was uneven treatment of the developing nations under the treaty, and said that the proposed limits on CO2 would damage the U.S. economy.

Reneging on his campaign pledge to regulate carbon dioxide emissions, the president now claims that CO2 is "not a pollutant under the Clean Air Act," and refuses to regulate it. In place of the Kyoto Protocol, President Bush has proposed instead a voluntary plan to reduce greenhouse gas emissions by 4.5 percent over 10 years.

The United States, with 5 percent of the global population, is responsible for 22 percent of global carbon dioxide emissions, more than any other nation.

Forests and Climate Change