Global climate change is happening — here and now.
It no longer is theoretical. We can measure it — and take action.
The Greenhouse Effect
Scientists around the world agree that the phenomenon of global climate change is happening now, and the overwhelming majority agree that it is chiefly caused by human actions.
According to the Union of Concerned Scientists, "Over the past 30 years there has been a pattern of increasingly higher average temperatures for the whole world. In fact, the first decade of this century (2001–2010) was the hottest decade recorded since reliable records began in the late 1800s.
"These rising temperatures—caused primarily by an increase of heat-trapping emissions in the atmosphere created when we burn coal, oil, and gas to generate electricity, drive our cars, and fuel our businesses—are what we refer to as global warming."
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.
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Greenhouse Gasses and Climate Change
Over the last 200 years, the levels of greenhouse gasses in the atmosphere have risen markedly — especially carbon dioxide, which accounts for 55 percent of the greenhouse effect.
Greenhouse gasses reached record high levels in the 1990s, according to the Intergovernmental Panel on Climate Change (IPCC), the leading international body for the assessment of climate change. Alas, nations did too little to curb CO2 emissions, and atmospheric carbon dioxide levels in the early 2000s stood at around 376 parts per million (ppm), compared to a pre-Industrial Revolution level of about 280 ppm. Then, on May 10, 2013, The New York Times reported what scientists had long feared as a worst-case scenario: levels of CO2 in the atmosphere had hit a milestone of 400 ppm.
Most of the increase in greenhouse gases 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.
Unfortunately, efforts to curb greenhouse gas emissions proved too little, too late. According to the NOAA, 2012 set a record as the hottest year to date in the United States by a wide margin. Temperatures were 3.2ºF above the 20th century average, and 1ºF above the previous record set in 1998.
Globally, average temperatures keep rising steadily each year. Climate models predict the planet's average temperature will rise between 2ºF and 9.7º F by 2100. Carbon dioxide and other greenhouse gas levels continue a steady increase as well. Sea levels are rising, threatening coastal cities such as New York. Snow cover in the Northern Hemisphere is beaing affected, with snows melting earlier each year compared to the long-term average.
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.
"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: global sea level rose 0.1 to 0.2 meters (about 4 to 8 inches);
arctic sea ice thinned 40 percent;
glaciers retreated around the globe;
permafrost thawed;
more frequent El Niño events took place;
plant and animal ranges shifted poleward and higher in elevation.
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 to take effect. With Russia's assent, the accord took force in February, 2005. On Dec. 8, 2012, in Doha, Qatar, the "Doha Amendment to the Kyoto Protocol" was adopted.
Under the Bush administration, the United States refused to take part in the Kyoto Protocol, and 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 Bush claimed that CO2 is "not a pollutant under the Clean Air Act," and refused to regulate it. In place of the Kyoto Protocol, 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
Impacts of Climate Change on California Forests