Global Climate Change: Major Scientific and Policy Issues

Publication Date: August 2006

Publisher: Library of Congress. Congressional Research Service

Author(s):

Research Area: Environment

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Abstract:

There is growing evidence that human activities are affecting the heat/energyexchange balance between Earth, the atmosphere, and space through an increase in "greenhouse gases." If these gases continue to accumulate in the atmosphere at current rates, most scientists believe significant global warming would continue to occur through intensification of Earth's natural heat-trapping "greenhouse effect." Over the past 100 years, particularly in recent decades, there have been measurable increases in global temperature and sea levels, decreases of sea ice in the Arctic, and melting among the world's continental ice sheets and mountain glaciers. A preponderance of the world's scientists have concluded that human activities, particularly the burning of fossil fuels, have increased atmospheric concentrations of carbon dioxide (CO2) by 36% from pre-industrial levels of 280 parts per million (ppm) to 380 ppm over the past 150 years, leading to an increase in global average temperature of 0.9oF over the past 100 years. There is broad agreement on those aspects of climate change, which have been measured and are reflected in global data. Disagreements focus mainly on the magnitude and rate of change, the severity of estimated warming, and its projected impacts -- both positive and negative. Moreover, wide variations of scientific opinion accompany model projections of a warmer world: if these increases in greenhouse gas emissions continue, global average temperature could rise anywhere from 2.7oF to 10.7oF over the next 100 years. Because the U.S. economy is so dependent upon energy, and so much of U.S. and worldwide energy is derived from fossil fuels, options for reducing emissions of carbon dioxide and other greenhouse gases pose major challenges and controversy.

The basic policy question remains: Given scientific uncertainties about the magnitude, timing, rate, and regional consequences of potential climatic change, what are the appropriate responses for U.S. and world decision makers?

The 1992 United Nations Framework Convention on Climate Change (UNFCCC), ratified by the United States , called for a "non-binding," voluntary aim for industrialized countries to stabilize their emissions of greenhouse gases at 1990 levels by the year 2000. This was followed by the 1997 Kyoto Protocol to the UNFCCC, which commits the major industrialized nations that have ratified it to specified, legally binding emissions reductions. On February 16, 2005, the Kyoto Protocol entered into force without ratification by the United States. As of July 10, 2006, 164 nations and economic regional integration organizations had ratified the Protocol. In March 2001, the Bush Administration rejected the Kyoto Protocol, and thus the United States is not party to it (and therefore is not subject to its requirements). President Bush concluded a cabinet-level climate policy review with an announcement in 2002 of a "new approach" for the United States based on reducing the greenhouse gas intensity (greenhouse gas emissions per unit of GDP) of the U.S. economy.

This report briefly reviews the status of climate science, international negotiations, and congressional activity focused specifically on climate change. It replaces CRS Issue Brief IB89005.