Global Warming Law and Legal Definition

Global warming is the increase in the average temperature of Earth's near-surface air and oceans. The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increase since the middle of the 20th century was very likely caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation.

In the 20th century the worldwide average temperature climbed 0.6 degrees Celsius. In 2001, the IPCC reported that the world’s average temperature will increase by between 1.4 and 5.8 degrees Celsius by the year 2100. As these rising temperatures melt ice, especially in Greenland and Antarctica, and create thermal expansion, sea levels will rise. Four of the world’s 20 cities most vulnerable to sea level rise are in the United States: New York, Virginia Beach, Miami and New Orleans.

Animals are migrating northwards or to higher altitudes, with a recent study of nearly 2,000 species of plants and animals showing movement “towards the poles at an average rate of 3.8 miles per decade. Such migrations can disrupt delicate ecosystems that have taken millennia to develop. Polar bears have started drowning as they have had to swim longer distances between ice flows, and the U.S. Geological Survey has predicted that if the Arctic ice cape continues melting at its current rate, two-thirds of the world's polar bear sub-populations will be extinct by mid-century.

The available options to compact global warming are mitigation to reduce further emissions; adaptation to reduce the damage caused by warming; and, more speculatively, promote geoengineering to reverse global warming.