Climate Change Overview


There is overwhelming scientific evidence that we are experiencing global warming, and that is it due to human-made greenhouse gas emissions, not to a “natural” cycle. Two key indicators of climate change had record-breaking years in 2016: the global mean surface temperature was the highest since recording began in 1880, and the average Arctic sea ice extent was the smallest annual average since record-keeping began in 1979. The greenhouse effect, caused by the burning of fossil fuels, has accelerated as carbon dioxide concentration in the atmosphere has soared to more than 400 parts per million (ppm). As a result of global warming, sea levels are projected to rise at least one-meter (39.4 inches), possibly two meters (78.7 inches), by 2100. It is vitally important that the nations of the world reduce CO2 emissions to slow down global warming. This chapter gives an overview of domestic and global trends in, and impacts from, climate change.
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Global Warming And Greenhouse Gas Emissions

The Earth’s average temperature has been rising over the past century; this phenomenon has been confirmed by many recorded observations of air and water temperatures, sea level, and ice. According to the Intergovernmental Panel on Climate Change (IPCC), the leading international body for the assessment of climate change. the rate of change is unprecedented in human history and “human influence has been the dominant cause of this observed warming” (IPCC, 2014). The IPCC was established by the United Nations Environment Programme (UNEP) in 1988; every few years, it convenes climate experts from around the world to develop comprehensive assessments based on the latest peer-reviewed scientific/technical literature.

In the United States, the government has acknowledged that climate change poses “a significant health threat” to Americans (USGCRP, 2016). Climate change has caused changes in the weather, including rising temperatures and more frequent extreme weather events, but the two terms should not be confused: weather is the state of the atmosphere at any given time and place. Climate is the average weather conditions over many decades. The weather may change in minutes or hours, but a change in climate requires multiple decades to centuries or longer.

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