Climate change is defined as a long-term shift in global or regional climate patterns. A majority of the world’s scientific community and most of the world’s political community now agree that man’s activities in burning carbon-based fuels (coal, petroleum, and natural gas) are resulting in raised concentrations of greenhouse gases that increase the earth’s average temperature and destabilize weather patterns. If the trend continues, results could be severe and include melting of ice packs, flooding of low-lying areas, interruption of food production, water shortages, and increased incidents of severe weather including storms and heat waves. Electric power production by fossil fuels is a significant contributor to greenhouse gas emissions. Coal generation is responsible for more CO2 than any other generation source. Coal generation emits about twice as much CO2 per unit of output than natural gas generation, but the advantage for natural gas is not as great if emissions during fuel production and transport are considered. Control technologies for CO2 emissions from traditional power plants are being researched and tested in pilot projects but are not currently widely commercially available.
Greenhouse gas emissions by generators are often measured in units of gCO2eq/kWh, which stands for grams of carbon dioxide equivalent per kilowatt-hour of electricity generated. A recent study by the Intergovernmental Panel on Climate Change (IPCC) estimated the following levels of greenhouse gas outputs for various forms of new generation:
Note that these are life cycle emissions that include emissions during construction and fuel production.
In late 2016 an international accord called the Paris Agreement went into effect. The accord was signed by 194 countries, and its goals included holding down the increase in global average temperature due to greenhouse gases, increasing the world's ability to adapt to climate change, making financing available for pathways to reducing greenhouse gas emissions, and achieving global peaking of greenhouse gas emissions as soon as possible. A number of countries, including China, the U.S., and the member states of the E.U. made non-binding commitments to achieve specific targets associated with limiting greenhouse gas emissions. In 2017, the U.S. administration announced that it would cease all participation in the agreement and planned to withdraw from the agreement completely by 2020. Meanwhile other countries continued their support, although as of 2019 many have yet to meet initial targets. In the U.S. numerous states, cities, and corporations stated their support for the agreement, and many took positive actions to reduce their greenhouse gas emissions. Thus as of 2019, the power generation industry's movement toward meaningful reductions of greenhouse gas emissions remains uncertain.