The earth’s climate is warming primarily due to human activities that emit heat trapping gases, known as greenhouse gases. The burning of fossil fuels (coal, oil, and natural gas) in vehicles, power plants and other industrial processes releases into the atmosphere carbon dioxide, the most prevalent greenhouse gas due to human activities. Carbon dioxide remains in the atmosphere for many years, so past emissions have already set in motion changes we will live with for generations. After carbon dioxide, methane is the second most prevalent greenhouse gas due to human activities. Methane is emitted by the raising of livestock, sanitary landfills and leaks from natural gas and petroleum production and transportation systems, including fracking. Methane persists in the atmosphere for a much shorter period of time than carbon dioxide but over a 100-year period, its heat trapping capacity is about 30 times greater than that of carbon dioxide.
Scientists cannot precisely estimate the extent of future global warming, but the severity of the consequences depends on how rapidly we can reduce greenhouse gas emissions. Without reductions, the consequences, especially for future generations, will be horrendous. They will vary by location and include more severe heat waves affecting human health; more severe droughts threatening food production; more extreme rainfall events leading to more flooding; the extinction of many species; and the melting of sea ice and glaciers and warming of the oceans leading to sea level rise, affecting homes, businesses and infrastructure.