Climate Change 101

Global warming is caused by an increase of greenhouse gases in the atmosphere. Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The main greenhouse gases in the Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

Carbon dioxide is a major greenhouse gas and is produced by human activities like burning fossil fuels and clearing forests. Carbon dioxide acts like a blanket that traps heat in our atmosphere and warms our climate. Oceans, forests, and land can absorb some of this carbon, but not as fast as we are creating it. Human activities since the start of the industrial era around 1750 have increased the levels of greenhouse gases in the atmosphere. The 2007 assessment report compiled by the Intergovernmental Panel on Climate Change (IPCC) observed that “changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system”, and concluded that “increases in anthropogenic greenhouse gas concentrations is very likely to have caused most of the increases in global average temperatures since the mid-20th century”.

Greenhouse Gas Emissions by Sector

The above graph shows the major sources of greenhouse gasses overall as well as the major sources of the most abundant and harmful greenhouse gases.  Burning fossil fuels, in coal-fired power plants and in automobile engines, creates most of the carbon dioxide emissions.  However, agricultural processes produce the bulk of the methane and nitrous oxide emissions. As a result, heat-trapping emissions are building up in our atmosphere to levels that could produce severe effects including extreme heat, prolonged droughts, intense storms, corrosive ocean acidification, and dangerous sea-level rise. Because these emissions linger in the atmosphere for 100 years or more, we must act quickly to avert the worst effects of global warming.