8. Global Warming Trends ‘ Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.' Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007
9. Global Warming Trends | Observations of recent climate change Global mean temperature Global average sea level Northern hemisphere snow cover
10. Global Warming Trends | Carbon Dioxide Concentration Adapted from USGCRP (US Global Change Research Program)
11. Carbon Dioxide Concentration 800 600 400 200 0 CO 2 (ppmv) Thousands of Years Before Present 240 300 270 210 180 Petit et al., 1999; Siegenthaler et al., 2005; EPICA Community members, 2004 Temp. Proxy Present CO 2 concentration (383 ppmv) CO 2 concentration after 50 years of unrestricted fossil fuel burning (600 ppmv)