Facts About Global Warming


  • The global average surface air temperature increased by 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the past hundred years.
  • Source: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Intergovernmental Panel on Climate Change (2007-02-05).
  • Most of the increase in global average temperatures since the mid-twentieth century is likely due to the observed increase in anthropogenic (human caused) greenhouse gas concentrations.
  • Source: same as #1
  • Naturally occuring phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.
  • Source: Ammann, Caspar; et al. (2007-04-06). “Solar influence on climate during the past millennium: Results from ransient simulations with the NCAR Climate Simulation Model”.
  • IPCC climate model projections indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.
  • Source: same as #1
  • Increasing global temperature is expected to cause the sea level to rise, increase the intensity of extreme weather events and change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, trade routes, glacier retreat, species extinctions and increased prevalence of diseases.
  • Source: Wikipedia page on global warming
  • The greenhouse effect is the process by which absorption and emission of infrared radiation by atmospheric gases warm a planet’s lower atmosphere and surface. Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable.
  • Source: IPCC WG1 AR4 Report — Chapter 1: Historical Overview of Climate Change Science p97. IPCC (2007).
  • The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid 1700s. These levels are considerably higher than at any time during the last 650000 years, the period for which reliable data has been extracted from ice cores.
  • Source: Neftel, A., E. Moor, H. Oeschger, and B. Stauffer. (1985). “Evidence from polar ice cores for the increase in atmospheric CO2 in the past two centuries”. Nature 315:45-47.
  • The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume. Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change.
  • Source: Tans, Pieter. Trends in Atmospheric Carbon Dioxide – Mauna Loa. National Oceanic and Atmospheric Administration.
  • Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land. The Northern Hemisphere has more land than the Southern Hemisphere, so it warms faster.
  • Source: Rowan T. Sutton, Buwen Dong, Jonathan M. Gregory (2007). “Land/sea warming ratio in response to climate change: IPCC AR4 model results and comparison with observations”. Geophysical Research Letters 34.
  • 10 of the hottest years ever recorded were in the last 14 years and the hottest was in 2005.