CCScientific evidence for warming of the climate system is unequivocal.
– Intergovernmental Panel on Climate Change
This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct  measurements, provides evidence that atmospheric CO<sub>2</sub> has increased  since the Industrial Revolution.  (Source: [[LINK||||NOAA]])
This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Credit: Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.)

The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.2 Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.

Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. They also show that in the past, large changes in climate have happened very quickly, geologically-speaking: in tens of years, not in millions or even thousands.3

The evidence for rapid climate change is compelling:

  • Republic of Maldives: Vulnerable to sea level rise.

    Sea level rise

    Global sea level rose about 17 centimeters (6.7 inches) in the last century. The rate in the last decade, however, is nearly double that of the last century.4

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  • Global temperature rise

    All three major global surface temperature reconstructions show that Earth has warmed since 1880.5 Most of this warming has occurred since the 1970s, with the 20 warmest years having occurred since 1981 and with all 10 of the warmest years occurring in the past 12 years.6 Even though the 2000s witnessed a solar output decline resulting in an unusually deep solar minimum in 2007-2009, surface temperatures continue to increase.7

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  • Warming oceans

    The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.8

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  • Flowing meltwater from the Greenland ice sheet

    Shrinking ice sheets

    The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.

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  • Visualization of the 2007 Arctic sea ice minimum

    Declining Arctic sea ice

    Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades.9

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  • The disappearing snowcap of Mount Kilimanjaro, from space.

    Glacial retreat

    Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.10

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  • Extreme events

    The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.11

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  • Ocean acidification

    Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent.12,13 This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.14,15

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  • Decreased snow cover

    Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier.16

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Scientific Consensus

Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities, and most of the leading scientific organizations worldwide have issued public statements endorsing this position.

Click here for a partial list of these public statements and related resources.


  1. IPCC Fourth Assessment Report, Summary for Policymakers, p. 5

    B.D. Santer, “A search for human influences on the thermal structure of the atmosphere,” Nature vol 382, 4 July 1996, 39-46

    Gabriele C. Hegerl, “Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method,” Journal of Climate, v. 9, October 1996, 2281-2306

    V. Ramaswamy, “Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling,” Science 311 (24 February 2006), 1138-1141

    B.D. Santer, “Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes,” Science vol. 301 (25 July 2003), 479-483.

  2. In the 1860s, physicist John Tyndall recognized the Earth’s natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first speculated that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect.

  3. National Research Council (NRC), 2006. Surface Temperature Reconstructions For the Last 2,000 Years. National Academy Press, Washington, DC.

  4. Church, J. A. and N.J. White (2006), A 20th century acceleration in global sea level rise, Geophysical Research Letters, 33, L01602, doi:10.1029/2005GL024826.

    The global sea level estimate described in this work can be downloaded from the CSIRO website.

  5. T.C. Peterson, “State of the Climate in 2008,” Special Supplement to the Bulletin of the American Meteorological Society, v. 90, no. 8, August 2009, pp. S17-S18.

  6. I. Allison, The Copenhagen Diagnosis: Updating the World on the Latest Climate Science, UNSW Climate Change Research Center, Sydney, Australia, 2009, p. 11 01apr_deepsolarminimum.htm

  7. Levitus, et al, “Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems,” Geophys. Res. Lett. 36, L07608 (2009).

  8. L. Polyak,, “History of Sea Ice in the Arctic,” in Past Climate Variability and Change in the Arctic and at High Latitudes, U.S. Geological Survey, Climate Change Science Program Synthesis and Assessment Product 1.2, January 2009, chapter 7

    R. Kwok and D. A. Rothrock, “Decline in Arctic sea ice thickness from submarine and ICESAT records: 1958-2008,” Geophysical Research Letters, v. 36, paper no. L15501, 2009

  9. C. L. Sabine, “The Oceanic Sink for Anthropogenic CO2,” Science vol. 305 (16 July 2004), 367-371

  10. National Snow and Ice Data Center

    C. Derksen and R. Brown, “Spring snow cover extent reductions in the 2008-2012 period exceeding climate model projections,” GRL, 39:L19504

    Rutgers University Global Snow Lab, Data History Accessed August 29, 2011.



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