This website is the digital version of the 2014 National Climate Assessment, produced in collaboration with the U.S. Global Change Research Program.

For the official version, please refer to the PDF in the downloads section. The downloadable PDF is the official version of the 2014 National Climate Assessment.

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Welcome to the National Climate Assessment

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

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Figure 33.5: Atmospheric Carbon Dioxide Levels

Atmospheric Carbon Dioxide Levels

Figure 33.5: Air bubbles trapped in an Antarctic ice core extending back 800,000 years document the atmosphere’s changing carbon dioxide concentration. Over long periods, natural factors have caused atmospheric CO2 concentrations to vary between about 170 to 300 parts per million (ppm). As a result of human activities since the Industrial Revolution, CO2 levels have increased to 400 ppm, higher than any time in at least the last one million years. By 2100, additional emissions from human activities are projected to increase CO2 levels to 420 ppm under a very low scenario, which would require immediate and sharp emissions reductions (RCP 2.6), and 935 ppm under a higher scenario, which assumes continued increases in emissions (RCP 8.5). This figure shows the historical composite CO2 record based on measurements from the EPICA (European Project for Ice Coring in Antarctica) Dome C and Dronning Maud Land sites and from the Vostok station. Data from Lüthi et al. 20081 (664-800 thousand years [kyr] ago, Dome C site); Siegenthaler et al. 20052 (393-664 kyr ago, Dronning Maud Land); Pépin 2001, Petit et al. 1999, and Raynaud 20053,4,5 (22-393 kyr ago, Vostok); Monnin et al. 20016 (0-22 kyr ago, Dome C); and Meinshausen et al. 20117 (future projections from RCP 2.6 and 8.5).

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References

  1. Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J. M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T. F. Stocker, 2008: High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature, 453, 379-382, doi:10.1038/nature06949. URL | Detail

  2. Meinshausen, M., S. J. Smith, K. Calvin, J. S. Daniel, M. L. T. Kainuma, J. F. Lamarque, K. Matsumoto, S. A. Montzka, S. C. B. Raper, K. Riahi, A. Thomson, G. J. M. Velders, and D. P. P. van Vuuren, 2011: The RCP greenhouse gas concentrations and their extensions from 1765 to 2300. Climatic Change, 109, 213-214, doi:10.1007/s10584-011-0156-z. URL | Detail

  3. Monnin, E., A. Indermühle, A. Dällenbach, J. Flückiger, B. Stauffer, T. F. Stocker, D. Raynaud, and J. M. Barnola, 2001: Atmospheric CO2 concentrations over the last glacial termination. Science, 291, 112-114, doi:10.1126/science.291.5501.112. | Detail

  4. Petit, J. R., J. Jouzel, D. Raynaud, N. I. Barkov, J. - M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. Delmotte, V. M. Kotlyakov, M. Legrand, V. Y. Lipenkov, C. Lorius, L. Pépin, C. Ritz, E. Saltzman, and M. Stievenard, 1999: Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature, 399, 429-436, doi:10.1038/20859. | Detail

  5. Pépin, L., D. Raynaud, J. - M. Barnola, and M. F. Loutre, 2001: Hemispheric roles of climate forcings during glacial-interglacial transitions as deduced from the Vostok record and LLN-2D model experiments. Journal of Geophysical Research, 106, 31,885-31,892, doi:10.1029/2001JD900117. URL | Detail

  6. Raynaud, D., J. - M. Barnola, R. Souchez, R. Lorrain, J. - R. Petit, P. Duval, and V. Y. Lipenkov, 2005: Palaeoclimatology: The record for marine isotopic stage 11. Nature, 436, 39-40, doi:10.1038/43639b. | Detail

  7. Siegenthaler, U., E. Monnin, K. Kawamura, R. Spahni, J. Schwander, B. Stauffer, T. F. Stocker, J. Barnola, and H. Fischer, 2005: Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium. Tellus B, 57, 51-57, doi:10.1111/j.1600-0889.2005.00131.x. URL | Detail

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

United States Global Change Research Program logo United States Global Change Research Program participating agency logos