Publication Abstracts

Hayhoe et al. 2017

Hayhoe, K., J. Edmonds, R.E. Kopp, A.N. LeGrande, B.M. Sanderson, M.F. Wehner, and D.J. Wuebbles, 2017: Climate models, scenarios, and projections. In Climate Science Special Report: Fourth National Climate Assessment, Volume I. D.J. Wuebbles, D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock, Eds., U.S. Global Change Research Program, pp. 133-160, doi:10.7930/J0WH2N54.

If greenhouse gas concentrations were stabilized at their current level, existing concentrations would commit the world to at least an additional 1.1°F (0.6°C) of warming over this century relative to the last few decades (high confidence in continued warming, medium confidence in amount of warming).

Over the next two decades, global temperature increase is projected to be between 0.5°F and 1.3°F (0.3°-0.7°C) (medium confidence). This range is primarily due to uncertainties in natural sources of variability that affect short-term trends. In some regions, this means that the trend may not be distinguishable from natural variability (high confidence).

Beyond the next few decades, the magnitude of climate change depends primarily on cumulative emissions of greenhouse gases and aerosols and the sensitivity of the climate system to those emissions (high confidence). Projected changes range from 4.7°-8.6°F (2.6°-4.8°C) under the higher scenario (RCP8.5) to 0.5°-1.3°F (0.3°-1.7°C) under the much lower scenario (RCP2.6), for 2081-2100 relative to 1986-2005 (medium confidence).

Global mean atmospheric carbon dioxide (CO2) concentration has now passed 400 ppm, a level that last occurred about 3 million years ago, when global average temperature and sea level were significantly higher than today (high confidence). Continued growth in CO2 emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens of millions of years (medium confidence). The present-day emissions rate of nearly 10 GtC per year suggests that there is no climate analog for this century any time in at least the last 50 million years (medium confidence).

The observed increase in global carbon emissions over the past 15-20 years has been consistent with higher scenarios (very high confidence). In 2014 and 2015, emission growth rates slowed as economic growth has become less carbon-intensive (medium confidence). Even if this trend continues, however, it is not yet at a rate that would limit the increase in the global average temperature to well below 3.6°F (2°C) above preindustrial levels (high confidence).

Combining output from global climate models and dynamical and statistical downscaling models using advanced averaging, weighting, and pattern scaling approaches can result in more relevant and robust future projections. For some regions, sectors, and impacts, these techniques are increasing the ability of the scientific community to provide guidance on the use of climate projections for quantifying regional-scale changes and impacts (medium to high confidence).

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BibTeX Citation

  author={Hayhoe, K. and Edmonds, J. and Kopp, R. E. and LeGrande, A. N. and Sanderson, B. M. and Wehner, M. F. and Wuebbles, D. J.},
  editor={Wuebbles, D. J. and Fahey, D. W. and Hibbard, K. A. and Dokken, D. J. and Stewart, B. C. and Maycock, T. K.},
  title={Climate models, scenarios, and projections},
  booktitle={Climate Science Special Report: Fourth National Climate Assessment, Volume I},
  publisher={U.S. Global Change Research Program},
  address={Washington, D.C.},

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RIS Citation

ID  - ha08810g
AU  - Hayhoe, K.
AU  - Edmonds, J.
AU  - Kopp, R. E.
AU  - LeGrande, A. N.
AU  - Sanderson, B. M.
AU  - Wehner, M. F.
AU  - Wuebbles, D. J.
ED  - Wuebbles, D. J.
ED  - Fahey, D. W.
ED  - Hibbard, K. A.
ED  - Dokken, D. J.
ED  - Stewart, B. C.
ED  - Maycock, T. K.
PY  - 2017
TI  - Climate models, scenarios, and projections
BT  - Climate Science Special Report: Fourth National Climate Assessment, Volume I
SP  - 133
EP  - 160
DO  - 10.7930/J0WH2N54
PB  - U.S. Global Change Research Program
CY  - Washington, D.C.
ER  -

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