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Assessing uncertainty in climate simulations

Nature Climate Change volume 1, page 63 (2007)Cite this article

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To the Editor

— In their Commentary “Quantifying climate change—too rosy a picture?”, Schwartz et al.1 suggest that the estimated uncertainties associated with future warming presented in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4)2 do not correspond to the AR4 assessment of uncertainties associated with radiative forcing (that is, a measure of the influence that a factor has in altering the Earth's balance of energy and thereby causing warming or cooling of surface temperatures). In doing so, they criticize estimates of climate sensitivity (that is, the increase in global mean surface temperature expected from a doubling of atmospheric CO2 levels) and estimates of future warming. However, they have misinterpreted the use of AR4 Fig. SPM-4 (shown here as Fig. 1) and, as such, their criticisms are misplaced. In the following, we summarize key aspects of the AR4 uncertainty analyses that were neglected by Schwartz et al.

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Figure 1: Comparison of observed continental- and global-scale changes in surface temperature with results simulated by climate models using natural and anthropogenic forcings.
Figure 2: Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations.

References

  1. Schwartz, S.E., Charlson, R.J., & Rhode, H. Nat. Rep. Clim. Change 1, 23–24 (2007).

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  2. Solomon, S. et al. (eds) Climate Change 2007: The Physical Science Basis (Cambridge Univ. Press for the Intergovernmental Panel on Climate Change, Cambridge, 2007).

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Authors and Affiliations

  1. School of Earth and Environment, University of Leeds, LS2 9JT, UK

    Piers Forster

  2. School of GeoSciences, University of Edinburgh, Grant Institute, W. Mains Road, Edinburgh, EH9 3JY, Scotland, UK

    Gabriele Hegerl

  3. Institute for Atmospheric and Climate Science, Universitätstrasse 16, ETH Zürich, CHN, CH-8092, Zürich, Switzerland

    Reto Knutti

  4. Geophysical Fluid Dynamics Laboratory, Princeton University Forrestal Campus, 201 Forrestal Road, Princeton, 08540–6649, New Jersey, USA

    V. Ramaswamy

  5. NOAA Earth System Research Laboratory, 325 Broadway, Boulder, 80305, Colorado, USA

    Susan Solomon

  6. Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern, 3012, Switzerland

    Thomas F. Stocker

  7. Met Office Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK

    Peter Stott

  8. Climate Research Division, Environment Canada, Toronto, M3H 5T4, Ontario, Canada

    Francis Zwiers

Authors
  1. Piers Forster
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  2. Gabriele Hegerl
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  3. Reto Knutti
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  4. V. Ramaswamy
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  5. Susan Solomon
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  6. Thomas F. Stocker
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  7. Peter Stott
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  8. Francis Zwiers
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Corresponding author

Correspondence to Gabriele Hegerl.

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Forster, P., Hegerl, G., Knutti, R. et al. Assessing uncertainty in climate simulations. Nature Clim Change 1, 63 (2007). https://doi.org/10.1038/climate.2007.46a

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