The Observed Global Warming Record: What Does it Tell Us?

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 94; no. 16; pp. 8314 - 8320
• Main Authors: Wigley, T. M. L., Jones, P. D., Raper, S. C. B.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 05.08.1997; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences of the USA
• Series: Colloquium Paper
• Subjects: Aerosols; Climate change; Climate models; Datasets; Global climate models; Global warming; Greenhouse effect; International environmental cooperation; Irradiance; Oceans; Papers from a Colloquium; Statistical variance; Temperature
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.16.8314

Global, near-surface temperature data sets and their derivations are discussed, and differences between the Jones and Intergovernmental Panel on Climate Change data sets are explained. Global-mean temperature changes are then interpreted in terms of anthropogenic forcing influences and natural variability. The inclusion of aerosol forcing improves the fit between modeled and observed changes but does not improve the agreement between the implied climate sensitivity value and the standard model-based range of 1.5-4.5 degrees C equilibrium warming for a CO2doubling. The implied sensitivity goes from below the model-based range of estimates to substantially above this range. The addition of a solar forcing effect further improves the fit and brings the best-fit sensitivity into the middle of the model-based range. Consistency is further improved when internally generated changes are considered. This consistency, however, hides many uncertainties that surround observed data/model comparisons. These uncertainties make it impossible currently to use observed global-scale temperature changes to narrow the uncertainty range in the climate sensitivity below that estimated directly from climate models.