Revised 21st century temperature projections

Abstract

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 23:1-9 (2002) - doi:10.3354/cr023001 Revised 21st century temperature projections Patrick J. Michaels1,2,*, Paul C. Knappenberger3,*, Oliver W. Frauenfeld1, Robert E. Davis1 1Department of Environmental Sciences, PO Box 400123, University of Virginia, Charlottesville, Virginia 22904-4123, USA 2Cato Institute, Washington, DC 20001-5403, USA 3New Hope Environmental Services, 5 Boar¹s Head Lane, Suite 101, Charlottesville, Virginia 22903, USA *Email: pjm8x@virginia.edu ABSTRACT: Temperature projections for the 21st century made in the Third Assessment Report (TAR) of the United Nations Intergovernmental Panel on Climate Change (IPCC) indicate a rise of 1.4 to 5.8°C for 1990-2100. However, several independent lines of evidence suggest that the projections at the upper end of this range are not well supported. Since the publication of the TAR, several findings have appeared in the scientific literature that challenge many of the assumptions that generated the TAR temperature range. Incorporating new findings on the radiative forcing of black carbon (BC) aerosols, the magnitude of the climate sensitivity, and the strength of the climate/carbon cycle feedbacks into a simple upwelling diffusion/energy balance model similar to the one that was used in the TAR, we find that the range of projected warming for the 1990-2100 period is reduced to 1.1-2.8°C. When we adjust the TAR emissions scenarios to include an atmospheric CO2 pathway that is based upon observed CO2 increases during the past 25 yr, we find a warming range of 1.5-2.6°C prior to the adjustments for the new findings. Factoring in these findings along with the adjusted CO2 pathway reduces the range to 1.0-1.6°C. And thirdly, a simple empirical adjustment to the average of a large family of models, based upon observed changes in temperature, yields a warming range of 1.3-3.0°C, with a central value of 1.9°C. The constancy of these somewhat independent results encourages us to conclude that 21st century warming will be modest and near the low end of the IPCC TAR projections. KEY WORDS: Temperature projections · Climate change · Global warming · Climate models · Impact assessment Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 23, No. 1. Online publication date: December 20, 2002 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2002 Inter-Research.