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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 9, NUMBER 12, DECEMBER 1996

PROFESSIONAL PUBLICATIONS...
SUN-CLIMATE RELATIONSHIPS

Item #d96dec16

Two related items in Science, 272(5264), May 17, 1996:

"Stratospheric Control of Climate," A. Robock (Dept. Meteor., Univ. Maryland, College Park MD 20742; e-mail: alan@atmos.umd.edu), 972-973. For many decades, statistical evidence has suggested a possible link between solar activity and weather and climate, but there has been no physical mechanism identified. The following paper identifies a possible mechanism, using a climate model with a sophisticated representation of stratospheric processes. Such new tools will lead to further progress understanding climatic variations.

"The Impact of Solar Variability on Climate," J.D. Haigh (Space & Atmos. Physics, Imperial College of Science, Technol. & Med., London SW7 2BZ, UK), 981-984. Used a global atmospheric model that simulates changes in solar irradiance and stratospheric ozone to investigate the response of the atmosphere to the 11-year solar activity cycle. At solar maximum, a warming of the summer stratosphere was found to strengthen easterly winds, leading to changes in tropospheric circulation similar to those observed in nature. Since the simulation of ozone changes was a key factor, these results imply that changes in stratospheric ozone brought about by any other means (such as destruction by CFCs) may also have an impact on tropospheric climate.

Item #d96dec17

"Sun-Climate Links," C. Covey (Lawrence-Livermore Natl. Lab., POB 808, Livermore CA 94550; e-mail: covey@triton.llnl.gov), Science, 272(5259), 179, Apr. 12, 1996.

Presents some brief physical arguments explaining why we should not jump to the conclusion that solar luminosity changes explain all or even most of the climate variations of the past few centuries.

Item #d96dec18

"Comparison of Proxy Records of Climate Change and Solar Forcing," T.J. Crowley (Dept. Oceanog., Texas A&M Univ., College Sta. TX 77843; e-mail tom@astra.tamu.edu), K.-Y Kim, Geophys. Res. Lett., 23(4), 359-362, Feb. 15, 1996.

Compares two estimates of solar variability since 1600 with two estimates of Northern Hemispheric temperature change. Sun-climate correlations are significant at the 95% level, but longer records are needed for a more convincing demonstration of a significant linkage. However, results of forcing an energy balance model with the solar time series supports the hypothesis that solar variability may be significantly contributing to climate change on decadal-centennial time scales.

Item #d96dec19

"The Sun and Climate," J. Lean (U.S. Naval Res. Lab., Washington D.C.; e-mail: lean@demeter.nrl.navy.mil), D. Rind, Consequences, 2(1), 26-36, 1996.

A review for non-specialists. The 11-year sunspot cycle causes a change of less than 0.1° C in the Earth's temperature, but what is known of solar behavior before 1979 suggests that other changes of possibly greater amplitude also occur. These long-term solar variations are incompletely understood, but could have contributed about 15% of the documented 0.5° C global warming since 1850. With the highest estimates of possible solar changes, the Sun could diminish the IPCC mid-range projected warming of 2° C by about 0.5° C.

Item #d96dec20

"Reconstruction of Solar Irradiance Since 1610: Implications for Climate Change," J. Lean (Ctr. Space Res., Code 7673L, Naval Res. Lab., Washington DC 20375; e-mail: lean@demeter.nrl.navy.mil), J. Beer, R. Bradley, Geophys. Res. Lett., 23(23), 3195-3198, Dec. 1, 1995.

The correlation of reconstructed solar irradiance and Northern Hemisphere surface temperature is 0.86 in the pre-industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55° C surface warming since 1860, and one third of the warming since 1970.