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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 7, NUMBER 9, SEPTEMBER 1994

PROFESSIONAL PUBLICATIONS... OF GENERAL INTEREST: CLIMATE CHANGE SCIENCE

Item #d94sep13

"Recent and Future Climate Change in East Asia," M. Hulme (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK), Z.-C. Zhao, T. Jiang, Intl. J. Climatol., 14(6), 637-658, July 1994.

Examines climate change over the past 100 years (from instrument records) and projects it over the next 100 years (using results from climate model experiments). The region has undoubtedly warmed over the last century; the substantial role of urbanization cannot account for all the temperature change. Illustrates a flexible composite-model approach to regional climate change scenario construction which can explicitly incorporate the effects of model uncertainty. The scenario presented suggests that by 2050, mean conditions are expected to be warmer than the extremely warm seasonal anomalies of the most recent decade.

Item #d94sep14

Three related items in Nature, 371(6493), Sep. 8, 1994:

"Testing the Iron Hypothesis in Ecosystems of the Equatorial Pacific Ocean," J.H. Martin, K.H. Coale (Moss Landing Marine Labs., POB 450, Moss Landing CA 95039), et al., 123-129. The idea that iron may limit phytoplankton growth in large regions of the ocean was tested by enriching with iron an area of 64 km2 in the open equatorial Pacific. Plant biomass doubled and plant production increased fourfold, indicating that iron can control rates of phytoplankton productivity in the ocean. The experiment was intended to explore ecosystem function and was not intended as a preliminary step to climate manipulation. It also demonstrated the feasibility of open-ocean manipulative experiments, which may signal the beginning of a new era in geochemical and ecological studies.

"Minimal Effect of Iron Fertilization on Sea-Surface Carbon Dioxide Concentrations," A.J. Watson (Plymouth Marine Lab., Prospect Pl., West Hoe, Plymouth PL1 3DH, UK), C.S. Law et al., 143-145. The possibility that iron limits phytoplankton productivity has led to the suggestion that iron may have played a role in modulating atmospheric CO2 levels between glacial and interglacial times. CO2 concentrations in the experiment described showed less of an effect than has been observed in incubation experiments, and does not support the idea that iron fertilization would significantly affect atmospheric CO2 concentration.

"Iron Limitation of Phytoplankton Photosynthesis in the Equatorial Pacific Ocean," Z.S. Kolber (Oceanog. & Atmos. Sci. Div., Brookhaven Natl. Lab, Upton NY 11973), R.T. Barber et al., 145-149. Changes in the photochemical energy conversion efficiency of the natural phytoplankton community were followed before and after artificial enrichment with iron in the open ocean. Results show that iron limits photosynthesis in all size classes by impairing intrinsic photochemical energy conversion, supporting the hypothesis of physiological ("bottom up") limitation by iron, rather than "top down" grazing pressure by herbivores, a mechanism that has also been proposed.

Item #d94sep15

Two related items in Nature, 370(6489), Aug. 11, 1994:

"Dirty Clouds and Global Cooling," G.L. Stephens (Dept. Atmos. Sci., Colorado State Univ., Ft. Collins CO 80523), 420-421. Offers a research perspective on the following paper.

"A Climate Model Study of Indirect Radiative Forcing by Anthropogenic Sulphate Aerosols," A. Jones (Hadley Ctr., Meteor. Off., London Rd., Bracknell, Berkshire RG12 2SY, UK), 450-453. The direct effect of aerosols has been estimated to be a significant fraction of the radiative influence of greenhouse gases, but their indirect effect, through the alteration of radiative characteristics of clouds, is much more difficult to assess. A 3-D chemical transport model and a GCM indicate that the indirect cooling effect of aerosols is about half the warming effect of greenhouse gases in the global annual mean. Although this estimate is subject to considerable uncertainty, it exceeds many estimates of the direct effect, indicating the potential importance of the indirect effect of anthropogenic aerosols in climate change.

Item #d94sep16

Two related items in Nature, 370(6489), Aug. 11, 1994:

"Cooler Estimates of Cretaceous Temperatures," B.W. Sellwood (Postgrad. Inst. Sedimentol., Univ. Whiteknights, Reading RG6 2AB, UK), G.D. Price, P.J. Valdes, 453-455. The high temperatures and CO2 levels of the Cretaceous period suggest that this time period could be used by modelers as an analog for future climate change. However, new records of ocean paleotemperature cast doubt on the idea that the Cretaceous was generally warmer, making the climatic role of atmospheric CO2 unclear and suggesting that the Cretaceous cannot be used as an analog for the future.

"Chill over the Cretaceous," E.J. Barron (Earth Systems Sci. Ctr., Pennsylvania State Univ., 248 Deike Bldg., Univ. Pk. PA 16802), 415. Comments on previous paper. The large number of differences between past and present climatic periods make it unlikely that any past climate can be a true analog for the future.

Item #d94sep17

"Global Decrease in Atmospheric Carbon Monoxide Concentration," M.A.K. Khalil (Global Change Res. Ctr., Oregon Graduate Inst., Beaverton OR 97006), R.A. Rasmussen, Nature, 370(6491), 639-641, Aug. 25, 1994.

During the 1980s there was evidence that atmospheric CO concentrations were increasing at about 1.2% per year, leading to feedbacks that could amplify global warming. A continuation of those measurements shows that from 1988 to 1992 global CO concentrations have been declining rapidly at about 2.6% per year. A decreasing trend in tropical biomass burning is a possible cause.

Item #d94sep18

"Evidence of a Long-Term Increase in Tropospheric Ozone from Pic du Midi Data Series: Consequences: Positive Radiative Forcing," A. Marenco (Lab. d'Aérologie, CNRS-URA 0354, Univ. P. Sabatier, 31062 Toulouse Cedex, France), H. Gouget et al., J. Geophys. Res., 99(D8), 16,617-16,632, Aug. 20, 1994.

Old ozone measurements recently discovered at the Pic du Midi Observatory (altitude 3000 m, southwestern France) were used to complete a time series covering 1874 to 1993. Ozone has increased by a factor of five since the beginning of this century. For the first two decades of the period, the mixing ratio was stable at 10 ppb, representing the preindustrial era. A tentative evaluation of radiative forcing confirms that ozone is currently the second most significant greenhouse gas, accounting for 22% of the radiative forcing changes in the Northern Hemisphere since 1980.

Item #d94sep19

"Modeling the Global Carbon Cycle: Nitrogen Fertilization of the Terrestrial Biosphere and the 'Missing' CO2 Link," R.J.M. Hudson (Inst. Marine Sci., Univ. California, Santa Cruz CA 95064), S.A. Gherini, R.A. Goldstein, Global Biogeochem. Cycles, 8(3), 307-333, Sep. 1994.

Describes and applies GLOCO, a global carbon cycle model with relatively detailed treatment of oceanic and terrestrial processes and anthropogenic activities. Confirms previous suggestions that because temperate and boreal forests are nitrogen limited, CO2 fertilization is less than predicted by short-term CO2 response factors. Fertilization by anthropogenic nitrogen emissions probably constitutes a significant portion of the "missing" CO2 sink.

Item #d94sep20

"Effects of Reductions in Stratospheric Ozone on Tropospheric Chemistry Through Changes in Photolysis Rates," J.S. Fuglestvedt (Ctr. Intl. Clim. & Energy Res.--Oslo (CICERO), Univ. Oslo, POB 1129 Blindern, 0317 Oslo, Norway), J.E. Jonson, I.S.A. Isaksen, Tellus, 46B(3), 172-192, July 1994.

Calculates effects of changes in UV radiation due to stratospheric ozone depletion for selected years from 1970 to 2050. Tropospheric ozone is reduced in most areas, but at a smaller percentage than the UV increase. Increased UV may have contributed about one third the reduction in the growth rate of methane, thus partially offsetting the climate change effect of ozone depleting substances.

Item #d94sep21

"Sea Level," C. Woodroffe (Dept. Geog., Univ. Wollongong, New South Wales 2522, Australia), Prog. Phys. Geog., 18(3), 436-451, Sep. 1994.

Reviews recent efforts to reconstruct or explain the past pattern of truly global (eustatic) sea level change over the Late Quaternary, and reviews attempts to monitor current sea level change.

Item #d94sep22

"The Atlantic Climate Change Program," R.L. Molinari (Atlantic Oceanog. Lab., NOAA, 4301 Rickenbacker Causeway, Miami FL 33149), D. Battisti et al., Bull. Amer. Meteor. Soc., 75(7), 1191-1199, July 1994.

Gives a detailed overview of this component of NOAA's Climate and Global Change Program, which is directed at determining the role of the thermohaline circulation of the Atlantic Ocean on global atmospheric climate.