Climate Change, Global Change: What Is The Difference?

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S.I. Rasool

The recent surge in committee activities, national and international, to define and promote a program of research in global change has left many of our colleagues wondering how this new program is going to be different from the World Climate Research Program (WCRP), which has the charge to study the problem of climate change. In fact, although the programs overlap, the difference between the two is both substantial and substantive.

Substantial, because the scope of the program to study global change is much broader; a very large number of scientific disciplines will be involved. The program will need support from an even larger number of programming agencies from around the world. Substantive, because the program will address research that is not emphasized in the WCRP:

  • studies of chemical compounds other than water as they cycle through the atmosphere, land, and oceans
  • measurements and modeling of the eutrophic zone in upper layers of the oceans, where rates of photosynthesis and transport regulate the exchange of gases between the atmosphere and deep oceans
  • documenting variability of the global vegetation cover and of soil chemistry and studying their impacts on the concentration of atmospheric gases
  • the study of how changes in regional climate affect the state of vegetation for periods of a few decades.

Understanding The Global Change: An Opportunity To Seize

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S.I. Rasool

That Earth is constantly changing has been known since the beginnings of human reflections on the nature of our environments. The minute-by-minute changes in winds and clouds and the long-term trends in the climate of the continents, the rapid fluctuations in the humidity of the air and the sudden arrival of monsoons and tropical storms, the seasonal greening of grass and changing vegetation patterns around the globe, the rapidly spreading ripples in ponds and the slow meanderings of the Gulf Stream, the bursts of violent snow storms and the waxing and waning of the polar ice caps, all testify to the dynamic nature of the environments.

Potential of Remote Sensing for the Study of Global Change

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J.R.G. Townshend and S. I. Rasool

COSPAR report to the International Council of Scientific Unions (ICSU), Volume 7, Issue 1, Codata Bulletin, 24 (4) (special issue on Data for Global Change), 1-14, 1993

Published for the Committee on Space Research by Pergamon Press

Intensities of 9.4 microns and 10.4 microns CO2 bands

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S.I. Rasool

Memoires SOC. R. Sc. Liege, Fifth Serie, tome IX, Extract 1963

For the purposes of studying radiative properties of the atmospheres of the other planets, Venus and Mars for example, where the amount of CO2 in the atmosphere may be greater than in the earth’s by several orders of magnitude, these bands become important (Jastrow and Rasool, 1963). Therefore, in the absence of generally accepted values of the intensities of 9.4 p and 10.4 p bands, they have attempted to estimate them independently.

Publisher: NASA, Goddard Space Flight Center, Institute for Space Studies.

Surface Albedo and the Sahel Drought

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M.F.Courel; R.S. Kandel ; S.I. Rasool

Nature 307, 528 – 531 (09 February 1984)

The persistence of the Sahel drought, which reached a peak in 1973, appears to be typical for such dry episodes over past decades and centuries. Such strong persistence can be understood if a strong positive feedback mechanism is operating, partly driven by changes in surface properties. The key factors in the mechanisms thus far studied are the surface albedo and the soil moisture, both of which affect the radiation balance at the surface, the first directly, the second indirectly through its influence on the latent heat flux. We have now studied the evolution of the albedo of this region since 1972. We find that dry season albedo in the Sahel (notably Ferlo and Gondo regions) declined from a maximum close to 0.30 in 1973 to values close to 0.20 in 1979. This decline is consistent with changes in plant cover determined by analysis of spectral changes in the Landsat multispectral scanner (MSS) data and field studies.

Cloud Heights and Nighttime Cloud Cover from TIROS Radiation Data

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S. I. Rasool

Goddard Institute for Space Studies, NASA, New York, N.Y.

Journal of the Atmospheric Sciences, volume 21, pages 152–156.

Radiation data obtained from TIROS III has been analyzed, separately for day and for night, for the period July through September 1961. The global distribution of the average effective temperatures measured by the 8–12 μ channel of the satellite radiometer shows a close correlation with the cloud cover data.

An estimate of the latitudinal distribution of cloud heights has been obtained using the TIROS radiation data for daytime and the distribution of cloud cover recently obtained from the TIROS photographs. Combining these values of the cloud heights with the nighttime radiation data determines the latitudinal distribution of nighttime cloud cover.

The results indicate that in the Southern Hemisphere the percentage cloudiness at night is considerably higher than in the day, while in the case of the Northern Hemisphere the cloudiness appears to decrease at night.

The Runaway Greenhouse and the Accumulation of CO2 in the Venus Atmosphere

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S.I. Rasool and C. De Bergh, 1970

Nature, volume 226, pages 1037-1039

Although Venus and the Earth are similar in size and mass, are adjacent in the solar system and were probably formed out of the same homogenous mix of gas and dust about 4.5 billion years ago, their atmospheres and surface conditions differ markedly. For example, the atmosphere of Venus is ~75 times more massive than that of the Earth and is largely composed of carbon dioxide, a gas which constitutes only 0.03 percent of the Earth’s atmosphere. The Venus atmosphere seems to be deficient in water, with respect to Earth, by as much as a factor of 104. The surface temperature of Venus is 700 K.

We believe that the chief differences can be explained by the single circumstance that venus was formed 30 percent closer to the Sun. If the Earth had formed only 6 to 10 million km nearer to the Sun, it may also have become a hot and sterile planet. As for Mars, it seems that is the relative smallness of its size and mass — a weaker internal activity — which has slowed its progress towards accumulating an Earth-type atmosphere and oceans.

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Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate

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S.I. Rasool and S.H. Schneider
Science 9 July 1971:
Vol. 173 no. 3992 pp. 138-141


Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere. For aerosols, however, the net effect of increase in density is to reduce the surface temperature of Earth. Because of the exponential dependence of the backscattering, the rate of temperature decrease is augmented with increasing aerosol content. An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5 ° K. If sustained over a period of several years, such a temperature decrease over the whole globe is believed to be sufficient to trigger an ice age.