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The Properties of Clouds at All Altitudes
Volume 10, Number 37: 12 September 2007

How well do scientists know the properties of the many types of clouds that surround the earth? And how well do they need to know these properties in order to accurately model earth's climatic response to anthropogenic CO2 emissions? Some answers to these important questions are provided by Muller and Fischer (2007) in their introduction to a group of eight research papers published in the International Journal of Remote Sensing, wherein they describe some of the highlights of the 1997-2000 EU-CLOUDMAP project.

Originally designed "to improve the measurement and characterization of cirrus and contrail cloud properties," the two researchers say the project was ultimately broadened "to include properties of clouds at all altitudes, as Cess et al. (1993) had shown that depending on how cloud processes are parameterized can lead to an order of magnitude difference [our italics] in predictions of surface temperature due to changes in CO2 radiative forcing," which they state is "by far the largest uncertainty in making accurate forecasts of global warming."

Conducted as a collaborative effort of five university and government research groups in the UK, Germany, Switzerland and the Netherlands, Muller and Fischer write that "the primary technological motivation of the project was to develop new techniques for deriving cloud-top properties (cloud-top height, amount, microphysics and winds) from a new series of meteorological sensors," and to apply these properties "to the generation of new cloud climatology products," while they say that "a secondary goal was to develop an automated technique, based on fuzzy logic, to detect contrails in non-thermal imagery where contrails can only be detected through their unique spatial characteristics."

So how did the project fare in terms of contributing to its ultimate goals?

Muller and Fischer generously conclude that "the principal scientific goals to improve the measurement and characterization of cirrus and contrail cloud properties as a first priority as well as clouds in general were attained." However, they say that "in the future, more extensive investigations on clouds are necessary [our italics] with respect to global observations to reach the essential knowledge [our italics] on clouds required [our italics] for significant improvements in ... climate modeling."

In light of this current assessment of the situation, it will likely take many more projects of this nature to fully acquire the "essential knowledge" needed to significantly reduce the order-of-magnitude uncertainty that is acknowledged by Muller and Fischer to be inherent in current simulations of surface air temperature change due to changes in CO2 radiative forcing. And until that knowledge is acquired, it would seem wise to forebear the implementation of any measures designed to discourage the use of fuels that release life-sustaining CO2 to the atmosphere, especially when CO2's aerial fertilization and water-use-efficiency-promoting effects will likely be needed to forestall mankind's taking from "wild nature" what little remains of the planet's cultivatable land and freshwater resources to grow the food that will be needed to sustain our still-growing numbers just a few short decades from now.

For more on this largely-neglected topic, see some of our earliest writings archived under Food in our Subject Index.

Sherwood, Keith and Craig Idso

Cess, R.D., Nemesure, S., Dutton, E.G., Deluisi, J.J., Potter, G.L. and Morcrette, J. 1993. The impact of clouds on the shortwave radiation budget of the surface atmosphere system - Interfacing measurements and models. Journal of Climate 6: 308-316.

Muller, J.-P. and Fischer, J. 2007. The EU-CLOUDMAP project: Cirrus and contrail cloud-top maps from satellites for weather forecasting climate change analysis. International Journal of Remote Sensing 28: 1915-1919.