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INDOEX (01)

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Greenhouse Warming or Aerosol Cooling?

Regional consequences of global warming depend critically on the potentially large cooling effect of another pollutant, known as aerosols. These tiny particles, of about a millionth of a centimeter or smaller in diameter, scatter sunlight back to space and cause a regional cooling effect. These aerosols consisting of sulfates, soot, organic carbon and mineral dust are produced both naturally and by human activities. Results of numerous global warming models suggest that the aerosol cooling is one of the largest, if not the largest, sources of uncertainty in predicting future climate. Still, the complex influence of aerosol cooling on global warming is not clearly understood. This issue will remain a mystery unless field experiments, such as the Indian Ocean Experiment (INDOEX), are undertaken to collect in-situ data on the regional cooling effect of sulfate and other aerosols. INDOEX addresses questions of climate change that are of high priority and of great value to the US and the international community. The project's goal is to study natural and anthropogenic climate forcing by aerosols and feedbacks on regional and global climate. This issue is at the core of the International Global Change Research Program and has been identified by IPCC as a major gap in the science of climate change prediction. INDOEX field studies will occur where pristine air masses from the southern Indian Ocean including Antarctica and not-so-clean air from the Indian subcontinent meet over the tropical Indian Ocean to provide a unique natural laboratory for studying aerosols. Scientists will collect data from the water surface through the lower stratosphere, on the aerosol composition, reactive atmospheric gases, solar radiation fluxes, wind and water vapor distribution. To this end, investigators will use multiple aircraft, ships and island stations over the Arabian Sea and the Indian Ocean. Building on data collected in 1995, 1996, 1997 and 1998, the intense field campaign will be undertaken during January to April, 1999. Field data will be used to calibrate the National Aeronautics and Space Administration's Earth Observing System instruments to obtain a regional map of the aerosol cooling effect. In conjunction with the regional scale satellite data, the field data will also be used to include aerosol effects in global warming prediction models. Premier environmental scientists, universities and national laboratories from the US, Europe and Indian Ocean region are committed to INDOEX through the support of their national global change research programs. In the US, the National Science Foundation is the primary sponsor. The US coordinator and co-chief scientist for INDOEX is Professor V. Ramanathan, Director of C⁴ at the Scripps Institution of Oceanography of the University of California, San Diego. The co-chief scientist of INDOEX who organizes the European component is Professor Paul J. Crutzen, Director of the Max-Planck Institut f�r Chemie, and a 1995 Nobel Laureate in Chemistry.

Proposal

Chapter 1
Aerosols, Clouds and Chemistry-Climate Interaction

It has been known for nearly a decade that the outstanding problems in global change are those at the intersection of the various disciplines of physics, chemistry, dynamics, biology and human intervention. However, it has been very difficult to translate this awareness into action, in part because we lack observations of such interdisciplinary phenomena. Of many such phenomena, those dealing with aerosols, clouds and tropospheric chemistry are the focus of the Indian Ocean Experiment (INDOEX). The urgency and the great impetus for studying these arise from several recent developments which demonstrate their significance to global climate and chemistry. 
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