More Knowledge of Interactions Between Asian Brown Haze, Global Warming and Ozone Urgently Needed


Nairobi/ Bangkok, April 9, 2001 – As emphasized by the Intergovernmental Panel on Climate Change (IPCC), developing a more complete picture of the roles and interactions of greenhouse gases, aerosols and ozone is urgently needed, according to Klaus Toepfer, Executive Director, United Nations Environment Programme (UNEP).

His comments come in the wake of the IPCC meeting in Nairobi, which ended last week, at which Governments accepted the IPCC's full Third Assessment Report.

Mr. Toepfer has just returned from Kathmandu where the chief scientists of the Indian Ocean Experiment (INDOEX) briefed him and a UNEP assessment expert.

"Their research suggests that the thick brown haze which forms over much of Asia during the tropical dry season, could have profound effects on human health, crop yield and rainfall patterns in the Asian region," said Mr. Toepfer.

Led by Professor Paul Crutzen of the Max Planck Institute of Chemistry and Professor V. Ramanathan of the Scripps Institution of Oceanography, University of California in San Diego, INDOEX involved 250 scientists from the United States, Europe, and India. In a US$25 million field experiment, atmospheric measurements were taken from ships, aircraft, satellites and ground-based instruments around the tropical Indian Ocean in 1999.

The results show that the brown haze - a mixture of pollutants, mainly soots, sulfates, nitrates, organic particles, fly ash and mineral dust, formed by fossil fuel combustion and rural biomass burning - is reducing the amount of sunlight reaching the tropical Indian Ocean surface, thousands of kilometers from its source, by as much as 10 percent; with larger percentage reduction over the Indian Subcontinent.

The researchers tracked the haze over an area of about 10 million square kilometers, and believe it forms over much of the Asian continent, home to more than half the world's people.

While in Kathmandu, the scientists and UNEP staff took a plane flight toward the Himalayas and found the haze extended vertically at least five kilometers - compared to the 3km ceiling measured during INDOEX.

"It is too early to tell how the haze might effect the formation of the monsoon and regional and global climate patterns, but the significance of these initial measurements suggest more knowledge is urgently needed," said Professor V. Ramanathan.

The scientists plan to establish a network of ground-based monitoring stations throughout Asia to study the composition and seasonal pattern of the haze.

UNEP has pledged to facilitate the continued research program and, in the longer-term, look to coordinate policy responses to address the problem.

"In the IPCC's Third Assessment Report we have a compelling picture of the causes and effects of global warming and the urgent need to shift towards a clean energy future," said Mr. Toepfer.

"Looking at the long term warming effect from greenhouse gases and the relatively acute, short-term effects of air pollution, and their interaction at regional levels, is an important area of further research, particularly if the hydrological cycle and human health are affected," Mr. Toepfer said.

Because of the potential scale of changes and the number of people affected, Professor Crutzen described the research challenge in the Asian Brown Haze problem, at least as important as his research on stratospheric ozone depletion, for which he received a Nobel Prize in Chemistry.

For further information contact:

Tim Higham, Regional Information Officer, UNEP, Bangkok, phone 662 2882127, or Tore Brevik, Director/Spokeman, Communications and Public Information, Nairobi, phone 254 2 623292,

Mario Aguilera, Assistant Director of Communications, Scripps Institution of Oceanography, UCSD, phone 858/534-3626 or

Results from INDOEX have been published extensively, including in the May 4, 2000 edition of Nature and the February 9, 2001 edition of Science magazine.

Additional Contacts

<p><font face="Arial"><font face="Arial, Helvetica, sans-serif">Tim Higham, Regional Information Officer, UNEP, Bangkok, phone 662 2882127, <a href=""></a> or Tore Brevik, Director/Spokeman, Communications and Public Information, Nairobi, phone 254 2 623292, <a href=""></a>.</font></font></p>

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