Scientists have been surprised to discover a massive haze of air pollution the size of the U.S. that covers the Indian Ocean during winter and combines with monsoon rains to cause acid rain over the Indian subcontinent, China, and Southeast Asia during the summer. The haze is composed of several minute byproducts from the burning of fossil fuels. The particles of pollution alter the climate by reflecting sunlight and cooling the earth beneath the haze. The new findings, announced Tuesday by the National Science Foundation and Scripps Institution of Oceanography, will complicate efforts to understand global climate change.