Scientists have studied the thick brown clouds, which estimate to be three kilometres thick,as said the haze stretches from the Arabian Peninsula to China,and the Western Pacific Ocean which is officially known as atmospheric brown clouds. Scientists, who come from China,India,Europe and the U..S. say the brown clouds are aggravating the impact of climate change caused by greenhouse gases in some regions .Scientists are issuing a warning now about the brown haze, it is a serious and significant environmental challenge facing the planet that poses a threat to human health and our food production. The brown clouds have darkened 13 cities in Asia, including Beijing,Shanghai,Bangkok,Cairo,Mumbai,New Delhi and Tehran,"dimming" sunlight in some places by as much as 25%. The brown clouds are causing serious health problems such as cardiovascular and respiratory diseases. One more serious problem is the melting of the Hindu Kush-Himalaya-Tibetan glaciers which provides the head-waters for the major river systems including the Ganges, Brachmaputra ,Mekona,and Yangtze rivers. The Ganges Basin,for example, is home to more than 400 million people and holds 40% of India's irrigated croplands. Scientists say melting has a serious impact for the water and food security of Asia