For example, we know almost beyond doubt that we, the human race, have substantially altered the earth’s atmosphere. In 2005 the concentration of carbon dioxide exceeded the natural range that has existed over 650,000 years. Eleven of the warmest years since instrumental records have been kept occurred during the last 12 years.

In the 20th century the increase in average temperature was 0.74 degrees centigrade; sea level increased by 17 cm; and a large part of the northern hemisphere snow cover vanished. Particularly worrisome is the reduction in the mass balance of the glaciers, and this has serious implications for the availability of water: 500 million people in South Asia and 250 million people in China are likely to be affected as a result.

These assessments have implications on policy. Due to global warming, there would be less water available in several parts of the world and a number of crops that the human race is dependent on are likely to see declines in yield and productivity.

The other area in which new clarity has emerged is the mitigation policy. There is now evidence that the cost of mitigation is very low across the world — in some sense it demolishes the misgivings people have voiced in the past. The critics have said that there was a lot of negative cost to mitigation — loss of jobs, fall in economic output. In fact, it is now showing there is actually increase in economic output.

According to estimates, the cost of stabilisation would not be very high. At the lower end of stabilisation options the cost in 2030 would not exceed 3 per cent of gross domestic product, which amounts to 0.12 per cent of gross domestic product on an annual basis. With new technologies, new methods and changes in behaviour, the costs would actually go down. In all, there is a fairly robust assessment of climate change available now.

... contd.