IPCC clear on evidence for global warming

Some aspects of global warming may not be entirely understood and data may be sparse, but scientists do not dispute that global temperature has increased, especially since 1950, as pointed out in the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC).

Indian scientists note the rise in the levels of the Indian Ocean along three cities in the country are close to the global averages stated in the report.

“The rate of warming averaged over the last 50 years is nearly twice that for the last 100 years,” says the IPCC report, in its conclusions drawn from available studies and data and reviewed by a several scientists. A detailed reading of the report reveals, contrary to what the current glacier goof-up may indicate, the report gives clear assessments about where the understanding of science is robust and where it may need more data. The glacier goof-up is not part of the summary for policymakers, a synthesized part of the document, which is widely read across the globe by decision-makers.

“No big fuss should be made (on the glacier issue),” said J Srinivasan, chairman of Divecha Centre for Climate Change at the Indian Institute of Science in Bangalore. “All modelling has some problems. Nations deal with it in their economic modelling. The overall science is well understood. Global warming is not a dramatic change, but a long-term change that will lead to serious consequences,” Srinivasan said.

The impact on India alone will be serious. Ocean experts say the mean sea-level rise along the coasts of Mumbai, Kochi and Visakhapatnam is due to the effects of global warming. “The Indian Ocean is rising by 1.3 mm every year,” A S Unnikrishnan, senior scientist at the National Institute of Oceanography, told Business Standard.

Srinivasan said glaciers, too, are retreating. People have measured them. “Large glaciers will be around, but the smaller ones are retreating,” he said.

From an analysis of 100 years of tide gauge data, Unnikrishnan and his team showed that sea levels along the coast of Mumbai, Kochi and Visakhapatnam rose by 0.78, 1.14 and 0.75 mm, respectively, per year. The data are close to the global average and could have serious implications for India’s coastline.

The IPCC report points out that observations since 1961 show the average temperature of the global ocean has increased to depths of at least 3,000 metres and that the ocean has been absorbing more than 80 per cent of the heat added to the climate system. “Such warming causes seawater to expand, contributing to sea level rise,” says the report. Experts point out the one issue that climate sceptics may have is that the report gives global averages. What may be true for one region may not apply to another, as it is only an average figure, they say.

Associate director at the Centre for Science and Environment Chandra Bhushan, says the report has already made a distinction between robust findings and uncertainties. The IPCC report provides a clear guideline for treatment of uncertainties. In fact, the fourth assessment report, provides, for the first time, an “uncertainty guidance.”

The authors distinguish the conclusions on the basis of “high confidence” in which an event is unlikely or extremely likely.