The United Nations climate panel's claim that global temperatures are rising relentlessly because of human pollution is now being questioned by scientists.
In its last assessment, the Intergovernmental Panel on Climate Change (IPCC) warned that greenhouse gases had already heated the world by 0.7C and that there could be 5C-6C more warming by 2100, with devastating impacts on humanity and wildlife.
However, some scientists suggest that the world may not be warming much at all.
"The temperature records cannot be relied on as indicators of global change," The Times quoted John Christy, professor of atmospheric science at the University of Alabama in Huntsville, as saying.
Christy and other researchers have begun doubting IPCC's claim, as it is based on thousands of weather stations around the world, which have been used to collect temperature data over the past 150 years.
They say these stations have been seriously compromised by factors such as urbanisation, changes in land use and being moved from site to site.
"The popular data sets show a lot of warming but the apparent temperature rise was actually caused by local factors affecting the weather stations, such as land development," Christy said.
Ross McKitrick, professor of economics at the University of Guelph, Canada, has questioned IPCC's methods.
"We concluded, with overwhelming statistical significance, that the IPCC's climate data are contaminated with surface effects from industrialisation and data quality problems. These add up to a large warming bias," he said.
Such warnings are supported by a study of US weather stations co-written by Anthony Watts, an American meteorologist and climate change sceptic.
His study is illustrated with photographs of weather stations in locations where their readings are distorted by heat-generating equipment.