The earth's response to increasing carbon dioxide is likely to be in a higher range than previously thought, according to the most comprehensive study ever conducted on the topic, released on Thursday.
Commissioned by the World Climate Research Program, the international study was led by Australian climate scientist and Professor Steven Sherwood from the University of New South Wales.
It concluded that if atmospheric carbon dioxide continued on its current trend, roughly double that of pre-industrial levels, the world will likely experience a temperature increase of 2.3 - 4.5 degrees Celsius.
Previous studies have relied on more than 40-year-old estimates which put the global temperature response to greenhouse gas emissions at as low as 1.5 - 4.5 degrees Celsius.
"Narrowing the range of climate sensitivity has been a major challenge since the seminal U.S. National Research Council paper came up with a 1.5 - 4.5 degrees Celsius range in 1979," Sherwood said.
"That same range was still quoted in the most recent IPCC (Intergovernmental Panel on Climate Change) report."
Sherwood and his team found that the likelihood of a less than 2 percent rise in the global temperature was just 5 percent.
Getting the most accurate picture yet of the earth's global warming trajectory required bringing together an international team of researchers from a wide range of climate disciplines.
The team combined several independent lines of evidence allowing them a higher degree of confidence than ever in their result -- evaluating modern and prehistoric temperature figures, satellite observations and mathematical models of interactions within the climate system.
"An important part of the process was to ensure that the lines of evidence were more or less independent," Sherwood said.
"You can think of it as the mathematical version of trying to determine if a rumour you hear separately from two people could have sprung from the same source; or if one of two eyewitnesses to a crime has been influenced by hearing the story of the other one."
The authors called on international policymakers to take a similar reasoned and collaborative approach to tackling greenhouse gas emissions in order to forestall the worst of global warming. Enditem
