New reports suggests global warming could be slower than first thought

New reports suggests global warming could be slower than first thought

New reports suggests global warming could be slower than first thought

Updated 20 May 2013, 19:25 AEST

A new report says the planet may be warming slower in the short-term than had been previously projected.

A new report says the planet may be warming slower in the short-term than had been previously projected.

The study published in the journal Nature Geoscience reveals that while the world has experienced its hottest decade since records began, the rate of average warming has been lower over the past decade.

By using modelling based on data from the past 10 years, the report says that after significant rises in the 1980s and 1990s, the most extreme projections are now looking less likely than before.

The lead author of the report, Dr Alexander Otto from Oxford University's Environmental Change Institute, estimates that in the coming decades, global average temperatures will warm about 20 per cent more slowly than expected.

"The shorter-term range, which is the rate of warming which we might expect over this century, might actually have to be adjusted down slightly," he said.

Audio: Listen to Sarah Clarke's report (The World Today)

Dr Otto says the previous worst-case scenarios predicted by some scientists may need to be slightly revised.

"If we take this hypothetical scenario of doubling the concentration of carbon dioxide in the atmosphere, then we would see an increase in temperature of 0.9 to 2 degrees," he said.

"This is lower than the range in the ensemble of models that are being used for example in the upcoming Intergovernmental Panel on Climate Change (IPCC) report, which have a range of 1 to 2.5 degrees.

"We have a range that's slightly lower and that certainly would execute some of the more extreme models that are being used for projecting temperatures."

Longer-term warming trend will not change

But Dr Otto cautions that the longer-term warming trend will not change and it will eventually result in the same higher temperatures as earlier forecast.

"It certainly is no reason to relax or become complacent in terms of climate policy, because the rate of warming that we will see eventually in the coming centuries has not changed from this data," he said.

It certainly is no reason to relax or become complacent in terms of climate policy because the rate of warming we will see eventually... has not changed.

Dr Alexander Otto

"If we were following our current emission trends... we would still look at temperatures at the end of the century significantly above the 2 degrees target that we are talking about."

The Nature Geoscience report suggests the slow-down in temperature rises can be explained by the fact that the world's oceans are capturing heat more rapidly than expected over the past decade.

The IPCC, the United Nations' chief climate science body, will release its next major report in September.

A contributor to the report, Professor Steven Sherwood from the University of NSW, is sceptical of the latest findings.

He says eventually the ocean will stop taking up the heat.

"Although the surface temperatures are not warming quite as fast, when you look down below the surface at the oceans where all the heat is going, that's still increasing about the same," he said.

"What they infer from that is that the ocean is taking up the heat a bit faster."

Rise may be part of natural and changeable cycle

He also suggests that the rise in ocean temperatures may be part of a natural and changeable cycle.

"They haven't taken into account the natural variations in the ocean that cause it to temporarily store heat and we know it does that," he said.

"For example, an El Nino is when the heat stored in the ocean temporarily glurges out so the surface warms up but the total amount of heat in the system doesn't change.

"They haven't accounted for that and I think it may just be that if we repeat this analysis in another 10 years and do this calculation again, the answer is going to go right back to where it was before."

The lead author of the next IPCC report says their forecasts are consistent with previous long-term estimates.

The IPCC's draft report indicates that the planet may be on track to reach a temperature rise of up to 4.5 degrees by the turn of the century.