LONDON Global temperature rise could exceed "safe" levels of two degrees Celsius in some parts of the world in many of our lifetimes if greenhouse gas emissions continue to increase, two research papers published in the journal Nature warned.
"Certain levels of climate change are very likely within the lifetimes of many people living now ... unless emissions of greenhouse gases are substantially reduced in the coming decades," said a study on Sunday by academics at the English universities of Reading and Oxford, the UK's Met Office Hadley Center and the Victoria University of Wellington, New Zealand.
"Large parts of Eurasia, North Africa and Canada could potentially experience individual five-year average temperatures that exceed the 2 degree Celsius threshold by 2030 -- a timescale that is not so distant," the paper said.
Two years ago, industrialized nations set a 2 degree Celsius warming as the maximum limit to avoid dangerous climate changes including more floods, droughts and rising seas, while some experts said a 1.5 degree limit would be safer.
It is widely agreed among scientists that global pledges so far for curbing greenhouse gas emissions are not strong enough to prevent "dangerous" climate change.
Next month, nations will meet for the next U.N. climate summit in Durban, South Africa, where a binding pact to reduce emissions looks unlikely to be delivered.
Instead, a global deal might not emerge until 2014 or 2015.
The study found that most of the world's land surface is very likely to experience five-year average temperatures that exceed 2 degrees above pre-industrial levels by 2060.
If emissions are substantially lowered, the two degree threshold might be delayed by up to several decades, it added.
However, even if global temperature rises are kept under two degrees by aggressive emissions cuts, some regions will still not avoid warming and the likelihood of extreme events such as heatwaves is still high in even a marginally warmer world.
A separate study by academics at Zurich's Institute for Atmospheric and Climate Science, the Potsdam Institute for Climate Impact Research and the UK's Met Office Hadley Center, among others, said it would be challenging to limit temperature rises to two degrees.
To achieve a greater than 66 percent chance of limiting temperature rise, global emissions will probably need to peak before 2020 and fall to about 44 gigatonnes of carbon dioxide equivalent by 2020.
"Without a firm commitment to put in place the mechanisms to enable an early global emissions peak followed by steep reductions thereafter, there are significant risks that the 2 degree target, endorsed by so many nations, is already slipping out of reach," the study said.