If humanity is to escape the worst effects of the global warming already being felt on every continent, we must by mid-century achieve deep reductions of greenhouse gas emissions of 40 to 70 percent, a United Nations report says.
Current national commitments to control such emissions will be insufficient to hold warming at 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels, a draft of the U.N. report obtained by Reuters said.
The 2-degree ceiling was set by the U.N. in 2010 with hopes it could stave off or at least ameliorate heat waves, storms, floods and rising sea levels caused by global warming.
The draft report was created using three science reports commissioned by the U.N. over the last year intended to provide data to world governments set to meet in Paris in 2015 to hammer out a new agreement on cooperative efforts to address climate change.
"Deep cuts in greenhouse gas emissions to limit warming to 2 degrees C ... remain possible, yet will entail substantial technological, economic, institutional, and behavioral challenges," the report said.
Such cuts from 2010 levels would have to be attained by 2050 if the world is to hold the increase to the 2 degree C level, the draft prepared by Intergovernmental Panel on Climate Change concluded.
Such reductions face significant challenges, given that emissions driven by coal-fired industrial growth experience by emerging economies such as India and China jumped from 40 billion tons in 2000 to nearly 50 billion tons in 2010, the report authors noted.
Despite opinion polls and surveys suggest many people are skeptical about climate change and especially about human involvement, the IPCC expressed the belief the human activities are the chief driver of changes in climate and global warming.
Although many people hold that it is natural variations causing the climate changes being experienced globally, the IPCC held to its assessment of human impacts.
"Human influence on the climate system is clear, and is estimated to have been the dominant cause of the warming observed since 1950," the draft report said.
That warming is creating heat extremes, changes in global rainfall patterns, is impacting yield of many vital good crops and is melting ice in Greenland and Antarctica with resultant rises in sea levels, it noted.
The draft, said to have already gone through a number of revisions after its authors met in June, will be provided to governments as a final draft in the final days of August, an IPCC spokesman said.
