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A warming of three degrees would trigger 'a very radical transformation' while four degrees would be 'potentially devastating', says the study by climate analystsREUTERS

Based on estimates of emission pledges made by EU, US and China, a study has concluded that dangerous climate change is inevitable unless much more is placed on the table.

Researchers including UK's Lord Nicholas Stern calculate that the commitments made so far will help bring down emissions from a projected 70 gigatonnes to around 55gt.

But it will still be much above the 40-42gt limit sought by 2030 to keep the planet from warming to 2C above pre-industrial levels.

Global emissions in 2010 were already around 47gt.

A warming of three degrees would trigger "a very radical transformation" while four degrees would be "potentially devastating", with societies disrupted by extreme weather events and sea-level rises, Lord Stern told Fairfax Media.

Net global emissions of carbon must drop 40-70% by 2050, hitting zero by the end of the century, the IPCC has said, in order to avoid a temperature rise beyond two degrees above pre-industrial levels – seen as the threshold for irreversible climate change.

The World Resources Institute also believes the indicated INDCs (Intended Nationally Determined Contribution) so far made by EU, US, China and Mexico will fall short of emission cuts required for the above.

In calculating the gap between a business as usual scenario and drastic cuts to limit warming, Lord Stern's estimates vary on when China's emissions peak. China has pledged to slow the growth of its annual emissions to reach a peak no later than 2030.

Other estimates used in the study include the EU's pledge to cut carbon emissions by 40% of 1990 levels by 2030 and the US's commitment to cut 2005 emissions 26-28% by 2025.

Australia plans to cut emissions by 5% of the 2000-levels by 2020, but has not disclosed its post-2020 pledge for Paris.

The country's Climate Change Authority recommended Australia pledge to cut emissions 30% on 2000 levels by 2025, and aim for 40-60% cuts by 2030.

Even a 2C warming comes with a potential for damage, with a ETH study showing that it can spur five times as many hot extremes than today, and two times as many hot extremes as with a 1.5C warming.

Human-induced global warming had turned 2014 to the hottest year on record. The trend may continue into 2015, given the NOAA prediction of a 60% chance the El Niño it declared last month will continue all year.

While most nations agreed in principle in 2010 in Cancún, Mexico, that global warming of more than two degrees would be dangerous, most have not so far committed to the emissions reductions required to prevent temperatures from exceeding that limit.

China and India while adopting green technology are not ready to let go of their larger dependence on coal-based power.

Dismissing Australian Prime Minister Tony Abbott's comments that "coal is good for humanity" Stern noted, "Coal is a big, big problem ... responsible for close to a third of the world's emissions…Coal is extremely expensive in human lives through air pollution, and human lives in the future through climate change."