By Alister Doyle
OSLO (Reuters) - Global warming is on track to breach a 2 degrees Celsius threshold by 2050 unless governments at least double their efforts to limit greenhouse gas emissions, scientists said on Thursday.
Plans by almost 200 governments to cut greenhouse gases are far too weak to match targets set in a Paris Agreement on climate change last December for a drastic shift from fossil fuels towards greener energies, they said.
"We've really got a problem," Robert Watson, a British-American scientist who was among the seven authors of the study and is a former head of the U.N.'s Intergovernmental Panel on Climate Change (IPCC), told Reuters.
The Paris Agreement sets a goal of limiting a rise in average world temperatures to "well below" 2C above pre-industrial times, while pursuing a tougher 1.5 Celsius (2.7F) limit.
"If indeed these governments are serious about trying to hit the 2C mark they really have to double or triple the effort of the current pledges made in Paris," Watson said.
The study, by Watson and other senior scientists, said the 2C limit "could be reached by 2050, even if pledges (in Paris) are fully implemented."
According to the U.N. Environment Programme, world greenhouse gas emissions, mainly from burning fossil fuels, are now about 54 billion tonnes a year and should be cut to 42 billion by 2030 to get on track to stay below 2C.
Current pledges under the Paris Agreement will keep emissions flat at around 54 billion tonnes in 2030, it says. That is 11 billion tonnes less than an estimated 65 billion without the promises but 14 billion above the 42 billion track.
"I think the 1.5 degree pathway is clearly not achievable. We'll pass it probably in the early 2030s," Watson said.
Global warming is projected to cause more heatwaves, droughts, downpours and rising sea levels. Average world temperatures this year are set for record highs, about 1C above pre-industrial times.
The Paris Agreement is set to be ratified by India on Sunday and perhaps by some European Union nations in coming days, pushing it over a threshold needed to enter into force.
It needs backing from 55 nations accounting for 55 percent of world emissions to enter into force. So far 61 nations accounting for 47.8 percent of emissions have ratified, led by China and the United States, according to U.N. data.
(Reporting By Alister Doyle; Editing by Janet Lawrence)