A U.S. plan to cut greenhouse gas emissions from power plants is not enough to achieve its goals for limiting climate change, and all nations will need to significantly step up actions to curb warming, a group of scientists said in a report on Wednesday.
Washington announced plans on Monday to cut emissions from power plants by 30 percent below 2005 levels by 2030, as the centrepiece of a U.S. policy to fight climate change.
Niklas Hoehne, of Ecofys - joint compiler of the Climate Action Tracker report with research group Climate Analytics and the Pik Potsdam Institute - said the plan would not even ensure that the United States meets an existing national goal, set in 2009, of a cut of 17 percent below 2005 levels by 2020.
The world is on track to exceed an agreed ceiling for average temperature rises of 2 degrees Celsius (1.4 Fahrenheit) above pre-industrial times, seen as a threshold for worsening droughts, heatwaves and rising seas, scientists say.
"Every little step has to be welcomed ... but this is not enough to get on a 2C pathway," said Climate Analytics' Bill Hare told a news conference.
"All governments will have to significantly increase their action on climate change - both before 2020 and after", to stay below 2 degrees, according to the report, released on the sidelines of a June 4-15 U.N. meeting in Bonn, Germany on ways to limit global warming.
The Climate Action Tracker suggested that overall U.S. emissions would be only about 10 percent below 2005 levels by 2030, roughly equal with existing levels, unless tougher action is taken in sectors from transport to agriculture.
And worldwide, it said that greenhouse gas emissions would have to fall to zero sometime between 2060 to 2080 - more ambitious than almost any nation's long-term plans - to give a strong chance of limiting warming to below 2 degrees Celsius.
On current trends, it said that temperatures were set to rise by about 3.7 degrees Celsius and have already risen by about 0.8 degrees since the Industrial Revolution.
Almost 200 nations agreed the 2-degree goal in 2010 and the Bonn meeting of senior officials and ministers is part of work towards a deal due to be done at a summit in Paris at the end of 2015 to limit warming.
The U.N's Intergovernmental Panel on Climate Change says it is at least 95 percent probable that human actions, led by burning of fossil fuels, are the main cause of climate change rather than natural variations in the climate.
Reporting by Alister Doyle