When world leaders meet in Paris later this month to hammer out a new international treaty on climate change, their goal will be limiting the rise in global temperatures to 2 degrees Celsius (3.6 degrees F.), the point after which, scientists say, disastrous climate change will be nearly unavoidable.
In pursuit of this goal, the UN’s environmental authority said that emissions of greenhouse gases must not exceed 44 billion tons in 2020, in their annual reports published in 2010, 2011, 2012, and 2013.
But in 2014, that changed. With concentrations of nearly all the major greenhouse gases rising at dramatically higher rates, the United Nations Environment Program downplayed its focus on 2020 as a make-or-break year for emissions reductions.
The original numbers were "no longer realistic," explained UNEP chief scientist Jacqueline McGlade.
In this year's Emissions Gap report, the UNEP adjusted this assessment level to 52 billion tons by 2020. They say the new goal is still consistent with the 2-degree target, as long as emissions fall to 48 billion tons by 2025 and 42 by 2030.
In addition, the new UN analysis assumes that emissions cuts will drop faster after 2030 than was assumed in previous reports.
"The challenge is to bend the emissions trajectory down as soon as possible to ensure that the net zero emissions goal in 2060-2075 is within reach," the UN’s environmental program said in a press release.
The new numbers might be painting too rosy a picture, say critics.
"The emissions gap report gives the questionable impression that despite increasing emissions there's always a way to reach the 2C target," said Oliver Geden, of the German Institute for International and Security Affairs in Berlin.
Last week, Christiana Figueres, executive secretary of the United Nations Framework Convention on Climate Change, said at a Monitor-hosted event that current national climate pledges are not enough to keep human-induced climate change in check.
"But countries can – and must – do more to cut heat-trapping emissions sooner rather than later," Cristina Maza reported for The Christian Science Monitor.
"The risks from global warming are so unmanageable, the human cost so unpardonable, and the economic uncertainty so complete, that keeping global warming within a generally agreed upon safe range is crucial for global stability," Ms. Figueres said....
"We have to be able to admit publicly, privately, and everything in between that those 157 national climate change plans do not constitute enough emissions reductions to put us onto the path of 2 degrees [C]," Figueres said, referring to a level of warming above preindustrial levels that scientists believe is relatively safe.
"However, what they do do is get us off of the business-as-usual trajectory that we were on just four or five years ago to a temperature increase of 4 or 5 degrees, and by some estimates, even 6 degrees," she added.
The UN reports that 146 countries, representing 85 to 88 percent of global greenhouse gas emissions, had submitted their national climate change strategies as of October 1 – but their projected emissions are still too high to meet the UNEP goals.
Even if all 146 nations meet their self-determined emissions levels, that adds up to 56 billion tons of greenhouse emissions in 2030, 33 percent higher than UNEP's newly eased goals.