The plans countries have put in place to ensure a maximum global temperature rise of 2degC are not working, scientists warn.
New research, led by Niklas Höhne from Germany's New Climate Institute, predicts the current targets would lead to a warming of between 2.6degC and 3.1degC by 2100.
"Even if all [national policies] are successfully implemented by 2030, the 2degC carbon budget might already be virtually exhausted by that time," the paper warns.
Last December, leaders from 196 countries made a historic agreement to limit global warming to less than 2degC by 2100, with a target of 1.5degC.
Earlier studies had speculated that the targets would need to be tweaked to successfully meet that goal.
Part of the problem is that countries are providing a range of emission reductions, rather than a set amount, the paper says. Seventy-five countries have plans based on a comparison to what emission levels would be without any policies to curb them, rather than a set amount to reduce emissions by.
Another issue is that a number of countries have placed conditions on their emission reduction plans - a third of countries who had submitted their plans by December 12 were conditional. Forty-five percent came with some conditions.
Countries' changing emissions policies mean scientists can't accurately predict what the temperature difference could be by 2100, even if the targets are met by 2030.
But even if targets are improved over time, a warming of 2.6degC to 3.1degC above pre-industrial levels is predicted.
The paper was published in the Nature journal on Thursday.