"Research suggests it is still possible to limit warming to 2 C above preindustrial levels.
"Governments' ambitions to limit warming to 2C now appear highly unrealistic.
The UN Paris climate agreement struck in December seeks to limit warming to 1.5C if possible.
"We should therefore be striving to limit warming to as far below 2C as possible.
Those objectives are to limit warming to 1.5 to 2 degrees.
They have thus become a cornerstone of calls to limit warming.
At the last minute [in Paris] countries agreed to "pursue efforts" to limit warming further.
Current climate policy aims instead to limit warming to below 2C to avoid the most severe impacts.
This prompted some, including the UN, to suggest 450ppm, which should limit warming to 2ºC, as a more realistic goal.
But it also agreed agreed to "pursue efforts" to limit warming to 1.5C, a target now looking highly optimistic.
If we have all agreed to limit warming to below 2C, then we need to see the action to match.
