In 2002, a large part of the Larsen B ice sheet, at the northernmost edges of southern polar region just above the Antarctic Circle, vanished. Much of the ice sheet composed a white expanse curving around a deep black bay. A series of photos taken by Nasa show the sheet’s transformation: it looks like a giant finger reached down and smudged the sheet out into the ocean. 
The sheet was estimated to be 10,000 years old. Its partial disappearance took three months.
Scientists were stunned. Larsen B ice sheet’s collapse, linked to climate warming in the Antarctic Peninsula, was a sudden event that succeeded long stretches of inaction.
Likewise, the climate agreement meant to stall its further demise was only arrived at after years of accumulation. And likewise, it is now moving faster than expected.
With another UN climate conference to start in Marrakech, Morocco, on Monday, and nearly a year after the Paris agreement was adopted by 195 countries – pledging to keep global temperature rise below 2 degrees – diplomats and analysts have been surprised at how quickly the accord entered into force.
One of the explanations for Paris’ success after so many failed attempts to hammer out a global agreement to combat climate change was the way it was structured: the accord sets out an overall goal but leaves the specifics for reaching that goal up to individual countries.
And while the agreement is legally binding, countries individual emissions reductions plans are not.
The plans already submitted by countries cumulatively fall short of reaching the under-2-degree goal.
Scientists estimate that under the current plans, the world will still warm by at least 2.7 degrees over pre-industrial levels.
But the Paris agreement also asks countries to submit improved plans – incorporating the best technology as it becomes available – at five-year intervals.
With individual reductions plans at the heart of the agreement, ensuring that carbon emissions drop globally relies in large part on how to manage the system, and many of those details still need to be sorted out.
These include making decisions on how to count emissions reductions and how to make sure countries are meeting their goals.
Countries that have ratified the agreement can take part in making the decisions as part of a UN body called the CMA, the first session of which is expected to take place in Marrakech. But many analysts say that the first CMA wasn’t expected to take place for a few years,
A report by the UN Environment Programme (UNEP) released on Thursday showed that global annual greenhouse gas emissions would have to be reduced by between 12bn to 14bn tons annually by 2030 to stay below 2 degrees, deep cuts that would have to take place in a very short amount of time.