President Donald Trump looks set to pull the US out of the Paris Agreement, the world’s first comprehensive treaty on climate change.
Here are the key questions about it.
:: What is the Paris Agreement?
A global deal, agreed under the United Nations in the French capital in December 2015, which will see action by all countries to curb rising temperatures.
:: Why do we need it?
If we continue to pump greenhouse gases into the atmosphere on current trajectories, we are facing a world with temperatures of more than 4C above pre-industrial levels by 2100, hotter globally than at any time in human history.
This will lead to sea level rises, more intense storms and flooding, more extreme droughts, water shortages and heatwaves as well as massive loss of wildlife and reduction in crop yields, potentially sparking conflict and mass migration.
The higher temperatures rise, the worse the situation will be so we need to halt the emissions that cause global warming.
:: What does the agreement involve?
The Paris Agreement commits countries to take action to limit temperature rises to “well below” 2C above pre-industrial levels and pursue efforts to keep them to 1.5C, which requires emissions to be cut to net zero by the second half of the century.
Current climate plans by countries are not enough to meet the targets so there is a five-year review and ratchet mechanism to increase ambition, and finance for poor countries to develop along a low-carbon path and to cope with the impacts of climate change.
:: Why is Donald Trump expected to pull out of the deal?
Then president Barack Obama signed up to the deal, without ratification by the US Senate, last year.
In pulling out Mr Trump, who has described climate change as a hoax by the Chinese to hurt US manufacturing, would be honouring a pledge made on the campaign trail to quit Paris and boost fossil fuel production at home.
:: Would the move be popular in the US?
Certainly in some quarters, with a strong vein of climate scepticism in parts of the establishment and among some of Mr Trump’s supporters.
But surveys show the majority of Americans want to stay in the accord, solar jobs are booming and US entrepreneurs such as Elon Musk are driving forward clean tech.
Even major oil companies have urged the US to stay in.
States such as California have already pledged to continue action to cut their emissions regardless of what the president does.
