The most important assessment of likely global warming impacts since the 2015 Paris accord on climate change is to be issued on Monday – with every indication it will show not enough is being done to cool the Earth.

This is the first time leading climate scientists attached to the UN Intergovernmental Panel on Climate Change (IPCC) have studied the effects of a global temperature rise of 1.5 degrees above pre-industrial levels – rather than 2 degrees – and how it can be achieved.

The final “summary for policymakers” will be released in South Korea after revisions and approval by governments. It will be the main scientific guide for combating climate change over coming years, and will set out the basis for efforts to raise national pledges for reducing greenhouse gas emissions, which are currently on track for a rise of around 3 degrees by 2100.

IPCC chairman Hoesung Lee told the opening of the meeting attended by scientists and government representatives: “Together we will produce a strong, robust and clear summary for policymakers that responds to the invitation of governments three years ago while upholding the scientific integrity of the IPCC.”

A rise of 1.1 degrees has already occurred, and greenhouse gas emissions remain at record highs. “If emissions continue at their present rate, human-induced warming will exceed 1.5 degrees by around 2040”, according to a draft copy of the report leaked in July. It broadly reaffirms findings in an earlier draft in January, but is more robust after 25,000 comments from experts were considered.

“It’s the biggest peer-review exercise there is,” said Jonathan Lynn, IPCC head of communications. “It involves hundreds or even thousands of people looking at it.”

‘Sobering read’

Speaking in Dublin at the Environment Ireland conference this week, Dr Koko Warner of UN Framework on Climate Change said the report was “a thrilling and sobering read”. It underlined the importance of strategy, and identified possible pathways and the risks and trade-offs that go with them.

It will set out progress since Paris, and support the scientific view that “a sustainable and equitable 1.5 degrees future” is possible, and will bring global benefits.

“Right now we are headed to 3 degrees collectively, so we have a lot of work to do,” added Dr Warner who helps countries find ways to address impacts, vulnerabilities and risks from climate change.

The report will play an important part in helping to generate much better information to inform strategy for governments, businesses and communities. “That is the thrilling bit,” she said .

In adapting to climate change, she said allocation of efforts and optimising use of resources was always a big consideration, especially as there was “so much to do; what do you do first?”

The 1.5 degree report will also help provide “better indication of when” 1.5 degrees is likely to be reached, and outline related global warming effects likely to happen, and what that means for people living in different parts on the planet. It is underpinned by a requirement for sustainable development and efforts to eradicate poverty.

The US go-it-alone stance on climate change was revealed this week in confidential US comments on the report which raise doubts about the science behind it, warn it risks curbing economic development and advocate use of carbon-catching technologies.

They also show the US pursuing its domestic energy agenda, casting doubt on climate models and heavily criticising the IPCC for not coming to grips with the scale of the challenge to meet Paris targets.

Political battle

The nine pages of comments, reported on by Climate Home News this week, are in response to the latest draft of the UN report, and reflect the views of multiple government agencies. They suggest the US diplomatic corps is trying to speak to multiple constituencies – the global community, their own domestic interests and the White House.

They will feed into a final political battle over the report summary, which was still being finalised on Friday.

Washington argues scientists have downplayed the scale of the challenge to limiting global warming to 1.5 degrees – the more demanding target of the Paris accord. To meet that challenge, the US calls for more emphasis on clean technologies that the Trump administration has consistently supported, including carbon capture and storage and nuclear power. At the same time, the US warns, measures to tackle global warming must not interfere with cutting poverty worldwide.