By Richard Black
Environment correspondent, BBC News website, in Brussels
Industrial countries are asked to work on reducing emissions
Considering the fact they had been working intensively all through the night, the leaders of the UN panel on climate change were extraordinarily debonair and alert as they presented their conclusions to ranks of impatient journalists in the bright Brussels morning.
The chair of the Intergovernmental Panel on Climate Change Working Group II, Rajendra Pachauri, apologised for not having shaved - a light touch from the unflappable Indian, who sports a fine beard.
The general view, after five years of scientific work and four days of discussions here between senior scientists and government bureaucrats, was that something pretty significant had been achieved.
"This report clearly assesses the impacts of climate change in different parts of the world," said Dr Pachauri.
"And we have far greater regional detail than in [our previous global assessment in] 2001 on things like glacier melting, and what the implications of that melting will be; on sea level rise, which clearly threatens a number of countries in the world including mega-deltas which are particularly vulnerable; and on agriculture, which has implications for food security."
The extra detail is testament to the vast amount of scientific observation which has been undertaken in recent years. Twenty-nine thousand real-world observations were included in the analysis.
"There is observational evidence of regional impacts on every continent on physical and biological systems," said Cynthia Rosenzweig, a climate impacts specialist with the US space agency Nasa.
"There are multiple lines of evidence that human-induced climate change is happening now, and the impacts are being seen now."
This is pretty strong stuff; but not quite as strong as some would have liked.
The IPCC is an unusual organisation in that the evidence is supplied by scientists, but the summaries of its reports are agreed between scientists and representatives of governments.
Because of this, "climate sceptics" and "climate catastrophists" alike have regularly contended that the conclusions are unreliable - that scientists' drafts are altered through political pressure to make them either too weak or too strong, depending on which direction the criticism is coming from.
Here, a number of governments have sought to tone down the degrees of certainty on various issues.
The draft for this meeting started off by stating with "very high confidence" that natural systems on land and sea are being affected by regional climate changes, which was badly received by Saudi Arabia, Russia, and China.
Deadlock continued until the early hours of the final day's negotiations, with Dr Rosenzweig presenting a note of protest to the chair on behalf of senior scientists, saying that their evidence-based conclusions were being ignored.
At one point she left the room, and the whole process could have unravelled. In the end it was diplomatic leadership by the US, favoured bogeyman of activists, that found a compromise which everyone could live with.
"The final document states that observational evidence on every continent and most oceans shows that natural systems are being affected by regional changes, particularly temperature increases," she said.
"And I'm very happy with that."
Martin Parry, one of the co-chairs of this working group, had this observation on what the involvement of government representatives means for the IPCC's significance.
"The real secret is that governments buy in," he said. "Otherwise it would be just another report."
Governments will soon have the conclusions thrust under their noses at an unprecedented level.
Later this month, the United Nations Security Council will discuss the security implications of climate change, the first time this has ever happened.
Poorer countries will be the hardest hit experts say
In June, the G8+5 group which includes the world's most powerful and populous nations will also have the IPCC's conclusions on their negotiating table.
"The science has come across as so strong and so confident in this report that really governments have nowhere to hide," commented Catherine Pearce, international climate campaigner with Friends of the Earth UK.
That presumes, though, that each government speaks with a single voice on climate change - and the reality is very different.
Many governments, including the UK's, have environment departments which include enthusiasts for tough action on emissions, even at the expense of a little economic hardship.
These views might not be shared, though, in departments of finance, transport, energy and industry.
And the arguments can be quite hard to win in rich northern countries which, as the IPCC report acknowledged, may actually benefit from a modest amount of warming, and where resources are enough to defend against rising sea levels and shrinking rainfall.
It is in the poorest countries that the climate axe will fall. Every delegate here I spoke to was convinced of that.
Unseasonably warm weather in north China has been linked to climate change
"There is strong commitment (in this report) to understanding the adaptation needs of Africa," said Anthony Nyong from the International Development Research Centre in Nairobi, a lead author on the chapter on African impacts.
"[But] mitigation is always the best form of adaptation. There is no way that you can effectively adapt to all the impacts of climate change; it's absolutely impossible.
"So while we work at adapting, let the main emitters of greenhouse gases work on reducing their emissions."
It is a call we have heard many times before. And there is little evidence to believe that a report painting severe consequences ahead for the poor of the world, however detailed and bought into by governments, will be enough to bring unprecedented change from all the well-off members of the community of nations.