As ministers begin arriving at the UN climate talks in South Africa, new science is showing the challenges they face in trying to curb global warming.
Using a new methodology, a Swiss team has calculated that about three-quarters of the warming seen since 1950 is down to human influences.
A second report says glacier loss in parts of the Himalayas is accelerating.
And an international research group has confirmed that emissions have soared despite the global financial crisis.
At the talks, the main task facing ministers and their negotiating teams is to find agreement on a 143-page draft text covering issues such as speeding up emission cuts, safeguarding forests and helping the poorest countries protect themselves against climate impacts.
One EU official suggested that the majority of governments favoured beginning discussions on a new legally-binding agreement as soon as possible.
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Action that helps cope with the effects of climate change - for example construction of barriers to protect against rising sea levels, or conversion to crops capable of surviving high temperatures and drought.
But a number of important countries including China, India and the US are not persuaded.
Even if those discussions do begin soon, other nations such as Japan and Canada say their existing pledges on cutting emissions by 2020 will not be amended.
Observers point out that without tightening these pledges, global emissions will not peak before 2020 - the timeframe scientists think is necessary if the target of limiting the global temperature rise to 2C from pre-industrial times is to be met.
'Convincing'As delegates prepared to launch into the second week of talks, the journal Nature Geoscience published a new analysis of factors driving the Earth's warming since 1950.
Using information about the Earth's "energy balance" - the difference between the amount of energy it receives from the Sun and radiates back into space - researchers from the Swiss Federal Institute of Technology in Zurich arrived at fresh estimates of the effects of greenhouse gas emissions and other human-induced factors.
Their main conclusion is that it is extremely likely that at least 74% of the observed warming since 1950 has been caused by man-made factors.
They also conclude that greenhouse warming has partially been offset by the cooling effect of aerosols - tiny particles of dust thrown into the atmosphere that can reflect solar radiation back into space.
"It's pretty convincing stuff," commented Piers Forster, professor of climate change at the UK's University of Leeds and a former lead author for the Intergovernmental Panel on Climate Change's assessment of factors driving global warming.
"Observations and the physical law of energy conservation have been used to show greenhouse gases are responsible for global warming and that alternative scenarios violate this law of nature.
"Previous proofs have relied on complex climate models, but this proof doesn't need such models - just careful observations of the land, ocean and atmospheric gases."
Careful observation of the Hindu Kush-Himalayas region, an area where climate change could bring major impacts to people, have been relatively scanty, due to the difficulty of doing science in remote areas, compounded by political disagreements.
The Kathmandu-based International Centre for Integrated Mountain Development (Icimod) has released a series of reports setting out what is known and what is not known about climate change in the region.
The number of glaciers identified has risen above 54,000, largely thanks to satellite observations.
But only 10 of these have been regularly and rigorously studied, it says.
In these 10, the rate of ice loss has roughly doubled since the 1980s.
But overall, the report's conclusion is that observations need to be stepped up to enable better projections of the future for the estimated 210 million people living in the region and the 1.3 billion living in river basins supplied by Himalayan meltwater.
"Up until now, there has been complete uncertainty on the numbers and area of glaciers and the present status of their environmental conditions in the region," said Basanta Shrestha from Icimod.
"This research gives us a baseline from which to measure the potential impact of climate change in the region, and to develop options for mitigating the impact of dynamic changes the region is expecting in the coming years."
'Triple whammy'Meanwhile, Nature Climate Change journal has published a new assessment of how greenhouse gas emissions have changed in recent years.
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End Quote Christiana Figueres UNFCCC executive secretary"Every one of us needs to change our behaviour, business needs to change their investment patterns, everybody?
Conducted by the Global Carbon Project, an international research collaboration, it confirms other analyses in showing that the financial crisis made but a small blip in the rising trend of emissions.
During 2010, emissions grew by 5.9%, they calculate - more than compensating for the fall of 1.4% seen in 2009, when the recession caused a dramatic downturn in developed countries (although not in the developing world's industrial giants such as China).
Even accounting for the 2009 drop, emissions have risen faster in the last decade than at any time in the last 50 years.
"Global CO2 emissions since 2000 are tracking the high end of the projections used by the Intergovernmental Panel on Climate Change, which far exceed two degrees warming by 2100," said co-author Prof Corinne Le Quere, director of the Tyndall Centre for Climate Change Research and professor at the University of East Anglia.
"Yet governments have pledged to keep warming below two degrees to avoid the most dangerous aspects of climate change such as widespread water stress and sea level rise, and increases in extreme climatic events.
"Taking action to reverse current trends is urgent," she said.
Senior lecturer in carbon management at Edinburgh University David Reay said: "From this latest study we see that the [2009] drop was all too ephemeral, and even the limp economic recovery of 2010 has put us back on a high emissions trajectory,"
"We now face the triple whammy of distracted world leaders, a scarcity of carbon finance, and a fast-closing window of opportunity to avoid dangerous climate change.
"For those striving for a breakthrough at the climate change conference in Durban, things just got even harder," he said.
At the conference itself, many delegates seemed aware that if the broad thrust of climate science is correct, time is running out for an agreement that can curb emissions enough to give reasonable odds of making the 2C target.
Equally, few were underestimating the political difficulties.
"Every one of us needs to change our behaviour, business needs to change their investment patterns, everybody," said UNFCCC executive secretary Christiana Figueres.
"That is very difficult to do. But there is no other option."
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Source: http://www.bbc.co.uk/go/rss/int/news/-/news/science-environment-16022585
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