The world is heading for the next major climate change conference in Cancun later this year on course for global warming of up to 3.5C in the coming century, a series of scientific analyses suggest. The failure of last December's UN climate summit in Copenhagen means that cuts in carbon emissions pledged by the international community will not be enough to keep the anticipated warming within safe limits.

Coastal megacities like Shanghai, and low-lying regions of countries such as Pakistan (above) are most at risk from rising sea levels. (AP) Two analyses of the Copenhagen Accord and its pledges, by Dr Sivan Kartha of the Stockholm Environment Institute, and by the Climate Action Tracker website, suggest that, with the cuts that are currently promised under Copenhagen, the world will still warm by 3.5C by 2100. Such a rise would be likely to have disastrous effects on agricultural production, water availability, natural ecosystems and sea-level rise across the world, producing tens of millions of refugees.

A month ago, in its annual State of the Climate report, published in conjunction with the UK Met Office's Hadley Centre, America's National Oceanic and Atmospheric Administration (NOAA) listed 10 separate indicators of a warming planet, seven of them rising - ranging from air temperature over land and humidity to sea level - and three of them declining: Arctic sea-ice, glaciers, and spring snow cover. "The scientific evidence that our world is warming is unmistakable," NOAA said.

Cancun, or "COP 16" as it is officially known, will again see ministers and officials from nearly 200 nations grapple with the politics of global warming, but no one thinks they will be able to close a widening breach in the world's defences against dangerously rising temperatures - the "gigatonne gap".

A gigatonne is a billion tonnes of carbon, and the emissions cuts currently promised by the nations of the world in the Copenhagen Accord - the last-minute agreement patched together by leaders after the conference in the Danish capital all but collapsed - will mean that, by 2020, when global emissions should be on a firmly downward trend, they will be several gigatonnes too high to limit the warming to C above the pre-industrial level. This is widely considered the most that human society can stand without serious consequences.

Yet the international community does not seem any closer to consensus on the need to make further reductions in carbon and at Cancun, which takes place from 29 November to 10 December, it is at best side issues on which any progress will be made.

Today, the Coalition's Climate Change Secretary, the Liberal Democrat Chris Huhne, will travel to Berlin to discuss strengthening the EU climate target in advance of the Cancun meeting from 20 per cent to 30 per cent, with his German and French counterparts, Norbert Röttgen and Jean-Louis Borloo.

Mr Huhne told The Independent: "There's hard work ahead to maintain and build on the level of commitment embodied in the Copenhagen Accord and to rebuild the credibility of the United Nations Framework Convention on Climate Change process.

"We in the EU still need to finalise our positions in advance of COP 16, but I think there's a real chance the negotiations could take important steps forward in Cancun, in particular to implement parts of what was agreed in Copenhagen and to work towards the global deal the world needs."

He added: "It's the UK's view - and one shared by my French and German counterparts - that the EU should raise its ambition and that the economic case for doing so stacks up.

"Cutting emissions by 30 per cent by 2020 would be a game-changer in shifting investment into new clean technologies, generating jobs and growth in supply chains across our economies. The great risk for Europe is in waking up late to these opportunities and losing out to other major blocs who are already eyeing up market share."

It is hard to exaggerate the dire effect which the failure at Copenhagen has had both on the climate change negotiating process itself, and on the belief of those involved that an effective climate deal might be possible.

A year ago, many environmentalists, scientists and politicians genuinely thought that the meeting in Denmark might produce a binding agreement to cut global CO2 by the 25-40 per cent, by 2020, which the Intergovernmental Panel on Climate Change (IPCC) has calculated is necessary to keep the warming to below C.

Today that optimism has vanished. The Danish meeting foundered on the disagreement between the developed countries and the developing nations over who should do how much, and when, in cutting emissions; the major point of disagreement was the Kyoto Protocol, the current treaty, which makes developed countries do a lot, and developing nations not very much.

The Kyoto treaty runs out at the end of 2012 and the developing nations, led by China and India, wanted it renewed, while developed countries, including Britain and the rest of the EU, want a completely new treaty to share out the carbon-cutting burden.

At Copenhagen last December, world leaders cobbled together an agreement which ended up devoid of any binding carbon emissions targets (but did recognise the need to stay under C for the first time). Instead of the legally-binding treaty which had been hoped for, nations were invited to "register" voluntary targets, saying by how much they thought they could cut their CO2 by 2020.

Britain is part of the EU target of a 20 per cent cut, on a 1990 baseline, which may be raised before Cancun to 30 per cent. (Britain's own domestic target is one of the highest, to cut CO2 by 34 per cent by 2020.) Other targets include 25 per cent for Japan, Australia by 5 to 25 per cent and the US by 17 per cent on a 2005 baseline - although the legislation to achieve it is firmly stalled in the Senate. Among the developing nations, China has promised to reduce the energy intensity of its economy by 40 to 45 per cent by 2020.

Various analyses of all these pledges suggest they amount to cuts of the global CO2 total of between 11 and 19 per cent by 2020, instead of the 25 to 40 per cent which the IPCC says is needed. This can also be expressed in real amounts of CO2, of which the world is currently emitting annually about 45 gigatonnes - 45 billion tonnes of carbon.

If the world continues with these levels of emissions it is thought this will increase to between 51 and 55 gigatonnes by 2020. Lord Stern of Brentford, author of a landmark report on the economics of climate change, has calculated that if, instead, global CO2 could be cut back to 44 gigatonnes by 2020, the world would be on a credible path to stay below a rise of C. Yet analysis suggests the Copenhagen Accord pledges will leave the figure at 48-49 billion tonnes - the gigatonne gap which Cancun is not going to close.

What the conference may do is agree the architecture for the new major climate funds to help developing countries which were agreed in Denmark - a "fast-start" fund of $30bn (£19.4bn) per year in new money for the years 2010-12, and a fund of $100bn annually to be set up by 2020.

If there are no further breakdowns, it is possible that the meeting may at least restore faith in the UN climate process. "Nobody thinks Cancun will be a big-bang moment," said Keith Allott, head of climate change for the World Wide Fund for Nature. "What the world needs to do is put some wheels back on the climate truck."