Almost half of humanity could lose clean water access due to climate change, according to a British report to be released tomorrow ahead of an international climate change conference in Mexico.

"The main message is that the closer we get to a four-degree rise, the harder it will be to deal with the consequences," Dr. Mark New, a climate expert at Oxford University, told The Observer.

The report will assume that global temperatures will rise 2 degree Celsius (3.6 degrees Fahrenheit)  this century even if nations agree to curb carbon emissions this year.

Climate change scientists believe that a mass global movement to "decarbonize" human activity in order to stay below this temperature is virtually impossible, especially after the UN climate talks in Copenhagen failed last December.

Still, nearly 200 countries will take part in the 12-day conference in the Mexican resort of Cancun.

Instead of grappling for an overarching treaty, negotiators are being asked to notch up progress on half a dozen issues to help revive faith in the UN climate arena.

The European Union's chief negotiator, Artur Runge-Metzger, said there was "no guarantee" the talks under the UN Framework Convention on Climate Change (UNFCCC) would follow this new, pragmatic, incremental path.

"But what I can hear very clearly over the last weeks and months (is) that all parties want to make headway here in Cancun," he told a press conference.

"They want to show the world that this process can deliver, it can move the international climate agenda forward."

The Copenhagen talks ended last year with a face-saving compromise penned in the final hours of the summit.

"Cancun should not be the Copenhagen Accord, Part II," the Bolivian delegation said in a statement.

The deal does not identify the stepping stones to achieving this -- and the promises to curb greenhouse gases, the toughest issue of all, are only voluntary.

Averting deforestation and formally adopting a Green Fund with which to send poor nations $100 billion a year for climate adaptation programs are areas of possible progress.

Poor countries are least to blame for the fossil-fuel pollution that causes global warming, yet are most exposed to the worsening drought, flood, storms and rising sea levels that will result.

"Only three billion dollars has been formally allocated for adaptation," said Saleemul Huq of the International Institute for Environment and Development (IIED).

Scientists told reporters recently that we can expect more rain, more drought and fiercer storms in the future if the world continues on its fossil-fuel gobbling track.

"Heat records are outpacing cold records at a factor of two to one now. That number is expected to increase to 20 to 1 by late this century if we continue on the course that we are on with fossil fuel burning," Michael Mann, a leading US scientist, said.

With AFP.