The UN Intergovernmental Panel on Climate Change is due to release a report in Paris on Friday entitled Climate Change 2007 in which 2,500 scientists from 130 countries unequivocally state that the current trend towards potentially catastrophic global warming has been induced by human activity, which began with the dramatic increase in fossil fuel use during the Industrial Revolution of the mid-19th century.

A draft of the report, the fourth climate change assessment conducted by the IPCC, has been circulated among major news organizations over the past week.

"As we add to [greenhouse] gases, we are just doing the same thing as putting another blanket on our bed at night," said Sir David King, British chief government scientific adviser, in an interview with CBS News. "The consequences are that you get warmer, and that is as simple as it is."

Dr Kevin Trenberth, head of Climate Analysis at the National Center for Atmospheric Research and also a lead author of the report told ABC News: "Certainly, it will say that global warming is happening, and secondly, that it is due to humans. The whole weight of the evidence has simply increased to show that stuff is already happening. What this report does is provide the basis for subsequent actions.”

The IPCC report highlights a number of consequences of climate change including:

· more warmer days and fewer cold ones;
· more heat waves;
· increasingly intense tropical storms and hurricanes; and
· higher sea levels.

In the aftermath of hurricanes Katrina and Rita, the implications of more intense hurricanes and rising sea levels could hardly be clearer for New Orleans.

"The sea level is rising worldwide, and that's going to have an immediate impact on New Orleans,” said Tulane University geoscientist Torbjorn Tornqvist. “It's all related to global warming. That's what's happening. We've seen in the past century, sea level is rising four times faster than in the preceding 1,000 years. We have to push harder than anyone else in the United States to reverse the problem of global warming because we are facing that problem here first.”

A major concern is the possibility that the current melting of Arctic ice is unstoppable, even with future reductions to greenhouse gas emissions, which would raise sea levels by more than 20 feet and see most of the world’s cities disappear into the sea. Sir David King told The Ecologist magazine that experts still have not determined whether a ‘tipping point’ has been reached: “We don't know. That's the problem. It is melting faster than anticipated. If we lose all the ice in Greenland, the sea level goes up 6.5m [21 feet] – 80 per cent of our global cities will go underwater.”

The report ominously predicts that sea levels will keep rising for more than 1,000 years even if governments manage to reduce greenhouse gas emissions. A source quoted by Reuters said: "Twenty-first century anthropogenic (human) carbon dioxide emissions will contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas."

In addition to catastrophic flooding, other predicted impacts of global warming include severe droughts, desertification and famines. The social effects would include hundreds of millions of “climate refugees” forced from devastated regions.

The report says that recent extreme weather events have resulted from a rise of only 1.5 degrees in global temperatures over the last 150 years, and that a further increase of at least 2 degrees is expected over the next 50 years. According to the previous IPCC report released in 2001 , the very worst case scenario sees the earth’s temperature rising by 11 degrees Fahrenheit by the end of the century.

The report is not without its critics in the scientific community. One senior British climate expert quoted in The Observer warned that the report’s predictions are relatively rosy, given its painstaking consensus process: “The really chilling thing about the IPCC report is that it is the work of several thousand climate experts who have widely differing views about how greenhouse gases will have their effect. Each paragraph of this report was therefore argued over and scrutinized intensely. Only points that were considered indisputable survived this process. This is a very conservative document - that's what makes it so scary.”

Other earth science experts expressed concern that the report does not include the recent and unexpected melting and breaking off of major polar ice sheets. Professor Lonnie Thompson of Ohio State University told the Associated Press that the report’s authors “don't take into account the gorillas - Greenland and Antarctica. I think there are unpleasant surprises as we move into the 21st century.”

Nevertheless, scientists are united in their hope that humanity can stave off the worst case scenarios by limiting greenhouse gas emissions, increasing production of electric and hybrid cars, building more energy-efficient homes, developing alternative power sources and reducing travel where possible.

Responding to long-standing concerns that the solutions are too costly, economists are also uniting behind the consensus that humanity can’t afford not to address climate change, because it poses the single greatest threat to the world economy. The recently released Stern Review on the Economics of Climate Change states that, “if we don’t act, the overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP each year. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20% of GDP or more. In contrast, the costs of action – reducing greenhouse gas emissions to avoid the worst impacts of climate change – can be limited to around 1% of global GDP each year. Tackling climate change is the pro-growth strategy for the longer term, and it can be done in a way that does not cap the aspirations for growth of rich or poor countries.”

The US Supreme Court is currently considering a case brought by a dozen states who are suing the federal government in an effort to force the Environmental Protection Agency to regulate and reduce carbon dioxide emissions from vehicles on the basis that “there is sufficient scientific evidence to enable the EPA to make a determination under section 202 of the Clean Air Act that greenhouse gas emissions may reasonably be anticipated to endanger public health or welfare.” The Supreme Court’s decision on the case is due in June.

Although President Bush recently referred to “the serious challenge of global climate change” in his State of the Union address, he has in practice resisted any binding measures to regulate greenhouse gas emissions in the US. Early in 2001, Mr Bush withdrew from the Kyoto Protocol.

Senator James Inhofe (R-Okla.), former chair of the Environment and Public Works Committee, labelled climate change “the biggest hoax ever perpetrated on mankind” and insisted that there is “no relationship between man-made gases and global warming”. He also repeatedly censored the scientific reports and public comments of top NASA climate scientist Dr Jim Hansen, who blasted the secretive nature of the Bush administration and once told an environmental journalists conference that, “In 39 years at NASA, I’ve never seen anything like the degree to which the information flow from our scientists to the public is as inhibited as it is now.”

This wayward course on climate change looks set to change with the new Congress. Senator Barbara Boxer (D-Calif.), who now chairs the Environment and Public Works committee, strongly supports mandatory caps on greenhouse gas emissions. She has scheduled a hearing on January 30 in which Democrat and Republican senators will present their own legislation to address the effects of global warming, and she believes that bipartisan support on the issue will make it difficult for President Bush to use his veto power. House Speaker Nancy Pelosi (D-Calif.) also supports legislation that cuts greenhouse gas emissions and provides for the development of alternative sources of energy.

Major industrial producers of greenhouse gas emissions, including oil companies, acknowledge human-induced climate change and have also been pushing for federal regulations. They prefer a consistent national system instead of environmental rules that change between states, so they can make informed long-term decisions concerning such projects as building factories and power plants.

Without doubt, the greatest impediment to the scientific solutions offered in the IPCC report will be the political wrangling that has characterized the climate change debate thus far.

IPCC chairman Rajendra Pachauri told Reuters that he hopes the report will galvanize governments into action: “I hope this report will shock people, governments into taking more serious action, as you really can't get a more authentic and a more credible piece of scientific work.”