There is now strong evidence that significant global warming is occurring and that most of the warming in recent decades can be attributed to human activities. So say the national scientific authorities of 11 countries ahead of next month’s G8 summit in the UK.

A joint statement from the science academies of Russia, the UK, Japan, Italy, China, Brazil, Canada, Germany and perhaps most significantly, the US, says: ”The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. It is vital that all nations identify cost-effective steps that they can take now, to contribute to substantial and long-term reduction in net global greenhouse gas emissions.”

With carbon dioxide levels having increased from 280 ppm in 1750 to over 375 ppm today – higher than any previous levels that can be reliably measured in the last 420,000 years – the academies state that such warming has already led to changes in the Earth’s climate, causing temperatures to rise by approximately 0.6 oC over the twentieth century.

Given the complexity of climate, a lack of full scientific certainty about some aspects of climate change is not a reason for delaying an immediate response, the statement says. Consequently, the academies call upon world leaders, particularly those of the G8 countries, to acknowledge that the threat of climate change is clear and increasing, to address its causes, and to prepare for its consequences.

However, despite the apparently overwhelming evidence, it seems that the White House and US president George W. Bush continue to insist that we still do not know enough.

The Academy statement comes as it is revealed that a former oil lobbyist has been editing Administration scientific reports in an apparent attempt to play up the uncertainty associated with climate change.

Philip Cooney, now chief of staff at the White House Council on Environmental Quality edited government climate reports to soften the link between greenhouse gases and global warming. Critics suggest that the documents from the Government Accountability Project reveal significant behind-the-scenes influence of White House officials with ties to the energy industry, although the White House denies there was any impropriety.

The irony of a White House aide sexing up documents to help portray a politically expedient result is seen by many as darkly comic, particularly given that UK prime minister Tony Blair, as president of the G8 for the coming year, plans to make global warming a major priority during the upcoming summit and is holding a series of meetings with the US president ahead of the summit itself. However, while the remaining climate change sceptics may be seen as an extremist fringe on a par with flat earthers, they are also in control of the world’s largest economy and with George Bush expected to cling determinedly to his climate change policy, prospects that a significant agreement on the issue will arrive during the G8 summit are slim, even if Blair calls in some favours accrued during the Iraq war.