As next month's Copenhagen conference approaches, politicians should not be distracted by the apparently growing volume of sceptical voices challenging the need for global action against climate change. Some of the sceptics may have scientific backgrounds but they are not in the mainstream of contemporary climate research. The real experts – hundreds of scientists worldwide who are examining the link between climate and carbon dioxide emissions – have no doubt that man-made global warming is a real crisis that must be addressed urgently.

When science and politics mix, scientists have to simplify their arguments to enable politicians to grapple with the issues. The sheer complexity of climate science, from atmospheric physics to polar glaciology, makes it harder to convey than some other science-based issues such as space policy, stem cells or HIV/Aids. And there has inevitably been oversimplification – sometimes amplified by environmental groups keen to present the threat of global warming in the starkest terms.

The most important point to grasp about global warming is that it has not proceeded and will not continue at anything like a uniform, predictable pace around the world. As sceptics like to point out, 1998 was the warmest year on record globally (because of a particularly intense El Ni?o event in the Pacific Ocean) but locally things have heated up considerably since then – especially in the Arctic, where summer sea ice has shrunk alarmingly over the past five years.