The primary contributors to the sharp rise in global temperatures are humans in a sea-ice region of the Arctic Ocean, scientists have observed polar bears stalking, killing and eating other polar bears. Many species of plants across the middle and higher latitudes of the northern hemisphere are now flowering earlier than a few years ago. Migratory birds in Europe, Asia and Australia are arriving early. And the population of Emperor Penguins in parts of Antarctica has dropped by half over the past 50 years. The signs of climate change are burgeoning. Now, research by an international team of scientists has shown that 90 per cent of a large set of myriad changes in plants, animals, and other terrestrial systems believed to be linked to climate change are very close to predictions of human-induced global warming. The study has shown that the changes over the past 30 years are unlikely to have been caused by natural variations in climate. "We're now seeing the fingerprints of human-induced climate change on all the continents and in most of the oceans,' says Annette Menzel, head of the ecoclimatology division at the Technical University of Munich, Germany, a member of the team. "The patterns of change we see closely match simulations of the impacts of global warming.' Recently published in Nature, Menzel and her colleagues from the National Aeronautics and Space Administration and other institutions analysed a number of changes observed since the 1970s on plants, animals and ecosystems. The study's significance lies in the use of statistical analysis to separate the impacts of human-induced warming from natural variations. "That was the real challenge,' says David Karoly, of University of Melbourne. Weather data shows that the average surface temperature on Earth has risen by 0.7 degrees over the past century. The UN panel on climate change had asserted last year that this warming was "very likely' due to an increase in greenhouse gases mainly through fossil fuel burning. But there are some disbelievers