IT has been difficult to believe in the existence of global warming during the last couple of weeks here on Majorca. Global freezing, more likely. Yet the evidence accumulates that there is a change taking place in the world's weather. Keen gardeners notice it as flowers bloom before their time but beyond such anecdotal observation there is increasing scientific evidence of change. The University of Berne has created a computer model that traces the European climate as far back as 1500 and has therefore been able to report that the last ten summers have been the hottest in 500 years. During this decade summer teperatures have been significantly higher than the long-term seasonal average and last year Britain experienced its highest temperature on record. The Swiss scientists have used data from such sources as ice cores and tree rings to recreate the climatic history of Europe over half a millennium. The leader of the research team, Dr Luterbacher, said: The warmth of the late 20th century is likely to be unprecedented in the Northern hemisphere in the past 1'000 years and cannot be explained by natural causes alone. The historical perspective provided by this research is important; there will always be short spans of warming and cooling - there was a spell of the latter between 1947 and 1977 - but the long view is what matters. Dr Luterbacher said that in his opinion the new data clearly supported other indications that greenhouse gas emissions are causing global warming. Meanwhile, for those interested only in the short term prospects for the coming summer, there is good news. According to Britain's Met Office there is an even chance that temperatures will again be above normal for much of Britain and Europe.