COPENHAGEN (AFP/Reuters) - The UNs top weather expert warned Tuesday the world is in its hottest decade on record as climate negotiators plunged into talks seeking a historic deal on cutting carbon emissions. The developing nations demanded deeper emissions cuts from rich nations, particularly the US. The World Meteorological Organisations assessment underlined the pressure for an agreement at a summit in Copenhagen, which was boosted when the US said it would start to regulate carbon dioxide as a dangerous pollutant. The decade 2000-2009 is very likely to be the warmest on record, warmer than the 1990s, which were in turn warmer than the 1980s, World Meteorological Organisation Secretary General Michel Jarraud told a press conference. Jarraud also said the year 2009 would probably rank as the fifth warmest since accurate records began in 1850. Britains Met Office released data from hundreds of monitoring stations worldwide showing that the global surface temperature has risen significantly over the last 150 years, including a finding that the rise has averaged more than 0.15 degrees celsius per decade since the middle of the 1970s. The Copenhagen talks, under the banner of the UN Framework Convention on Climate Change (UNFCCC), are the boldest attempt in a 17-year odyssey to turn back the threat of climate change through consensus. If all goes well, the conference will yield an outline agreement that sets down pledges by major emitters of greenhouse gases to curb pollution. It will also set down principles of long-term financing to help wean poor countries off high-carbon technology and beef up their defences against climate change. Further negotiations would be needed over the next year to flesh out the agreement. Once ratified, the accord would take effect from 2013. Delegates said the next few days would see countries lay out their positions before some 110 world leaders - including US President Barack Obama, Chinese Premier Wen Jiabao and Indian Prime Minister Manmohan Singh - arrive for the climax. Climate change is already forcing people to migrate, according to a report released Tuesday by the UNs International Organisation for Migration, with most moving within their countries or to a neighbouring country. Large-scale human movement from climate change and environmental degradation is not only inevitable but is already happening, said the study. However, much of it is internal or cross border migration, belying some fears that millions of poor people will go to rich countries as a result of climate change, added the report entitled Migration, Environment and Climate Change: Assessing the Evidence. The UN refugee agency has estimated that some 24 million people worldwide have fled their homes due to environmental factors. In Ethiopia, Mali, Burkina Faso and Senegal, there has been fairly common movements of populations in response to drought, said the report. Were off to a good start, Yvo de Boer, head of the UN Climate Change Secretariat, said of the Dec 7-18 talks. He urged delegates to sort out technical details of an accord but said that the big issues such as emissions targets for rich nations and funds for the poor would have to wait for a December 18 summit that will be attended by over 100 world leaders. Emission cuts offers from rich nations were far below what was needed, Dessima Williams of Grenada, chair of the 43-nation Alliance of Small Island States, told Reuters. AOSIS wants emissions cut 45 per cent by 2020 from 1990 levels. Our 45 per cent remains on the table. Germany is at 40, the EU as a whole and some other countries are at 30. This is the time to escalate, to be ambitious, she said.