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Humans blamed for climate change
Peter Walker and agenciesFriday February 2, 2007Guardian Unlimited A polar bear in a melting ice field. Photograph: Getty Images
Global warming is "very likely" to have been caused by human activity, the most authoritative global scientific body studying climate change said in a report today.
The likelihood that the phenomenon has been created by the burning of fossil fuels and other actions is greater than 90%, the Intergovernmental Panel on Climate Change (IPCC) concluded in its fourth report.
In 2001, the body - which brings together 2,500 scientists from more than 30 countries - said global warming was only "likely", or 66% probable, to have been caused by humans.


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The study said global warming is an "unequivocal" fact and likely to continue for centuries, warning of a likely rise in world average temperatures of up to 4C.
In comparison, the world is currently around 5C warmer than during the last ice age.
Environmental and science groups said the report meant the main arguments on global warming were now effectively over.
"This day marks the removal from the debate over whether human action has anything to do with climate change," Achim Steiner, the head of the UN environment programme, said.
Stephanie Tunmore, of Greenpeace, said. "If the last IPCC report was a wakeup call, this one is a screaming siren."
The 21-page summary (pdf) of the findings, called Climate Change 2007: The Physical Science Basis, was formally agreed by the IPCC in Paris yesterday and released earlier today.
It steers clear of policy recommendations, instead providing a rigorously scientific assessment of the likely risks.
The report predicts that global average temperatures would rise by between 1.1C and 6.4C (2-11.5F) by 2100 - a slightly broader range than that shown in the 2001 figures.
However, it said the best estimate was for increases of between 1.8C and 4C.
It forecasts a rise of between 18cm and 58cm in sea levels by the end of this century, a figure that could increase by as much as 20cm if the recent melting of polar ice sheets continues.
"Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level," the summary said.
The report said greenhouse gases were already responsible for a series of existing problems, including fewer cold days, hotter nights, intense heatwaves, floods and heavy rains, droughts and an increase in the strength of hurricanes and tropical storms.
In a dramatic illustration of stronger storms, at least 14 people were killed as severe thunderstorms and at least one tornado flattened homes and a church in Florida today.
The scale of such events in the 21st century "would very likely be larger than those observed during the 20th century", the study said.
It warned that, no matter how much humanity reduces greenhouse gas emissions, global warming and sea level rises would continue for hundreds of years.
"This is just not something you can stop. We're just going to have to live with it," co-author Kevin Trenberth, the director of climate analysis for the US-based National Centre for Atmospheric Research, said.
"We're creating a different planet. If you were to come up back in 100 years, we'll have a different climate."
The environment minister, David Miliband, today said the study's findings were "another nail in the coffin of the climate change deniers".
"What's now urgently needed is the international political commitment to take action to avoid dangerous climate change," Mr Miliband said.
The US president, George Bush, faced fresh criticism for his previous scepticism about the scale of global warming and his refusal to sign up to the Kyoto protocol on greenhouse gas emissions.
"Although President Bush just noticed that the earth is heating up, the American public, every reputable scientist and other world leaders have long recognized that global warming is real and it's serious," John Kerry, the Democratic senator who lost the 2004 presidential election to Mr Bush, said. "The time to act is now."
The White House issued a statement defending Mr Bush's record on climate change, saying his administration had devoted almost £15bn to related science, technology, international assistance and incentive programmes, "more money than any other country".
Some nation at the frontline of the effects of global warming said today that the IPCC report showed it might already be too late.
"The question is, what can we do now? There's very little we can do about arresting the process," Anote Tong, the president of Kiribati, a group of 33 Pacific coral atolls threatened by rising seas, said.
Bangladesh faces "increased level of drought, flooding and storms, especially in coastal belts, salinity and loss of land," Ainun Nisshat, the country's representative on the International Union for Conservation of Nature, said.
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