Climate change sceptics and fossil fuel companies that have lobbied against action on greenhouse gas emissions have squandered the world's chance to avoid dangerous global warming, a key adviser to the government has said.
Professor Bob Watson, chief scientist at the department for environment and rural affairs, said a decade of inaction on climate change meant it was now virtually impossible to limit global temperature rise to 2C. He said the delay meant the world would now do well to stabilise warming between 3C and 4C.
His comments come ahead of key UN negotiations on a new global climate treaty in Copenhagen next month that the UK government insists should still aim for a 2C goal, despite doubts over whether a meaningful deal can be sealed.
In an interview with the Guardian, Watson said: "Those that have opposed a deal on climate, which would include elements of the fossil fuel industry, have clearly made making a 2C target much, much harder, if not impossible. They've clearly put the world at risk of far more adverse effects of climate change."
The decision of former US president George W Bush to walk away from the Kyoto protocol, the existing global treaty on carbon emissions, sent a message to other countries not to act, he said. "The last decade was a lost opportunity. Elements within the fossil fuel industry clearly had major implications for the Bush administration."
He added: "I think they've clearly been partly to blame, without any question at all. But you have to say it is not just the fossil lobby. Within the US, there is not strong support for the Kyoto protocol in both parties. Even Obama now will have to persuade a still somewhat sceptical Senate that we should be doing this."
The Copenhagen talks are not expected to deliver a legally binding treaty as originally hoped, but could still make progress on issues such as emissions cuts for rich countries and financial assistance for the developing world. A strong agreement rests on how far Obama is willing to push towards strong carbon cuts in the US.
European officials fear the agreement could eventually do no better than return emissions in 2020 to 1990 levels; scientists say they must fall by 25-40% to have a good chance of staying within the 2C limit.
Watson, a former head of the Intergovernmental Panel on Climate Change, said: "I think we will do well to stabilise between 3 and 4C. Even that is going to take strong political action to decarbonise the energy system and to require us peaking greenhouse gas emissions in the next 10 or more years," he said. "We have to make sure we understand what it would mean to see 3-4C. How would we adapt our agriculture, our water resources, coastal protection and human health systems."
A Guardian poll this year showed that almost nine out of 10 climate scientists thought the 2C target would be missed.
The British government last month published a map that laid out the stark details of a world warmer by 4C. It showed that the rise would not be evenly spread across the globe, with temperature rises much larger than 4C in high latitudes such as the Arctic. Because the sea warms more slowly, average land temperature will increase by 5.5C, which scientists said would shrink yields for all major cereal crops on all regions of production. A 4C rise would also have a major impact on water availability, with supplies limited to an extra billion people by 2080.
Watson backed controversial calls for research into geoengineering techniques, such as blocking the sun, as a way to head off dangerous temperature rise – one of the most senior figures so far to do so. "We should at least be looking at it. I would see what the theoretical models say, and ask ourselves the question: how can we do medium-sized experiments in the field?"
Such an effort could divert attention and funds from efforts to cut carbon and switch to cleaner technology, he said. "I think it should be a real international effort, so it isn't just the UK funding it."