By Peter Griffiths
Public awareness about the "catastrophe" of climate change is not high enough to pressure politicians into taking action, former Vice President Al Gore said on Tuesday.
Gore, who shared a Nobel Prize in 2007 for his environmental campaigning, said politicians will only do more once the people who elect them force the issue.
Voters need to tell leaders they must act on the environmental concerns if countries are to strike a new deal on global warming at U.N. climate talks in Denmark later this year.
"The only way we can get one is if politicians in each country act and the only way that can happen in turn is if awareness rises to the level to make them feel it is a necessity," Gore said in a speech.
"We can berate politicians for not doing enough and for compromising too much and for not being bold in addressing this existential threat to civilization.
"But the reason that they don't is because the level of awareness and concern among populations still has not risen to cross the threshold that makes the political leaders feel they must address it."
Countries will meet in the Danish capital Copenhagen in December to try to agree a new global deal to restrict manmade climate change. Scientists say global warming is taking place at a quicker pace than previously thought and will lead to more diseases, flooding, extreme weather and crop failures.
Preparatory talks on planned emissions cuts have stumbled on rows between rich countries and poor states, who say they did least to contribute to global warming and will suffer the most.
However, Gore said there were some optimistic signs in the run-up to the talks. China, the United States and Australia have made good progress on the issue, young people are increasingly aware of the dangers of inaction and countries have all the technology needed to fix the problem.
"We have the tools available to us to solve three climate crises," Gore told an environment conference at the University of Oxford, southern England. "We only have to solve one."
Energy efficiency and more use of renewable energy will help cut emissions from coal-fired power plants, he added.
Geothermal power alone could meet the world's current energy needs for the next 30,000 years, Gore said. Geothermal projects involve drilling wells deep into the earth to tap steam or hot water to power turbines.
Halting deforestation, building more efficient buildings and making transport networks less reliant on fossil fuels will also help to cut emissions dramatically, he said.