- Carbon capture and storage involves trapping carbon-dioxide emissions from coal or gas-fired power stations and storing them underground. Disused oil and gas wells are the most cost-effective places for storing the CO2.

- Carbon-capture technology involves passing flue gases from power stations through chemical solvents to remove the carbon dioxide. The removed gas is then compressed to liquify it, and sent by pipeline to oil or gas rigs. There, it is pumped underground into strata once filled with the fossil fuels.

- Carbon capture and storage is regarded as an important measure to limit climate change. It has the potential to remove 90 per cent of the CO2 produced by power stations, which would effectively make the largest contributor to greenhouse gases carbon-neutral.

- Once underground, the carbon dissolves in salt water (saline aquifer) over hundreds of years without causing harm to the atmosphere.

- Norway has been running a pilot sequestration project at the Sleipner field since 1996 in which more than a million tonnes of carbon dioxide have been pumped into empty oil strata in a stable and sustainable fashion.

- There have been environmental concerns that carbon dioxide stored in this way might not be stable, and might yet be released suddenly into the atmosphere, but most geologists consider the technique safe and practical.

- At present carbon-capture technologies are hugely energy-intensive putting their financial viability in doubt. Shell and StatoilHydro recently scrapped plans to build a green power plant that would capture and store carbon dioxide because the project was found to be uneconomic.

- In 1997 the world was generating the equivalent of 40billion tons of CO2 a year; Carbon emissions rose to 50 billion tons in 2006.

- Cutting carbon emissions is immensely politically sensitive for a country such as the United States. It emits the equivalent of 20 tons of CO2 every year for each person living there, double the amount emitted per capita in Britain and 20 times greater than in Mozambique. So if America is to take serious action on climate change, its citizens have a lot more to lose than most.

- Britain's obligation under Kyoto was to cut greenhouse gas emissions by 12.5% by 2012, compared with 1990 levels. It has already managed 13.5%. Britain's Climate Change Bill has fixed on a 60% reduction in carbon dioxide emissions by 2050, but many scientists now believe that an 80% cut is required. The Copenhagen treaty expected in two years' time will probably demand that Britain cut its emissions by 25% by 2020.

Source: Times and Sunday Times archive

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