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Climate change is top of the agenda at the G8 summit taking place this week in Italy.

It is all part of plans to come up with a pact to tackle global warming by the UN's Climate Change Copenhagen meeting in December.

However, facts and figures about global warming can be confusing.

David MacKay is a professor at Cambridge University and the author of a book called Sustainable Energy Without The Hot Air.

Should the world wean itself off oil, gas and coal for the sake of the future of the planet?

The scientific consensus is that global warming is caused by the gas they emit, carbon dioxide.

Global warming is a term in general use today, but it was only coined in 1975, by US scientist Wallace Broecker.

Once derided, nuclear power is now seen by many as a source of energy that many feel could be the way ahead.

The ´óÏó´«Ã½'s Rob Broomby reports from Finland, where the world's biggest nuclear reactor is under construction.

James Lovelock is known as the father of the Gaia theory, the view that the planet operates as a single self-regulating organism.

Our environment correspondent, Matt McGrath asked him if he was now in favour of nuclear power?

According to a report commissioned by the United Nations Environment Programme or UNEP, new investment in renewable energy around the world is now outstripping investment in traditional fossil fuels.

Solar power in particular has been touted by some as the answer to many of the world's energy needs.

The World Today heard this report from solar energy project in Ethiopia:

Professor Hans Joachim Schellnhuber is a key advisor to the German Chancellor and the European Commission.

First broadcast 7-9 July 2009