A NASA scientist has asked Prime Minister Kevin Rudd to halt all coal exports from Australia, claiming they are causing irreparable damage to the planet.

Mr Rudd, who is currently on a world tour that takes in the United States, Europe and Asia, also at the weekend spoke with US President George W. Bush about climate change, applying further pressure for a real world pact.

NASA's chief climate scientist James Hansen has today written to Mr Rudd, requesting that he halt all further exports of coal from Australia, and phase out fossil-fueled power stations.

Dr Hansen is believed to have written that exports from Australia are causing more damage to the environment, and are not helping in a reduction of greenhouse gases.

President Bush yesterday said that despite America's unwillingness to join the Kyoto pact, he believed the solution to climate change was in new technology, and moving reliance from non-renewable energy sources.

Prime Minister Rudd says that Australia has a target of 20% renewable energy use by 2020, with a 60% reduction in carbon output by the year 2050.

The Government is also considering further investment in solar and renewable technologies.