Hansen says Obama has four years to curb emissions

Just days before his inauguration, Barack Obama received a stark warning of the scale of the climate change challenge he will face upon taking office this weekend after leading climate change scientist Jim Hansen warned decisive action would be required during his first term.

Following his recent letter to the president-elect calling for the introduction of a carbon tax, Hansen said that "Obama" had "only four years left " to halt catastrophic levels of climate change.

"We cannot afford to put off change any longer," said Hansen. "We have to get on a new path within this new administration. We have only four years left for Obama to set an example to the rest of the world. America must take the lead."

He warned that so-called climate "feedbacks", such as increased warming of Arctic oceans as retreating ice results in less heat being reflected, meant that global warming was accelerating and that official UN estimates that sea levels could rise by between 20cm and 60cm by 2100 are far too conservative.

He said that faced with the threat of rising sea levels Obama should authorise a full investigation into the state of the planet's ice caps as soon as taking office.

In addition, he reiterated his view that cap-and-trade schemes, such as that proposed by Obama, would not deliver effective cuts in emissions and called on him to re-consider the adoption of a carbon tax. He also called for a moratorium on all coal-fired power stations.

Obama last week unveiled a major package of low carbon measures as part of his proposed $825bn economic stimulus package, including $20bn in fresh tax cuts for alternative energy developers, tax credits for energy efficiency research projects, a $32bn upgrade of US grid technologies, $16bn home insulation program and $2.4bn for the development of carbon capture and storage technologies.

Hansen's comments came as new figures from the World Glacier Monitoring Service (WGMS) warned that most of the planet's glaciers will disappear by 2050 if current rates of melting continue.

The latest data from the UN-backed body showed that while melt rates were lower in 2007 than they had been in 2006 it still marked the third worst year since records began.

WGMS director, Prof Wilfried Haeberli, said that it was realistic to expect that all small glaciers in regions such as the Andes, Rockies and Pyrenees would disappear within a matter of decades, while larger glaciers in regions such as the Himalayas would get much smaller putting at risk the billions of people who rely on their melt water.