President Obama's science adviser got into a spat with the media last week after appearing to advocate geo-engineering as a way to mitigate the effects of global warming.
John Holdren, who became the president's adviser for science and technology in December, was quoted in an interview with the Associated Press suggesting that climate change has become so severe that drastic moves may be required.
Geo-engineering involves large engineering projects on a global scale as a means of changing the planet's climate. Examples that have been proposed include dropping sulphur in the upper reaches of the atmosphere to stop some of the sun's heat reaching the earth's surface.
"We're talking about all these issues in the White House," Holdren was quoted as saying by the AP in a discussion about geo-engineering. "There's a very vigorous process going on of discussing all the options for addressing the energy climate challenge."
Holdren reacted ...