Smoke and mirrors touted as solution

Backers of extreme technologies to curb global warming advocate dumping iron dust into the seas or placing smoke and mirrors in the sky to dim the sun.

But, even though they are seen by some as cheap fixes for climate change when many nations are worried about economic recession, such "geo-engineering" proposals have to overcome wide criticism that they are fanciful and could have unforeseen side effects.

"We are at the boundaries, treading in areas that we are not normally dealing with," said Rene Coenen, head of the Office for the London Convention, an international organization that regulates dumping at sea.