The world must act now to curb climate change, as doing nothing will cost more long-term. British government official and former World Bank chief economist Sir Nicholas Stern said pursuing alternative energy made economic and environmental sense.

His 700 page report was commissioned by the UK Government and published at the end of last month.

Environment Secretary David Miliband quoted findings reached by Sir Nicholas in his report . "He shows that the longer action is delayed, the more expensive it is," Mr Miliband said. "What he says is that... it is imperative we take action to prevent further climate change because the economic costs – never mind the human costs and the costs to the environment – will far outweigh the costs of mitigation."

The Stern Review forecasts that one per cent of global gross domestic product (GDP) must be spent on tackling climate change immediately. It warns that if no action is taken:

  • floods from rising sea levels could displace up to 100 million people;
  • melting glaciers could cause water shortages for 1 in 6 of the world's population;
  • wildlife will be harmed; at worst up to 40 per cent of species could become extinct; and
  • droughts may create tens or even hundreds of millions of "climate refugees"

Other economic costs include greater harvest losses, a rise in the spread of tropical diseases, greater soil erosion and less certainty in energy supplies.