Cost of extra year's climate inaction $500 bln-IEA

* Delay of a few years would put climate target out of reach

* Major overhaul in energy system needed

By Gerard Wynn

LONDON, Nov 10 (Reuters) - The world will have to spend an extra $500 billion to cut carbon emissions for each year it delays implementing a major assault on global warming, the International Energy Agency said on Tuesday.

At United Nations climate talks in Barcelona last week negotiators from developed countries said the world would need an extra six to 12 months to agree a legally binding, global deal to cut carbon emissions beyond a planned December deadline.

The IEA, energy adviser to 28 industrialised countries, said the world must act urgently to put greenhouse gases on a track to limit global warming to no more than 2 degrees Celsius.

Every year's delay beyond 2010 would add another $500 billion to the extra investment of $10,500 billion needed from 2010-2030 to curb carbon emissions, for example to improve energy efficiency and boost low-carbon renewable energy.

"Much more needs to be done to get anywhere near an emissions path consistent with ... limiting the rise in global temperature to 2 degrees," said the IEA's 2009 World Energy Outlook. "Countries attending the U.N. climate conference must not lose sight of this."