So what is all this going to cost?

The short answer is trillions of dollars over the next few decades. It is a significant sum but a relatively small fraction of the world's total economic output.

In energy infrastructure alone, the transformational ambitions that delegates to the UN climate change conference are expected to set in the coming days will cost more than $10 trillion in additional investment from 2010 to 2030, according to a new estimate from the International Energy Agency.

As scary as that number sounds, the agency said that the costs would ramp up relatively slowly and be largely offset by economic benefits in new jobs, improved lives, more secure energy supplies and a reduced danger of climate catastrophe.

Most of the investment will come from private rather than public funds, the agency contends. "People often ask about the costs," said Kevin Parker, the global head of Deutsche Bank Asset Management, who tracks climate policy for the bank. "But the figures people tend to cite don't take into account conservation and efficiency measures that are easily available. And they don't look at the cost of inaction, which is the extinction of the human race. Period."

Whatever global warming's effects - and most scientific projections are less dire - there are also varying estimates of the economic costs of failing to act to address the problem soon, some of them very high.

In Copenhagen, some of the most intense and difficult discussions for negotiators centre on any potential agreement's near-term financial arrangements.

Some of the poorest and most vulnerable nations are calling for a gigantic transfer of wealth from the industrialised world to island nations and countries in Africa, Asia and Latin America that are most likely to feel the ravages of a changing climate.

The money would be used to help developing nations reduce emissions by switching to renewable energy sources like wind and solar and by compensating landowners for not cutting down or burning forests, a major source of carbon dioxide emissions.

Other funds might be used be used to adjust to effects of a changing climate like rising sea levels, by building flood walls or relocating settlements to higher ground.

Perhaps the most detailed analysis of the financing needs of any climate change agreement comes from Project Catalyst, an initiative of the European Union and ClimateWorks , a foundation-supported policy group based in San Francisco.

The group's work has helped shape the negotiations in Copenhagen. The group estimates that roughly $100 billion will be needed by 2020 to finance climate change programs in the developing world.

About half could come from the growing global market in carbon emissions credits under a cap-and-trade system, which will be worth an estimated $2 trillion a year by 2020. A cap-and-trade system is already operating in Europe and is under consideration by Congress.

An additional $10 billion to $20 billion would come from taxes on fuels used in aviation and shipping. The rest, perhaps $25 billion to $35 billion, would be loans and grants from industrialised nations to poorer countries, split roughly three ways among the US, the European Union and Canada, Japan and Australia.

The good news is that everybody now is supporting our proposal for financing," said Umaña , the Costa Rican delegate at Copenhagen . "The bad news is that it's happening 15 years too late. Without real money on the table, this will be a disaster."

BUDGET DEFICIT

Roughly $100 billion will be needed by 2020 to finance climate-change schemes in the developing world. About half could come from the growing global market in carbon emissions credits under a cap-and-trade system. An additional $10 billion to $20 billion would come from taxes on fuels used in aviation and shipping. The rest, perhaps $25 billion to $35 billion, would be loans and grants from industrialised nations to poorer countries

YOUR POCKET

ENERGY

The overall costs of Copenhagen are impossible to quantify. Most of the money will be spent by rich countries switching to a "low carbon economy" in order to meet targets on cutting greenhouse gases. This will mean investing in renewables and nuclear energy and will most likely end up on your fuel bills. Electricity costs will rise, though in the distant future power could even be free as energy is generated from natural sources

TAXES

Carbon taxes that are imposed on polluting industries are likely to be passed onto the consumer. There could also be direct carbon taxes on individuals if "carbon allowances" are introduced to limit the amount of energy, travel and other electricity each person is allowed to use

AIR TRAVEL

Airlines do not currently have a lowcarbon alternative to jet fuel. Unless one is found, they will bear the full burden of higher fuel costs and carbon taxes, and average fares will rise by at least 140 per cent. Video conferencing and mobile technology should get cheaper as it becomes more popular as an alternative to travel

TRANSPORT

Developed countries will be investing in high speed trains to bring down emissions. But the prices will not fall in the short term because of the investment needed. Electric vehicles should become cheaper as nations encourage manufacture and a switch from petrol cars fuels demand

FOOD

Cost of food flown from abroad could go up with the cost of transport. Prices of locally-grown food could also increase because of a rise in the cost of fertilisers

OTHER GOODS

Cost of clothing is likely to rise by one per cent and of other household goods like washing machines by two per cent, according to a New Scientist study conducted this year