As director of the Earth Institute at the New York-based Columbia University, economist Jeffrey Sachs has advised prime ministers, scientists and United Nations diplomats on climate change. Hindustan Times caught up with him for an interview in New Delhi. Excerpts:

To be strong negotiators at Copenhagen, both India and the US will have to make a credible domestic commitment to fighting climate change. Do you think either nation has made that kind of commitment?

Neither of us has passed the main test, which is putting it through the parliament. In the United States the Senate is still divided over climate legislation. In India, Minister (Jairam) Ramesh has said that the government is going to put forward a climate action plan before parliament. But we’re running out of time.

Should rich nations be paying for the adoption of low carbon technologies by developing countries such as India and China?

I am completely in favour of the United States helping to finance climate change mitigation in India. We should be helping India to pay the costs of India’s solar mission, for example. In 10 to 15 years, when India reaches a higher level of income, then they’ll be able to assume the costs themselves.

In the case of China, I don’t think rich nations need to be paying for them. We feel China will be a leader in low-carbon technologies very soon, so there’s a little bit of reticence (on the part of rich nations) to finance that leadership. I think it will cost around 1 per cent of global GNP (gross national product), every year, so we can definitely afford it.

You’ve supported a carbon tax in the past. Do you think developing countries should also have such a tax?

If the United States were to put price on carbon, say $15 a ton, they could transfer a percentage of that revenue to India so that India could compensate low energy users. But India too will need to find a way to put a price on carbon emissions over time that will tilt the market forces towards energy efficiency. If it remains completely free to put carbon up into the air then the incentives to control it won’t be there.

We focus a lot on the economic costs of switching to low-carbon technologies. How would this switch create opportunities for India?

Whenever we are in a period of technological change there is opportunity.

Countries that become technological leaders in green technologies will have a major global competitive advantage because these will be the products on sale all over the world for the next 30 years.

If India moves fast enough, it will be the exporter of these technologies. This is already happening. There are Indian electric vehicle manufacturers that are exploring US sites. So climate change is an opportunity for the next generation of technological leadership.