US Secretary of State John Kerry has placed climate change on the top of world agenda, alongside Ebola and Isis, saying it has an immediacy that people have come to understand.

In remarks to foreign ministers of the 20 biggest economies, Kerry said climate change should be at the top of the agenda despite competition from more immediate challenges, according to The Guardian.

Experts and climate activists are raising the pitch to get world leaders to commit to limiting global temperatures to 2 deg C using strong policies.

This is the tipping point in temperature beyond which climate change effects will become irreversible.

"If Obama and the others decide that 2C has to be the limit, then negotiators will subsequently find it so much easier to hammer out a framework for curtailing carbon dioxide emissions over the next year," said Nicholas Stern, the British economist and climate expert who will be attending the UN climate meeting in New York.

While burning of fossil fuels has added 1,950 tonnes of carbon dioxide to the atmosphere over the last 200 years, it is important to restrict this number from exceeding 3,670 tonnes. But current trends will see that happen in the next three decades alone.

The UN aims to use the gathering to press world leaders to do more by way of cutting emissions and giving more funds to help poor countries cope with climate change.