Global temperatures are on track to rise by more than double the two-degree Celsius (3.6-degree Fahrenheit) warming goal set by the UN unless urgent measures are taken, the International Energy Agency warned Monday.

"The path we are currently on is more likely to result in a temperature increase of between 3.6 and 5.3 C (6.5-9.5F)," IEA chief Maria van der Hoeven said in presenting a new report on greenhouse gases.

The Paris-based agency urged governments to act, saying the 2C target could still be met with little economic pain.

"Much more can be done to tackle energy-sector emissions without jeopardising economic growth, an important concern for many governments," it said.

The IEA report was issued as nations gathered in Bonn for a second week of talks on forging a global pact to limit carbon emissions. It would be signed in late 2015 and take effect in 2020.

"Once again we are reminded that there is a gap between current efforts and the engagement necessary to keep the world below a 2C temperature rise," UN climate chief Christiana Figueres said of the IEA report in a statement from Bonn.

"Once again we are reminded that the gap can be closed this decade, using proven technologies and known policies, and without harming economic growth in any region of the world."

The United Nations is targeting a global average temperature rise of 2C from pre-industrial levels for what scientists believe would be manageable climate change, avoiding worst-case-scenario increases in droughts, storms, floods and sea level rises.

In its "Redrawing the Energy-Climate Map" report, the IEA said carbon dioxide (CO2) emissions from fossil fuel use rose by 1.4 percent last year to a record 31.6 billion tonnes.

The agency recommended four energy policies it said could halt the growth in energy-related emissions by the end of the decade, at no net economic cost.

Boosting energy efficiency in buildings, industry and transport could account for half of an eight-percent greenhouse gas reduction by 2020 envisioned under the plan, the report said.

Limiting coal-fired power stations would contribute another 20 percent of the reduction, cutting the escape of methane gas when extracting oil and gas 18 percent, and a partial phasing-out of fossil fuel subsidies another 12 percent.

The financial impact of such policies would show a net benefit, the agency said, with revenue from existing renewables-based and nuclear power plants increasing by $1.8 trillion (1.4 trillion euros) to 2035 -- offsetting a decline from coal plants.

If its proposals were met, no oil or gas field currently in production would need to shut down prematurely, the IEA said.

But it warned that delay in tackling climate change "would result in substantial additional costs to the energy sector and increase the risk of assets needing to be retired early."

It also cautioned "the energy sector is not immune from the physical impacts of climate change" -- signalling threats from extreme weather, as well as more gradual changes such as rising sea levels.

Last month, the level of carbon dioxide in Earth's atmosphere breached a threshold of 400 parts per million -- a level never before experienced by humans and considered the absolute maximum for the two-degree target to remain within reach.

Observers said the IEA report was a timely reminder that something could still be done.

"The real energy-related threat to economic prosperity is no longer an oil shock but a climate shock," said the Environmental Defense Fund, a US-based non-profit organisation.

But green campaigners WWF said the proposals did not go far enough.

"The IEA should back the full phasing out of all fossil fuel subsidies by 2020 globally," it said.