The world may have to resort to technology that sucks greenhouse gases from the air to stave off the worst effects of global warming, the UN climate change chief has said before talks on the issue beginning on Monday.

"We are putting ourselves in a scenario where we will have to develop more powerful technologies to capture emissions out of the atmosphere," said Christiana Figueres, executive secretary of the UN Framework Convention on Climate Change. "We are getting into very risky territory," she added, stressing that time was running out.

The UN climate talks starting on Monday in Bonn, which run for the next two weeks, will try to revive the negotiations before the next climate conference, taking place in Durban, South Africa, in December. But little progress is expected, as the negotiating time is likely to be taken up with details such as rules on monitoring emissions.

Figueres tried to inject a greater sense of urgency into the proceedings by pointing to research from the International Energy Agency that found that emissions had soared last year by a record amount. The strong rise means it will take more effort by governments to curb emissions.

Figueres told the Guardian in an interview that governments should act now to save money: "We add $1 trillion to the cost [of tackling climate change] with every year of delay."

However, as the latest talks begin, the world's leading climate change official has upset governments by insisting that the aim of the negotiations ought to be to hold warming to less than 1.5C. That would be a much tougher goal than that set by governments last year, which seeks to limit the temperature rise to no more than 2C – the safety threshold, scientists say, beyond which warming becomes catastrophic and irreversible.

"In my book, there is no way we can stick to the goal that we know is completely unacceptable to the most exposed [countries]," Figueres said.

The difference between the two goals may not seem great, but since it has taken more than 20 years of talks for countries to agree on the 2C limit, many are unwilling to reopen the debate. Delegates are conscious that wrangling over whether to stick to 1.5C or 2C was one of the main sources of conflict at the Copenhagen climate summit in 2009; the hope has been that talks can move on to other issues such as how to pay for emissions curbs in poorer countries.

"This is an extraordinary intervention," said one official involved in the climate talks, who could not be named.

Figueres said that she had the support of the world's least developed countries, most of Africa, and small island states.

Another factor casting a pall over this year's talks, which are intended to forge a new global treaty on climate change, is criticism of the South African government, which will host the Durban talks. No interim meetings have yet been set up, and countries have complained of disorganisation and a lack of enthusiasm. But Figueres said: "South Africa has been very carefully listening, trying to understand where there are commonalities and where the weaknesses are."

She also predicted the US would play a strong role in the talks, despite the Obama administration facing Republican opposition in Congress to action on emissions. "It's very evident that the legislative body in the US has disengaged, but … the administration continues to be engaged." she said.

But Todd Stern, chief negotiator for the US, called for participants in the talks to "roll up their sleeves and be constructive."