Representatives from nearly 200 countries yesterday agreed at the COP28 climate summit to begin reducing global consumption of fossil fuels to avert the worst of climate change, a first of its kind deal signalling the eventual end of the oil age.

The deal struck in Dubai after two weeks of hard-fought negotiations was meant to send a powerful signal to investors and policy-makers that the world is united in its desire to break with fossil fuels, something scientists say is the last best hope to stave off climate catastrophe.

COP28 President Sultan Al Jaber called the deal "historic" but added that its true success would be in its implementation.

"We are what we do, not what we say," he told the crowded plenary at the summit. "We must take the steps necessary to turn this agreement into tangible actions."

Several countries cheered the deal for accomplishing something elusive in decades of climate talks. "It is the first time that the world unites around such a clear text on the need to transition away from fossil fuels," said Norway Minister of Foreign Affairs Espen Barth Eide.

The lead negotiator for the Alliance of Small Island States, Anne Rasmussen, criticised the deal as unambitious. "We have made an incremental advancement over business as usual, when what we really need is an exponential step change in our actions," she said.

But she did not formally object to the pact, and her speech drew a standing ovation.

The deal calls for "transitioning away from fossil fuels in energy systems, in a just, orderly and equitable manner ... so as to achieve net zero by 2050 in keeping with the science."

It also calls for a tripling of renewable energy capacity globally by 2030, speeding up efforts to reduce coal use, and accelerating technologies such as carbon capture and storage that can clean up hard-to-decarbonize industries.

More than 100 countries had lobbied hard for strong language in the COP28 agreement to "phase out" oil, gas and coal use, but came up against powerful opposition from the Saudi Arabia-led oil producer group OPEC, which argued that the world can slash emissions without shunning specific fuels.

That battle pushed the summit a full day into overtime yesterday, and had some observers worried the negotiations would end at an impasse.

Members of the Organization of the Petroleum Exporting Countries control nearly 80 percent of the world's proven oil reserves along with about a third of global oil output, and their governments rely heavily on those revenues.

Small climate-vulnerable island states, meanwhile, were among the most vocal supporters of language to phase out fossil fuels and had the backing of huge oil and gas producers such as the United States, Canada and Norway, along with the EU bloc and scores of other governments.

"This is a moment where multilateralism has actually come together and people have taken individual interests and attempted to define the common good," US climate envoy John Kerry said after the deal was adopted.

Danish Minister for Climate and Energy Dan Jorgensen marvelled at the circumstances of the deal: "We're standing here in an oil country, surrounded by oil countries, and we made the decision saying let's move away from oil and gas."

A representative for Saudi Arabia welcomed the deal, saying it would help the world limit global warming to the targeted 1.5 degrees Celsius (2.7 Fahrenheit) over pre-industrial times set in the 2015 Paris deal, but repeated the oil producer's stance that tackling climate change was about reducing emissions.

"We must use every opportunity to reduce emissions regardless of the source," he said.

Several other oil producer countries, including the summit host UAE, had advocated for a role for carbon capture in the pact. Critics say the technology remains expensive and unproven at scale, and argue it is a false flag to justify continued drilling.

Former US Vice President Al Gore also welcomed the deal, but said: "The influence of petrostates is still evident in the half measures and loopholes included in the final agreement."

Now that the deal is struck, countries are responsible for delivering through national policies and investments.