The Climate Action Tracker group looked at new climate promises from China and other nations, along with the carbon plans of US President-elect Joe Biden.

These commitments would mean the rise in world temperatures could be held to 2.1C by the end of this century.

Previous estimates indicated up to 3C of heating, with disastrous impacts.

But the experts are worried the long-term optimism is not matched by short-term plans to cut CO2.

But the creation in 2015 of the Paris climate agreement, which was designed to avoid dangerous warming of the Earth, made a considerable impact. As a result of the international deal, countries slowly started to switch away from fossil fuels.

In September this year, the group concluded that the world was heading for warming of around 2.7C by 2100.

This figure was still far above the 2C goal contained in the wording of the Paris pact, and nowhere near the more challenging 1.5C target that scientists endorsed as the threshold to destructive warming in 2018.

Their new “optimistic analysis” now suggests a rise of 2.1C by 2100.

The past three months have seen some key developments.

In September, China’s President Xi Jinping told the UN that his country will reach net zero emissions by 2060, and that its emissions will peak before 2030. According to the CAT researchers, this could reduce warming by 0.2 to 0.3C by the end of the century.

Japan and South Korea have both followed suit, pledging to reach net zero by 2050. South Africa and Canada have also announced their own net zero targets.

The other significant change is the election of Joe Biden in the US.

Tackling climate change is a major part of his agenda. He has promised to bring the US to net zero emissions by 2050. That move would reduce global temperatures by 0.1C by 2100.

“We now have north of 50% of global emissions covered by big countries with a zero emissions by mid-century goal,” said Bill Hare from Climate Analytics, who helped lead the Climate Action Tracker analysis.

“When you add all that up, along with what a whole bunch of other countries are doing, then you move the temperature dial from around 2.7C to really quite close to two degrees.”

“It’s still a fair way off from the Paris Agreement target, but it is a really major development,” he told BBC News.

The CAT researchers say they have taken a fairly conservative approach but they readily acknowledge that their optimistic analysis comes with some major caveats.

The biggest problem as they see it, is that the near-term plans to cut carbon by 2030 are just not up to the job.

“Countries have not yet adjusted their short-term actions to be on a pathway towards the long-term target,” said Niklas Höhne, from the NewClimate Institute, who also works on the Climate Action Tracker.

“Long-term targets are easier, they are far away. But short-term actions are happening right now and they affect citizens, they affect voters. And that’s why this is much more difficult,” he told BBC News.

The countries that have signed up to the Paris agreement are expected to lodge new carbon-cutting plans for 2030 by the end of this year.

It’s expected that a number will do so, including the UK and the EU.

But there are several countries who are still reluctant to set goals, and many poorer nations are still looking to invest in coal.

“There are countries that still remain bad actors, including Saudi Arabia, Brazil, Australia, Russia, and a few others,” said Bill Hare.

“And we also have a pipeline of coal plants in the region where I’m working now in Asia. It has not collapsed, it has not gone away, so yes, there’s much to be concerned about. And there’s much that can go wrong.”

According to observers, the response of countries to the Covid crisis is a huge opportunity to focus their short-term spending on renewable energy and increased decarbonisation.

“The pandemic opened a window to not only get countries to outline their long-term goal, but to actually move onto the right path so that they can actually achieve the long term goal,” said Dr Maisa Rojas, who is the director of the Center for Climate and Resilience Research at the University of Chile in Santiago.

“Are we going to harness that opportunity? My impression is that many, including the EU, are harnessing it.”