Russia's war in Ukraine has forced a short-term scramble for fossil fuels but the rise of solar, wind and other clean energies is "unstoppable", the head of International Renewable Energy Agency told AFP.

Speaking at the UN COP27 climate summit in Egypt, Francesco La Camera said market forces now all but ensure renewables will keep growing fast -- but also warned that the pace will need to double to prevent a climate catastrophe.

The Ukraine war has led to a serious energy supply crunch and oil and gas price spikes that have forced especially European countries to quickly search for new suppliers as they head into winter.

"In the short term, this will have an impact," said La Camera, director general of IRENA.

"But in the medium and long term, there is no other way than to accelerate decarbonisation. Because ultimately renewables are not only good for the climate, jobs, GDP, but are a real way to ensure energy independence."

NATO chief Jens Stoltenberg also highlighted the strategic aspect of a shift away from dependency on Russia and other oil and gas suppliers to clean and safe renewables.

Russia's "use of energy as a weapon", he said, "is a stark reminder of the need to transition from dependence on fossil fuels to renewables, because that will make us less dependent on Russian gas and Russian oil".

Helping NATO allies and countries everywhere shift to green power will not just help mitigate global warming, he said, but will also "be good for our security".

- 'Market is the engine' -

As delegates meet in Egypt, US President Joe Biden was assessing the likely election loss of the House of Representatives to the Republicans, many of whom are hostile to his climate policies.

But La Camera said he saw no danger of the United States backsliding in Biden's push to expand clean energies.

"The market is the engine," he said. "The market is already saying clearly that we are moving toward a system based on renewables and complemented by hydrogen, mainly green. No one can stop this progress."

Even under ex-president Donald Trump, "coal-fired power plants were already closing in the United States," said La Camera.

"The question is not where we are going but how fast and at what scale."

IRENA calculated in a report published for COP27 that the energy transition is not yet on track to meet the Paris Agreement goals of keeping global warming well below two degrees Celsius and preferable at 1.5 degrees compared to the pre-industrial era.

"The figures say that we must double the ambition between now and 2030," he stressed.

Countries worldwide are now on track for 5.4 terawatts of installed renewable electricity capacity by that year -- only half of the 10.8 TW that would be needed to meet climate commitments.

- 'Phenomenal potential' -

Africa, where the COP is being held this year, has enormous potential to harness renewables, especially the power of the sun, but is so far lagging behind, experts say.

Investment in renewables there fell to an 11-year low last year, according to a report by research organisation BloombergNEF.

The continent captured only 0.6 percent of global investments in the sector.

"Africa has phenomenal potential," said the IRENA chief. "They can produce 1,000 times the electricity and energy they need. This continent is an incredible powerhouse.

"But we need to review the way cooperation works," he added. "Africa cannot develop and move towards a clean energy system without the right physical and legal infrastructure."

La Camera warned against the temptation to promote new fossil fuel projects, a dream cherished by several countries including Senegal and the Democratic Republic of Congo.

"It's in the interest of the continent to jump on the new train" and not "stay stuck in old technologies," he said, predicting this would generate millions of new jobs and accelerate economic growth.

"But this can only be done," La Camera said, "if developed countries are ready to facilitate, to support, to work with Africans to make this possible."

© Agence France-Presse