A U.N. report summarizing the revised climate action plans - covering about 40 percent of countries in the 2015 Paris Agreement and 30 percent of planet-heating emissions - said they would deliver a combined emissions reduction of only 0.5 percent from 2010 levels by 2030.

"That simply is not good enough," said Patricia Espinosa, urging governments - including those that have already updated their plans - to come up with larger promised cuts before COP26.

The Intergovernmental Panel on Climate Change has said global emissions must fall by about 45 percent by 2030 from 2010 levels to give the world a good chance of limiting the rise in average temperatures to 1.5 degrees Celsius above pre-industrial times.

Under the Paris accord, nearly 200 countries pledged to keep warming to "well below" 2C, and strive for a ceiling of 1.5C.

So far, the planet has heated up by about 1.2C, bringing worsening extreme weather and rising seas.

Espinosa said the synthesis report made clear "current levels of climate ambition are very far from putting nations on a pathway" to meet the 1.5C goal.

"It is incredible to think that just when nations are facing a (climate) emergency that could eventually end human life on this planet ... many are sticking to their business-as-usual approach," she told journalists.

But if governments invest trillions of dollars in planned spending to revive their economies from Covid-19 on green, climate-resilient measures, "we stand a chance of changing the trajectory," she added.

Espinosa emphasized that the report released on Friday was just a "snapshot" of climate action plans to date and another more complete assessment would be compiled before COP26.

Many countries missed a 2020 deadline to submit stronger climate action plans because of disruption caused by the pandemic, with the COP26 summit in Glasgow postponed for a year.

The 75 countries that did submit revised plans on time include COP26 host Britain and the 27 member states of the European Union, which are covered by one EU-wide plan.

Pressure growing

Chile's Environment Minister Carolina Schmidt, who presided over the COP25 summit in Madrid in 2019, said the report "clearly indicated that significant work must be done, in particular by major emitters."

Only two of the 18 largest emitters - Britain and the European Union - had so far presented an updated "nationally determined contribution" (NDC) containing a "strong increase" in their emissions reduction targets, she noted.

"Other major emitters either submitted NDCs presenting a very low increase in their ambition level or have not presented NDCs yet," she added in a statement.

Niklas Höhne, who set up a tracker for national climate policies as a founding partner of the NewClimate Institute, said countries that had not boosted ambition in their new plans could be described as "violating the spirit of the Paris Agreement.".\

The accord calls on governments to voluntarily deliver more ambitious climate plans every five years, starting in 2020.

But the updated NDCs of Australia, Brazil, Japan, Mexico, New Zealand, Russia, Singapore, South Korea, Switzerland and Vietnam fail that test, according to Climate Action Tracker, which is separate from the U.N. research report.

"It is a very, very small change that has happened so far, in comparison to the huge gap there is," Höhne said.

The United States is due to announce its much-anticipated new 2030 emissions reduction target before a world leaders' climate summit hosted by President Joe Biden on April 22.

Experts say China and India could announce new goals there too, and Japan plans to increase its 2030 target before COP26.

Helen Mountford, vice president of climate and economics at the World Resources Institute, noted that more than half of G20 nations had now made commitments for net-zero emissions by mid-century but few had set 2030 interim targets in line with that.

Those that did set bold targets last year - including Colombia, Argentina, Britain and the European Union - were now being overshadowed by those falling behind, she said.

"These laggards must stop fiddling while the world burns. It is in the interest of their own people and their economies to address the climate crisis, which knows no boundaries," she said.

U.N. Secretary-General Antonio Guterres called Friday's report "a red alert for our planet" and urged major climate-polluting countries to offer "much more ambitious" 2030 emissions reduction targets well before COP26.

"Long-term commitments must be matched by immediate actions to launch the decade of transformation that people and planet so desperately need," he said in a statement.