The world should fight climate change with the same determination it is showing in the battle against the new coronavirus, the United Nations said on Wednesday.

The UN's World Meteorological Organization said it was time to flatten the curve on climate change as well, with its impact on the planet "reaching a crescendo" in the past five years - the hottest on record.

The trend is expected to continue, the WMO said on Wednesday, as it marked the 50th anniversary of Earth Day - an annual event to demonstrate support for environmental protection.

Carbon dioxide levels at one key global observing station are about 26 percent higher than in 1970, while the average global temperature has increased by 0.86 degrees Celsius in that time, the WMO said.

Temperatures are also 1.1 Celsius warmer than the pre-industrial era, it added.

The agency said the COVID-19 crisis was exacerbating the socioeconomic impacts of climate change - for example, making it harder to keep people safe from tropical cyclones.

However, the WMO's climate monitoring programme has recorded a reduction in key pollutants and improvements in air quality as a result of the industrial downturn during the pandemic. "We estimate that there is going to be a six percent drop of the carbon emissions this year because of the lack of emissions of transportation and from industrial energy production," WMO Secretary-General Petteri Taalas said.

But he said the drop would only be temporary and "in the most likely case we will go back to normal next year", adding that failure to tackle climate change could threaten people's wellbeing, ecosystems and economies "for centuries" to come.

"We need to flatten both the pandemic and climate change curves," he said.

"We need to show the same determination and unity against climate change as against COVID-19," calling for action not only in the short-term "but for many generations ahead".