Lockdowns did not halt increase in greenhouse gases

Greenhouse gas levels in the atmosphere are higher than ever despite a drop in emissions resulting from coronavirus restrictions, the United Nations has warned.

Concentrations of carbon dioxide (CO2) and other heat-trapping gases in the atmosphere rose at a faster rate last year than over the previous decade and the economic slowdown caused by the pandemic had no discernible impact, the UN’S World Meteorological Organisation (WMO) said.

The CO2 concentration rose by 2.5 parts per million last year, reaching a global average of 413ppm. This increase was slightly smaller than in 2019, but was above the average annual increase of 2.4ppm over the past decade.

The increase last year happened despite the 5.6 per cent drop in fossil fuel CO2 emissions caused by the pandemic restrictions.

British Prime Minister Boris Johnson said yesterday that it was ‘‘touch and go’’ whether the Cop26 climate change conference, which starts in Glasgow on Sunday, would succeed in convincing all countries to adopt targets to reach net-zero emissions by 2050. The government admitted in a report that rich nations had fallen short of fulfilling a promise to provide poor nations with US$100 billion (NZ$140 billion) a year to combat climate change.

The last time the Earth had similar concentrations of CO2 in the atmosphere was three to five million years ago, when the temperature was 2C to 3C higher than it is now and sea levels were 10m to 20m higher. CO2 concentration is now at 149 per cent of the preindustrial level, methane at 262 per cent and nitrous oxide at 123 per cent.

In July the CO2 concentration at Mauna Loa observatory in Hawaii, where levels have been monitored since 1958, reached 416.96ppm, compared with 414.62ppm a year earlier.

About half the CO2 emitted by human activities stays in the atmosphere and the remainder goes into oceans and land. The WMO warned that the ability of oceans and land to act as ‘‘carbon sinks’’ may decrease in future, reducing their ability to act as a buffer against more rapid temperature increases.

In July scientists said that the Amazon rainforest, previously a major carbon sink, was emitting more CO2 that it was able to absorb.