Rise in greenhouse gas concentrations jeopardizes Paris Agreement temperature targets, WMO warns

The abundance of heat-trapping greenhouse gases in the atmosphere once again reached a new record last year, with the annual rate of increase above the 2011-2020 average. That trend has continued in 2021, according to the World Meteorological Organization (WMO) Greenhouse Gas Bulletin.

Concentration of carbon dioxide (CO₂), the most important greenhouse gas, reached 413.2 parts per million in 2020 and is 149% of the pre-industrial level. Methane (CH₄) is 262% and nitrous oxide (N₂O)  is 123% of the levels in 1750 when human activities started disrupting Earth’s natural equilibrium. The economic slowdown from COVID-19 did not have any discernible impact on the atmospheric levels of greenhouse gases and their growth rates, although there was a temporary decline in new emissions.

As long as emissions continue, global temperature will continue to rise. Given the long life of CO_2, the temperature level already observed will persist for several decades even if emissions are rapidly reduced to net zero. Alongside rising temperatures, this means more weather extremes including intense heat and rainfall, ice melt, sea-level rise and ocean acidification, accompanied by far-reaching socioeconomic impacts.

Roughly half of the CO₂ emitted by human activities today remains in the atmosphere. The other half is taken up by oceans and land ecosystems. The Bulletin flagged concern that the ability of land ecosystems and oceans to act as “sinks” may become less effective in future, thus reducing their ability to absorb carbon dioxide and act as a buffer against larger temperature increase.

The Bulletin shows that from 1990 to 2020, radiative forcing – the warming effect on our climate – by long-lived greenhouse gases increased by 47%, with CO₂ accounting for about 80% of this increase. The numbers are based on monitoring by WMO’s Global Atmosphere Watch network.

“The Greenhouse Gas Bulletin contains a stark, scientific message for climate change negotiators at COP26. At the current rate of increase in greenhouse gas concentrations, we will see a temperature increase by the end of this century far in excess of the Paris Agreement targets of 1.5 to 2 degrees Celsius above pre-industrial levels,” said WMO Secretary-General Prof. Petteri Taalas. “We are way off track.”

“The amount of CO₂ in the atmosphere breached the milestone of 400 parts per million in 2015. And just five years later, it exceeded 413 ppm. This is more than just a chemical formula and figures on a graph. It has major negative repercussions for our daily lives and well-being, for the state of our planet and for the future of our children and grandchildren,” said Prof. Taalas.

“Carbon dioxide remains in the atmosphere for centuries and in the ocean for even longer. The last time the Earth experienced a comparable concentration of CO₂ was 3-5 million years ago, when the temperature was 2-3°C warmer and sea level was 10-20 meters higher than now. But there weren’t 7.8 billion people then,” said Prof. Taalas.

“Many countries are now setting carbon neutral targets and it is hoped that COP26 will see a dramatic increase in commitments. We need to transform our commitment into action that will have an impact of the gases that drive climate change. We need to revisit our industrial, energy and transport systems and whole way of life.  The needed changes are economically affordable and technically possible. There is no time to lose,” said Prof. Taalas.