WMO Greenhouse Gas Bulletin 2021

Table of Contents

WMO Greenhouse Gas Bulletin 2021: Relevance

According to the recently released Greenhouse Gas Bulletin , the abundance of heat-trapping greenhouse gases in the atmosphere has once again reached a new record last year.
Greenhouse Gas Bulletin is published by World Meteorological Organization (WMO).

The WMO Greenhouse Gas Bulletin reveals that the annual rate of increase in greenhouse gases was above the 2011-2020 average.
Concentration of carbon dioxide (CO2), the most important greenhouse gas reached 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.
According to the Greenhouse Gas Bulletin, 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.

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 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.
Carbon dioxide is the single most important greenhouse gas in the atmosphere, accounting for approximately 66% of the warming effect on the climate, mainly because of fossil fuel combustion and cement production.

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.
Ongoing climate change and related feedbacks, like more frequent droughts and the connected increased occurrence and intensification of wildfires might reduce CO2 uptake by land ecosystems.
Such changes are already happening. Example: transition of the part of Amazonia from a carbon sink to a carbon source.
Ocean uptake might also be reduced due to higher sea surface temperatures, decreased pH due to CO2 uptake and slowing of the meridional ocean circulation due to increased melting of sea ice.

Methane is a powerful greenhouse gas which remains in the atmosphere for about a decade.
Methane accounts for about 16% of the warming effect of long-lived greenhouse gases.
Approximately 40% of methane is emitted into the atmosphere by natural sources (for example, wetlands and termites), and about 60% comes from anthropogenic sources (for example, ruminants, rice agriculture, fossil fuel exploitation, landfills and biomass burning).

Nitrous Oxide is both a powerful greenhouse gas and ozone depleting It accounts for about 7% of the radiative forcing by long-lived greenhouse gases.
N2O is emitted into the atmosphere from both natural sources (approximately 60%) and anthropogenic sources (approximately 40%), including oceans, soils, biomass burning, fertilizer use, and various industrial processes.
Global human-induced N2O emissions, which are dominated by nitrogen additions to croplands, increased by 30% over the past four decades.
Agriculture, owing to the use of nitrogen fertilizers and manure, contributes 70% of all anthropogenic N2O emissions.
- This increase was mainly responsible for the growth in the atmospheric burden of N2O.