Levels of heat-trapping greenhouse gases in the atmosphere have reached another new record high, according to the World Meteorological Organization. This continuing long-term trend means that future generations will be confronted with increasingly severe impacts of climate change, including rising temperatures, more extreme weather, water stress, sea level rise and disruption to marine and land ecosystems.
The WMO Greenhouse Gas Bulletin showed that globally averaged concentrations of carbon dioxide (CO2) reached 407.8 parts per million in 2018, up from 405.5 parts per million (ppm) in 2017.
Global levels of CO2 crossed the symbolic and significant 400 parts per million benchmark in 2015.
CO2 remains in the atmosphere for centuries and in the oceans for even longer.
Concentrations of methane and nitrous oxide also surged by higher amounts than during the past decade, according to observations from the Global Atmosphere Watch network which includes stations in the remote Arctic, mountain areas and tropical islands.
“It is worth recalling that the last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago. Back then, the temperature was 2-3°C warmer, sea level was 10-20 meters higher than now,” said WMO Secretary-General Petteri Taalas.
And Humans did not exist at that time, nor could they exist under those conditions.
Emissions vs Concentrations
The WMO Greenhouse Gas Bulletin reports on atmospheric concentrations of greenhouse gases. Emissions represent what goes into the atmosphere. Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere, lithosphere, cryosphere and the oceans. About a quarter of the total emissions is absorbed by the oceans and another quarter by the biosphere.
Carbon dioxide is the main long-lived greenhouse gas in the atmosphere related to human activities. Its concentration reached new highs in 2018 of 407.8 ppm, or 147% of pre-industrial level in 1750.
Methane (CH4) is the second most important long-lived greenhouse gas. Atmospheric methane reached a new high of about 1869 parts per billion (ppb) in 2018 and is now 259% of the pre-industrial level.
Nitrous oxide also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun. Its atmospheric concentration in 2018 was 331.1 parts per billion. This is 123% of pre-industrial levels..