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Levels of greenhouse gases in the atmosphere reach new record high

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Levels of heat-trapping greenhouse gases (GHGs) in the atmosphere have reached a new record high, according to the World Meteorological Organisation (WMO). According to the WMO, this trend means future generations will be facing 'increasingly severe impacts' of climate change, such as rising temperatures, extreme weather, water stress, sea-level rise and disruption to marine and land ecosystems.

The WMO Greenhouse Gas Bulletin found that globally averaged concentrations of carbon dioxide (CO2) reached 407.8 parts per million (ppm) in 2018, up from 405.5 ppm in 2017. The increase in CO2 from 2017 to 2018 was close to that observed in 2016 to 2017. Concentrations of methane and nitrous oxide also surged by higher amounts than over the last decade, according to the Global Atmosphere Watch network, which includes stations in the remote Arctic, mountain areas and tropical islands.

According to the WMO, since 1990, there has been a 43% increase in total radiative forcing (the warming effect on the climate) by long-lived GHGs. CO2 accounts for around 80% of this, according to figures from the US National Oceanic and Atmospheric Administration, quoted in the WMO bulletin.

"There is no sign of a slowdown, let alone a decline in greenhouse gas concentration in the atmosphere, despite all the commitments under the Paris Agreement on Climate Change," said WMO secretary-general Petteri Taalas.

"We need to translate the commitments into action and increase the level of ambition for the sake of the future welfare of mankind. It is worth recalling that the last time Earth experienced a comparable concentration of CO2 was 3-5 million years ago. Back then, the temperature was 2-3oC warmer, sea level was 10-20 metres higher than now."

The Greenhouse Gas Bulletin includes a focus on how isotopes confirm the dominant role of fossil fuel combustion in the increase of atmospheric CO2. There are several indications, according to the WMO, that the increase in the atmospheric levels of CO2 is related to fossil fuel combustion. The level of concentration of CO2 reached 147% of the pre-industrial level in 1750.

Methane is the second most important long-lived GHG and contributes around 17% of radiative forcing. Around 40% of methane is emitted by natural sources such as wetlands and termites, and around 60% comes from human activities, such as cattle breeding, rice agriculture, fossil fuel exploitation, landfills and biomass burning. Nitrous oxide is emitted from both natural (60%) and anthropogenic (40%) sources, including oceans, soil, biomass burning, fertiliser use and industrial processes.

Inger Andersen, executive director of the UN Environment Programme (UNEP) said: "The findings of WMO's Greenhouse Gas Bulletin and UNEP's Emissions Gap Report point us in a clear direction - in this critical period, the world must deliver concrete, stepped-up action on emissions. We face a stark choice: set in motion the radical transformations we need now, or face the consequences of a planet radically altered by climate change."