The gases mainly responsible for the greenhouse effect, and therefore the global warming and climate change, have reached a new record: this is yet another alarm launched by the UN that returns to ask the international community to intervene quickly. Carbon dioxide, methane and nitrous oxide are far above pre-industrial levels, with no sign of reversing the upward trend, according to the latest report by the World Metereological Organization. «Without a rapid cut in CO2 and other greenhouse gases, climate change will have increasingly destructive and irreversible impacts on life on earth», warned UN agency manager Petteri Taalas. «The window of opportunity for action is practically closed», he said.
According to the WMO, average global carbon dioxide concentrations reached 405.5 parts per million in 2017, with a continuously increasing trend (400.1 parts per million in 2015). The action of greenhouse gases in the atmosphere has grown by 41% from 1990 to today.
Greenhouse gases capture part of the sun’s rays that pass through the atmosphere, which in turn heats up. And Co2 is by far the main cause of this warming. «Co2 has persisted over the centuries in the atmosphere and even more in the ocean. Now, we do not have a magic wand to make this excess of carbon dioxide disappear», said Deputy Secretary-General Elena Manaenkova. Its concentration in the atmosphere reached 405.5 ppm in 2017, with an increase of 2.2 ppm, lower than that recorded in 2016 (+3.2 ppm), a year characterized by El Niño, which had caused droughts in tropical regions and had reduced the ability of forests and vegetation to absorb CO2. «The last time the Earth had a comparable carbon dioxide content, it was between 3 and 5 million years ago: the temperature was from 2 to 3°C higher and the sea level was 10-20 meters higher than to the current one», explained Taalas.
Methane, which ranked second in the range of the most important greenhouse gases, reached a new peak in 2017, representing 257% of the level it had in pre-industrial times. The experts also observed last year an unexpected “resurgence” of a powerful gas capable of reducing ozone content, CFC-11 (trichlorofluoromethane), whose production is regulated by an international agreement to protect the ozone layer. The concentrations of greenhouse gases in the atmosphere depend on the quantities emitted but also on the interactions occurring between the atmosphere, the biosphere, the lithosphere, the cryosphere and the oceans. The ocean now accounts for about a quarter of total emissions and the biosphere absorbs another quarter.
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