The concentration of carbon dioxide in the atmosphere rose to its highest level in over 800,000 years in 2016, according to the United Nations’ World Meteorological Organization (WMO) in its annual Greenhouse Gas Bulletin which was released today.
Atmospheric concentrations of CO2 reached 403.3 parts per million (ppm), compared to 400.0 ppm in 2015, marking the most rapid annual increase in CO2 levels in 30 years, and lifting concentrations 145% higher than pre-industrial levels.
Such a rise threatens to push global temperature increases compared to pre-industrial levels well beyond the 2 degrees Celsius (3.6 degrees Fahrenheit) mark enshrined in the Paris climate agreement.
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“Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement,” said WMO Secretary-General Petteri Taalas in a press release. “Future generations will inherit a much more inhospitable planet.”
The WMO measures atmospheric greenhouse gas levels through research stations in 51 countries, according to the BBC.
The change in 2016 CO2 concentrations was driven partly by the year’s powerful El Niño, according to the WMO report.
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El Niños are semi-annual climatic events that happen when warm waters in the Pacific Ocean amplify weather patterns, leading to extreme precipitation and droughts in many countries.
The report said that droughts caused by the 2016 El Niño reduced the ability of trees, vegetation, and oceans to absorb carbon, leading to the surge.
This increase comes as global carbon emissions from burning fossil fuels have shown little growth in the past few years, suggesting that greenhouse gases that had been absorbed by the biosphere in the past are being released into the atmosphere through deforestation, desertification, and other events, according to the WMO.
Historically, around a quarter of greenhouse gas emissions have been absorbed by the ocean and another quarter have been absorbed by the biosphere, the report said.
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The last time the atmosphere regularly had this much carbon in it was 2-3 million years ago, when sea levels were 30-60 feet higher, and temperatures were 2 to 3 degrees Celsius higher, according to the WMO.
The report also noted that concentrations of methane and nitrous oxide — the two other primary drivers of climate change — rose in 2016. Some of this increase was driven by the natural release of emissions that happens as ice melts.
For instance, as Arctic ice melts, methane gas that had been trapped is escaping. Scientists fear that this could cause a feedback loop of escalating atmospheric concentrations — as the world warms from rising emissions, more ice will melt, releasing more emissions, causing more ice to melt, and so on.
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"The numbers don't lie,” said Erik Solheim, head of UN Environment, in a press release. “We are still emitting far too much and this needs to be reversed. The last few years have seen enormous uptake of renewable energy, but we must now redouble our efforts to ensure these new low-carbon technologies are able to thrive. We have many of the solutions already to address this challenge. What we need now is global political will and a new sense of urgency."