WMO: Carbon dioxide levels hit the highest recorded in human history

• "Carbon dioxide is the most important long-lived greenhouse gas, with a single molecule lasting in the air for hundreds to around 1,000 years," science journalist Andrew Freedman has noted for Axios. "The continued buildup of carbon dioxide due to human activities, such as burning fossil fuels for energy, is driving global temperatures up and instigating harmful impacts worldwide."

By the numbers: The WMO's Greenhouse Gas Bulletin reports that globally averaged concentrations of CO2 reached 407.8 parts per million last year. That means for every 1 million molecules of gas in the atmosphere, almost 408 were carbon dioxide.

• It's an increase from 405.5 parts per million (ppm) in 2017. "The increase in CO2 from 2017 to 2018 was very close to that observed from 2016 to 2017 and just above the average over the last decade," the WMO notes.
• Global levels of CO2 crossed the symbolic and significant 400 parts per million benchmark in 2015.

What they're saying: United Nations Environment Programme (UNEP) executive director Inger Andersen said in a statement the WMO data and preliminary findings in the 2019 UN Emissions Gap Report, released in September, "point us in a clear direction — in this critical period, the world must deliver concrete, stepped-up action on emissions."

"There is no sign of a slowdown, let alone a decline, in greenhouse gases concentration in the atmosphere despite all the commitments under the Paris Agreement on Climate Change. We need to translate the commitments into action and increase the level of ambition for the sake of the future welfare of the mankind."

The big picture: This continuing long-term trend means that future generations can expect "rising temperatures, more extreme weather, water stress, sea level rise and disruption to marine and land ecosystems" unless drastic action is taken, the WMO says.

• The WMO says global emissions are "not estimated to peak by 2030, let alone by 2020," if current climate policies and ambition levels of the Nationally Determined Contributions (NDCs) are maintained.
• Separate findings in the UN Environment's Emissions Gap Report assessing the latest scientific studies on current and estimated future greenhouse gas emissions, was due to be released Tuesday, ahead of next month's UN Climate Change Conference in Madrid.

Read the WMO bulletin:

Go deeper:

• Earth's carbon dioxide level slips past another ominous milestone
• New studies paint sobering climate picture
• The economic toll of climate change