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Smoke billows from stacks at a coal-fired power plant in Shanxi, China. Photo: Kevin Frayer/Getty Images

Atmospheric levels of the greenhouse gas carbon dioxide (CO2) reached the highest ever recorded in human history in 2018, the World Meteorological Organization (WMO) announced in a new report Monday.

Why it matters: If the trend continues, as predicted, the impact of climate change will become even more severe, the intergovernmental organization warns. "The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago," WMO Secretary-General Petteri Taalas said in a statement accompanying the report.

  • "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."
— Statement by WMO Secretary-General Petteri Taalas

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:

Go deeper

Scoop: Stephanie Murphy announcing challenge to Marco Rubio

Rep. Stephanie Murphy. Photo: Tom Williams/CQ-Roll Call, Inc via Getty Images

Democratic Rep. Stephanie Murphy is planning to announce a campaign for the U.S. Senate in Florida against Republican Sen. Marco Rubio in early June, people familiar with the matter tell Axios.

Why it matters: Murphy is a proven fundraiser. Jumping in now would give her an early start to build her case for the Democratic nomination and potentially force Rubio and allied GOP groups to spend heavily to retain a seat in a state that’s trending Republican.

59 mins ago - Politics & Policy

Inside the GOP's infrastructure strategy

Sen. Roger Wicker. Photo: Stefani Reynolds/Bloomberg via Getty Images

Top Republican senators are hoping the White House will make some sort of counteroffer to their infrastructure proposal when they meet with President Biden on Thursday, lawmakers and their aides tell Axios.

Why it matters: This is a sign of how serious the negotiations are, they say. In advance of the meeting, some of the senators are already publicly signaling the areas in which they have flexibility.

By the numbers: Senate seats to watch in 2022

Data: Axios Research, Dave Leip's Atlas of U.S. Elections; Chart: Andrew Witherspoon/Axios

While Republicans are giddy about their chances for regaining the House next year, GOP prospects for taking the Senate remain more uncertain, data reviewed by Axios suggests.

By the numbers: At least five Republican senators are retiring after the midterms, and four of their seats are in battleground states. That makes a simple Republican-for-Republican election exchange all the more difficult.