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Smoke and steam rise from a coal-fired power plant in Germany. Photo: Oliver Berg/picture alliance via Getty Images

The concentration of carbon dioxide, the main, long-lived greenhouse gas causing global climate change, in Earth's atmosphere has reached new heights, according to scientists at Scripps Institution of Oceanography.

Why it matters: The new reading of 415.26 parts per million (ppm) on May 11 was the first daily baseline at Hawaii's Mauna Loa Observatory to eclipse 415 ppm. That observatory has kept long-term record of carbon dioxide in the atmosphere since 1958. That data, known as the Keeling Curve, traces the continuous increase in the amount of this greenhouse gas in the Earth's atmosphere since the Industrial Revolution.

  • Other observatories around the world also track this increase, which mainly results from burning fossil fuels, deforestation and other human activities. Studies of so-called proxy records detailing the composition of the atmosphere throughout Earth's history show that carbon dioxide levels are now at their highest point in at least 800,000 — and possibly as many as 3 million — years.

Details: The daily carbon dioxide milestone is largely symbolic, as peaks tend to occur in the Northern Hemisphere each spring. Scientists pay more attention to longer-term trends, rather than the daily data.

  • "The average growth rate is remaining on the high end," says Ralph Keeling, director of Scripps Institution of Oceanography's CO2 program, via Twitter. Keeling's father, Charles, began the original CO2 observations in Hawaii.
  • "The increase from last year will probably be around three parts per million whereas the recent average has been 2.5 ppm," Keeling said.

The big picture: Scientists have warned that if the world is to limit global warming to 1.5°C, or 2.7°F, above pre-industrial levels, then sharp emissions cuts have to begin in the next few years, with the world headed for negative emissions — meaning more carbon dioxide is removed by the planet's oceans, forests and other systems — than is emitted by the end of the century.

  • Otherwise Earth will see carbon dioxide concentrations exceeding 450 ppm, which will yield larger increases in global sea levels than we've seen so far, along with increasingly severe extreme weather events, such as heat waves and heavy precipitation events.

What's next: Scientists from Scripps and the National Oceanic and Atmospheric Administration will likely announce a new carbon dioxide monthly record in early June. A new annual figure will come out in early 2020.

Go deeper: Global carbon dioxide emissions reached record high in 2018

Go deeper

Federal judge says Florida ban on "sanctuary cities" racially motivated

Florida Gov. Ron DeSantis. Photo: Joe Raedle/Getty Images

A federal judge on Tuesday struck down parts of a Florida law aimed at banning local governments from establishing "sanctuary city" policies, arguing in part that the law is racially motivated and that it has the support of hate groups.

Why it matters: In a 110-page ruling issued Tuesday, U.S. District Judge Beth Bloom said the law — signed and championed by Gov. Ron DeSantis (R) — violates the Constitution's Equal Protection Clause because it was adopted with discriminatory motives.

Biden steps into the breach

Sen. Joe Manchin heads to a meeting with President Biden today. Photo: Kevin Dietsch/Getty Images

President Biden ramped up the pressure on his fellow Democrats Wednesday, calling a series of lawmakers to the White House in the hope of ending infighting and getting them in line.

Why it matters: Divisions within the party are threatening to derail Biden's top priorities. After several weeks of letting negotiations play out, the president is finally asserting his power to ensure his own party doesn't block his agenda.

2 hours ago - Politics & Policy

Scoop: Dems seek new green deal

Rep. Stephanie Murphy. Photo: Chip Somodevilla/Getty Images/Bloomberg via Getty Images

House Democrats discussed with President Biden on Wednesday a plan to exempt billions of dollars of new climate spending from his requirement that his $3.5 trillion "soft" infrastructure plan be offset with additional revenue.

Why it matters: The accounting proposal — a version of "dynamic scoring" — would dramatically lower the amount of taxes Democrats would need to raise while creating wiggle room to increase the ultimate size of the package.