The average annual concentration of carbon dioxide in the atmosphere last year broke 400 parts-per-million (ppm) for the first time — in both modern direct measurements and ice core records dating as far back as 800,000 years — according to a major report on 2016 climate conditions released Thursday.

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Data: National Oceanic and Atmospheric Administration; Chart: Andrew Witherspoon / Axios

The State of the Climate report, compiled by the National Oceanic and Atmospheric Administration, finds that the increase in CO2 levels of 3.5 ppm over 2015, to reach an average of 402.9 ppm last year, was the largest annual jump in 58 years of modern measurements.

  • So hot right now: The wide-ranging annual report, based on input from scientists worldwide and multiple datasets, again confirms prior measurements that 2016 was the warmest year globally in records that date back to the late 1800s.
  • The report states: "Owing at least in part to the combination of El Niño conditions early in the year and a long-term upward trend, Earth's surface observed record warmth for a third consecutive year, albeit by a much slimmer margin than by which that record was set in 2015."
  • Why it matters: the report shows continued evidence of global warming and related climatic changes, and arrives amid intense focus on Trump administration policies to abandon Obama-era climate regulations and policies.

The latest annual State of the Climate study is likely to provide fresh political ammunition for green groups and Democrats attacking White House moves on climate and energy policy.

A few more key findings:

  • Global average sea level reached a new record high and "and was about 3.25 inches (82 mm) higher than the 1993 average, the year that marks the beginning of the satellite altimeter record," a summary notes.
  • Alpine glaciers continued their long-term retreat.
  • Average Arctic land temperatures broke records and were 3.6°F (2.0°C) above the 1981-2010 average. The maximum reach of Arctic sea ice measured in March was at its lowest in the 37-year satellite record, tying 2015 at 7.2 percent below the 1981-2010 average.
  • "The strong El Niño at the beginning of the year that transitioned to a weak La Niña contributed to enhanced precipitation variability around the world." South America saw "repeated heavy flooding" in several countries.
  • At the same time, the area covered by drought was significant. "The global drought extent surpassed most years in the post-1950 record and was strongly influenced by the El Niño, with every month of 2016 having at least 12% of global land experiencing severe drought conditions," the report states.

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