A firefighter works at the scene of the Bobcat Fire burning on hillsides near Monrovia Canyon Park in Monrovia, California on Tuesday. Photo: Ringo Chiu/AFP via Getty Images

Smoke from the historic wildfires ravaging the U.S. West was observed over the United Kingdom and other parts of Europe this week, and it will return to the continent this weekend, per European scientists' research.

Why it matters: "The fact that these fires are emitting so much pollution into the atmosphere that we can still see thick smoke" some 5,000 miles away "reflects just how devastating they have been in their magnitude and duration," said Mark Parrington, senior scientist at the European Commission's Copernicus Atmosphere Monitoring Service (CAMS), which studied the data, in a statement.

  • Smoke usually travels from North America to Europe one or two times in a year, from "wildfires in British Columbia" but not from the U.S., Parrington told the Washington Post.

What they found: CAMS observed via satellite imagery the transportation of smoke from mega-fires in California, Oregon and Washington to Europe between Aug. 15 and Sept. 14.

  • The activity this year has been "tens to hundreds of times more intense than the 2003–2019 average in the US in general, as well as in several affected states," according to CAMS' report.
  • The fires in California and Oregon in particular "have already emitted far more carbon in 2020 than in any other year since CAMS records begin in 2003."

Of note: Parrington pointed out in his statement the massive scale of the smoke thickness, or aerosol optical depth (AOD), from the wildfires.

"Over the western US, AOD levels have been observed to reach values of seven or above; to put this into perspective, an AOD measurement of one already implies very hazy conditions and potentially poor air quality."

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