Smoke from the deadly wildfires in California, Oregon and Washington has hitched a ride on the jet stream and will make it across the Atlantic Ocean, entering the atmosphere above Europe about 5,000 miles away by this weekend, according to observations from the Copernicus Atmosphere Monitoring Service, a science agency that is part of the European Commission.

Such transport of smoke at high altitude from North America to Europe is typically seen once or twice a year with wildfires in British Columbia, not the United States, said Mark Parrington, a senior scientist at CAMS, in an email.

Not only that, but satellite data using detections of heat abnormalities at the surface shows that the ongoing fires in these three western states, which have burned more than 5 million acres in the past two weeks, are burning with a far greater intensity than the 17-year average for wildfires in that three-state region as well as the entire United States.

Since greenhouse gas emissions from wildfires are related to their intensity, CAMS data also shows that these fires have pushed California and Oregon to their greatest annual amounts of wildfire-related carbon emissions since at least 2003, while bringing the United States into the top 10 list for the same period.

Specifically, Parrington said in an email, the total estimated wildfire-related carbon emissions in megatonnes of carbon so far this year for California are 23.4 from Jan. 1 through Jan. 14, 7.4 for Oregon, 1.5 for Washington and 56.0 for the U.S. total. This is about the same as driving an average passenger vehicle 509,512 miles per year, according to the U.S. Environmental Protection Agency.

Our latest forecast is showing that more smoke from California and Oregon will reach northern Europe again toward the end of the week. While long-range transport of smoke across the Atlantic is not completely unusual, we typically see one to two events and usually from forest fires in Canada; to see relatively high smoke values from California over Europe is not very common.

"The scale and magnitude of these fires are at a level much higher than in any of the 18 years that our monitoring data covers, since 2003," Parrington stated in a news release.

According to observations from CAMS's Global Fire Assimilation System, or GFAS, the greenhouse gas emissions from the fires are part of what scientists know as a positive feedback loop, in which human-caused global warming is creating conditions more conducive to massive, rapidly spreading fires, and these fires are in turn emitting gases into the air that will further warm the climate, thereby increasing fire frequency and severity.

The measurements are not exact but are the best that scientists have for gauging the climate impacts of blazes in some parts of the world, such as the Arctic, where ground observations are few to nonexistent.

According to Jessica McCarty, a wildfire expert at Miami University of Ohio, the data from modelers like Parrington, who is based within the European Center for Medium-Range Weather Forecasts in the UK, uses sensors aboard satellites to measure the temperature of heat anomalies on the Earth's surface.

By relating that to a unit of physical energy they call "fire radiative power" in joules or megawatts, they make an assumption that in order to reach that surface temperature, a particular amount of biomass - such as trees and other vegetation - would need to burn.

Scientists can then translate that figure into an estimate for carbon emissions. McCarty and others use this data and other tools like it to monitor fires in rapidly changing but poorly observed ecosystems in the Arctic, including Siberia, which saw a record uptick in wildfires this summer.

The fires, fueled by a climate change-supercharged heat wave in California, record dryness throughout the region and powerful winds blowing from land-to-sea during an extreme weather event that culminated over Labor Day weekend, have killed at least 17, and vaulted at least 4 fires to the top 10 list of all-time largest blazes in California history, including the August Complex at No. 1 on that list.

The fires were particularly unusual for where they occurred in Oregon, focused on the typically wet slopes of the western Cascades and burned into populated areas, including the suburbs of Medford, Ore.

As with the Australian wildfires in early 2020, many of the fires in the West exhibited extreme behavior, with giant, billowing thunderheads of ash and smoke, known as pyrocumulus clouds, transporting fire emissions into the upper levels of the atmosphere, above the height of typical airliner cruising altitudes. Because the smoke reached such lofty heights, it's likely on an around the world journey, similar to the Australian event.

In addition to playing the role of a climate change feedback, a much broader impact of the flames has been unhealthy air quality, with days of noxious pale to orange-tinged skies hovering near ground level across the west. The smoke was so thick and unhealthy that Alaska Airlines, whose pilots and ground crews are used to operating in the most intense storms in the Aleutians and Alaskan Arctic, stopped flights to Portland, Ore., Monday in the interest of its workers' health.

“The fact that these fires are emitting so much pollution into the atmosphere that we can still see thick smoke over 8000 kilometres away reflects just how devastating they have been in their magnitude and duration,” Parrington said in a news release.