Smoke from the devastating bushfires in Australia has traveled so high it has reached the stratosphere—the second major layer of Earth's atmosphere. It has also completed a full circuit around the world, arriving back in the skies over the country where it was produced, according to NASA.
The smoke had reached South America by January 8, turning skies hazy in some regions, causing colorful sunrises and sunsets, the space agency said.
Since September last year, hundreds of fires have burned millions of hectares in Australia, leaving at least 28 people dead, destroying around 2,000 homes and killing more than one billion animals, the BBC reported.
Scientists say that record-breaking hot and dry conditions are creating the perfect environment for the fires to spread. These kinds of conditions are likely to become more common in Australia as the world's climate changes, Stefan Rahmstorf, from Germany's Potsdam Institute for Climate Impact Research, told Time.
According to NASA, the heat and dryness has also led to the formation of "an unusually large number" of so-called pyrocumulonimbus (pyrCbs) events. These are thunderstorms that are generated by the fires themselves.
"They are triggered by the uplift of ash, smoke, and burning material via super-heated updrafts. As these materials cool, clouds are formed that behave like traditional thunderstorms but without the accompanying precipitation," a NASA statement read.
While the formation of pyrocumulonimbus clouds is relatively common, meteorologist Michael Fromm and colleagues from the U.S. Naval Research Laboratory have detected more than 20 fire-induced storms in the last week of December 2019 and the first week of 2020.
"By our measures, this is the most extreme pyrocumulonimbus storm outbreak in Australia," Fromm said in a statement.
PyrCbs can help the smoke to spread around the world, by enabling it reach the stratosphere, which begins at around 6.2 miles in altitude (above the equator.) Some of the smoke pushed into the stratosphere by pyroCbs events above Australia has reached altitudes of between 9 and 12 miles.
"It is premature to compare and rank the height of this plume with others because smoke plumes like this rise in altitude over the course of weeks," said Fromm.
"That said, preliminary evidence indicates that the current Australian event will probably fall within the top five of all the plumes ever documented in terms of height. And the overall volume of smoke injected into the stratosphere appears to be among the largest observed in recent decades."
Once the smoke is in the stratosphere, it can remain there for several months, travelling thousands of miles from its source and affecting atmospheric conditions globally.
New Zealand—which lies more than 1,000 miles away from Australia's east coast—is being particularly badly affected by the fire smoke. The country has experienced poor air quality in some areas and visibly darkened snow has been spotted on mountaintops, according to NASA.
More locally, several Australian cities such as Sydney, Melbourne, Canberra and Adelaide, have experienced dangerous air quality levels recently as a result of the smoke, with more than 100 fires still burning in the east of the country, the BBC reported.
Many of these fires are yet to be controlled. However, firefighters announced Monday that they had finally brought Australia's largest "megablaze" under control in what was a rare piece of good news this fire season.
The Gospers Mountain fire had burnt more than 800,000 hectares northwest of Sydney over a three-month period. But firefighters in the state of New South Wales said that "containment prognosis looks promising," with much-needed wet weather forecast for the area in the next few days, AFP reported.
This story has been updated to include more recent data from NASA about how far the smoke has traveled.