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Editor’s note: This story previously embedded a picture of the Amazon rainforest that had been taken prior to the current forest fire. The photo has now been removed.

In the middle of the afternoon on Monday, the Brazillian city of Sao Paulo suddenly descended into darkness.

“It was as if day had turned into night,” Sao Paulo resident Gianvitor Dias told the BBC.

“Everyone here commented because even on rainy days it doesn’t usually get that dark,” Dias said. “It was very impressive.”

Several shared photos of the city on social media, saying it looked “apocalyptic.”

Good morning. Perhaps, you wanna know what the apocalypse is gonna look like? This was São Paulo, yesterday at 3pm #PrayforAmazonia pic.twitter.com/8uvSlZe1mO — André Só (@AndreTheSolo) August 20, 2019

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The darkness lasted just over an hour.

What caused the darkness?

According to Global News meteorologist Ross Hull, a few factors came together at “just the right moment” to place Sao Paulo under a shroud of darkness.

“A frontal boundary which helps to create lift and condensation was the catalyst for thunderstorms to move in,” he said. “Lightning and thunderstorms were actually reported at the airport in Sao Paulo on Monday, and you can see lightning flashes in some of the images from the event.”

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Hull says this would have contributed to the darkened skies.

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“Add to that the fact that the upper level winds, as well as the front, helped to steer smoke from fires burning northwest of the city in a more remote parts of Brazil,” he said.

“These factors all came together to reduce visibility and enveloped this part of Brazil in an eerie, dark haze.” https://twitter.com/WMO/status/1163853178749825024 Tweet This

According to Copernicus EU — The European Union’s Earth Observation Programme — smoke from wildfires burning in Amazonia had reached the Atlantic coast and Sao Paulo on Monday.

According to Copernicus EU, there has been increased fire activity in the states of Amazonas and Rondonia since August 1.

Wildfires on the rise

Earlier this month, the state of Amazonas declared a state of emergency due to the rising number of forest fires in the area.

Last week, NASA released satellite images which depicted large swathes of Brazil, Paraguay and Bolivia affected by the fires and smoke.

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And, according to data released by the National Institute for Space Research (INPE) earlier this week, forest fires in Brazil have risen by more than 80 per cent this year.

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Since Thursday, INPE said satellite images spotted 9,507 new forest fires in Brazil, mostly in the Amazon basin, home to the world’s largest tropical forest which is seen as vital to countering climate change.

What is causing the fires?

Scientists from Brazil’s National Space Research Institute (INPE) have said the Amazon has suffered losses in the Amazon at an “accelerated rate” since President Jair Bolsonaro took office in January.

However, speaking at a press conference last month, Bolsonaro said the data “doesn’t relate to the reality.”

Shortly after, Bolsonaro fired the director of INPE.

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When asked about the spread of uncontrolled fires, Bolsonaro brushed off criticism, saying it was the time of the year of the “queimada” or burn, when farmers use fire to clear land.

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“I used to be called Captain Chainsaw. Now I am Nero, setting the Amazon aflame,” he told reporters. “But it is the season of the queimada.”

INPE said the large number of wildfires could not be attributed to the dry season or natural phenomena alone.

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While wildfires are common in the dry season, they are also deliberately set by farmers illegally deforesting land for cattle ranching.

INPE researcher Alberto Setzer told Reuters that there is nothing abnormal about the climate this year or the rainfall in the Amazon region, which is “just a little below average.”

“The dry season creates the favorable conditions for the use and spread of fire, but starting a fire is the work of humans, either deliberately or by accident,” Setzer said.

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By Tuesday afternoon #prayforamazonia was trending on Twitter globally.

“I really can’t express how sad I am,” one Twitter user wrote. “Someone save [the] Amazon.”

This is how the sky looked yesterday here in São Paulo at 3 pm. This is the ashes that came from Amazon. I really can’t express how sad I am, someone save Amazon #PrayforAmazonia pic.twitter.com/O7VgZ5rxTi — ナターシャ ❄️ (@tinybluecake) August 20, 2019

— With files from Reuters.