Why are Canadian wildfires causing 'vivid' sunrises and sunsets in the UK?

A vivid Colorado sunset in 2021 created by smoke from wildfires.
A vivid Colorado sunset in 2021 created by smoke from wildfires. Credit: AP

Vivid sunrises and sunsets could be seen across the UK over the next couple of days due to the arrival of wildfire smoke from Canada, the Met Office has forecast.

Many Britons have already spotted the spectacular conditions at the start of this week, sharing pictures of postcard-worthy visuals.

But what is it exactly about the addition of wildfire smoke that changes how we see our sunrises and sunsets. ITV News explains.

Where is the wildfire smoke coming from?

Canada, in the past month, has been affected by hundreds of wildfires, creating a dangerous haze which has spread south into the US and across the Atlantic Ocean to Europe.

The smoke has engulfed some of the most famous skylines in the US and triggered air quality alerts in areas home to millions of people.

Countries, including the UK, are experiencing the smoke as it has been carried thousands of miles away from Canada by strong atmospheric winds.

Canada's wildfire season started early this year and has been exasperated by prolonged periods of extreme heat, according to the country's Interagency Forest Fire Centre.

Famous city skylines, including New York, have been engulfed by the wildfire smoke at points. Credit: AP

How does wildfire smoke affect our sunrises and sunsets?

The science behind the spectacle relates to the size of wavelengths that different colours of the rainbow fall on.

Reds and oranges, for example, have longer wavelengths, while blues and violets enjoy shorter versions. Longer wavelengths can travel further distances and so are more likely to be spotted by the human eye.

Humans can see sunsets without the addition of wildfire smoke as the phenomenon already possesses these longer wavelengths. Wildfire smoke only enhances that effect.

US-based meteorologist Daphne Thompson told CPR News: "The thing with wildfires is that the smoke puts a lot of extra particles up in the atmosphere. So now we're getting the red scattering over even more of those particles, and you can get some amazing red sunsets during wildfires."

Speaking to the same publication, experimental physicist Kevin Davenport, said these extra particles - which are around the length of one-millionth of a metre - make reds and oranges pop by diffusing the other colours on shorter wavelengths.

"Certain colours of light will interact with them and scatter in a random direction. Longer wavelengths of light, like reds and oranges, don't interact with them and they can just pass through," he said.

Is wildfire smoke dangerous?

Prolonged exposure to smoke can be dangerous particularly to vulnerable people, including children and anyone living with a respiratory condition.

Officials in the US and Canada have warned that the conditions could result in shortness of breath and irritated eyes. The smoke, in severe cases, could also worsen asthma and heart disease.

Data from the World Health Organisation (WHO) showed that in 2019 ambient air pollution was estimated to have caused 4.2 million premature deaths worldwide.

To prevent exposure, people have been asked in some areas to limit outdoor activities as much as possible.

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