Clouds: a climate uncertainty

In November, Horizon takes a deep dive into the captivating, diverse world of clouds to understand what they mean for climate change. We speak to atmospheric physicist Prof. Pier Siebesma about why clouds are still one of the biggest sources of uncertainty when it comes to climate change and how new field studies are helping to reduce some of the unknowns. We speak to a researcher about flying through tropical clouds to collect particles at high altitudes to paint a full picture of the role of clouds and aerosols in our planet’s climate. And we also delve into research investigating how global warming is changing clouds and why this could bring about extreme weather and rain, and we look at how aerosols – crucial for cloud formation - are changing due to anthropogenic pollution.

Clouds that form in a polluted area will have different properties from those that form around natural particles such as desert dust. Image credit: Pixabay/Pixabay Licence

Environment, Frontier research

Black carbon and other pollution seeds clouds. We’re just starting to understand the climate implications

Particles swirling around our atmosphere add to climate change, yet much about how they interact with sunlight and influence the seeding of clouds remains puzzling. Studies are lifting the lid on how these tiny particles influence something as big as climate by analysing them from jet aircraft, satellites and ground measurements.

A complex system of clouds and aerosols forms over much of South Asia as part of the monsoon - the challenge was to find out what it contains. Image credit - Sparsh Karki/Pexels, licenced under CC0

Environment, Frontier research

The mission to decipher a mysterious aerosol layer above Himalayan monsoon clouds

For Stephan Borrmann, a day of high altitude detective work begins early. He wakes at about 05:30am in a hotel in the outskirts of Kathmandu, Nepal. After a quick breakfast, he and his team are driven to the city’s airport. Their job is to prepare a converted Russian espionage plane so that it can investigate one of the biggest mysteries of the atmosphere.

Tropical thunderstorm clouds are unique because they self-organise even when the conditions below and above them are uniform, and do so with 'memories' of past formations. Image credit - NASA Johnson Space Center

Environment, Frontier research

Cloud shapes and formations impact global warming – but we still don’t understand them

Above the Atlantic Ocean, puffy white clouds scud across the sky buffeted by invisible trade winds. They are not ‘particularly big, impressive or extended’, says Dr Sandrine Bony, a climatologist and research director at the French National Centre for Scientific Research. ‘But they are the most ubiquitous clouds on Earth.’

Clouds are important from a climate point of view for how they reflect and absorb sunlight, according to Professor Pier Siebesma, an atmospheric physicist. Image credit - Pier Siebesma

Environment, Frontier research, Interview

Q&A: Why clouds are still ‘one of the biggest uncertainties’ in climate change

They might be beautiful at times, but clouds are still one of the biggest sources of uncertainty in understanding how the climate will change due to global warming, explains Professor Pier Siebesma, an atmospheric physicist at Delft University of Technology (TU Delft) in the Netherlands.

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