UK scientists probe links between clouds and climate

22 October 2008 by Tom Marshall

A 20-strong team of British scientists is on its way to Chile to take part in a major international effort to improve our understanding of how clouds affect the climate.

Storm clouds

Some of the planet's biggest cloud systems form off the country's coast - often they cover a larger area than the entire USA. Scientists know these have a profound effect on the climate by reflecting sunlight away from the Earth's surface and keeping the sea beneath cooler than it would otherwise be.

But they don't understand the phenomenon as well as they'd like, and most computer models still don't represent these weather systems accurately. Researchers hope the new experiments will change this.

The research is being coordinated by the National Centre for Atmospheric Science (NCAS) and the UK Met Office. It includes researchers from the universities of Leeds, Manchester and Reading.

"These are some of the largest cloud systems in the world and we know that they must play a very significant role in climate change, yet we know that climate models do not represent them very well," says lead scientist Professor Hugh Coe of NCAS.

"This campaign is a fantastic opportunity to make cutting-edge measurements in a unique environment and merge them with state-of-the-art climate models," he adds.

The UK team are taking part in to an international experiment called VOCALS-REX. This is itself a component of a much larger programme called VAMOS Ocean Cloud Atmosphere Land Study, or VOCALS.

This £30m programme aims to study in detail the complex feedback relationships between clouds, ocean and land - in this case the Andes - and how these relationships affect the global climate.

From October 26, the scientists will be flying through and around these immense cloud systems in two research aircraft, using newly-developed cloud and dust probes to answer questions including how the clouds form, how reflective they are and what determines their lifetime.

We hope to finally hit some of the uncertainties in current climate models on the head.

- Professor Hugh Coe

Another key area of inquiry is whether man-made pollution from mining activities along the Chilean and Peruvian coasts has a big effect on the cloud systems. Mining generates tiny particles that are known to vastly increase the number of water droplets that form in clouds; they may also affect the amount of rain they produce.

Scientists will also test whether clouds that include these particles are more reflective than normal clouds; if so, they may be having a disproportionately large effect on the climate.

"By working closely with the Met Office and international colleagues in this way, we hope to finally hit some of the uncertainties in current climate models on the head," Coe at NCAS says.

UK scientists are joining forces with more than 200 international scientists from 18 universities and 13 research labs in 10 different countries, with five research aircraft and two research ships involved.

The British team will be using two specially-adapted research aircraft - a Dornier 228, operated by the NERC's Airborne Research & Survey Facility, and a BAe-146 aircraft managed by NCAS via the Facility for Airborne Atmospheric Measurements (FAAM), which is owned and operated jointly by NCAS and the Met Office.