CLOUD gives clarity on climate change


University of Leeds experts have helped scientists get a step closer to understanding how aerosol particles are formed in the atmosphere and the effect these particles have on our climate.

Working with scientists from the CLOUD experiment at the European Organisation for Nuclear Research (CERN), in Geneva, climate change experts from the University have shown that amines – atmospheric vapours closely related to ammonia, largely derived from activities such as animal husbandry – combine with sulphuric acid to form highly stable aerosol particles at rates similar to those observed in the lower atmosphere.

To conduct the experiment, the research team has access to a special laboratory chamber with unprecedented cleanliness, allowing them to simulate the atmosphere and introduce minute amounts of various atmospheric vapours under carefully controlled conditions – in this case amines and sulphuric acid. 

The results of the experiment, published in the journal Nature, are significant because aerosols cause a cooling effect by reflecting sunlight and by seeding cloud droplets, suggesting that both natural and sources of amines caused by man could influence climate.

The team has also shown that ionisation by cosmic rays are unimportant when it comes to the generation of these particular aerosol particles in the atmosphere.

The effect of cosmic rays on climate has been a highly controversial topic. It has been suggested that cosmic ray-induced particle formation could affect climate change, but this seems not to be the case for the particles studied at CERN. 

Ken Carslaw, of the Institute for Climate at Atmospheric Science at the University of Leeds and lead author of the paper, said: “Leeds has been one of the steering members of the CERN CLOUD experiment for over a decade.

“This is an important discovery and will lead to a significant advance in our ability to understand how particles form in the atmosphere and how they affect climate. Research is now under way with our climate models to assess the impact of the laboratory findings.”

Further information

Ken Carslaw is available for interview. Please contact Ben Jones, Press Officer on 0113 34 38059 or email