The Clouds Part for Climate Change Modelling

A new ground-breaking research project, co-led by scientists at the University of Leeds, is attempting to make sense of one of the biggest mysteries in our skies: clouds. The high-tech five week survey will analyse formation characteristics and changes of shallow trade-wind clouds in Barbados, which will be a highly beneficial aid in essential climate modelling initiatives.

Why are clouds important? The relationship between clouds and climate change is very much an unsolved mystery of science. Clouds are known as an important feedback mechanism influencing global climate, however it is not known whether they help or hinder increases in global temperature.

Water vapour is actually the most effective greenhouse gas, and therefore clouds play a vital role in trapping heat within the Earth’s atmosphere and reflecting it back to the surface. However, clouds have a high albedo, which means they reflect incoming solar radiation from the Sun back out into space; preventing it from reaching and warming the Earth’s surface. It is often believed that, with increasing global temperatures, more water will be evaporated from the oceans which will lead to the formation of more clouds. However, according to NASA, a warmer climate means that more water vapour molecules are required to become saturated in order for them to condense into clouds. This might make clouds less likely to form, for example there are generally fewer clouds during the summer months than during winter, despite greater humidity.

The complex behaviour and responses of clouds to climate change is very difficult to model due to their unpredictable nature and unknown mechanisms. Climate models therefore often omit or simplify the effect of clouds, which limits the overall accuracy of outputs. Many projections for future climate changes in response to global warming that we see on a regular basis use variations of models which do not entirely account for the impacts of clouds.

The National Centre for Atmospheric Science (NCAS) has coordinated a five-week large-scale field study co-led by scientists at the University of Leeds and in partnership with the University of Manchester, British Antarctic Survey and University of East Anglia, involving scientists from the UK, USA, France and Germany. The project is known as EUREC4A (Elucidating the Role of Clouds-Circulation Coupling in Climate) and will utilise cutting edge field equipment including five aircraft, four research vessels, and high resolution ground and satellite remote sensing.

A component of the study will involve flying research aircraft into trade-wind cumulus clouds. These are isolated white clouds usually with a flat, darker base and whose movement is predominantly influenced by permanent easterly prevailing winds, known as trade winds. Cumulus clouds that form over a hot surface, such as near the equator, may accrue to form larger, menacing cumulonimbus clouds which are responsible for heavy rain and thunderstorms.

The research will assess how these clouds form and develop over time in response to climate changes such as temperature, wind and humidity among other factors.

Results from this novel study will be essential in the development of more robust climate models

How will the study be beneficial? Results from this novel study will be essential in the development of more robust climate models able to more accurately predict future changes in climate. Dr Leif Denby from the School of Earth and Environment at the University of Leeds stated that “the concurrent and diverse observations from this campaign will give us the means to verify which models and theories are correct. We will be able to apply this new found understanding of what’s happening to the low-clouds in Barbados to the low-clouds in trade-wind regions over the whole tropics.”

The University of Leeds and NCAS are also working with the Met Office to develop a new model which will predict behaviour changes of convective clouds. This can help to accurately project how weather patterns may change under future climate change.

Overall, the project will be of the utmost importance in making sense of the complexities of global warming and will help with our understanding of how our climate may change in the future.

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