A new research conducted by an international team of research scientists on the 2014-2015 eruption at Holuhraun in Iceland could provide the crucial key for scientists to unlock the role aerosols play in climate change, through their interactions with clouds. The research is published in the renowned journal Nature issued today, Thursday. The article is entitled Strong constraints on aerosol-cloud interactions from volcanic eruptions. Among the main authors is Þorvaldur Þórðarson, Professor at the University of Iceland's Faculty of Earth Sciences.
The research focuses on aerosols in the atmosphere and their interaction with the clouds in the sky. Aerosols play a pivotal role in determining the properties of clouds as they act as the nuclei on which water vapour in the atmosphere condenses to form clouds. Scientists have known for a long time that aerosols potentially have a large effect on climate, and particularly through their interactions with clouds. However the magnitude of this effect has been uncertain.
Sulphate aerosol has long been recognised as the most significant atmospheric aerosol from industrial sources. However, other natural sources of sulphate aerosol also exist, including that formed from sulphur dioxide release as a result of volcanic eruptions.
A spectacular six-month Icelandic lava field eruption in 2014 presented a crucial key for scientists to unlock the role aerosols play in climate change, through their interactions with clouds. They found that the 2014-15 Holuhraun fissure eruption, the largest since Laki which erupted for 8 months in 1783-4, emitted sulphur dioxide at a higher rate than all 28 European countries added together for the period of one year, causing a massive plume of sulphate aerosol particles over the North Atlantic.
The huge volcanic eruption provided the perfect natural experiment in which to calculate the interaction between aerosols and clouds. Using state-of-the-art climate system models, combined with detailed satellite retrievals supplied by NASA and the Université libre de Bruxelles, the research team were able to study the complex nature of the cloud cover formed as a result of the eruption.
They found that the size of the water droplets produce was reduced, which in turn led to cloud brightening - which results in an increased fraction of incoming sunlight being reflected back into space and, ultimately, providing a cooling effect on the climate. Crucially however, these aerosols had no discernible effect on many other cloud properties, including the amount of liquid water that the clouds hold and the cloud amount. The team believe the research shows that cloud systems are “well buffered” against aerosol changes in the atmosphere.
By transferring these results onto emissions of sulphide from industry, scientists believe they can reduce the uncertainty in predictive models for climate change. In other words the research sheds new light on the role played by aerosols in climate change. The results entail that certain climate models that have been used hitherto can be eliminated; and predictions for climate change will become more accurate.
An international team of climate scientists, led by the University of Exeter, conducted the research. As stated above, Þorvaldur Þórðarson, professor at the Faculty of Earth Sciences at the University of Iceland, is one of the lead researchers on the team. He says the results are highly significant.
"The Holuhraun eruption in 2014-15 is one of three eruptions from the same fissure in the last 225 years. The first eruption was in 1797, the second in 1867, and the third and largest 2014-15. This eruption is a watershed in research on the effects of volcanic emissions on the lower troposphere, regarding the amount and spread of the plume. The results also provide us with means to measure with more precision the impact of industrial sulphate pollution on the atmosphere", says Þorvaldur.
