As the Earth’s climate warms, Northern Europe could be set to see a significant rise in lightning strikes
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There’s a growing body of evidence that climate change is influencing severe weather events. A number of studies conclude that storms, particularly tropical storms, will become more frequent or intense. One study of lightning in the US – published in the journal Science in 2014 – suggests that for every degree of rise in global average air temperature, we could see a 12 per cent increase in lightning strikes.
It might seem obvious for lightning to increase as storms become more common; in reality, it’s not so simple. ‘What we’re seeing is contrasting stories across Europe,’ says Abdullah Kahraman, lead author of a new study that uses the latest Met Office climate simulations to forecast what these future changes might mean for severe storms. The results present a picture of changing weather patterns across the continent: more lightning in Northern Europe and over mountainous regions such as the Alps, but less lightning over Central Europe.
The physical processes behind lightning are complex. Thunderstorms, Kahraman explains, need three ingredients: moisture, instability (caused by warm, moist air near the Earth’s surface and cold dry air above), and lift (warmer, less dense air rising). But it’s the microphysical processes within the storm clouds that produce lightning. Kahraman, who defines himself as a severe weather meteorologist, has worked as a forecaster for many years, specialising in severe convective storms – thunderstorms that produce lightning, hail, tornadoes and other meteorological phenomena. ‘These phenomena are very sensitive to local temperature changes, moisture changes and circulation changes,’ he explains.
Unlike previous studies, which have pointed to an overall increase in lightning, these new climate simulations are a much higher resolution, containing more accurate details of the Earth’s surface and atmosphere down to a two-kilometres grid. ‘The models that we use here allow individual storm clouds to appear in a more natural way within the climate simulations, so that we can actually see the processes – the vertical and upward and downward motions within the thunderstorms – and that gives us a better representation of the lightning.’
When lightning strikes, it’s caused by the vertical movement of small ice particles, known as graupel, and much smaller cloud ice. When they collide it causes electrons to jump from one to the other, altering the distribution of electrons in the cloud and eventually resulting in the electricity being discharged. Even if we see more thunderstorms occurring in the future, Kahraman says, a warmer atmosphere means those storms will have less cloud ice than today’s storms, which explains why we might see less lightning across Central Europe.
While this is good news for the more densely-populated areas of Europe, it’s a concern for northern countries which may need increased investment in climate adaptation measures; lightning strikes can cause substantial damage to buildings and infrastructure. Hayley Fowler, professor of climate change impacts and co-author of the study, says that research has revealed ‘more bad news for critical national infrastructure in northern Europe,’ following on from a UK Parliament Joint Committee report that concluded the UK’s infrastructure is very vulnerable to extreme weather.
However, Kahraman emphasises that these predictions are just one possibility and may not come true – since they are based on an unmitigated future climate, he hopes they won’t. But even with next-generation climate modelling, lightning is difficult to predict. ‘It’s crystal clear that, globally, we are having more heatwaves, fewer cold waves, more extreme precipitation and drought. But when it comes to storms, the future is very uncertain.’
