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Monday, 9 February 2015

Professor Dame Julia Slingo: Modelling climate risk

Dame Julia Slingo DBE collects her Cabot Institute
Distinguished Fellowship award from Cabot Institute
Director, Prof Rich Pancost.
Image credit: Amanda Woodman-Hardy
When Professor Dame Julia Slingo visited the Cabot Institute last week, her message was clear: We need to look at climate risk in real world contexts.

Dame Julia was in the city to receive a Cabot Institute Distinguished Fellowship, which involved giving a talk about her work as a world leading meteorologist and Chief Scientist at the Met Office.

One of the first things she highlighted was that climate change isn’t isolated from other pressures like population growth and limited resources, so we need to understand the risks it poses in a real world context. We need to define the effects it may have on the security of food, water, health and energy around the world, and use the science as a guide to define an evidence-based and cost effective plan of action going forward. This, she said, is “one of the greatest challenges of the 21st century”.

Are we making extreme weather worse?

Today, the huge global population boom is putting an ever increasing strain on limited resources like land and water, which are also at risk from the cyclical climate variations that occur naturally. The big and controversial question is whether climate change caused by human activity has exacerbated the problem.

Dame Julia described an annual report produced by the American Meteorological Society (AMS) that analyses extreme weather events around the world each year, aiming to determine whether the effects were magnified by anthropogenic climate change. As she pointed out, it is important that we recognise that not every bit of bad weather can be attributed to climate change, however the AMS often do find that we have played a role in making the situation worse.

Image: Hurricane Sandy killed 233 people and caused over $68 billion worth of damages

One example she picked out was 2012’s Hurricane Sandy, which killed 233 people across eight countries in central and north America. The AMS report found that if sea level had been at the level that it was 50 years ago, the devastating effects of the storm would not have been as bad. It also suggested that continuing on our current path of climate change will mean minor storms will have increasingly severe impacts, leading to Sandy-level hurricanes more frequently in the future.

“We need a more nuanced discussion”

Last year was the warmest on UK record, making a total of 8 out of 10 of our hottest years having occurred since 2002. While of course there is variability in our climate from year to year and even decade to decade, intricate scientific climate models have shown that these record-breaking UK temperatures are made ten times more likely due to anthropogenic climate change.
Image: Low lying islands like the Marshall Islands in the Pacific Ocean are threatened by sea level rise.

While we may prefer a hot summer, temperatures don’t change uniformly across the entire planet. Worryingly, the Arctic is warming twice as fast as the rest of the planet, leading to a huge decrease in the amount of sea ice cover and corresponding sea level rise, which is already threatening communities living on low lying islands. Dame Julia reminded us all that it’s not as simple as trying to prevent a 2°C global temperature increase. The danger that climate change poses depends on who you are and where you live, and we need models to show what the risks will be.

Predicting climate risk

So how can we predict what the effects of climate change will be across the world? It begins with having a sophisticated model of the current global system. The Met Office has led decades of climate modelling, producing incredibly sophisticated simulations of climate systems on both short term (weather) and long term (climate change) scales.

I was absolutely amazed by the intricacy of these models. Millions of lines of computer code recreate the true physical nature of the planet, to the extent where large scale meteorological patterns like El Niño are emergent properties of the model, that is to say that they are a result of the basic physics encoded in the model, rather than being specifically programmed into it.

By altering the model with new data taken from the present extent of climate change or its predicted level in the future, the Met Office can model the global response at incredible resolution, showing the specific risks posed with increasingly detailed clarity (while still incorporating the inherent uncertainties present in all models). These models can then be used to test potential mitigation approaches and of course inform the global communities of the dangers they face.

What can we do?

Dame Julia explained that her role as Chief Scientist is to determine the needs of the people around the world, their risk tolerance and the information they require to make their own decisions. Science, she says, has a lot to offer in enabling governments to make wise, informed and efficient decisions with how best to spend their funds within the wider context of other societal issues, upholding the global securities of food, water, health and energy for the future.

Flooded Pakistan

Image: “There is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly rain events” – Professor Dame Julia Slingo

This blog is written by Cabot Institute member Sarah Jose, Biological Sciences, University of Bristol.

Sarah Jose

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