July 5, 2014 — andyextance

Taking the train along the Devon, UK, coast earlier this week I was hypnotised by the lapping waves I saw through the window, and their concealed power. On such a sunny day, the rail journey through Dawlish is perhaps the most beautiful I’ve been on. But in February its ocean-hugging route became its downfall, when storms demolished the sea wall it rests on. Now, thanks to 300 fluorescent-jacket clad workers who performed £35 million worth of repairs, the dangling tracks I saw on TV news are a fading memory. It’s an impressive achievement, but could we afford it if – due to climate change, for example – such ‘orange armies’ had to do battle more often?

The significance of that question was emphasised by Chris Field from Stanford University in California, when I saw him talk recently. Highlighting that all parts of the world are vulnerable to climate change, Chris showed the below image of New York City in 2011, during Hurricane Sandy. “The existing climate created a situation that caused over $50 billion in economic damage for a region of the world that had a vast amount of economic resources and had a response plan in place,” he underlined. “It just wasn’t a plan that was up to the challenges that they faced.” If climate change causes more $50 billion-damage events, can we afford that?

Just before the ocean crippled the south-west UK’s rail services, Jochen Hinkel from the Global Climate Forum in Berlin, Germany, and his team were answering a similar question. In a paper published in the Proceedings of the National Academy of Sciences of the USA in February, Jochen looked at coastal flood damages from projected sea level rise. When I therefore asked him about his work, he was quick to put climate change-driven sea level rise’s role in Hurricane Sandy and this year’s UK storms into context.

Indicating the future

“Climate change and sea level rise are just starting to unfold,” Jochen stressed. “If you think about sea level having risen 20 cm in the past century and you think about storm surges of several metres then this tells you that the current contribution from climate change and sea level rise to such events is rather small. On the other hand they also give you an indication of what we might experience if we add another metre to those storm surge levels we have seen today.”

Until his team’s study, there had been an obvious gap in climate change impact assessment, Jochen explained. No one had looked at damage from ‘storm surges’ worldwide taking in wide ranges of both socioeconomic changes like population growth and sea level rise. So over the course of a decade he painstakingly assembled a team including nine other scientists, experts in many different disciplines. Together they toiled to bring together the widely varying and large data sets needed, and got the expensive time they needed on powerful computers to do so many simulations.

The team’s simulations took in three different scenarios of greenhouse gas emission growth in four different climate models. The warming arising from those emissions drove simulated sea level rise through heat expanding the oceans, and melting glaciers and ice sheets across the world. The researchers also incorporated different detailed models of the Earth’s coastal landscape, where people are in that landscape, and five different scenarios of population growth. Finally, they looked at how much two different strategies to use dikes for protection would help.

There’s a lot of uncertainty in each of these elements, and so Jochen’s team’s results spanned a wide range. However, their message was clear. Without adaptation, they forecast 25–123 cm of global mean sea level rise from the average for 1985-2005 by 2100, leading to 0.2–4.6% of the world’s population being flooded by storm surges annually. That would cause annual losses of $17,000-$120,000 billion, or 0.3–9.3% of global gross domestic product. Protecting the coast against these losses with dikes wouldn’t be cheap, but at $12–71 billion annually in 2100 the strategy is obviously much cheaper than not acting.

Sea level isn’t fair

“If we ignore the problem of rising sea levels then the damages are catastrophic, this is something we will not want to happen,” Jochen said. “However if we adapt – and we’ve shown how you can adapt by building dikes – then by and large for the whole globe this is quite effective. At the same time for most regions of the world it’s also economically quite efficient. It’s much cheaper to adapt than to just sit there and let sea level rise happen. This is a very strong message targeted at action against rising sea level.” With sea level set to rise no matter what happens in the climate negotiations thanks to the warming we’ve already had, we have to take measures to adapt, he added.

Though this conclusion makes adaptation to sea level rise seem generally effective and desirable, spare a thought for those in the places where it doesn’t. “While globally it is cost efficient, this does not hold true for particular regions, countries and locations,” Jochen noted. “The rich countries, densely populated areas, it is clearly cost-efficient to protect and this is what we’re seeing today in Hamburg or in London or the Netherlands, they’re protecting themselves against rising sea levels. But for poor countries with very exposed coasts like Mozambique or small island countries it is a much bigger problem – for them, adaptation is very expensive relative to national GDP and not necessarily cost-efficient”

The fate of the poor people in these countries who financial analysis indicates it’s too expensive to protect makes my concern for my local railway line seem ridiculous. Acting promptly to limit emissions could help many. However, even in Jochen’s team’s lowest greenhouse gas emission scenario without dikes 0.2–2.9% of the world’s population will be flooded each year. Whatever we do, climate change looks set to force tough decisions in the face of the ocean’s awesome strength.

Journal reference:

Hinkel, J., Lincke, D., Vafeidis, A., Perrette, M., Nicholls, R., Tol, R., Marzeion, B., Fettweis, X., Ionescu, C., & Levermann, A. (2014). Coastal flood damage and adaptation costs under 21st century sea-level rise Proceedings of the National Academy of Sciences, 111 (9), 3292-3297 DOI: 10.1073/pnas.1222469111