At the regional level, however, the picture is much fuzzier. Significant uncertainties remain around how certain meteorological systems will change – and what eventually happens will shape the lives of billions.
The potential slowdown of ocean currents associated with the Atlantic Meridional Overturning Circulation (Amoc) is one such scenario, with significant repercussions for the UK, as well as elsewhere in Europe, Africa and North America. The conveyor belt-like system of ocean currents carries warm water from the tropics northwards, causing significantly milder winters for the UK compared with other countries at the same latitude. Input of cold water from melting ice plays a key role powering the circulation – but as that melt increases, it is expected to weaken the overall system, and some researchers fear it could stop entirely.
The risk of such a dramatic change is still being studied. A Nature paper published earlier this year by scientists from the Met Office and the University of Exeter found that the Amoc is unlikely to collapse over the next 75 years but “very likely” to weaken. A reduction in circulation might offset some of the warming effect of greenhouse gases for Western Europe, while a complete shutdown would have more extreme consequences.
Potential changes to Amoc currents would have “profound implications for the outcome of our current adaptation and resilience-building strategies”, according to the organisers of a recent IMechE event on the topic. Designed to increase focus on the Amoc slowdown and associated uncertainties in climate adaptation, the webinar on 20 May brought together experts in the field to consider the potential changes to the climate, and to assess the possible physical impacts to the built environment and other infrastructure.
As with other aspects of climate adaptation, there will be a significant role for engineers – and preparation needs to start as soon as possible.
‘Weird’ changes
Conventional climate scenarios roughly assume a gradual increase in greenhouse gas concentrations and a gradual response from the climate system, according to Professor Nigel Arnell, climate science specialist at the University of Reading. But, he asked, “What happens if something weird happens?”
One of those “weird” changes could well be an Amoc slowdown – and the effects could lead to a “step change” in what actually happens to the climate, Arnell continued. He set out a scenario for a location in South East England if the circulation switched off in 2030, based on experiments led by the University of Exeter and Met Office.
“By 2050, temperatures are about six degrees cooler than they would have been otherwise, and then gradually increasing again, slowly, as the greenhouse effect continues to kick in. That's really quite a substantial change; we're looking at temperatures three to four degrees below what we're currently experiencing,” he said.
“That will be well outside the range of human experience, and this is on average – around that we would get extremes, cold extremes and some occasional ‘mild’ winters. But a mild winter would be really, really cold. We would likely see slightly less rainfall in winter and a lot less rainfall in summer… and we would also expect, for reasons which will be very complicated to explain, a higher sea level as the Amoc switches off, because the movement of water across the North Atlantic is going to change.”
The changes could also be compounded by the collapse of the ‘subpolar gyre’, he warned, another ocean circulation that could, if switched off, lower temperatures by about 2ºC. “They're plausible worst-case scenarios. I think it would be remiss not to consider them,” he said.
Climate of uncertainty
One major challenge for planners is that we do not know how close we are to the threshold for Amoc collapse, Arnell said, so the potential warning time could vary massively. “It's not going to happen overnight, so we don't need to worry about a The Day After Tomorrow-type scenario – we may get 25 years warning that it's switching off, it may be 10 years, it may be 40. We don't know, which is a challenge for how we want to adapt.”
Such uncertainty only increases the tension between preparing for different climate scenarios. If Amoc slowdown is negligible, for example, then the UK needs to prepare for the full force of higher global temperatures. If it is dramatic, or even total, then it needs to prepare for significantly lower temperatures.
“That's an awful lot of challenging changes for the engineering community to deal with, given the track that we're on at the moment,” said Dr Tim Fox, chair of IMechE’s working group on climate change adaptation.
“The built environment, physical infrastructure and many other engineered systems potentially will be subjected to environmental conditions for which they simply have not been designed – or indeed, more recently, adapted.”
Engineers in the UK and Northern Europe should therefore focus on developing and deploying “no-regrets” technologies, he told Professional Engineering after the event – technologies that work equally effectively in extreme heat and cold, and during both flooding and drought.
“In the case of the latter, an example is large-scale rainwater harvesting, and for the former, suitable insulation materials for use in new-build and retrofit construction is a good example,” he said.
“We must also concentrate on developing innovative solutions that futureproof engineered infrastructure at the point of construction by enabling cost-effective changes or additions.”
Engineering standards also play an important role in adaptation but so far have not really considered potential “tipping points”, said Professor John Dora, director at climate adaptation-focused consultancy Climate Sense. That is beginning to change, however, with standards including the overarching adaptation framework of ISO 14090 being revised.
‘Adaptation pathways’ can provide the required flexibility for dealing with the uncertainties associated with the two major climate change scenarios, Fox added. The BS 8631:2021 standard, for example, provides “a full description together with the methodology,” he said.
“This approach, combined with futureproofing engineered infrastructure… [to] enable cost-effective changes or additions to be made relatively easily at a later date, for example to accommodate the increased wind and snow loading anticipated in an Amoc slowdown scenario, is the best engineering technique to employ.”
The business proposition
While climate adaptation is becoming a more prominent topic with each warming year, further awareness is needed to ensure it fully accounts for changes to Amoc and other ocean currents. But with net zero efforts already threatened by populist politicians around the world, how can engineers ensure that adaptation is taken seriously and not abandoned in the decades to come?
One of the best ways is highlighting the risks to clients’ business operations – and therefore profits and shareholder value – posed by climate change, said Fox. “Increasing this awareness is the first step on the journey to ‘adaptive maturity’ as it leads to a desire for adaptation action through increased interest in identifying the associated risks to the business and understanding how best to cost-effectively mitigate and manage them.
“However, it is crucial that when we do communicate with clients about the risks and potential adaptation and resilience-building solutions, we do so in a language that they can relate to – for example, focusing on adaptation value propositions, benefits to be accrued, co-benefits that can potentially be exploited, timescales for action and the likely costs to the business of inaction.
“Through taking this opportunity, our profession can help to ensure that adaptation is taken seriously and not abandoned in the decades to come.”
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.