Drinking water and climate tipping points

The infrastructure that means we can turn on a tap and fresh water flows out takes massive planning and considerable amounts of time and money to install and maintain. It’s not an agile industry. Building a new reservoir may take many years. The problem is that climate change has the potential to upset the apple cart, because change can come very rapidly and very dramatically. This is referred to as a “tipping point” - things remain stable for a very long time and then some threshold is breached and things change very far, very fast. More or less rain may arrive than anticipated, temperatures may climb or sink far further than we’re prepared for. And if the water industry can’t keep up, we may be in trouble. This is the thrust of the analysis that Petar van Thienen, from the KWR Water Research Institute, has carried out…

Petar - Climate tipping points are these thresholds where you push the system a little and it will change a lot. So for example, a big ice sheet – you start heating the atmosphere and it will melt a little bit more, but it will still be the same ice sheet. But at some point, you cross a certain boundary and it just completely melts away. This is what we call a tipping point. Climate scientists talk about this a lot. We also see they are not well represented – they seem not well presented in climate models, and as a result, they are not included in climate scenarios that everybody is using to plan their futures. I'm working in the drinking water industry, and what we see is that we are a very slow-moving industry, by necessity. We build infrastructure that is meant to operate for many decades, and often even longer in practice. So we really need to think ahead, and that's why it's really important to understand these tipping points – they may cause changes on a much shorter timescale than we're used to dealing with.

Chris - Why do you think that, despite talking about them extensively, climate models capture them so poorly?

Petar - That's because they are not completely understood. They are the result of a complex interaction of many different processes. It's probably also a matter of model resolution – the detail with which you can model the processes. They're not intentionally left out, but they are very difficult to model adequately.

Chris - So what are you proposing as an alternative, or how do you propose to surmount the problem?

Petar - We need to recognise that these tipping points may have significant consequences. That was actually the objective of our paper – to evaluate how relevant these potential tipping points could be and what their potential consequences could be for drinking water provision.

Chris - And when you say you've looked at the potential impacts of them, how have you done it? What's been the approach here?

Petar - We started out by reviewing the scientific literature on tipping points and describing what's going on there. Then we tried to evaluate the confidence levels of how these tipping points are represented in Earth system or climate models. Then we tried to make an overview of the climate hazards that may result from these tipping points, and what their impacts would be on water sources, abstraction, treatment, and distribution. We also tried to make an overview of possible mitigation or adaptation measures.

Chris - How did you identify them in the first place? I know you've given us the definition of what's regarded as a tipping point, but how did you actually say, right, I'm going to go and find the representation of that tipping point and its possible impact in the literature, so we can put that one down and say we've now gauged the potential risk from that one?

Petar - We based ourselves on the climate science literature, which provides overviews of what are considered to be possible tipping points. Then we tried to answer a number of questions. For each of these tipping points that have been identified, we tried to answer: how strong would its effect be, how long would it take to start, and how long would it take to complete? Combined, these questions more or less describe the risk for us – or the possible imminence and effects of such a tipping point.

Chris - And how many do you think there are that we really need to worry about?

Petar - There are actually two that we probably really need to consider. That's the AMOC – the Atlantic Meridional Overturning Circulation – of which the Gulf Stream that provides us with a mild climate in Europe is part, and the associated system of the Labrador Sea or subpolar gyre convection. These are two somewhat deviating tipping points, because many of the tipping points in Earth's climate system would result in a heating of the atmosphere. These two, at least on a regional scale in Europe, could result in a cooling of our climate.

Chris - And how will we know when we've breached them? And if we do, what will be the impact?

Petar - Climate scientists and oceanographers are working on identifying early warning signals for the activation of these tipping points. A paper published two years ago predicts that the AMOC might collapse later this century. That would result in significant cooling over Europe – up to several degrees in annual mean temperature, possibly more in winter. We could get very cold winters, a drying of the continent with less precipitation, and sea levels could rise by 3,200 centimetres over a relatively short period – in addition to what is already happening due to melting ice sheets. That would impact the availability of water in Europe for drinking water and food production. It would also affect water quality, particularly in coastal areas, due to increased saltwater intrusion. It would also affect our infrastructure, as buried pipes are sensitive to freeze–thaw cycles and freezing soil.

Chris - Therefore, having identified these as critical points that we may be approaching, can you make some recommendations so that we can safeguard against this? Are these likely to be surmountable challenges?

Petar - In terms of water practice, I think it’s crucial to be aware of these tipping points and to consider tipping scenarios – in particular, AMOC collapse – when planning infrastructure. This means accepting a wider range of uncertainty with respect to future climate conditions. It may go one way, but it may also go the other – warming and drying, or cooling and drying – and those require different adaptation measures. So it is very important that the water sector closely watches for the early warning signs being monitored by climatology and oceanography communities. It's also important that the sector moves from a rigid, robustness-focused approach to infrastructure – where systems are built to last 50 or 100 years – to a more flexible approach. Obviously, this is difficult for drinking water distribution networks, which are buried in the ground. Once they’re there, it's a major effort to replace them entirely or move them to deeper levels, for example, to prevent freezing.