Dealing with Uncertainty

Throughout the blog, I've been talking about how we have utilised both climatic and hydrological computer models to make predictions for how the hydrological cycle may change in the future, and the effect it will have on humans. This week, I'd like to focus on the overall methodology and philosophy behind this method, and address the topic of uncertainty. While the scientific community is generally in agreement in what the impacts of climate change on the hydrological cycle may be, note that in previous posts I've mostly used the words 'could' or 'may' when talking about potential changes. Nothing is set in stone, and the process of trying to predict the future is inherently something of a dark art. 

In theory, the study of the effects of climate change on the hydrological cycle is undertaken to allow us as humans to understand why changes may be occurring, and how we can adapt to those changes. However, one of the key challenges in factoring climate change into management of water resources is uncertainty. In England and Wales, a small set of only three climate scenarios (derived from a variety of climate models) has been used to suggest a potential range of impacts, mostly focusing on one central scenario, and using very simple mathematical approaches to apply the scenarios (Arnell, 2011). In contrast, some approaches have used very large numbers of scenarios to assess impact (e.g. Christierson, et al. 2012), and assess the probability of certain impacts occurring, a feature that is very useful in risk assessment. However, it has been suggested that assessing the probability of hydrological changes in this way is impossible due to the considerable scientific uncertainty on how the climate system and hydrological system may change, and how to represent these possible changes. Stainforth, et al. (2007) argue that it is not possible to develop purely quantitative probability distributions of the impacts of climate change on water resources, and that the philosophy of representing uncertainty needs to change, potentially by interpreting the outcome of modelling studies less quantitatively - e.g. looking for a overall patterns and general magnitudes of change, rather than absolute values. 

This really is something of a debate in the scientific community; some feel we can use models to identify the risks of hydrological change and inform adaptation, while some feel they are simply not reliable enough to do this. Koutoyiannis, et al. (2008) compare the hydrological outputs of a variety of climate models to observations around the globe, and argue that global climate models perform very poorly at a both a small and large spatial scale. Wilby (2010) develops this argument further, suggesting a conceptual divide in the hydrological science community between those who advocate a scenario-led approach to water resource adaptation, and those who feel scenarios are better used to assess potential adaptation options. Wilby notes that hydrological processes are incredibly diverse in  in time, and as a result the management questions that need to be answered vary dramatically in time too, spanning minutes for real time flood protection through to multiple decades for provision of water. It is suggested that climate models are not reliable enough to answer the questions required for future adaptation as a result of their inability to accurately reproduce the temporal characteristics found in hydrological records.

The other side of the debate are those who think models are robust enough to inform hydrological adaptation, and feel that the critique of climate models is unjust. In a particularly strongly worded journal article, Huard (2011) attacks the publication of papers suggesting climate models cannot inform water management, claiming they are based on the misconception that climate models predict natural climate variability in a deterministic way, involving no randomness and always producing the same result given a certain input. Huard notes that this is indeed how hydrological models operate, but that this is not the way global climate models work. They are inherently chaotic and non-deterministic in their nature, with both the natural variability of the climate system and the influence of external factors playing a role. As such, a climate projection is not a deterministic prediction of climate, but 'an experiment probing the model's response to changes in greenhouse gas concentrations'. Assuming this, it is unreasonable to suggest that individual climate models should be able to predict past hydrological observations with supreme accuracy, given that they have to randomly simulate natural climate variability. To properly assess a climate model's performance, it is necessary to extract the response to external anthropogenic forcing from the inherent random natural variability.

Uncertainty in climate modelling is a huge topic, and I've only presented a short introduction to it here, but I think it is an extremely important topic to discuss, seeing as we are making a lot of predictions and decisions based on climate models. While it is a boring and non-controversial opinion, I sit somewhat on the fence on this issue. I certainly feel that climate models are of great value, but that they are experimental sandboxes that should be used to inform adaptation, as opposed to being what we base adaptation on. Quite frankly we do not have enough time to debate how we should interpret uncertainty, and need to actually get on with finding a framework of how to use all the data and projections available to inform adaptation!

Christmas Warmth

It's Christmas Eve, and Santa will be loading up his sleigh. However, he might have quite a sweat on while he does this - news headlines today have included the story that temperatures at the North Pole may be 20°C above average today, which would break all records. I realise this isn't strictly related to hydrological change, but this is so interesting I think it is worth taking a quick festive look at. These sorts of temperature changes will no doubt have an influence on the hydrological cycle; as we know, warm air can hold more water.

Two weeks back, I touched on how 2016 has been a record breaking year for temperatures globally, but this heatwave event in the Arctic really is something else, likely a 1 in 1000 year event. The temperature at the North Pole today is about 0°C, which for Santa is very warm - he prefers the -20°C average. Scientists are confident these anomalous temperatures are a result of the influence of anthropogenic climate change. It's quite pleasing to see this story make the headlines today, as I think it is something the general public were not particularly aware of. Global public awareness of anomalous climate events and their link to anthropogenic warming can only be a positive thing - though I think the story only made the news due to it's link to Santa and Christmas! I don't think a temperature anomaly of 20°C in the Amazon would have been reported today....

I will leave the final words to Dr Thorsten Markus, chief of NASA's Cryospheric Sciences Laboratory, who has discussed what is really the true issue of the day - Santa's sledding attire.:

"Santa is most likely overdressed. Maybe in the future we'll see him in a light jacket or plastic mac."

The Boxing Day sales could prove useful if this is the case. Happy Hydrological Christmas!

A Mental Struggle

Over the past weeks, I've touched on some of the key issues that changes to the hydrological cycle as a result of climate change may cause for human physical health - a lack of  water causing illness and famine, the spread of water-borne diseases through drinking contaminated water, and the threat to health from extreme flood and drought events. However, human health extends beyond physical health issues to mental health issues. It isn't something that is talked about very much, but climate change and its resultant effects on the hydrological cycle pose a risk to mental health, a key aspect of human well-being. Dealing with problems of this scale and complexity is not easy, and this can take its toll on the human brain.

Changes in the hydrological cycle can cause changes to the environments with which people feel familiar, whether through flooding, drought, storm surges, or pollution of water resources. Humans complex brains are able to develop strong bonds between other people and the physical environmental that surrounds them - the 'sociophysical' environment. The disruption that hydrological climate change can cause to the environment so cherished by humans can cause grief, a sense of loss, and great anxiety. This has been coined 'solastalgia' - the distress caused by environmental change (Albrecht, et al. 2007). 

There are many case studies that provide examples of solastalgia. For example, Brubaker, et al. (2011) demonstrate the stress and fear that has been experienced in Alaskan villages that have become increasingly vulnerable to flooding and storm surges during the storm season, with residents reporting sleepless nights and stress during spells of bad weather. Interestingly, residents reported feeling 'safer' and 'happier' after the construction of a 1,000m long sea wall; hard engineering is often perceived by the public to be what will keep them safe from disaster. 

The Lancet Commission report on global health and climate change provides another example, suggesting that  the recent decade-long drought in Australia has caused an increase in depression, anxiety and possibly suicide rates in rural populations. Drought means the livelihoods and key sources of financial income of these rural populations are affected (crop and animal farming), causing great distress. This distress is compounded by feelings of powerlessness in the face of climate change; try putting yourself in their shoes and you can see why the drought has taken such a toll on these populations.

As climate change progresses, some local communities will have to face the task of planning and adapting to environmental change. Mentally, this is not an easy process. Coastal communities that may be suffering from erosion as a result of storm surges and rising sea levels provide an example of how mentally difficult the decision making process might be. In some coastal communities, the only solution is a managed retreat, which can cause great distress associated with place attachment - it is hard to accept that a cherished place to which you are attached may be allowed to erode away, with no attempt at defending it (Ageyman, et al. 2009). Imagine you were told that your seaside cottage will not be defended and left to fall into the sea; this has happened in the UK, and some have taken matters in their own hands and have attempted to engineer their own coastal defences, whether legally or illegally. You can see why.

An example of do it yourself coastal engineering in Suffolk - the darker band of soil is a man-made addition by the homeowner, who was taken to court. Credit: www.geographyphotos.com

Understanding these links between hydrological climate change and mental health is not easy - climate change works in the language of  numbers, and mental health works in the language of emotions. Quantitative (numeric) study of the link has been proposed through an 'Environmental Distress Scale'  (Higginbotham, et al. 2007), which 'combines dimensions of hazard perception, threat appraisal, felt impact of changes, ‘solastalgia’’ (loss of solace), and environmental action'. While this index may potentially be useful in some cases, it is hard to model some climate-mental health relations due to their inherently non quantitative nature, so we may need to develop some innovative qualitative (descriptive, non-numeric) ways of understanding the impacts of climate change on mental health. Climate change is not just about numbers and graphs when we are talking about the effects on humans. 

While I've talked about some serious issues in this post, don't have nightmares, and keep everything about hydrological climate change in perspective! We as humans have caused these changes, and it is within our grasp to mitigate, adapt, and reverse them. However, do remember that climate change is already happening, and for some is causing great mental distress. It really is important to talk about this - just as important as the physical effects of climate change on humans.

COP21 - One Year On

We are currently one year on from the historic COP21 Negotiations in Paris, where some agreement was made between politicians of all nations to attempt to reduce emissions. This is obviously very important with respect to the potential changes to hydrological cycle I have already talked about. The target is to keep the warming of the earth's climate below 2C, but I personally believe that is now impossible. Why? This is a very popular animation of global temperatures that recently became viral, but it indicates an important point - we are coming close to pushing 1.5C of warming already, with 2016 being a year that has broken records temperature wise. Just look at the end of the animation; it will comfortably become the warmest year on record. Admittedly, it is a year with a strong El Nino (a climate phenomenon that leads to warmer temperatures globally), but even accounting for this, it is incredibly warm.

Credit: Ed Hawkins

To celebrate anniversary of COP21 , I thought I'd share a cartoon that amused me. This is a bit of fun and not at all realistic, but behind the cartoon there is an important message - will we ever really do anything major to act internationally as things stand?  Only time will tell if the agreements reached at COP21 will have any impact, particularly given events such as a the recent election of Donald Trump in the USA. I still worry for the changes to the hydrological cycle that are yet to come, but also remain optimistic that humans do have to power to enact change. We just have to give ourselves the chance to enact change - we are so dependent on water. Enjoy the cartoon.

Credit: The Economist