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May 2013: 21st Century research: water

The UK public was told to expect future hotter, drier summers and milder, wet winters. For the past few years they have experienced the opposite and are now told that this could still be because of global warming via changes in the normal position of prevailing weather systems. One of the key public concerns for climate change, then, is the extent to which the mid-latitude weather systems deviate from their climatic norms. The socio-economic consequences were evident last summer (2012) and for the past two winters in the UK and Europe through freezing temperatures interspersed with drought then flooding!

Climate change, then, is not just about temperature. Amongst many other things, it concerns changes in our water resources. Water resource planning in the UK is based on 25-year time horizons and indeed provides an exemplar for long-term environmental resource planning. Precipitation records for the UK are some of the longest in the world, but still, at best, provide, perhaps 8 to 10 preceding “states” based on this time horizon.

Some of the novel research currently being undertaken within the Institute is focused on enhancing knowledge of water cycle variability and its interaction with other biochemical cycles. A key part of that research involves establishing how precipitation changed each decade, not just over the past couple of hundred years, but over the past few thousand years. In the past (pardon the pun), where differences were observed within 100km, for example, this might be questioned as error. Now, we recognise that such regional differences can tell us a lot about what was taking place in the atmosphere to drive those changes.

Where rain falls and its chemical composition depends on where it has come from. It has a fingerprint. This fingerprint can be found in modern rainfall distribution and chemistry. It should also be found in past records of these two indicators. Those records come from some of the most unlikely of places: buried plants and dead creatures. Extracting chemical stories from the remains of these former living beings, it is possible to map changes in the regional distribution of the amount of precipitation and chemistry of the water. In so doing, we can work out the latitudinal position or intensity of the westerly winds.

So what evidence is there to suggest that any of this is true? Stretching over to the other side of the planet, we are already able to observe these types of changes. In the last 30 years, the westerly winds that drive frontal rain-bearing depressions have moved south and intensified. The result has been more intense precipitation on the south-western side of the Andes and drying conditions on the eastern side. Warm air from the north has also been drawn down to mix with cooler air over the southern pampas of Argentina. In this region, where much of the drinking water is derived from glacial run-off, changing precipitation patterns matter greatly.

In the UK, drinking water sources vary across the country. Some regions rely on surface water (from captured rainfall). Others rely on “fossil” water from deep abstraction. Crucially, where the southern hemisphere westerlies have moved poleward, the pattern in the past seven years in NW Europe has been quite different and it is essential to know if this is unusual. Our team, made up of colleagues from near and colleagues from far is currently searching for these past “fingerprints” of change. This is not an issue to be scuttled sideways around. Instead, I propose that knowledge of the potential changes in where our water will come from is absolutely central to the sustainability of the UK in Europe.

Tim Daley is Director of the Institute for Sustainability Solutions Research (ISSR)

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