Ogmius Exchange: Part II
This is the crux of the problem. What can be done now, in practice, to ‘climate-proof’ the future given the cascade of scientific and societal uncertainties attached to the likely behavior of the climate system? Whilst it is important to acknowledge uncertainty, the time is fast approaching when we will need to move from awareness-raising to action.
The challenges confronting decision-makers are already tangible. For example, the River Thames basin in the UK has available water resources per head of population similar to that of Israel, yet the London Plan envisages a further half million dwellings by 2016 in a region that is projected to become significantly hotter and drier (Hulme et al., 2002). Natural land movements, increased storminess and sea level rise mean that the cost of infrastructure to protect London from a 1 in 1000-year flood event to the year 2100 will be about £4 billion over the next 40 years. Sea level rise and associated coastal erosion also pose risks to radioactive waste repositories, and threatens valuable inter-tidal habitats (such as salt marsh) with ‘coastal squeeze’. The official position with respect to species cited under the UK Biodiversity Action Plan is one of “assisted adaptation” but this raises many questions about prioritizing some species and habitats ahead of others, what to do about exotic species, and how to define “normal” conditions? Regulators must also accommodate new legislation associated with the European Water Framework Directive that will set stringent environmental objectives governing surface and groundwater quality by 2010. All this and more in the face of proliferating climate change outlooks.
An important step towards reducing uncertainty surrounding the consequences of future climate change is to quantify the impacts of present-day variability. The so-called “bottom-up” approach may not be in vogue but it can teach us a lot about the key climate sensitivities of the system(s) of interest and help to focus limited resources on critical assumptions and thresholds. For example, the reliable yield of a reservoir may depend upon the length of dry-spells at critical times of the year. Persistent dry-spells may, in turn, be linked to the occurrence of specific weather patterns over the region. This leads us naturally to question the ability of General Circulation Models to reproduce such weather phenomena for the present climate, as well as changes in the future. Some impact studies show that natural climate variability may be as great as, or even greater than, projected impacts associated with human-induced climate change (e.g., Hulme et al., 1999). In either event, there is considerable scope for capitalizing upon the wealth of palaeo-data for benchmarking levels of climate variability beyond the limited scope of the instrumental record.
Future global emissions of greenhouse gases will remain a largely intractable source of uncertainty affecting climate predictions. However, it is anticipated that ongoing research into small-scale physical processes (e.g., clouds) and large-scale biogeochemical feedbacks (e.g., the carbon-cycle) will progressively reduce the scientific uncertainties surrounding climate model predictions (Hulme et al., 2002). Higher resolution climate models and innovative ways of testing regional scenarios using seasonal forecasts may also facilitate model verification using hitherto unseen events (e.g., Leung et al., 2002). But the probabilistic description of extreme events or abrupt climate changes, such as the complete shut down of the North Atlantic thermohaline circulation, are largely beyond the scope of even present-day observational data.
A useful alternative to the probabilistic paradigm has already been suggested. The climate change strategy of the Western Water Assessment project has much in common with the guidance of the UK Environment Agency’s Centre for Risk and Forecasting. Both are invoking options appraisal rather than probabilistic estimates of climate change impacts. The decision-making framework advocated by Willows and Connell (2003) envisages eight stages:
- identify problem and objectives
- establish decision-making criteria
- assess risk
- identify options
- appraise options
- make decision
- implement decision
- monitor, evaluate and review outcomes
The framework is circular, allowing decisions to be revisited in the light of new information and iterative to encourage the refinement of objectives and decision-making criteria. The involvement of stakeholders is seen as an important means of including all potential impacts and of identifying adaptation-constraining decisions.
At the very heart of the risk assessment framework is the philosophy of no regret climate adaptation options. These options deliver benefits under any forseeable climate scenario, including present day variability (e.g., water conservation measures). Unfortunately, no regret options may not always be available, so a second mantra is invoked, namely to keep open or increase the options that will allow climate adaptation measures to be implemented in the future when the risks attached to different measures are less uncertain. This recognizes that some adaptation measures may affect the ability of other decision-makers to manage climate change impacts. For example, the siting, construction and operation of flood defense infrastructure (to address the impact of extreme hydrological events) may compromise water levels and nutrient fluxes of adjacent wetlands (threatened by increased summer drying). An important part of the process is, therefore, to identify potential conflicts between adaptation objectives.
Finally, it is perhaps germane to note that agencies on either side of the Atlantic have arrived at a similar framework for climate change impact adaptation and mitigation. Of course, the true value of the proposed methodology will lie in the appraisal of ‘real-world’ decisions. At least there is no shortage of risks to assess!
Climate Change Science Advisor
UK Environment Agency
- Hulme, M., Barrow, E.M., Arnell, N.W., Harrison, P.A., Johns, T.C. and Downing, T.E. 1999. Relative impacts of human-induced climate change and natural climate variability. Nature, 397, 688-691.
- Hulme, M., Jenkins, G.J., Lu, X., Turnpenny, J.R., Mitchell, T.D., Jones, R.G., Lowe, J., Murphy, J.M., Hassell, D., Boorman, P., McDonald, R. and Hill, S. 2002. Climate Change Scenarios for the UK: The UKCIP02 Scientific Report, Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, Norwich, UK. 120pp.
- Leung, L.R., Mearns, L.O., Giorgi, F. and Wilby, R.L. 2003. Regional climate research: needs and opportunities. Bulletin of the American Meteorological Society, 84, 89-95.
- Willows, R. and Connell, R. (Eds.) 2003. Climate adaptation: Risk, uncertainty and decision-making. UK Climate Impacts Programme (UKCIP) Technical Report. UKCIP, Oxford.