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Climate Digest for July 2010
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Climate science
Climate impacts
Climate change adaptation
Climate policy
Climate science
1 Towards projections of future UK droughts
The authors use extreme value analysis of precipitation and soil moisture-based indices representing dry conditions over periods of 1–18 months to assess the likelihood of droughts over the UK during the 20th century and potential future changes due to increased atmospheric greenhouse gases. They assessed the ability of the Hadley Centre regional climate model (Had RM3) to reproduce historical characteristics of dry months over the UK and then developed and explored the nature of projections of changes in the future. The expectation is that the method developed for producing future projections will form the basis of a methodology for probabilistic projections of drought.
The authors’ comparison of the modelled and observed (reference) data show that in general the HadRM3 ensemble members have between 30% less to 30% more accumulated precipitation then the reference data, with some regional differences These differences suggest that there is some downscaling bias in the regional model. A possible explanation for some of this bias is that in the Had RM3 too little moisture is rained out over the western regions high ground during westerly atmospheric flow resulting in the atmosphere being too moist over the eastern regions and producing excessive rain in the east.
A comparison of model and reference climate drought indices shows that the 11 ensembles are able to capture many of the characteristics of the reference dry periods. For example, precipitation drought indices from the model and reference data were found to have correlations greater than 0.4 for nearly all grid cells, with values of up to 0.8 in some regions. On a regional basis, correlations were found to be generally greater in north-west Scotland and south-east England – the areas of highest and lowest precipitation.
The projections showed an overall increase in drought occurrence. The spread, however, is considerable ranging from little change or a slight decrease to a significant increase depending on the drought index, ensemble member and to a much smaller extent, location within the UK. The majority of the ensembles, like the projections of other authors, project an increase in short duration droughts over the UK. There are, however, large uncertainties associated with these projections. The authors discuss the need to develop methodologies to comprehensively describe the associated uncertainties and to account for the variations in the credibility of alternative model versions towards providing probabilistic projections on the changing risk of drought to support adaptation.
Source: Eleanor J, Burke; Richard H.J. Perry and Simon J. Brown; (2010), An extreme value analysis of UK drought and projections of change in the future. Journal of Hydrology, 388: 131–143.
Decrease in CO2 uptake capacity in an ice-free Arctic Ocean basin
Approximately 30% of the CO2 released into the atmosphere since industrial times has been taken out again by the oceans. The oceans therefore play a significant role in carbon cycling but it is not known how this will play out in a warmer world. An understanding of how the oceans might respond to warming, and particularly whether they will take up more or less CO2 is important if we are to understand how much warming the Earth is likely to experience for a given amount of CO2 emitted.
The oceanic response will not be uniform, with the greatest change likely at the poles. It has been postulated that the Arctic Ocean will sequester much greater amounts of CO2 from the atmosphere as a result of sea ice melt leading to increased primary productivity.
This study reports on a survey of sea surface CO2 concentration across the Canada Basin in 2008 and discusses the implications for the idea that the Arctic Ocean will sequester more CO2 from the atmosphere in a warmer future. The survey reports significant increases in surface CO2 concentrations since earlier observations indicating that the air-sea CO2 flux has been enhanced by ice melt. However they suggest that a shallow mixing layer, strong stratification, surface warming and low biological fixation (low productivity) means that surface CO2 concentrations quickly reach equilibrium with the atmosphere and act as a barrier to further uptake.
The authors interpret this evidence to contradict the current view and suggest that the Arctic Basin is unlikely to become a large atmospheric sink for CO2 under ice free conditions.
Source: Cai, W.-J., Chen, L., Chen, B., Gao, Z., Lee, S. H., Chen, J., Pierrot, D., Sullivan, K., Wang, Y., Hu, X., Huang, W.-J., Zhang, Y., Xu, S., Murata, A., Grebmeier, J. M., Jones, E. P. & Zhang, H. (2010) Decrease in the CO2 Uptake Capacity in an Ice-Free Arctic Ocean Basin. Science, 329: 556-559.
Climate impacts
Urban greening to cool towns and cities
Urban greening has been suggested as one approach to help mitigate the increased temperatures in towns and cities resulting from climate change and the associated negative impact on human health. This study reviews the available evidence and analyses published data to assess whether greening interventions, such as tree planting, the creation of parks and the construction of green roofs, can affect the air temperature in urban areas.
Five specific types of green areas were investigated: parks, trees, forests, ground (grass) and roof vegetation. On the basis of the predefined selection criteria within the systematic review methodology, 47 published articles were found that measured and compared temperatures at ground level in green and non-green urban areas in various countries.
For parks, an average temperature reduction was observed relative to non-green urban sites, with similar reductions in both the day and at night. Given the relatively few separate studies available, only limited analysis could be carried out on the significance of factors affecting temperature but the cooling effect tends to be greater for larger parks and there is also evidence to suggest that the reduction in temperature extends beyond the park boundaries. For trees and forests, evidence suggests that the air temperature below single trees and clusters of trees is lower than temperatures in open areas at least during the day although there is some evidence that a tree canopy can retain heat at night. Different species vary in their ability to reduce air temperature due to a number of factors such as size and canopy characteristics which affect the penetration of solar radiation. Fewer studies investigated the effects of short vegetation. All were consistent in finding lower surface temperatures for grass than for common hard materials such as concrete but the findings for grass roofs were more variable with the temperature difference often dependent on the time of day or season.
Overall, this paper highlights the very limited observational data currently available on which to base potential strategies for urban greening. Broadly, the evidence suggests that green areas can be cooler than non-green areas but the impact of specific greening interventions on the wider urban context and the interactions between the variety of factors which may affect air temperature in a local urban environment have yet to be studied in detail.
Source: Bowler, D.E., Buyung-Ali, L., Knight, T.M. and Pullin, A.S. (2010) Urban greening to cool towns and cities: A systematic review of the empirical evidence. Landscape and Urban Planning, doi:10.1016/j.landurbanplan.2010.05.006
Climate change adaptation
Observed adaptation to climate change in the UK
This paper investigates the extent to which the UK is already adapting to climate change. It is a snap-shot of adaptation in the UK in 2005. It documents the process by which examples of adaptation practice have been captured as part of the UK government’s adaptation policy framework.
An inventory of adaptation examples was compiled drawing initially on published literature, company reports, trade documents and UKCIP material. Four additional activities were then conducted to widen the search for examples: all government departments’ annual reports were reviewed, expert advisors to projects were questioned, an internet search was conducted and a request for evidence of adaptation was sent out through UKCIP’s monthly enews. Over 300 adaptations were identified and catalogued in a database which formed the basis of the UKCIP resource, The Brain.
The authors distinguished three types of adaptation examples: building adaptive capacity, implementing adaptation decisions and developing a supportive legislative and policy framework. Most of the identified actions were related to building adaptive capacity. The sectors displaying the highest levels of activity were those which tended to be most affected by current weather. This can be considered to be one driver of adaptation but finding the true motives for most adaptation was very difficult. Often the drivers for adaptation were not documented or adaptation to climate change was used as a means for justifying change that would have been made anyway. That aside, the most cited reason for adaptation was real or perceived climate change with legislation, flooding, conservation goals, cost saving/risk management and population pressures also cited as drivers. However, there was found to be multiple triggers of adaptation with few adaptation initiatives solely instigated in response to the changing climate.
The findings of the paper lead to the question of whether adaptation activity should be promoted through the risk management agenda rather than framing adaptation within the sustainable development debate. This is because many adaptations are a result of mitigation activities or activities not related to climate and are currently categorised as risk management.
Source: Tomkins E.L, Adger, W.N., Boyd, E, Nicholson-Cole, S, Weatherhead, K and Arnell N. 2010. Observed adaptation to climate change: UK evidence of transition to a well-adapting society. Global Environmental Change. doi: 10.1016/j.gloenvcha.2010.05.001.
Turning adaptation principles into practice: the case of freshwater ecosystems
Although climate change poses serious threats to the natural environment, and adaptation to climate change is widely recognised as a need, there is still relatively little scientific knowledge about how to adapt. Opinion is divided on how to move forward and there are concerns about the sustainability of some environmental policies.
Within the freshwater ecosystems field there are a variety of uncertainties to consider. Firstly, there are uncertainties in the regional climate change projections. UKCP09 goes some way to quantifying these uncertainties, however, when this is added to the choice of impacts model the uncertainties envelope expands further. Secondly, the responses of freshwater ecosystems are uncertain. For instance, there are major knowledge gaps in the impacts of climatic changes on salmon growth and condition. Lastly, there is lack of consensus on the desired outcomes of adaptation planning.
Hence, Wilby et al. conclude that there is a strong case for planning no-regret, reversible adaptation measures that will yield benefits no matter what the outcome of the climate. This includes instituting measures that have multiple benefits such as limiting pollution or providing habitat. Addressing this challenge requires bringing together multi-disciplinary researchers, government and other stakeholders into a thematic programme to build a shared evidence base. Routine monitoring and review are also needed to constantly reassess the implemented adaptation strategies.
Source: R.L. Wilby, H. Orr, G. Watts, R.W. Battarbee, P.M. Berry, R. Chadd, S.J. Dugdale, M.J. Dunbar, J.A. Elliott, C. Extence, D.M. Hannah, N. Holmes, A.C. Johnson, B. Knights, N.J. Milner, S.J. Ormerod, D. Solomon, R. Timlett, P.J. Whitehead, P.J. Wood. (2010). Evidence needed to manage freshwater ecosystems in a changing climate: Turning adaptation principles into practice. Science of the Total Environment 408: 4150–4164.
Anticipatory learning for climate change adaptation and resilience
Adaptation to climate change, the authors assert, is now commonly presented as a process of learning and yet there is surprisingly little support for such learning or guidance on how to do it well. The authors quote various texts describing the kind of adaptive capacity required for the complex risks and uncertainties presented: Adger (2003) the ability to learn from mistakes; Berkes et al. (2003), the ability to generate experience of dealing with change; and Armitage, (2005) the capability for innovation. In contrast to “hard” technological and infrastructural response options, holding a dynamic notion of adaptation as a process promotes building resilience to enhance adaptive capacity now rather than targeting adaptation in the future. The key question explored in the paper is thus: ‘how should we be facilitating learning, information exchange, reflection, innovation and anticipation – all key elements of the practical application of adaptation process?’
The authors assert that despite numerous researchers arguing for collaborative, iterative, self-organising processes of learning-by-doing, there is currently a dearth of methods and tools to facilitate and sustain such learning. This situation is considerably worse in the Global South where the impacts of climate change are already being felt yet access to information, knowledge networks and climate learning tools that build resilience into people’s livelihoods, institutions and ecosystems remain particularly scarce.
The authors examine the potential of two theoretical frameworks to address this need: resilience thinking and action research/ action learning (AR/AL) and conclude that both have a great deal to offer in terms of providing support for anticipatory learning and suggest that the two schools of thought would benefit from being more closely linked. The learning described in resilience thinking (incremental, spasmodic, profound and transformational (Holling, 1986)) has significant crossovers with the core values of AR/AL thinking which includes: ‘questioning of assumptions through reflection, creativity, systems thinking and enabling the emergence of novel patterns through self organisation’. Both framings offer practical ways to move forward despite imperfect knowledge, uncertainty and non-linear systems, to support innovation and experimentation with the potential for transformation of existing systems should they become insufficient.
The paper goes on to present a methodological framework to facilitate iterative learning processes and adaptive decision making in practice and in this stress that the monitoring of key drivers of change, scenario planning, and measuring anticipatory capacity are key elements of enhancing adaptation and building resilient pathways, offering a significant advance on learning by shock.
Source: Tschakert, P. and Dietrich, K.A. (2010) Anticipatory Learning for Climate Change Adaptation and Resilience. Ecology and Society 15 (2), article 11.
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