There are two approaches to assess vulnerability, as is presented in the figure below from
O’Brien, K. L., S. Eriksen, L. Nygaard, and A. Schjolden, (2007), Why different interpretations of vulnerability matter in climate change discourses. Climate Policy 7 (1): 73–88
Füssel, H.-M. (2009), Review and quantitative analysis of indices of climate change exposure, adaptive capacity, sensitivity, and impacts. Development and Climate Change: Background Note. to the World Development Report 2010, 35 pp. Available online at http://siteresources.worldbank.org/INTWDR2010/Resources/5287678-583 1255547194560/WDR2010_BG_Note_Fussel.pdf.
Figure caption: Framework depicting two interpretations of vulnerability to climate change: (a) outcome vulnerability and (b) contextual vulnerability. From: Füssel  and O’Brien, K. L. et al. .
We discuss these two types of vulnerability in our submitted paper
Pielke Sr., R.A., R. Wilby, D. Niyogi, F. Hossain, K. Dairuku, J. Adegoke, G. Kallos, T. Seastedt, and K. Suding, 2011: Dealing with complexity and extreme events using a bottom-up, resource-based vulnerability perspective. AGU Monograph on Complexity and Extreme Events in Geosciences, submitted.
The outcome vulnerability is the IPCC approach where “climate change” in the left side of the figure is typically obtained from the IPCC-type multi-decadal global climate model projections. With the contextual vulnerability, however, “climate variability and change” represent just one of the stressors.
We presented this perspective in 2004 in our book
Kabat, P., Claussen, M., Dirmeyer, P.A., J.H.C. Gash, L. Bravo de Guenni, M. Meybeck, R.A. Pielke Sr., C.J. Vorosmarty, R.W.A. Hutjes, and S. Lutkemeier, Editors, 2004: Vegetation, water, humans and the climate: A new perspective on an interactive system. Springer, Berlin, Global Change – The IGBP Series, 566 pp
where we used the terminology “scenario” which is the “outcome vulnerability approach and the term “vulnerability” with is the same as the “contextual vulnerability” used by O’Brien et al. The summary table from Kabat et al 2004 with respect to these two approaches is reproduced below (from Pielke and Guenni, 2004).
|Assumed dominant stress||Climate, recent greenhouse gas emissions to the atmosphere, ocean temperatures, aerosols, etc .||Multiple Stresses: Climate (historical climate variability, land use and water use, altered disturbance regimes invasive species, contaminants/pollutants, habitat loss, etc.|
|Usual timeframe of concern||Long-term, doubled CO2 30 to 100 years in the future.||Short-term (0-30 years) and long-term research.|
|Usual scale of concern||Global,sometimes regional. Local scale needs downscaling techniques. However, there is little evidence to suggest that present models provide realistic, accurate, or precise climate scenarios at local or regional scales.||Local, regional, national, and global scales.|
|Major parameters of concern||Spatially averaged changes in mean temperatures and precipitation in fairly large grid cells with some regional scenarios for drought.||Potential extreme values in multiple parameters (temperature, precipitations, frost-free days) and additional focus on extreme events (floods, fires, droughts, etc.) measures of uncertainty.|
|Major limitations for developing coping strategies||Focus on single stress limits preparedness for other stresses.Results often show gradual ramping of climate change-limiting preparedness for extreme events.Results represent only a limited subset of all likely future outcomes – usually unidirectional trends.Results are accepted by many scientists, the media, and the public as actual “predictions”.Lost in the translation of results is that all models of the distant future have unstated (presently unknowable) levels of certainty or probability.||Approach requires detailed data on multiple stresses and their interactions at local, regional, national, and global scales – and many areas lack adequate information.Emphasis on short-term issues may limit preparedness for abrupt “threshold” changes in climate sometime in the short or long term.Requires preparedness for a far greater variation of possible futures, including abrupt changes in any direction – this is probably more realistic, yet difficult.|
Figure caption: Contrast between a top-down versus bottom-up assessment of the vulnerability of resources to climate variability and change [from Kabat, P., Claussen, M., Dirmeyer, P.A., J.H.C. Gash, L. Bravo de Guenni, M. Meybeck, R.A. Pielke Sr., C.J. Vorosmarty, R.W.A. Hutjes, and S. Lutkemeier, Editors, 2004: Vegetation, water, humans and the climate: A new perspective on an interactive system. Springer, Berlin, Global Change – The IGBP Series, 566 pp.]
The recent Nature article Overstretching attribution by Parmesan et al 2011 clearly shows why the outcome vulnerability approach is inadequate and is actually misleading policymakers. As they headline in that article
“The biological world is responding rapidly to a changing climate, but attempts to attribute individual impacts to rising greenhouse gases are ill-advised.”
The conclude their article with
“We advocate striving for a richer understanding of interactions between multiple drivers of change through doing empirical research, emphasizing tractable questions and using model-based attribution approaches more as a tool for improving projections of biodiversity impacts than as an end in itself. To do so should clarify the dialogue between climate scientists, biologists and policymakers, and generate much-needed assessments of the current and future impacts of anthropogenic climate change on biota.”
The adoption of the contextual vulnerability approach means that instead of the IPCC global climate models dominating the effort (as with the outcome vulnerability approach), the climate model projections are only one part of the assessment of threats to key social and environmental resources. This is going to be difficult for that community to accept, but it is required if we are to develop more inclusive and scientifically robust assessments of the risk we face in the coming decades.