Page 131 - Climate Change and Food Systems

chapter 4: an overview of climate change impact on crop production and its variability in europe, related uncertainties and research challenges
defined, including Representative Concentration Pathways (RCPs)3. This has resulted in a new
CC dataset with a larger range of climate model simulations, called CMIP5 (Taylor et al., 2012; Peters et al., 2013). A one-to-one comparison of the new RCPs with the former Special Report on Emissions Scenarios (SRES) family of emission scenarios is not possible; however, there are generally large similarities between the climate sensitivities of SRES and RCPs. For example, temperature changes and spatial distribution patterns under SRES A2 are quite similar to those under RCP8.5 (Knutti and Sedlacek, 2013).
Regional changes within Europe
Based on simulation from CMIP5 for RCP4.5, Rummukainen (2014) describes how projected changes during the twenty-first century in annual mean temperature and precipitation at the global level vary considerably by region. For Europe, regional variations in temperature change vary by factors ranging from 1 (implying change equal to global change) in the northwestern parts of Europe, to 2.5 in the northeastern parts. For precipitation, the factors of change relative to the global mean ranged from no change (in southern parts) to 1.5 (in the northeastern parts). In terms of precipitation change, this confirms a rule of thumb for CC projections, which suggests that “wet gets wetter” and “dry gets drier” (Rummukainen, 2014).
According to Deser et al. (2012), in many parts of the world regional-scale changes in climate are not only formed by global drivers, but also strongly affected by modifications of regional circulation patterns (Lamb, 1995). As for climate model predictions on changes in circulation patterns
and associated climatic variability, for some time
it has been suggested by many GCM studies that there will not be major shifts in variability (IPCC, 2007). Large-scale variability patterns that strongly influence weather conditions and represent the internal variability of the climate system in Europe include, for instance, the North Atlantic Oscillation and the Arctic Oscillation (Rummukainen, 2014). While most projections have suggested that these circulation patterns will remain in place, recently
it has been postulated that the retreat of Arctic sea ice (poorly predicted by most climate models) could influence atmospheric circulation such
that it would tend towards more “meridionality”
or meridional patterns (Lamb, 1995)4. This
would particularly affect the mid-latitudes of the northern hemisphere, producing more extreme winters characterized by prolonged cold spells and summers characterized by more extended droughts, flooding and heat waves (Francis and Vavrus, 2012).
Analysis of results from the CMIP3 climate model ensemble on temperature-related extreme events indicates that, generally, daily minimum (Tmin) and maximum (Tmax) temperature changes are in line with average temperatures (Tmean). However, there are also distinct deviations,
such as Tmin experiencing the largest change
(i.e. more warming) in the winter of the Boreal climatic zone, meaning that the colder end of
the distribution warms up more than the warmer end. Similarly, Tmax shows the largest change during the summer months in the continental and Mediterranean climatic zones of Europe (Orlowsky and Seneviratne, 2012).
The scatter plots presented in Figure 2 illustrate changes in temperature and precipitation for different seasons (i.e. winter, Dec.-Feb. and
4 There is a meridian atmospheric circulation dominated by the Hadley circulation of the tropical atmosphere with mean upwelling near the equator, poleward flow aloft, subsidence in the subtropics
and equatorward return flow near the surface. This circulation transports heat poleward within the tropics but becomes much weaker in middle latitudes and does little heat transport there (Marshall and Plumb, 2007).
3
Representative Concentration Pathways (RCPs)
are four greenhouse gas concentration trajectories adopted by the IPCC for its fifth Assessment Report (AR5) (Moss et al., 2008). The pathways describe four possible climate futures represnting a broad range of possible levels of greenhouse gases expected to be emitted in the years to come. The four RCPs, RCP2.6, RCP4.5, RCP6, and RCP8.5, are named after a possible range of radiative forcing values in the year 2100 relative to pre-industrial values (+2.6, +4.5, +6.0, and +8.5 Watts/m2, respectively) (Weyant et al., 2014).
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