Climate change is expected to affect both the average level and the variability of crop yields. In this modelling study, we quantified mean and inter-annual variability of grain yield for maize Zea mays L., winter wheat Triticum spp. L. and winter canola Brassica napus L. for climatic conditions corresponding to current and doubled atmospheric CO 2 concentrations. Climate scenarios with and without taking into account changes in the inter-annual variability of climate were developed from the output of a regional climate model for the time window 2071 to 2100. Climate change effects on the mean yield of maize and canola were consistently negative, but a positive impact was simulated for mean yield of winter wheat for elevated CO 2 concentration. The coefficient of yield variation increased in the scenarios for maize and canola, but decreased for wheat. Higher thermal time requirements increased mean yield and reduced yield variability for all crops. Shifts in the sowing dates had a beneficial impact on the yield of maize, but not on the yield of canola and wheat. It is concluded that in the Alpine region, the potential effect of climate change is crop-specific. However, the introduction of new cultivars may provide means by which to maintain or even increase current productivity levels for most of the crops.KEY WORDS: Climate change · Climate scenario · Inter-annual variability · Crop yield · Maize · Winter wheat · Winter canola Resale or republication not permitted without written consent of the publisherClim Res 34: [59][60][61][62][63][64][65][66][67][68][69] 2007 increase in mean temperature. Enhanced climate variability may lower mean yields because of a higher incidence of years with adverse conditions (Southworth et al. 2000), but sign and magnitude of the impacts will likely vary from region to region and depend on the crop (Porter & Semenov 2005). In Europe, productivity is likely to increase in northern Europe but decrease in southern Europe, unless adaptive measures are implemented to cope with the negative impact of climate change (Olesen & Bindi 2002).The specific response of crops to climate change will depend on how growth and yield formation are stimulated by elevated CO 2 concentrations. Direct stimulation of photosynthesis and increase in transpiration and water use efficiencies both play a role (Fuhrer 2003). The potential for a direct effect is larger in C3 than C4 crops, because ribulose-1, 5-bisphosphate carboxylaseoxygenase (RuBisCO) in the latter is already CO 2 saturated at current atmospheric levels (Long et al. 2004).The overall objective of our study was to examine the effects of climate change on productivity for 3 of the main crops grown in Switzerland and Europe, namely Zea mays L. (maize), a C4 crop, Triticum spp. L. (winter wheat) and Brassica napus L. (winter canola), both C3 crops. Specific aims were to (1) develop a climate change scenario that accounts not only for the change in mean conditions but also in year-to-year variability; (2) compare mean yield levels an...

A simple model of yield was used along with climate scenarios to assess the impact of climate change on grain maize productivity and associated economic risk in Switzerland. In a first application, changes in the precipitation regime alone were shown to affect the distribution of yield considerably, with shifts not only in the mean but also in the standard deviation and the skewness. Production risk was found to respond more markedly to changes in the long-term mean than in the inter-annual variability of seasonal precipitation amounts. In a further application, yield projections were generated with respect to a full climate scenario, with the emission pathway as specified in the IPCC A2 scenario. Anticipation of the sowing date was found to reduce the negative impact of climate change on yield stability, but was not sufficient to ensure average productivity levels comparable to those observed at present. We argued that this was caused by the reduction in the duration of the growing season, which had a stronger impact than suggested by previous studies. Assuming no change in price relations, the results also revealed a strong increase in production risk with climate change, with more than a doubling in the probability of yield falling short of a critical threshold as compared to today's situation.

The effectiveness of hedglng drought risks with weather derivatives was investigated for rain-fed grain maize production in Switzerland under current ( I 98 I-2003) and projected future {2O7O-2LOO) climatic conditions. Depending on location, hedging reduced the value-at-risk [VaR) measure to a variable degree, although with a considerable basis risk, but hedging may provide a rralid risk transfer since loading of 90% to 24Oo/o of the fair premium can be paid to obtain a hedged situation with improved outcomes relative to the reference. However. the fair premium of a specific contract may vary by a factor of two to four over the 7O-year period considered, which represents a substantial uncertainty for both the farmer and the institution writing the contract.

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