Simulated crop yield changes by 2080s relative to the period 1961-1990 according to a high emission scenario (IPCC A2) and two different climate models: (left) HadCM3/HIRHAM, (right) ECHAM4/RCA3, map elaboration by EC JRC/IES.
(Figure 10 in the Green Paper on Adaptation)
How the results have been computed
In general terms, agriculture yields (the number of tons harvested per hectare) depend on climate conditions, such as temperature and the amount of precipitation, in addition to the role played by the decisions of farmers, such as the selection of crops and the use of fertilizers.
These mechanisms are simulated with a crop yield model. A changing climate in the future, compared to the historical climate of the 1960-1990 period, might change the agriculture average yields. Lower precipitation can, for instance, decrease the production of certain crops. Farmers can take adaptation measures to limit the yield change. For example, farmers could change crop or planting date. The PESETA results assume a relatively optimistic degree of adaptation where farmers can use as much additional irrigation water and/or fertilizers as wished, without any constraint.
Effects of climate change on livestock are not considered.
Limitations of the approach
There are many sources of uncertainty that should be considered when interpreting the results. First of all, it is not possible to forecast exactly how the climate will be in 80 years time from now. This is why several climate scenarios and models are used. Secondly, how land use will evolve to the year 2085 is not considered in the agriculture study (it is assumed that the current land use pattern is kept). Thirdly, how farmers will adapt to climate change is a very complex dynamic process which is difficult to quantify. Finally, how agriculture policies might react to a changing climate is another critical factor which cannot be incorporated in the simulations.
How to interpret the maps
The maps give indications of the general spatial pattern of changes in agriculture yields across Europe. Results for two different global circulation models are presented. Both maps assume the same evolution of the socioeconomic systems and thus the same greenhouse gas emissions. The only difference between the maps comes from the use of a different climate model.
Concerning the left-hand map (whose climate model is the same as for the rest of the sector maps appearing in the Green Paper), in the south and west of Europe a decrease of yields of 10% or more could happen. In central and north east of Europe, the diminution of crop yields could be lower, in a range of 0 to 5%. For the Nordic countries, an improvement of yields of more than 15% is projected by this model. The map on the right-hand side, coming from a different climate model, indicates in general larger changes in crop yields than the first map, due to the different climate conditions.
Due to constraints in the crop yield models and the availability of observed data to construct these models, the spatial details at a resolution lower than a country or group of countries are not considered meaningful. Therefore, it is not possible to extract conclusions concerning specific regions within a country.