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given the best estimates of climate scenarios from a coupled
Atmospheric-Oceanic GCM' (RegClim website, 2002). *
RegClim predictions consist of a single, average figure for each
weather variable for the 20-year period from 2030 to 2050. The
RegClim scenario only presents one climate change outcome
for Northern Europe, whereas other outcomes can be just as
likely given a large number of uncertainties involved in such
climate scenario estimates.
pre dict ing
future yields
The crop and county cases where the model was able to explain
a sizeable proportion of the annual yield variation through
changes in annual precipitation and/or GDD during the grow-
ing season, and yielding significant coefficients, were selected
for the RegClim projections (see Table 19.1). RegClim data,
which forecasts the average percentage change in climate vari-
ables between two time periods, 1980-2000 and 2030-2050,
were then used as the basis for future predictions. We take 2040
as a representative mid-year for the RegClim period.
Before any calculations could take place, however, it was
necessary to adjust both model and RegClim weather data
to improve their compatibility. As RegClim figures were
only available for individual 50 km 2 grid cells throughout
Norway, data were first of all aggregated up to county level.
Furthermore, to bring figures in line with model data, pre-
dicted weather values were calculated to correspond to regions
of agricultural activity, rather than to the county as a whole.
Then, using RegClim data, average figures for the relative,
forecast percentage change in GDD and annual precipitation
between 1980-2000 and 2030-2050 were calculated for almost
every county (with the exception of Vestfold). The next step
was to find model estimates of the yield for all relevant crops
and counties based on average GDD and precipitation for the
period 1980-2000. In some cases, our interest extended to
all four crops in a particular county, while in others, it was
restricted to just one or two. Similarly, in some counties, the
model referred to the entire time period of the study; in others it
was limited to one or two sub-periods. Next, the average GDD
and precipitation for each county was multiplied by the percent-
age change given by the RegClim scenario. Finally, RegClim
GDD and precipitation values were entered into the model to
give yield predictions for the selected crops and counties. The
effects of changes in GDD and precipitation were calculated
separately to measure the independent impact of each variable
* For further details of the RegClim Project, visit http://regclim.met.no.
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