Mapping climate change - barriers and opportunities for action

3. A common starting point for climate change adaptation efforts
With focus on 2050, the Danish Meteorological Institute has described the projected future climate
changes in Denmark based on the most recent Danish and European scenario simulations.The
assessment of future climate change is based on the same scenarios that are used by the UN
Intergovernmental Panel on Climate Change (IPCC). Changes are expected to increase towards
2100.
As a common starting point for climate change adaptation in Denmark, since 2010 the
recommended climate scenario has been the A1B scenario from the Intergovernmental Panel on
Climate Change (IPCC) for the period up to 2050, as there are only minor differences between the
different climate scenarios over this relatively short time span. For the period up to 2100, the
climate model projections are much more reliant on the emissions scenario applied. On the basis of
the Danish strategy for adaptation to a changing climate from 2008, in addition to results for A1B
(an average scenario), descriptions for two of the IPCC's other SRES scenarios: B2 (an average-low
scenario) and A2 (an average-high scenario), are included here in order to illustrate the range. The
Danish Meteorological Institute has moreover performed calculations for a scenario which assumes
global anthropogenic increases in temperature of no more than 2ºC relative to the pre-industrial
level. This scenario is called 2C.
Climate simulations and our understanding of the uncertainties linked to them are improving all the
time. The Danish Meteorological Institute has calculated the figures in the tables presented in the
following and these figures are the most recent figures, based on EU studies in which a number of
climate simulations were run with several regional climate models 1 . Thus the assessments of future
climate change will be much more robust than if the figures had been based on only a single climate
model. The tables give the mean value of the model as best estimate, and the uncertainty range
indicates the standard deviation from the mean value of the results from the different models. This
means that, with the assumptions underlying the model simulations, there is a 68% probability that
a given future value will fall within the range.
Future global sea level rises depend on the melting of snow and ice as well as on increases in ocean
temperature. Projections of ice melt are associated with great uncertainty, and estimates for sea
level rises for the 21st century are therefore rarely linked to a well-specified climate scenario. The
sea level rises described in the following are best estimates by the Danish Meteorological Institute
and the Geological Survey of Greenland and Denmark on the basis of existing studies, and the
uncertainty range corresponds to a standard deviation.
When planning, assessing and performing risk analyses in connection with climate change
adaptation, it is important to think carefully about whether to include the whole spectrum of values
(as given by the uncertainty range) or to include only the indicated best estimate.
3.1 IPCC projections of future changes in climate
In its fourth and most recent report (Fourth Assessment Report (AR4) from 2007), the
Intergovernmental Panel on Climate Change (IPCC) concluded that there is a more than 90%
probability that most of the observed global warming since the middle of the 20th century can be
attributed to anthropogenic greenhouse gases. It is moreover very likely that continued emissions, at
1 An ensemble of 14 model runs is included for the year 2050 and an ensemble of 8 for the year 2100.
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