Climate change impacts and vulnerability in Europe 2016

Changes in the climate system
Box 3.1
Projecting climate change with models
Climate models, often termed general circulation models (GCMs), are numerical models that simulate the climate system at
the global scale based on the physical, chemical and biological properties of its components, their interactions and feedback
processes, and accounting for its known properties (IPCC, 2013a) (Figure 3.3). Climate models are the most advanced
tools available for modelling the state of the climate system and simulating its response to changes in atmospheric
concentrations of greenhouse gases and aerosols. Models differ in their complexity, in the number of spatial dimensions
and in the complexity of describing physical, chemical or biological processes. Climate models are evolving towards Earth
system models (ESMs), which include a representation of the carbon cycle, an interactive calculation of atmospheric CO 2 or
compatible emissions, and other climatic components (e.g. atmospheric chemistry, ice sheets, dynamic vegetation and the
nitrogen cycle). The simulations of future climate depend highly on boundary conditions, which are not sufficiently known
for the future, and hence the results are highly uncertain. Most global climate change studies and assessments (including
IPCC AR5) have been using GCMs from CMIP5. These models simulate atmospheric processes at a horizontal resolution of
between 50 and 250 km and with 30 to 80 vertical layers, and the ocean processes at a horizontal resolution of between
20 and 150 km and with up to 40 vertical layers.
For more detailed regional climate impact assessments, regional climate models (RCMs) have been used. RCMs are limited
in area but can provide information on the climate in higher spatial resolution than GCMs. RCMs typically have a horizontal
resolution of between 2 and 50 km, which allows for a better representation of topographic features (e.g. mountain ranges)
and of regional-scale climate processes. As a result, they can provide more detailed projections of changes in regional
precipitation patterns, weather extremes and other climate events. The World Climate Research Programme CORDEX
(Jones et al., 2011) has developed a set of high-resolution downscaled climate data based upon the CMIP5 experiments with
various domains for different regions of the world, including Europe. The EURO-CORDEX study (Jacob et al., 2014; Kotlarski
et al., 2014) has used combinations of five different GCMs and seven different RCMs over the European region (approximate
27 °N–72 °N, 22 °W–45 °E), at a horizontal resolution of 12.5 km and representing the time period from 1951 to 2100.
As models differ in their use of numerical methods, the description of physical processes and the characterisation of climate
variability, their simulations of past and current climate show deviations from the observed climate. Furthermore, different
models provide somewhat different climate projections when forced with the same emissions scenario (see Section 1.3).
Nevertheless, the scientific community is confident that climate models provide credible quantitative estimates of future
climate change, as these models are based on fundamental physical laws and are able to reproduce the key features of
observed climate change. These projections are usually presented as a multi-model ensemble, in order to represent the
spread of possible future climate change.
Figure 3.3
Components needed for modelling climate change and its impacts
GCM
RCM
GHG emission and
concentration scenarios
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
Climate
models
Impact
models
Water
AOGCM projections
Downscaling
Impacts
Energy
Food
Ecosystems
Health
Note:
Source:
AOGCM, atmosphere–ocean general circulation model; GHG, greenhouse gas.
EEA.
66 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report