Page 12 - climate-change2013
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Modelling change                            Natural Volcanic CO  vents of Italy used to assess the

                                                                 response of communities to increased seawater acidity.
                     When dealing with climate change, we should con-
                     sider projections instead of forecasts. For example, the
                     weather or the state of the sea (waves, currents) can
                     be forecast with some accuracy over a short period of
                     days as they are subject to well-known physical laws.
                     Projections, on the other hand, indicate that the out-
                     come is conditional on some hypothesis about the fu-
                     ture, such as the rate of CO  emissions in an externally
                     prescribed economic scenario.
                     The evolution of the climate partly depends on physical
                     laws, but also on variables which cannot be predicted
                     with certainty, such as future greenhouse gas emission                       Photo: J. Hall-Spencer
                     rates, the development and use of energy technologies,
                     or the growth of the human population. Therefore, the
                     Intergovernmental Panel on Climate Change (IPCC) has   The scenarios can provide good estimates of future
                     constructed different plausible scenarios for the evolu-  greenhouse emissions and give information about the
                     tion of these factors in order to project the future state   uncertainty associated with any particular climate mod-
                     of the climate.                                el prediction.
                                                                    A variety of models have been developed, from one-
                     The IPCC issues comprehensive reports          dimensional energy-balance models through models of
                     every five to seven years, with the next one   intermediate complexity to fully coupled atmosphere–
                     due out by the end of 2013. The reports        ocean general circulation models (AOGCMs), describ-
                     summarize the state of scientific knowledge    ing the atmosphere, oceans, sea ice and land, and pos-
                     on climate change, and are used as the         sibly chemistry, the carbon and nutrient cycles and ice
                     underpinning of international climate talks    sheets. The level of uncertainty of each of them varies
                     aimed at reducing greenhouse gas emissions     when the variables are projected into the future, pro-
                                                                    ducing a range of possible results. Nevertheless, global
                                                                    climate models rarely give adequate resolution for man-
                                                                    agement on a regional scale such as the Mediterrane-
                                                                    an. For this reason, regional models are now being de-
                     Computer-generated models have been built from   veloped so that climate can be predicted in finer detail
                     these scenarios, the evolution of the earth’s climate   and at smaller spatial scales applicable to specific geo-
                     over the last century and the available observations to   graphical regions in the Mediterranean (Lionello, 2012).
                     estimate how air and seawater temperatures, precipita-
                     tion, salinity and other variables will change in the dif-  Regional climate models can currently make projec-
                     ferent scenarios considered (Christensen et al., 2007).   tions for spatial areas smaller than those considered in
                                                                    general circulation models, with spatial resolutions of
                                                                    25 km or better, but this resolution is still too low for
                                                       Scenarios    the management of protected areas. Given that the ob-
                                                          A1B       servational data needed to build these models is not
                    25                                    A1T       yet available at high spatial resolution (Vargas-Yáñez et
                                                          A1FI      al., 2012), the information currently provided by these
                  CO 2  emissions (Gt C)  15              B2        interest is currently insufficient to aid in producing ad-
                                                                    models about the evolution of sites of special ecological
                                                                    aptation and conservation strategies for Mediterranean
                                                                    MPAs. For the future, regional models clearly need to
                    10                                              improve if they are to provide projections that can serve
                                                                    this purpose.
                    5                                               Modelling efforts at high spatial resolutions (less than 1
                        2000  2020  2040  2060  2080  2100          km) might, however, be able to cope with the complex
                                                                    coastal  hydrodynamic  processes  that  exist  in  some
                                                                    MPAs and help to simulate climate change scenarios
                       Scientists use a range of scenarios based on vari-  at smaller scales. This type of approach could provide
                       ous assumptions about future economic, social,   managers with a clear picture of expected changes in
                       technological and environmental conditions and al-  temperature regimes, including summer stratification
                       ternative development pathways. A1B refers to one   variations, in the areas for which they are responsible.
                       of the scenarios described in the Special Report on   Nevertheless, more research into management tech-
                       Emissions Scenarios prepared by the IPCC in 2000.   niques and greater efforts to gather basic monitoring
                       It relates to a scenario with very rapid economic   data will be needed to develop an understanding of
                       growth, peaking global population and balanced
                       use of fossil and non-fossil energy sources.  how MPA environments might shift in response to cli-
                                                                    mate change.

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