Page 12 - climate-change2013

Modelling change Natural Volcanic CO vents of Italy used to assess the

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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
2
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
A2
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
B1
20
IS92a
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.

10 COLLECTION