Climate change and its impact - Mediterranean Mountain Environments - page 181

climatic changes in Mediterranean mountains (Nogues-Bravo et al., 2008a) predict
significant warming of between 1.6 ◦ C and 8.3 ◦ C for 2085, and even more impor-
tantly, climate models also project a reduction of precipitation, mainly during spring
(17% under A1FI and 4.8% under B1 for 2085; see Figure 9.1 for an explanation
on emission scenarios). This is of utmost importance as Mediterranean mountains
are the main sources of water supply to their usually dry and highly populated sur-
rounding lowlands. In this context, this chapter intends to assess the recent and
future trends of climate in Mediterranean mountains, to summarize recent impacts
and to couple the future implications of predicted climate change for human and
physical features. Specifically, the first part of this chapter is devoted to summa-
rizing recent trends of key climatic variables such as temperature of rainfall, and
to compare them against future projections. Then, we summarize impacts of cli-
mate change on the cryosphere and the hydrosphere, and finally we discuss climate
change impacts on biodiversity.
9.2 Climate change in Mediterranean mountains
Mediterranean mountains are expected to become warmer and to suffer a reduc-
tion of rainfall during the twenty-first century (Nogues-Bravo et al., 2008a). The
magnitude of this future climate change varies in relation to the economic, polit-
ical and technological future evolution of our societies; in other words, it varies
in relation to the different narrative storylines used to develop IPCC emission
scenarios(Figure 9.1). A future world with very rapid economic growth and in-
tensive fossil fuel use (A1FI could be considered a pessimistic scenario for the
future in terms of climate change) yields the warmest climate change scenario
(3.18 ◦ C in 2055 and 5.28 ◦ C in 2085). Even when we use the most optimistic
scenario, the expected warming rates (2.28 ◦ C and 2.88 ◦ C under B1 in 2055) will
become markedly more intense than the observed 0.76 ◦ C warming for the Mediter-
ranean Basin reported by Giorgi (2002) for the twentieth century. Similarly, pre-
dictions for the twenty-first century are much larger than the 0.98 ◦ C warming
observed, for example, in the Pyrenees during the twentieth century (Bucher and
Dessens, 1991). Also, climate models project reductions of annual and spring pre-
cipitation in the Mediterranean mountains (e.g. 11.3% and 17% during spring
under a pessimistic scenario for 2055 and 2085, respectively). Thus, Mediter-
ranean mountain ecosystems (structure, functions and services) will likely be sub-
ject to intensive transformation in the coming decades, even assuming the most
conservative estimates.
These projections are based on high-resolution Atmospheric-Ocean-coupled
General Circulation Models, AOGCMs. Downscaled climate models for specific
regions of the world, such as Regional Climate Models (RCMs), show similar
trends, and therefore confirm the ability of high-resolution AOGCMs to forecast
climate change in topographically complex areas. Specifically for the Pyrenees,