Projected Climate Change and Variability and Their Impact on the Canadian Rocky Mountains - Impact of Global Changes on Mountains: Responses and Adaptation - page 406

There have only been few model simulations to examine how mountain
regions will respond to climate change, due mainly to the fact that the
present global and regional climate models do not possess suffi ciently
adequate spatial resolution to resolve the topographical details of the
mountains, as well as the detailed characteristics of the surface, such as
various ecosystems (vegetation, snow/ice, etc.), that are needed to properly
represent such important feedback mechanisms as snow/ice albedo
feedback. But also in the case of precipitation, the infl uence topography
has on precipitation process is not adequately represented in models, not
only in terms of spatial resolution but also in terms of the basic physics.
In addition to the overall trend in climate change on a multi-decadal
scale, the west coast of North America is also influenced by ENSO
(El-Niño and Southern Oscillation), one of the prominent low-frequency
variability modes of the atmosphere. ENSO is a quasi-periodic oscillation
that switches between El Niño (the warm SST anomaly phase of the tropical
Pacifi c Ocean) and La Nina (the cold SST anomaly phase of the tropical
Pacifi c Ocean) with an average period of about 4 years (ranging from 2 to
7 years) (MacMynowski and Tziperman 2008). ENSO is a manifestation of
a set of complicated processes of nonlinear air-sea feedback interactions,
and it produces inter-annual and decadal variability in temperature and
precipitation patterns of the western portion of Canada (Zhao et al. 2012,
Bonsal and Shabbar 2011, Shabbar et al. 1997, Shabbar and Khandekar 1996)
that has signifi cant impact on the mountain ecosystems and freshwater
supply downstream. See Fig. 18.5. Yet, at the present time, “despite
considerable progress in our understanding of the impact of climate change
on many of the processes that contribute to El Niño variability, it is not yet
possible to say whether ENSO activity will be enhanced or damped, or if
the frequency of events will change” (Collins et al. 2010).
Simulations of the present climate by the models in the mountain
regions are relatively unrealistic and perhaps not so reliable because of
inadequate understanding of some of the physical processes that generate
the observed climate and the lack of suffi cient spatial resolution to represent
even those processes we understand well. The models are also defi cient in
realistically reproducing the characteristics of ENSO which has signifi cant
impact on the Canadian Rockies. However, because of the importance of
the impact of climate change in the Rockies will have, not only within the
mountain regions, but also downstream in the Canadian prairies (affecting
the socio-economic and ecosystem functions there), we need to address these
impacts and explore possible consequences based on available observational
evidence and existing climate model projections that are based on our
understanding of physical mechanisms that operate in the mountainous
regions (IPCC-AR4 2007).