Projections of changes in the precipitation patterns in mountain are tenuous in most General Circulation Models because mountain toporaphy is poorly resolved and, as a result, the controls of topography on precipitation are not adequatly represented. It has also been recoginized that there are superimposed effects of natural modes o climate variability such as El Nino/ENSO, NAO... ...can perturb mean precipitation patterns on time scales ranging from seasons to decades. Such mechanisms are not well predicted by climate models.

Because temperature decreases with altitude by 5–10 ◦C/km, a first-order approximation regarding the response of vegetation to climate change is that species will migrate upwards to find climatic conditions in tomorrow’s climate which are similar to today’s (e.g., McArthur, 1972; Peters and Darling, 1985). According to this paradigm, the expected impacts of climate change in mountainous nature reserves would include the loss of the coolest climatic zones at the peaks of the mountains and the linear shift of all remaining vegetation belts upslope. Because mountain tops are smaller than bases, the present belts at high elevations would occupy smaller and smaller areas, and the corresponding species would have reductions in population and may thus become more vulnerable to genetic and environmental pressure (Peters and Darling, 1985; Hansen-Bristow et al., 1988; Bortenschlager, 1993). However, the migration hypothesis may not always be applicable because of the different climatic tolerance of species involved, including genetic variability between species, different longevities and survival rates, and the competition by invading species (Dukes and Mooney, 1999). Adaptation pathways in the face of changing environmental conditions include the progressive replacement of the currently dominant species by a more thermophilous (heat-loving) species. It is expected that, on a general level, the response of ecosystems in mountain regions will be most important at ecoclines (the ecosystem boundaries if these are gradual), or ecotones (where step-like changes in vegetation types occur). Those that reproduce slowly and disperse poorly, and those which are isolated or are highly specialized, will therefore be highly sensitive to seemingly minor stresses.

The hydrological cycle will be enhanced under warmer changing climatic conditions, the current distribution, seasonality, and amount of precipitation may undergo significant changes in various regions. The consequences for river runoff are likely to affect not only the watersheds within the mountains themselves,but also in the lowland regions that are heavily dependent on this mountain ressoures.

For every 1°C increase in temperature, the snowline will rise by about 150 m. Shifts in snow-pack duration and amount as a consequence of sustained changes in climate will be crucial factors in water avaibility for hydrological basins.

For assessing current and future trends in regional climate, the current spatial resolution of General Circulation Models (GCM) is generally too crude to adequately represent the orographic detail of most mountain regions. On the other hand, most impacts research requires information with fine spatial definition, where the regional detail of topography or land-cover are important determinants in the response of natural and managed systems to change.