A decade of research in elevation dependent climate change (EDCC): A review of past discoveries and perspectives on future developments

Although the concept of enhanced mountain warming has been around for several decades, it was not until just over a decade ago that the concept of elevation-dependent warming, whereby warming rates may be stratified by elevation, was widely identified by the scientific community as an important phenomenon. Unlike Arctic amplification, which is broadly homogenous, elevation dependent warming (EDW) is more complex, and although systematic changes in warming rates over the elevation gradient are often present, the pattern of the elevation profile is often non-linear and it can change with season, time of day and location. This is probably because there are a wide variety of drivers which can be responsible for contrasting warming rates, including patterns of surface albedo change (often driven by retreating snow cover and/or vegetation changes), aerosol loadings (and deposition on snow), changes in the free atmospheric lapse rate, Planck feedback and moisture controls on downward longwave emission (DLR) and clouds. In any one season or location, one or more of these drivers may have a dominant impact, leading to contrasting elevation patterns of change. 
Over recent years there has been an acknowledgement that elevation dependent changes involve broad adjustments in the climate system, which includes vertical gradients of precipitation, condensation, wind speed and shear, humidity and clouds. There has been a change in emphasis from EDW towards EDCC (elevation-dependent climate change). However our understanding of elevation dependent changes in variables other than temperature is in its infancy, in part because of lack of reliable observations at high elevations. Mountain precipitation (rain and snow) is particularly hard to measure accurately, and gridded datasets often interpolate to higher elevations based on limited observations. 
Future developments in EDCC research must involve both improving high elevation observations and learning from the new tranche of convection permitting models which can explicitly resolve more atmospheric processes such as mountain slope winds and small scale convection. Particular questions concern how orographic precipitation gradients may change, both for widespread stratiform precipitation and more intense localised convective storm development (often in summer). How the frequency and intensity of extreme events in mountain regions will change is also an important unanswered question, in particular how enhanced hourly precipitation extremes and heatwaves will be impacting high elevation regions. How EDCC will interact with the rate of snow loss and cryospheric change is also a major area of future concern, including impacts on downstream water supply. Other areas of EDCC research which have so far received relatively little attention include teleconnections with large scale circulation features such as the jet stream and Asian Monsoons, and interactions with ecological zonation and habitat hypsometry. The impact on mountain micro-climates, including the frequency, intensity and location of cold air pools is also not well understood. Thus, there are still numerous unanswered questions about climate change in mountain regions and at high elevations.