Geology Reference
In-Depth Information
15
Climate Change and
Periglacial Environments
This chapter examines the impact of predicted climate change upon periglacial envi-
ronments. Emphasis is placed upon permafrost, seasonal snow cover, and vegetation
changes. All will be signifi cantly affected by enhanced atmospheric concentrations of
greenhouse gases.
Projected climate changes will most likely lead to decreases in the global extent of
permafrost, seasonal snow cover, and sea ice. This will affect both local and global
hydrology (meltwater fl ow, peak discharge, seasonal distribution of runoff, and sea-level
rise), nature and distribution of plants and animals, local and regional terrain instability
(thermokarst, slope failures, and other mass movements), and urban infrastructures.
15.1. GLOBAL CHANGE AND COLD REGIONS
Over 15 years ago, in 1990, The Intergovernmental Panel on Climate Change (IPCC)
Scientifi c Assessment predicted an increase of global mean temperature during the fol-
lowing century of about 0.3 °C per decade (Houghton et al., 1990). This was based upon
assumptions concerning present and future emissions of greenhouse gases, especially
carbon dioxide (CO
2
) and methane (CH
4
). Several general circulation models (GCMs),
based upon a doubling of CO
2
, suggested that changes for the months of December-
January-February would be of the order of 8-12 °C (Houghton et al., 1992) and that mean
surface temperature may rise by 1.5 °C to 4.5 °C by the middle of the twenty-fi rst century.
More recently, in 2001, The Intergovernmental Panel on Climate Change (IPCC) Third
Assessment Review (Anisimov et al., 2001) has confi rmed these trends. It is generally
accepted that human activity is the major cause of the increase in greenhouse gases.
However, it is also being suggested that pre-industrial anthropogenic changes rival those
of the industrial era (Figure 15.1) (Ruddiman, 2004). Long-term climatic variability must
also be considered. Whatever the exact cause, it is clear that global temperatures rose in
the twentieth century at a rate unprecedented in the last millennium (Bradley, 2000). In
2006, a National Oceanographic and Atmospheric Administration (NOAA) report indi-
cates that the average concentration of CO
2
in the atmosphere has increased over the
previous 40 years from 315 parts per million to 381 parts per million.
It is clear, therefore, that the periglacial environments of the world will be affected
by these changes. Unknown is the speed at which these changes will occur. However,
it is predicted that land surfaces will warm more rapidly then oceans and that high lati-
tudes will warm more than the global mean, particularly in winter. All aspects of the
landscape will be affected, including permafrost, cryogenic processes, snow, sea-ice cover,
