Policy and Perspectives
Some of the impacts from changes in ice and snow are im-
mediately visible, often showing up as increased frequen-
cies of events that are within the range of natural varia-
tion. For example, winter roads might be open on average
fewer days in the Arctic; feeding conditions might be poor
for caribou and reindeer more frequently than in the past;
amount and timing of runoff from snowmelt in the An-
des, Alps or Himalayas might result in local water short-
ages in more years. Over time these short-term events
lead to longer-term consequences including changes in
biodiversity, ecosystems and regional economies.
In several chapters the theme of gradual and abrupt
changes is discussed. Projections for future change are
built on climate models, incorporating to the extent
possible the complexity of interactions and feedbacks
Photo: Christopher Uglow/UNEP/Still Pictures
among atmosphere, oceans and land. The results are
projections of incremental change – a bit warmer each
Wrap up of key messages decade, on average a bit more ice melting from the
Greenland ice sheet each year. This type of change is
The underlying theme in the preceding chapters is that somewhat predictable, as long as one takes into account
changes are now observed in ice and snow and bigger the natural year-to-year variability in climate conditions.
changes are projected. The greenhouse gases from past In discussing changes in ice and snow in the preced-
and current emissions remain in the Earth’s atmosphere ing chapters, authors reference the possibility of another
for decades to centuries. Most of the extra heat on Earth type of change – abrupt, ‘catastrophic’ and unpredictable
caused by emissions of anthropogenic greenhouse gas- change that results in a jump in the line on the graph, a
es is stored in the oceans. These two factors will lead to shift from one state to another. We know from ice cores
further changes in ice and snow no matter how quickly in Greenland that abrupt climate change may happen
the world acts to reduce emissions. There is a danger naturally. These ‘tipping points’ can be related to the
of this time gap between policy implementation and cryosphere itself. For example the break up of a section
real results leading to thinking that the situation is be- of an ice shelf in Antarctica may remove the plug at the
yond control – but the projections for future change also end of glaciers draining the ice sheet, leading to a sud-
make it clear that policies implemented now will have den increase in the rate of movement of land ice to the
a real impact in slowing global warming in the decades sea, directly translated into sea-level rise. Some of these
and centuries to come. abrupt changes are related to ecosystems, biodiversity
216 GLOBAL OUTLOOK FOR ICE AND SNOW