The 2009 United Nations Environment Program Yearbook 2009 confirms some astonishing things that happened in climate science last year. The following is straight from the report:
The changing climate is pushing many Earth systems towards critical thresholds that will alter regional and global environmental balances and threaten stability at multiple scales. Alarmingly, we may have already passed tipping points that are irreversible within the time span of our current civilization…
The news to date is bad and getting worse. Ice loss from glaciers and ice sheets has continued, leading to the second straight year with an ice-free passage through Canada’s Arctic islands and accelerating rates of ice-loss from ice sheets in Greenland and Antarctica. Combined with thermal expansion—warm water occupies more volume than cold—the melting of glaciers and ice sheets from the equator to the poles is contributing to rates and an ultimate extent of sea-level rise that could far outstrip those anticipated in the most recent global scientific assessment (IPCC 2007). There is alarming evidence that important tipping points, leading to irreversible changes in major Earth systems and ecosystems, may already have been reached or passed…
Climate feedback systems and environmental cumulative effects are building across Earth systems, demonstrating behaviors we cannot anticipate.
The potential for runaway greenhouse warming is real and has never been more clear.
For the second year in a row, there was an ice free channel in the Northwest Passage through the islands of northern Canada. But this year also saw the opening of the Northern Sea Route along the Arctic Siberian coast. The two passages have probably not been open simultaneously since before the last ice age, some 100 000 years ago (NERSC 2008).
The largest mass of ice in the Arctic covers the island of Greenland. In places, the ice sheet is three kilometers thick. If it melts, it will raise sea levels by an estimated six meters. Until recently, glaciologists presumed that the ice would thaw slowly over millennia, as warming at the surface of the ice sheet permeates downward and gradually melts the ice. That thinking is reflected in the IPCC fourth assessment report (IPCC 2007). But the ice sheet is currently losing mass much faster than would be expected if melting alone was to blame. Current losses are more than 100 cubic kilometers a year. New findings in 2008 revealed that the flow into the ocean of the Jakobshavn Isbrae glacier in western Greenland, one of the most important routes for ice loss, has doubled since 1997 (Holland and others 2008)… A new analysis of historical data on the extent of the Greenland ice sheet shows that total meltdown is quite possible as a result of warming on the scale that is being forecast for the next few decades (Charbit and others 2008).
Researchers estimated in 2008 that loss of ice from the West Antarctic ice sheet increased by 60 per cent in the decade to 2006 (Rignot and others 2008). Ice loss from the Antarctic Peninsula, which extends from West Antarctica towards South America, increased by 140 per cent.
The last IPCC assessment forecast that global sea levels would rise by between 18 and 59 centimeters in the coming century – just from the thermal expansion of warmer oceans and the melting of mountain glaciers (IPCC 2007). But since the report was completed, many researchers involved in that assessment have predicted that a much larger rise is possible, indeed probable. The new prediction originates in part from reassessments of the potential for physical breakup of the ice sheets of Greenland and Antarctica. For instance, a study presented at a conference of the European Geosciences Union at Vienna in April suggested that a rise of between 0.8 and 1.5 meters was most likely (Schiermeier 2008). Another study on the dynamics of ice-sheet loss argued that sea levels could rise by as much as two meters in the coming century as a result of outflows of ice from Greenland alone (Pfeffer and others 2008).
But whatever the detailed modeling may reveal, research in 2008 indicates that sea level rise – from thermal expansion, mountain glacier retreat, and ice sheet melt – is likely to be much greater and to arrive much sooner than believed even two years ago. No matter how quickly climate change is mitigated, sea level will rise.
For now, the evidence suggests that we may be within a few years of crossing tipping points with potential to disrupt seasonal weather patterns that support the agricultural activities of half the human population, diminish carbon sinks in the oceans and on land, and destabilize major ice sheets that could introduce unanticipated rates of sea level rise within the 21st century (Lenton and others 2008, Schellnhuber 2008).
United Nations Environment Program Yearbook 2009, Chapter 23, February 2009. http://www.unep.org/geo/yearbook/yb2009/PDF/3-Climate_Change_ UNEP_YearBook_09_low.pdf