Tipping elements in the Earth's climate system
Global change may appear to be a slow and gradual process
on human scale, however a number of key components of the earth’s
climate system could pass their 'tipping point' this century, according
to new research led by an international team of scientists. In some
regions, changes in the climate could "kick start" abrupt
and potentially irreversible changes.
Research published last month in the "Proceedings
of the National Academy of Sciences" (PNAS), states that a number
of key components of the earth's climate system could pass their "tipping
point" this century, creating large long-term consequences on
human and ecological systems. Researchers have coined a new term, 'tipping
elements', to describe those components of the climate system that
are at risk of passing a tipping point.
"Society may be lulled into a false sense of security by smooth
projections of global change," Timothy Lenton from the British
University of East Anglia in Norwich and Hans Joachim Schellnhuber
from the Potsdam Institute for Climate Impact Research report.
Drawing on a workshop of 36 leading climate scientists in October
2005 at the British Embassy, Berlin, Germany, a further elicitation
of 52 experts in the field, and a review of the pertinent literature,
the authors compiled a short-list of nine potential tipping elements.
These nine elements have been ranked as requiring the highest consideration
in international climate politics and policy. Most of them could be
tipped within the next 100 years.
The nine tipping elements and the time it will take them
to undergo a major transition are:
• Melting of Arctic sea-ice (approx 10 years)
• Decay of the Greenland ice sheet (more than 300 years)
• Collapse of the West Antarctic ice sheet (more than 300 years)
• Collapse of the Atlantic thermohaline circulation (approx 100 years)
• Increase in the El Nino Southern Oscillation (approx 100 years)
• Collapse of the Indian summer monsoon (approx 1 year)
• Greening of the Sahara/Sahel (approx 10 years)
• Dieback of the Amazon rainforest (approx 50 years)
• Dieback of the Boreal Forest (approx 50 years)
Arctic sea-ice and the Greenland Ice Sheet are regarded as the most sensitive
tipping elements. These elements are "candidates for surprising society
by exhibiting a nearby tipping point," the authors state in an article
published in PNAS Online Early Edition.
The West Antarctic Ice Sheet is probably less sensitive, facing greater
uncertainty as a tipping element, researchers have determined. This
also applies to the Amazon rainforest and Boreal forests, the El Niño
phenomenon, and the West African monsoon.
Source: Potsdam Institute for Climate Impact
Research
http://www.pik-potsdam.de/
