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WWF Backgrounder
If you think higher greenhouse gas
mitigation pledges can’t be afforded,
see what the Arctic is going to throw in
The pledges of greenhouse gas reductions made to date under the Copenhagen Accord are not
enough to protect the Arctic from a major thaw. This will cause global consequences affecting
the livelihood of more than a quarter of the world’s population, and enormous human, ecological
and financial costs.
Up-to-date science shows that only 2 out of 10 developed countries’ reduction targets submitted
to the Copenhagen Accord qualify as ‘sufficient’ to keep global temperature rise below 2
degrees C, compared to pre-industrial levels. The reduction targets of all countries currently
associated with the Accord do not even come close to meeting the 2 degrees C average global
warming goal defined in the Accord. The current pledges leave the world heading for global
warming of over 3 degrees C above pre-industrial levels by 2100 (Ecofys, 2010).
The Arctic has warmed at about twice the rate of the rest of the globe in response to humaninduced global warming over the past few decades and is forecast to continue this amplified
warming over the 21st century (IPCC, 2007). A global mean temperature rise of over 3 degrees
Celsius over pre-industrial levels by the year 2100 is close to the best estimate of the IPCC
SRES scenario A2 (3.4 degrees C) for the same period. Under this scenario, the Arctic would
warm by 7 degrees C and more by the year 2100 (Figure 1).
Figure 1. Multi-model mean of annual mean surface warming (surface air temperature change, degrees C) for the
IPCC SRES A2 scenario, and three time periods. The best estimate of mean global temperature rise by the year
2100 projected by the A2 scenario (3.4 degrees C) is close to what would result from the current pledges to the
Copenhagen Accord, and projects mean arctic warming of 7 degrees C and more for the year 2100. (Source: Figure
10.8., IPCC, 2007)
Evidence shows that the current mean global warming of less than 1 degree C is already
destabilising important arctic systems including sea ice, the Greenland Ice Sheet, mountain
glaciers, and aspects of the arctic carbon cycle including an increase of methane release from
soils, lakes, and wetlands (Richter-Menge et al., 2009). More than 7 degrees C projected arctic
warming by the year 2100 will have a dramatic impact on the Arctic’s physical systems,
ecosystems, and biodiversity resulting from large-scale deterioration and loss of all frozen
elements of the Arctic (AMAP, 2009a). The resulting loss of landscape integrity and ecosystem
services will have grave effects on Arctic peoples, regional economic infrastructure, and will
directly affect global food supplies such as arctic fisheries that currently contribute a large
proportion of fish to both Europe and North America are forecast to decline (ACIA, 2005).
In addition to the regional consequences of arctic climate change are its global impacts. Acting
as the Northern Hemisphere’s refrigerator, a frozen Arctic plays a central role in regulating
Earth’s climate system. A number of critical arctic climate feedbacks affect the global climate
system, and there is now emerging evidence and growing concern that these feedbacks are
beginning to accelerate global warming significantly beyond the projections currently being
considered by policymakers. With an arctic warming of 7 degrees C and more, as now projected
for the year 2100, all these arctic climate feedbacks would be triggered and would significantly
accelerate global climate change (Sommerkorn and Hassol, 2009).
For example, the additional heat absorbed by an increasingly ice-free Arctic Ocean in summer
is already accelerating local and regional warming and preventing sea ice from recovering. This
“arctic amplification” will become more pronounced as more ice cover is lost over the coming
decades. The most recent comprehensive research suggests that the Arctic Ocean will lose its
summer sea ice cover as early as in the late 2030s (Figure 2).
Figure 2. September sea ice extent as projected by six IPCC models that simulated the mean minimum and
seasonality with less than 20 per cent error of the observations up until 2007. All six models show rapid decline in the
ice extent and reach ice-free summer (<1.0 Million square kilometres) well before the end of 21st century. The
median duration interval of all models for the sea ice to reduce from 4.6 (in 2007) to 1.0 Million square kilometres is
30 years. This provides an expected value for a September nearly sea ice free Arctic in the year 2037 (Source: Wang
& Overland, 2009).1
1
The coloured thin lines represent each ensemble member from the same model under A1B (blue solid) and A2 (magenta dashed) emission
scenarios, and the thick red line is based on HadISST analysis. The best estimate of mean global temperature rise by the year 2100 projected by
the A2 scenario is close to what would result from the current pledges to the Copenhagen Accord. Grey lines in each panel indicate the time
series from the control runs (without anthropogenic forcing) of the same model in any given 150 year period. The horizontal black line shows
Take the Arctic Ocean’s ice cover out of the equation and we are left with a very different, much
warmer world. The loss of arctic sea ice and snow cover is accelerating northern hemisphere
warming as the additional heat absorbed by the darker surfaces warms the atmosphere in
autumn and early winter. With ongoing warming this is projected to alter weather patterns in the
Arctic, Europe and North America, affecting agriculture, forestry and water supplies
(Sommerkorn and Hassol, 2009).
An even larger concern arises from the increased warming spreading over high-latitude land
areas, hastening degradation of permafrost and leading to increased release of greenhouse
gases, such as methane and CO2 from thawing soils (Figure 3). Arctic emission estimates over
this century are between 50 to 110 gigatonnes of carbon — a similar amount of that predicted to
be released by some middle- to top-range global deforestation scenarios during the same
period (Zhuang et al., 2006). The combined effect of the additional heat absorbed and the
additional greenhouse gases emitted into the atmosphere will lead to substantial further global
warming, adding significantly to current projections of human emissions of greenhouse gases.
a)
b)
Figure 3. a) Expected surface air temperature trends associated with periods of rapid sea ice loss (left) and moderate
or no ice loss (right) during this century. Rapid ice loss promotes strong warming over the Arctic Ocean, but
atmospheric circulation spreads the heat out to influence land areas far from the costs, potentially leading to thawing
of permafrost and release of stored carbon to the atmosphere. (Source: Lawrence et al., 2008a). b) Time series of
simulated global permafrost area (excluding glacial Greenland and Antarctica). As much as 90 per cent of the nearsurface permafrost may disappear by the end of this century. This has the potential to release large amounts of
carbon into the atmosphere, contributing significantly to warming (Source: Lawrence et al., 2008b). Both simulations
were made with IPCC SRES scenario A1B that predicts less warming than the A2 scenario that forecasts similar
warming as caused by the current mitigation pledges to the Copenhagen Accord.
A similarly direct feedback link to the globe from a warming Arctic is the contribution of the
melting Greenland Ice Sheet to global sea level rise. The ice sheets on Greenland and
Antarctica are melting into the ocean faster than expected. Melt rates are sensitive to climate
and are accelerating as both land and ocean temperatures rise. The net ice loss from the
Greenland Ice Sheet has accelerated two-to three-fold over the last decade (Chen et al., 2006)
(Figure 4) and if those trends continue sea level will rise worldwide by 31 centimetres from
Greenland alone by the year 2100 (Sommerkorn and Hassol, 2009). Global sea level rise by the
year 2100 is now projected to be more than 1 metre (Figure 5), largely due to increased mass
loss from the ice sheets. This is more than twice the projection of IPCC (2007).
the ice extent at 4.6 million square kilometres value, which is the minimum sea ice extent reached in September 2007 according to HadISST
analysis.
Figure 4. Changes in mass of the Greenland Ice Sheet from 1958-2007. The blue diamonds are observations of ice
discharge and snowfall combined. The blue curve fills in data gaps by using a linear reconstruction of anomalies in
ice discharge from anomalies in surface runoff (snow and ice melt) (Source: Rignot et al., 2008).
Figure 5. Future sea-level rise based on simple relationship between rate of sea-level rise and global average
temperature. Projecting global sea level rise this way is currently thought to yield the most realistic result, as
mechanistic models of ice sheet dynamics are not yet available (Source: Rahmstorf, 2007).
Scientists warn now that with ongoing warming ice sheet melt will continue irreversibly on
human timescales and will be the primary contributor to sea-level rise far in the future, well
beyond this century (AMAP, 2009b). In the last interglacial (a period between ice ages), when
global air temperatures were only 2 to 3 degrees C above present temperatures, sea level was
4 to 6 metres higher (Jansen et al., 2007). During that period, a large part of the ice sheets on
Greenland and West Antarctica had melted into the sea. It is almost certain that if the Earth
experienced the same climate again, it would only be a matter of time before the ice sheets and
global sea level would reach that state again (Gregory et al., 2004).
Sea-level rise is a major concern for populations living in low-lying coastal regions because it
will give rise to inundation (both temporary and permanent flooding), wetland loss, shoreline
erosion, saltwater intrusion into surface water bodies and aquifers, and a rise in water tables.
The livelihood of more than a quarter of the world’s population will be affected by sea level rise
of this magnitude (Nicholls 2007). The insurance industry has recently estimated global sea
level rise of 0.5 metres by 2050 to increase the value of assets at threat in all 136 global port
mega-cities by around 25 000 billion US Dollars, as a result of combined changes of sea level
and projected socioeconomic factors such as urbanization and increased exposure of the
resulting greater coastal population (WWF & Allianz, 2009).
Global feedbacks arising from arctic climate change suggest that anything but the most
ambitious constraints on greenhouse gas concentrations may not be sufficient to avoid
dangerous human interference with the climate system. To stay below the 2 degrees C of
warming compared to pre-industrial levels requires that a global carbon emission budget until
2050 of 886-1158 gigatonnes CO2 cannot be exceeded (Meinshausen et al., 2009). Such a
budget corresponds to a 20-33 per cent risk of exceeding the 2 degrees C of warming and
would likely avoid triggering climate feedbacks that accelerate global warming beyond control
and cause global upheaval and runaway costs to society.
The current pledges, equivalent to an IPCC SRES A2 scenario, will leave mankind with zero
chance to avoid such upheaval and costs (Figure 6, top right).
Figure 6. The probability of exceeding 2 degrees C warming versus CO2 emitted in the first half of the twenty-first
century. a) Individual scenarios’ probabilities of exceeding 2 degrees C (dots; for example, for SRES B1, A2, Stern
and other scenarios) and smoothed (local linear regression smoother) probabilities for all climate sensitivity
distributions (numbered lines). Coloured areas denote the range of probabilities (right) of staying below 2 degrees C
in IPCC (2007) terminology. b) Total CO2 emissions already emitted between 2000 and 2006 (grey area) and those
that could arise from burning available fossil fuel reserves, and from land use activities between 2006 and 2049
(median and 80 per cent ranges). The A2 scenario at top right results in 100 per cent probability to exceed 2 degrees
of warming, as would the current pledges to the Copenhagen Accord. (Source: Meinshausen et al., 2009).
Contact:
Keith Stewart, Climate Change Program Director, WWF-Canada, 416-985-5936,
[email protected]
Martin Sommerkorn, WWF International Arctic Programme, Oslo, Norway,
[email protected], +4792606995
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