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Climate change has changed
Presented by WWF
Recent observations of ice, atmospheric CO2 and methane, sea level rise and global emissions of
greenhouse gases indicate that climate change is impacting natural systems, including the oceans,
sooner than predicted in existing modelling and scenarios. Early signs suggest that feedbacks are
active now, from marine and coastal environments, which are accelerating climate change and that
some tipping points have been passed. Many of these processes are not included in standard
climate modelling and predictions. Mitigation efforts are increasingly urgent.
What has changed?
Since the compilation of the most comprehensive and up to date science; the IPCC’s AR4,
published in 2007, several aspects of climate science, understanding and observations in the field
have advanced.
● The melt of Arctic summer sea ice in summer September 07 and the record amount of thin and
young sea ice in the winter of 2008 demonstrate that the Arctic is losing sea ice decades ahead of
projections. This triggers feedback mechanisms which accelerate global warming, climate change
and impacts further and faster than currently documented. The majority of Arctic sea ice scientists
declare that the Arctic sea ice is past its tipping pointi, the point at which change becomes selfperpetuating until an altogether different state is reached. NSIDC suggest that the North Pole may
be ice free this summerii.
● 2007 saw another high in the growth of atmospheric CO2 in recent yearsiii. This coincides with a
reduction of the natural carbon sink capacity of the oceans, for example seeiv. Data show that
atmospheric CO2 levels are higher than the IPCC worst case scenario, A1F1v.
● Atmospheric methane concentrations have begun to rise again, after a plateau of 10 years. The
source of this methane appears to be from northern wetlands, strongly suggesting that the release
of methane from boreal and Arctic soils is accelerating vi.
● Sea level is rising faster than forecastvii and some oceans are acidifying faster thanviii;
● Many of the processes observed and detailed above have the potential to feedback to the climate
system, exacerbating and accelerating climate changeix. Indications suggest that in some
examples, the feedbacks have become active already.
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Why does this matter?
The changes in the Arctic matter in particular for two reasons:
i) Speed and causes of impacts. For several key Arctic systems, recently observed changes are
happening at rates significantly faster than accommodated for in climate models. This reflects the
current limits of scientific understanding of essential processes controlling these Arctic systems and
therefore raises questions about the range of predictions that guide mitigation strategies to date.
ii) Potential to cause more positive feedback. The most prominent result from losing Arctic sea ice is
a positive feedback to warming through the albedo effect, with potentially dangerous
consequences. Further consequences will include warming of Arctic shallow shelf seas and the
very real danger of release of methane from shallow shelf seas and coasts. Early evidence
suggests that methane is increasingly being released from these sources already. Additionally, the
Greenland Ice Sheet could also be impacted by loss of Arctic sea ice, through regional warming.
The rate of loss of Greenland Ice Sheet has increased three fold between 2004-2006. It is
estimated that if Greenland temperatures rise 3oC above pre-industrial levels, the Greenland ice
sheet may pass a tipping point and be committed to complete lossx. Loss of Greenland ice has the
potential to increase global sea levels by 7.2m over time. NASA’s Hansen recently predicts 3-5m
sea level rise by 2100xi.
How does this fit in with the other climate science ?
Looking at the data in the table below, even big cuts in CO2 emissions carry a serious risk of
exceeding 2oC. We have passed the levels of greenhouse gases in the atmosphere which we would
need to stabilise at in order to have a chance of staying below 2 oC. If we stabilise at current levels,
we will likely exceed 2oC. What the Arctic is telling us, is that 2oC is too much. Pacific Islanders
echo the same conclusion. It is reported that in the past (Pliocene), when global average
temperatures were 2-3oC warmer than now and CO2 was around 385-425ppm, sea levels were 25m
higher than now (plus or minus 10m)xii. Greenhouse gas levels have risen above the desired
stabilisation target of atmospheric greenhouse gas concentrations, but it is considered that if this is
followed by a steep decline in emissions, that it may still be possible to limit temperature rise to
below 2oC. However, the modelling clearly demonstrates that any delay, even a few years, in the
peak and decline, significantly reduces the possibility to stay even below 2 oC. The table below
summarises some data released pre 2007/8 field observations, so these may be an underestimate.
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Status in 2007
IPCC 2007xiii
IPCC 2007ibid
(NASA)
Hansen et alxiv
(ippr)
Baer and
Mastrandreaxv
Meinshausenxvi
Parry et al.xvii
Projected or
target global
mean temp
rise since
pre-industrial
0.76oC
Associated
CO2 ppm or
Equivalents
Stabilisation
level.
385ppm CO2
430equiv
2-2.4oC in B1, 350-400 CO2
best scenario
0.6-1.4oC
350equiv
1.7oC total
300-350ppm
CO2
o
<=2 C total
366-380ppm
CO2
2oC total
2oC
Predicted
sea level
rise by
2100 in
metres
17mm/y
Peak in
emissions
by given year
or since paper
published
Associated
Reduction in
global CO2
emissions by
2050
0.5m
2000-2015
50-85%(or more)
below 2000 levels
3 to 5m
A few years
Risk of overshooting 2oC
350equiv=0-31%(mean 8%)
400equiv =2-57%(mean 27%)
400-470ppm
CO2 equiv
2010
81% below 1990
= 9-26% risk of
exceeding 2oC
For 400ppm 30-40% below
CO2 e model, 1990 levels
2-5y from ‘06
80% below 1990
When the predictions for emissions targets and temperature increase targets are combined with the
new field observations from 2007 and 2008, it becomes clear that the system seems to be reacting
faster and more sensitively than predicted. The modelling and predictions need to be updated and
the mitigations targets established on the basis of these re-calculated data.
Conclusions
This new information indicates that many aspects of climate change have been underestimated; the
impacts are felt sooner, the feedbacks are active sooner, the climate is more sensitive than
anticipated and the models used for IPCC 4th AR have failed to accurately predict the pace of
change. While it is already considered a challenge to limit global average temperature rise to below
2oC, given the impacts underway, the feedbacks in action and tipping points, it is now highly likely
that a rise of 2oC would be too much. The aim of UNFCCC is to avoid “dangerous interference with
the climate system”; the changes now underway and the feedbacks in action indicate that we may
have already reached ‘dangerous’ levels of climate change. The implication of this recent evidence
is that our mitigation and adaptation responses to climate change now need to be more rapidly
implemented and greater than previously assessed.
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i
ii
WWF, 2008. Arctic Climate Impact Science – an update since ACIA. Pp 1-123.
National Snow and Ice Data Centre, 2008. http://nsidc.org/Arcticseaicenews/2008/050508.html
iii
Pieter Tans, NOAA/ESRL, ph. 303 497 6678, [email protected],
http://www.esrl.noaa.gov/gmd/ccgg/trends/
iv
Le Quéré, C et al. 2007. Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change.
Science 316:1735-1738.
v IPCC, 2000. A Special Report of Working Group III of the IPCC, Based on a draft prepared by:N.
Nakic´enovic´, O. Davidson, G. Davis, A. Grübler, T. Kram, E. Lebre La Rovere, B. Metz,
T. Morita, W. Pepper, H. Pitcher, A. Sankovski, P. Shukla, R. Swart, R. Watson, Z. Dadi.
vi
Hofmann, D. 2008. The NOAA Annual Greenhouse Gas Index. NOAA Earth System Research Laboratory,
R/GMD, 325 Broadway, Boulder, CO 80305-3328
vii Surminski, S. 2008, Insurance Risk at the Coast. In, Proceedings of the Coastal Management for
Sustainability, Coastal Futures 2008 – Review and Future Trends
viii
Feely, R., C. Sabine, M. Hernandez-Ayon D. Ianson and B Hales, 2008. Evidence for Upwelling of
Corrosive "Acidified" Water onto the Continental Shelf. Science DOI: 10.1126/science.1155676
ix
Reid, C. et al., 2008, Impacts of the Oceans on Climate Change. Submission to OSAPR Commission.
ACIA, 2005. Arctic Climate Impact Assessment, Cambridge, Cambridge University Press.
xi Hansen, J., Sato, M., Pushker, K, Beerling, D., Masson-Delmotte, V., Pagani, M., Raymo, M., Royer, D. and
Zachos, J. 2008. Target Atmospheric CO2: Where Should Humanity Aim?. Pp1-38.
xii Hansen, J., M. Sato, P. Kharecha, G. Russell, D. Lea and M Siddall, 2007. Climate change and trace
gases. Phil Trans Royal Soc. A. (2007) 365, 1925-1954.
xiii Solomon, S., et al., 2007: Technical Summary. In: Climate Change, 2007: The Physical Basis. Contribution
to Working Group I to the Fourth Assessment Report of the IPCC. Cambridge University Press, UK and USA.
xiv Hansen, J., Sato, M., Pushker, K, Beerling, D., Masson-Delmotte, V., Pagani, M., Raymo, M., Royer, D.
and Zachos, J. 2008. Target Atmospheric CO2: Where Should Humanity Aim?. Pp1-38.
xv Baer, P. and Mastrandrea, M. 2006. High Stakes: Designing emissions pathways to reduce the risk of
dangerous climate change. ippr. Pp 1-37.
xvi Meinshausen, M. 2006. What Does a 2°C Target Mean for Greenhouse Gas Concentrations? In Avoiding
Dangerous Climate Change, Editor, Schellnhuber. Camb Uni Press. Pp 1-406.
xvii Parry, M., Palutikof, J., Hanson, C., Lowe, J. 2008. Climate Policy: Squaring up to Reality. Nature Reviews,
Climate Change. 29th May 2008.
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