Scientific aspects of UNFCCC Article 2, Stabilisation scenarios, and Uncertainty. Ben Matthews...

Scientific aspects of UNFCCC Article 2, Stabilisation scenarios, and Uncertainty.

Ben Matthews [email protected]

Jean-Pascal van Ypersele [email protected]

Institut d’astronomie et de géophysique G. Lemaître,

Université catholique de Louvain, Louvain-la-Neuve, Belgium

Web: www.climate.be (UCL-ASTR)

jcm.chooseclimate.org (interactive model)JCM also developed with: DEA-CCAT Copenhagen,

UNEP-GRID Arendal, KUP Bern

For European Strategy on Climate Change, Firenze 11th Sept 2003

In preparation for WCCC2003 Moscow

Jean-Pascal van Ypersele ([email protected])

Framework Convention on Climate Change (Rio, June 1992)

Ultimate objective (Art 2): 'stabilization of greenhouse gas concentrations

in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient - to allow ecosystems to adapt naturally to climate change, - to ensure that food production is not threatened and - to enable economic development to proceed in a sustainable manner.'

Article 2 in IPCC AR4

IPCC Plenary decided «the scientific, technical, and socio-economic issues associated with Article 2 » would be a CCT in AR4.

Scoping paper suggests a structure:

WEHAB framework to assess Key Vulnerabilities

=>Critical Limits (thresholds) of climate parameters

=>Critical Levels (e.g. Concentrations)

=>Possible Emissions Pathways

including Risk/Uncertainty framework


Temperature and « reasons for concern »

Source: IPCC WG2 (2001)

EU 2C Target

In practice, global debate will revolve around simple indicators, e.g. Global Annual Average Temperature

EU Council Of Ministers 1996 "the Council believes that global average temperatures should

not exceed 2 degrees Celcius above pre-industrial level and that therefore concentration levels lower than 550 ppm CO2 should guide global limitation and reduction efforts.

This means that the concentrations of all GHGs should also be stabilised. This is likely to require a reduction of emissions of GHGs other than CO2, in particular CH4 and N2O"


Stabilisation scenarios:Uncertainty depends on Indicator

Sets of scenarios stabilising Concentration, Forcing, Temperature, (Sea-level), all reaching equivalent 2C level on average

Core science very similar to IPCC-TAR models, Over 3000 variants of model parameters per set- probabilistic approach.

Carbon cycle: LUCF emissions, CO2 Fertilisation, T-Respiration feedback, Ocean mixing

Other gas emissions: Scaled so all gases (inc Sulphate and Ozone precursors)

reduced by same proportion with respect to 6 SRES baselines

Forcing/Climate Sensitivity: Vary Solar and Sulphate forcing 7 GCM parameterisations as IPCC TAR (apx9.1) Constrain combinations by consistency with historical temperature

record ( ¾ variants rejected )

Caveats

The distributions are skewed (e.g. for stabilising Temperature=2C, mean CO

2 concentration is 475ppm, the lower end of plotted range. This is due

to nonlinearities).

Climate Sensitivity may be higher than TAR model range (and increasing at higher temperatures). Not well constrained by historical temperatures.

Mitigation of other gases in proportion to CO2 (reduction wrt SRES) is a

simplistic assumption. Beter to have socioeconomic/landuse model.

Uncertainty in several factors not yet considered: Atmospheric chemistry, Ice-melting etc.

Shape of land-use emissions curve influences terrestrial carbon-cycle balancing


Inertia in the climate systemStabilising CO2 alone doesn't stabilise temperature (as below from TARSYR Q6)However stable CO2 may correspond to stable Temperature if other gases with shorter lifetimes are also mitigated to a similar extent.

Shifting the Burdern of Uncertainty

Fixing a temperature rather than a concentration target reduces the burden of uncertainty for impacts/adaptation

(assuming we commit to adjust emissions to reach it as the science evolves)

however it increases the uncertainty regarding emissions pathways.

Which is better?

To solve Article 2, we need Article 6

IPCC cannot decide interpretation of Article 2. More people must be involved in the global dialogue, to assess risk and value judgements as well as scientific uncertainties. The Ultimate Integrated Assessment Model remains the global network of Human Heads.

Java Climate Model Interactive - explore cause-effect with draggable controls

Available on web jcm.chooseclimate.orgTransparent (open source code, 50,000 words documentation) Multi-lingual for global dialogueApplications for both research and teaching

Scientific aspects of UNFCCC Article 2, Stabilisation scenarios, and Uncertainty. Ben Matthews...

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