IPCC Forum 2007 - Meeting Report

Highlights of the 4th IPCC Assessment report were presented in Bern

Wetter und Klima (Symbolbild)
Image: NASA

On 5 September 2007 ProClim organised a public forum in Bern to present the recent 4th Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). Swiss authors involved in the elaboration of the report and other researchers familiar with the IPCC process presented a number of highlights of the AR4. The topics addressed ranged from forcing agents on the climate system, paleoclimate, regional climate change, extreme events and model projections to impacts on ecosystem, financial services, and mountain areas, and to adaptation and mitigation options on different levels. An outlook on future IPCC activities concluded the forum.

In the introductory remarks, Thomas Kolly, ambassador at the Swiss Federal Office for the Environment emphasized the importance of climate research and the IPCC process for Swiss policymakers. He highlighted the high credibility and reputation of the IPCC as a unique scientific body supporting political decision making.
Ulrike Lohmann explained the different forcing factors including greenhouse gases, ozone, land-use change and aerosols as well as different feedbacks of the climate system like changes in water vapour concentration changes, albedo changes or changes in cloud cover. At present changes in cloud cover are responsible for the most important part of remaining uncertainties concerning the physical climate system, while the knowledge about the effects of aerosols has much improved since the Third Assessment Report in 2001 (TAR). (--> Presentation, 2.7 MB)
Fortunat Joos showed that state-of-the-art climate models could reproduce the multidecadal variability of Northern hemisphere temperatures over the last seven centuries adequately by representing the influence of volcanic activity and solar radiation changes. However, since the late 19th century only models including anthropogenic forcing (greenhouse gases and aerosols) can reproduce the temperature evolution reasonably. (--> Presentation, 1.3 MB)
Thomas Stocker explained that some aspects of the hydrological cycle, including more precipitation in high latitudes and less precipitation in subtropical regions like the Mediterranean, could now be projected and that climate sensitivity (the warming resulting from a doubling of atmospheric CO2 concentration) could now be better constrained giving a best estimate of 3ºC and practically ruling out a sensitivity of lower than 1.5ºC. (--> Presentation, 1 MB)
Christoph Schär pointed out that the intensification of the water cycle would lead in general to more moist as well as more dry extremes. In the Alpine region there would be more precipitation and more runoff in wintertime and less precipitation and more evapotranspiration in summer, i.e. a less pronounced yearly cycle. (--> Presentation, 0.6 MB)
Concerning the impacts of climate change Martin Hölzle showed the already evident changes in the cryosphere concerning the melt of glaciers, ice caps, Arctic sea ice and permafrost and their consequences in the Alps, especially for Tourism. (--> Presentation, 2.1 MB)
Andreas Fischlin presented the impacts on ecosystems and the danger of biodiversity loss which both also affect the corresponding goods and services in support of human society provided by ecosystems. Furthermore, he pointed out that ecosystems which at present act as carbon sink and take up a part of the anthropogenic CO2 emissions could become a net source in the second half of the 21st century. (--> Presentation, 3.8 MB)
Gerhard Wagner emphasized the important role of the carbon price for economic development, which would influence the price of future energy consumption. A significant carbon price leads to a competitive advantage of renewable energy resources and could benefit Switzerland because of its rather carbon free electricity production and the rising demand for technical innovations.
Martin Beniston pointed out the importance of changes in mountain regions, which are the major source region for water and its influence on large-scale atmospheric flow. Mountain cryosphere, hydrology, and vegetation will be very sensitive and vulnerable to rapid climate changes. (--> Presentation, 1.1 MB)
Daniel Spreng underlined the importance of the development path of developing countries for climate change mitigation. Besides specific climate policies also non-climate policies influence future greenhouse gas emissions in the developing world including fiscal policies, forest protection, energy demand management, differentiated insurance premiums, or lending policies of banks and thus have to be considered in development decisions. (--> Presentation, 0.4 MB)
Philippe Thalmann explained that voluntary actions to limit GHG emissions would be useful but insufficient and that national policies are necessary. He underlined the need for international coordination which amongst others allowed to reduce abatement costs by reducing emissions as cost-efficient as possible. A successful next agreement would require climate-effective goals and targets, specific actions, clear timetables and incentives for participation and compliance. (--> Presentation, 0.2 MB)
Renate Christ, secretary of the IPCC, presented the future IPCC activities. In November 2007, the Synthesis Report of AR4 will be published, and in April 2008 a Technical Paper on Climate Change and Water will be finalized. There are ongoing discussions about possible special reports on renewable energy and other proposed topics. IPCC will catalyze international efforts to establish new scenarios which will be needed for a possible next assessment report (AR5). This next report will also involve the world research programmes WCRP, IGBP and IHDP. There are ongoing discussions about more staggered reports, about more special reports instead of a comprehensive one, or possible changes in the Working Group structures. (--> Presentation, 0.7 MB)