World Energy Outlook 2007

Box 5.3: IPCC Fourth Assessment Report
The World Meteorological Organisation (WMO) and the United Nations
Environment Programme (UNEP) established the Intergovernmental Panel
on Climate Change (IPCC) in 1988 to assess scientific, technical and socioeconomic
information relevant for the understanding of climate change, its
potential impacts and options for adaptation and mitigation. The IPCC has
three working groups (WGs) which assess knowledge of the climate system
(WG I), the impact of the adaptation to climate change (WG II) and the
mitigation of climate change (WG III), plus a Task Force on national
greenhouse-gas inventories. The assessments are performed by scientists
nominated by governments and scientific organisations. They are managed
by an elected bureau and are supported by the IPCC Secretariat and the
Technical Support Units of the working groups. The IPCC meets in
plenary session about once a year to approve the work programme and the
assessment reports,.
A main activity of the IPCC is to provide at regular intervals an assessment
of the state of knowledge about climate change. It recently finalised and
released the three working group reports that will make up its Fourth
Assessment Report, providing a comprehensive and up-to-date appraisal of
the current state of knowledge on climate change. A synthesis report is due
to be released in November 2007.
5
The global atmospheric concentration of CO 2
has increased from a
pre-industrial level of about 280 parts per million to 379 ppm in 2005.
This level exceeds by far the natural range over the last 650 000 years
(180 to 300 ppm) as determined from ice cores. It is estimated that, were
CO 2
concentrations to rise to 400 to 440 ppm and stabilise at that level, the
eventual rise in global average temperature would amount to around 2.4° to
2.8°C (IPCC, 2007). In order to stabilise the concentration of CO 2
in the
atmosphere, emissions would need to peak and decline thereafter. The lower
the target stabilisation level, the more quickly this peak and decline would
need to occur. For this reason, mitigation efforts over the next two to three
decades will affect our ability to achieve lower stabilisation levels. Based on
current understanding of climate-carbon cycle feedback, the IPCC
concludes that, in order to stabilise CO 2
-equivalent 4 concentrations at 445-
490 ppm, CO 2
emissions would need to peak by 2015 at the latest and fall
to between 50% and 85% below 2000 levels by 2050. A later peak and less
sharp reductions in emissions would lead to higher concentrations and
bigger increases in temperature (Table 5.4).
4. All greenhouse gases expressed in CO 2
-equivalent terms (adjusted for differences in radiative
forcing).
Chapter 5 - Global Environmental Repercussions 205