Stacy -
Yes, it depends on the temp target, but in the real world (ie not
politics) it also depends on the sensitivity of the climate, and for all
intents and purposes everything seems to happen faster and sooner
indicating that the climate system may be more sensitive than we thought.
Another approach to this, ultimately to be turned into percentages if
you wish, is that propagated in the America's Climate Choices
(Limiting/Mitigation) report (NRC, 2012). They essentially took an
emissions/carbon budget approach, saying that if we want to stay under x
temperature, then we have a carbon budget of y, and at the current rate
of emissions, we will have used that remaining budget up by year z. To
stay within that budget we have to reduce some percent per year
starting... well, yesterday. It gives you a simple math approach to
seeing that 2 degrees C is all but an economically (well, o.k. back to
THAT real world... i.e. politically) infeasible goal.
Hope that helps (even if just for the US and not global, but similar
papers have been written for global carbon budgets),
Susi
On 8/5/2012 6:25 PM, Soledad Aguilar wrote:
I use this one also from AR4 which includes sea level rise, which I find
interesting to discuss with students living near coastlines as it gives them
something they can easily relate to.
Soledad Aguilar
Investigadora Principal
FLACSO Argentina
Programa en Desarrollo, Innovación y Sociedad
Síguenos en el Foro de Cambio Climático y Comercio
http://www.ambienteycomercio.org<http://www.ambienteycomercio.org/>
On Aug 5, 2012, at 3:41 PM, Avery Cohn wrote:
Actually, the 450ppm target is for 2050, not for 2020. The 25-40% reduction for
Annex I countries (from 1990 levels) is an intermediate target-- sort of a way
station. Annex I countries would need to continue to reduce emissions at a
similar rate until 2050. Ultimately the Annex I cuts would need to be much
deeper to hit 450ppm.
Though I find the Annex I responsibilities a useful way to measure our lack of
progress (even in commitments) in the near term (see
http://iopscience.iop.org/1748-9326/5/3/034013/fulltext/), they are a confusing
way to think about global emissions reductions.
I think it is more straightforward to think of it this way. According to the
fourth assessment report, by 2050, GLOBAL emissions would need to fall 50-85%
from 2000 levels in order to stabilize warming at 2-2.4 degrees Celsius over
the pre-industrial equilibrium
(http://www.ipcc.ch/publications_and_data/ar4/wg3/en/spmsspm-d.html see chart
SPM.5 ) .
Best,
Avery
On Sun, Aug 5, 2012 at 11:48 AM, Radoslav Dimitrov
<[email protected]<mailto:[email protected]>> wrote:
Depends on the temperature target: To keep global temperature rise below 2
degrees C, carbon-equivalent atmospheric concentrations must be kept below 450
ppm - which can be achieved by reducing emissions by 25-40% by 2020. The latter
range is in the 2007 IPCC report and was the policy target advocated officially
by the European Unionat the Bali conference. This was a subject of intense
negotiations. No one else in the industrialized camp supported the EU on this.
As a result, the Bali text only contains a footnote that indirectly refers to
the IPCC-endorsed target, without actually containing the 25-40 numbers.
Radoslav S. Dimitrov, Ph.D.
Associate Professor
Department of Political Science
University of Western Ontario
Social Science Centre
London, Ontario
Canada N6A 5C2
Tel. +1(519) 661-2111 ext. 85023<tel:%2B1%28519%29%20661-2111%20ext.%2085023>
Fax +1(519) 661-3904<tel:%2B1%28519%29%20661-3904>
Email: [email protected]<mailto:[email protected]>
On 2012-08-05, at 1:27 PM, VanDeveer, Stacy wrote:
Hi all,
I got a question from a summer school student, and I am trying to find the
‘consensus’ answer in IPCC documents and I seem to be finding different
numbers. So here is the question: The IPCC estimates that global emissions
must fall by how much, to stabilize the climate systems during this century.
Are the best estimates from the 2007 report (which gives quite large ranges for
each of four warming scenarios)??
Stacy D. VanDeveer
Associate Professor
University of New Hampshire
Dept. of Political Science
Horton SSC
Durham, NH 03824 USA
[email protected]<mailto:[email protected]>
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