Via West Coast Climate Equity:

The scientists behind recent papers on carbon dioxide emissions and climate change have issued an open letter [see full text below] calling on the negotiators in the Bonn Climate Change Talks to acknowledge the need to limit cumulative emissions of carbon dioxide.

Here is the open letter.

Open Letter to the Negotiators of the UNFCCC:

The need to limit cumulative carbon dioxide emissions to avoid dangerous
climate change

We welcome the efforts of governments around the world to reach agreement on
measures to reduce greenhouse gas emissions, and wish to draw attention to
recent scientific research indicating that a key determinant of the risk of
dangerous climate change is cumulative emissions over all time of the
longest-lived greenhouse gases, in particular carbon dioxide. This has three
important implications:

* First, current emission trends are incompatible with the goal of limiting
cumulative emissions to a level that provides an acceptably low risk of
dangerous climate change. Estimates of tolerable risk and allowable
emissions vary, but in all cases costs rise sharply with the speed of
emission reductions, so any affordable strategy to avoid releasing too much
carbon dioxide in total will require global emissions to peak soon.
* Second, in devising emission targets for 2020 and 2050, governments need to
be aware of their implications for cumulative emissions. A policy that
allows carbon dioxide emissions to rise over the coming decade in the hope
of reducing them rapidly after 2020 results in a substantially higher
contribution to the cumulative budget, and hence a greater contribution to
the risk of dangerous climate change, than a policy of steady reductions
reaching the same 2050 target.
* Third, fossil carbon reserves substantially exceed the amount that can
safely be released into the atmosphere. Net global carbon dioxide emissions
will eventually have to decline towards zero leaving a substantial fraction
of available fossil carbon stored, in some form, out of the atmosphere
indefinitely.

We urge the participants in December’s Conference of the Parties to the
United Nations Framework Convention on Climate Change to acknowledge the
need to limit cumulative carbon dioxide emissions as one element of their
vision for long-term cooperative action to avoid dangerous climate change.

* Myles Allen, Department of Physics, University of Oxford
* David Archer, Department of Geophysical Sciences, University of Chicago
* David Frame, Smith School of Enterprise and the Environment, University of
Oxford
* Damon Matthews, Department of Geography, Planning and Environment,
Concordia University
* Malte Meinshausen, Potsdam Institute for Climate Impacts Research
* Stephen Schneider, Department of Biology, Stanford University
* Andrew Weaver, School of Earth and Ocean Sciences, Victoria University
* Kirsten Zickfeld, Canadian Centre for Climate Modelling and Analysis