Summary: The latest science establishes that we are in the early stages of runaway climate change. This is not however considered to be unstoppable. We do still have a window of opportunity for intervention before the onset of unstop-ability, but it is a narrow window and it is shrinking inexorably.

The task is to lower the concentration of carbon dioxide in the atmosphere. The amount emitted annually must be less than the amount drawn down. At the moment the opposite is the case. This trend must be reversed. Moreover the sooner this is achieved the better. As runaway climate change is already taking place, it gets more and more difficult to halt it as each year goes by.

Quotes from some recent reports:

1. James Hansen and others

"Continued growth of greenhouse gas emissions for just another decade practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects. If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm. The largest uncertainty in the target arises from possible changes of non-CO2 forcings. An initial 350 ppm CO2 target may be achievable by phasing out coal use except where CO2 is captured and adopting agricultural and forestry practices that sequester carbon. If the present overshoot of this target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects." Source and here

2. Peter Cox and others

In June 2007 another group of climate scientists, Peter Cox, Deepak Rughani,Peter Wadhams and David Wasdell, reported to the House of Commons All Party Parliamentary Climate Change Group:

"Over the last two years there has been a profound shift in the scientific understanding of the behaviour of the earth's climate system. Although some specific feedback mechanisms were included in the more advanced climate models, the analysis of climate dynamics as a whole has proceeded far beyond that portrayed in the latest IPCC Assessment Report. It was not taken into consideration in the Stern Report, in the formulation of the Climate Bill currently before the UK Parliament, or in the process of target-setting of the present round of International negotiations.

Almost all of the systems known to affect climate change are now in a state of net positive (amplifying) feedback. Each feedback mechanism accelerates its own specific process. The output of each feedback is an input to all other feedbacks, so the system as a whole constitutes an interactive set of mutually reinforcing sub-systems.

This "second order" feedback system accelerates the rate of climate change and faces us with the possibility of a "tipping point" in the whole earth system. If we go beyond the point where human intervention can no longer stabilise the system, then we precipitate unstoppable runaway climate change.

The implication is that climate change is non-linear. Once set in motion it is acceleratingly self-perpetuating. There is then only a small time-window within which human intervention has any (rapidly diminishing) chance of halting the process and returning the system to a stable state. Failure to act effectively within that window of opportunity would inevitably precipitate cataclysmic change on a par with the five mass extinction events known to have obliterated almost all life on earth.

Strategically we have to generate a negative feedback intervention of sufficient power to overcome the now active positive feedback process. We then have to maintain its effectiveness during the remaining period of rising temperature, while temperature-driven positive feedbacks continue to operate. That is an extraordinarily difficult task, out of all comparison with strategies currently in place." Planet Earth We have a Problem - Feedback Dynamic and the Acceleration of Climate Change. See

3. The PIRC Report Climate Safety

In November 2008 PIRC, a small independent think-tank, launched their report on the implications of the latest science for the UK. The foreword to the report is by Sir John Houghton, former co-chair of the IPCC and former Director General of the UK Met Office: ..."the report brings two important messages. The first is that climate change is accelerating more rapidly and dangerously than most of us in the scientific community had expected or that the IPPC in its 2007 Report presented. The second is that, because political inaction has delayed progress for so long, the imperative for extremely urgent action on both national and global scales is now paramount"

As the PIRC report points out, even 350 ignores the precautionary principle. "We need to manage the risks of climate change responsibly. This means reducing atmospheric concentrations to within the range that we now know the climate will maintain stability - 300 ppm CO2 equivalent." See, where the report can be downloaded free

4. David Wasdell

David Wasdell's paper "Radiative Forcing and Climate Sensitivity" Appollo-Gaia Project December 2008 explains the nature of the "extremely limited" window of opportunity currently open to humanity, in scientific and systems terms. "Climate re-stabilisation (reduction of radiative forcing to zero) can still theoretically be achieved by preventing all further additions to the stock of anthropogenic greenhouse gases, coupled with the aggressive draw-down of carbon dioxide already in the atmosphere. The window of opportunity afforded by the time-lag between radiative forcing and increasing temperature is, however, extremely limited. It is narrowed even further by the temperature-sensitive feedback-driven acceleration in the value of radiative forcing." See

What would be needed to get back to 350, let alone 300? Nobody knows. The nearest comparison seems to be the scale of mobilisation achieved in WW2. Source

Once the need is recognized for sudden and major reductions in global greenhouse gas emissions, the question becomes how to do this fairly, described on the Justice page.