Friday, 6 December 2013

Never mind the widgets - here comes the bomb

Perhaps a little late, but I've just got through Hansen et. al. : 

Assessing “Dangerous Climate Change”: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature

Here's the abstract:

We assess climate impacts of global warming using ongoing observations and paleoclimate data. We use Earth’s measured energy imbalance, paleoclimate data, and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on today’s young people, future generations, and nature. A cumulative industrial-era limit of ~500 GtC fossil fuel emissions and 100 GtC storage in the biosphere and soil would keep climate close to the Holocene range to which humanity and other species are adapted. Cumulative emissions of ~1000 GtC, sometimes associated with 2°C global warming, would spur “slow” feedbacks and eventual warming of 3–4°C with disastrous consequences. Rapid emissions reduction is required to restore Earth’s energy balance and avoid ocean heat uptake that would practically guarantee irreversible effects. Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice. Responsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels.

And here is a graphic from the paper which I'll be referring to:

Doing my usual trick, I'm going to try and extract the points which struck me in the simplest form possible:

  1. Setting a 2c target for future warming (the current 'standard' policy approach) is no good. This level is likely to result in 'dangerous' impacts.
  2. A 1c target is better. It is also, with radical action, achievable.
  3. We need a 6% per annum reduction in emissions from 2013, with other actions, to limit warming to 1c this century.
  4. We've got about 128GTc of fossil fuels left for use if we want to avoid 'dangerous' change.
  5. Failing to act now (or, as in the article, in the 2014/15 cycle of the UNFCCC), represents 'an act of extraordinary witting intergenerational injustice'; in other words, our leaders know the consequences of inaction and may choose to account for them or not.
  6. From the paper: Ultimately, however, human-made climate change is more a matter of morality than a legal issue. Broad public support is probably needed to achieve the changes needed to phase out fossil fuel emissions. As with the issue of slavery and civil rights, public recognition of the moral dimensions of human-made climate change may be needed to stir the public’s conscience to the point of action.
  7. Mitigation is desirable, achievable and (arguably) essential for the future of the planet's ecosystems and the welfare of humanity.
  8. short term delays now result in much greater difficulties in mitigation later, in time scales of less than a decade.
  9. (see the graphic above) We have known about this since at least 1992, yet the progress of action to date is derisory, as evidenced by the rate of growth of emissions in the timescale referred to.
  10. We have a choice: act now and make a difference, or avoid acting now and accept the moral responsibility for the consequences, with all their implications.
I have been involved in discussions, for example at Stoat and Rabett Run, in which I have tried to point out that the moral dimension of Climate Science is not just important, but is central to the arguments about policy implications. Hansen seems to agree with me.

No doubt, more on this paper later.