|IPCC Temperature Holocene/Anthropocene|
David Wasdell: The set of computer models used by the IPCC only work with the feedback mechanisms that can be quantified. Inevitably that only gives part of the picture. In contrast, the history of planetary change includes by definition all the feedback processes, known and unknown, positive and negative (that is amplifying or damping), together with all the complex interactions between them. The computer models predict that the temperature change from doubling the concentration of CO2 would be about 3°C. Using the history of the actual relationship between temperature and CO2 concentration we find the outcome is more like 8°C. That is a huge difference with massive strategic implications. The reality of earth System Sensitivity is about 2 and a half times that stemming from the partial computer models.
|Going back 400,000 years|
Moving from the specific example of change since the last ice-age, we can derive the value of the more generalized “Climate Sensitivity”, the equilibrium change in average surface temperature of the planet following a doubling of the concentration of atmospheric CO2. The temperature change required to compensate for the effect of doubling concentration of CO2 on its own is calculated to be 0.97°C. Climate sensitivity when only fast feedbacks are taken into consideration stands at 3°C. Including the effects of the carbon-cycle feedbacks raises the value of Climate Sensitivity to 4.5°C. Adding the contribution from the ice-sheet dynamics correlates with a 6°C value for Climate Sensitivity. While the Sensitivity value representing the equilibrium dynamics of the Earth System as a whole stands at 7.8°C. Though please note that this figure is derived from slow and close to equilibrium conditions of change in the Quaternary period. It may be too low in the current conditions of the Anthropocene.
Now if you are working with computer models using only the fast feedbacks, you would predict that 2°C would be achieved at around 440 ppm. But if you are using the Earth System Sensitivity, then at 440 ppm [which we will likely hit between 2030 and 2035] we would be looking at more like 5°C of change. However, as I keep reminding you, the computer simulation, inadequate and partial though it may be, is what is still being fed into the process of strategic policy-making on the assumption that the temperature change will only be 2°C for a concentration of 440 ppm of CO2.
Alex Smith: At various conferences, in the business press and in scientific circles, there has been a lot of effort to work out how much carbon we can still burn, in the form of oil, gas, and coal, and still remain below the supposed 2 degree warming safety limit. No doubt diplomats at the Paris Conference will talk about this "carbon budget." How much of a budget do we really have left?
David Wasdell: At present the CO2 concentration stands at 400 ppm. If it is thought to be safe to go up to 440 ppm, then we have a good budget to play with. There is still plenty of room in the sky-fill site. However, if we don't use the inadequate computer models, and instead apply the real Earth System Sensitivity, then we were already committed to passing the 2°C ceiling when CO2 concentration stood at 334 ppm. That was back in 1978. We have already overspent the budget by a large amount! Getting the picture?
***National promises (“INDCs”)(Independent Nationally Determined Contributions) concerning reduction in CO2 emissions, have been tabled ahead of the COP21 in Paris. Those promises look like pushing us to about 700 ppm by the end of the century (if they are implemented, and there is no guarantee about that whatsoever!). Business as usual is driving us up towards 800 or 900 ppm up here. If we cannot improve the level of promised emissions reduction, then “We might hit 4°C” predicts the IPCC using its low value for sensitivity. But if we use the full Earth System Sensitivity to examine the way the climate behaves at the level of 700 ppm. We are not looking at something around 4°C, but an increase of more like 10°C. That is twice the temperature shift between the ice ages and the pre-industrial benchmark. If we are not able to cut back on our current “business as usual” behavior, then the temperature rise increases to more like 12 or even 15°C, (and two or three times that amount in the Arctic!) Good bye all the ice on earth. Welcome to something like 90 feet of sea level rise, or even more when all the Greenland ice-cap and the whole of the Antarctic ice sheet melts. Civilization would have collapsed and we would have evacuated London and New York well before then!
The Subsidiary Body for Scientific and Technological Advice (SBSTA) and the Subsidiary Body for Implementation (SBI) will continue to jointly consider the report of the Structured Expert Dialogue (SED) on the 2013–2015 review at the upcoming session to be held in Paris in December 2015, with a view to concluding their considerations on this matter and reporting their findings to the COP, which shall take appropriate action based on the review.
Parties sought clarification on
- the window of opportunity for staying under 2°C of warming and the risks created by overshooting,
- the practicality of achieving negative emissions,
- the marginal costs of mitigation for 40–70 per cent emission reduction from 2010 levels by 2050,
- the Cancun pledges (“INDC”s),
- the impact of mitigation on economic growth, and
- production-versus consumption-based accounting for emissions.
|BECS Net Sequestration Potentials by Sector (eCO2, 2015)|
"The practicability of negative emissions depends on costs, trade-offs and the feasibility of various scenarios. The IPCC presented options for generating large amounts of energy from BECS [Biomass Energy with Carbon Capture and Storage] and the associated risks for biodiversity and food security and prices, stressing that policymakers need to consider the trade-offs [translation: consider unregulated use of genetically engineered fuel-stocks, soil- and livelihood-destroying monocrop plantations, and expensively capturing the carbon as smoke using toxic scrubbers that then have to be locked away somewhere forever]."
|Jason Lowe, Hadley Centre, at SED-4.|
Bill McKibben, writing a short entry for a science fiction anthology, Visions 2100 – Stories From Your Future, to be released at the COP on December 5, said:
“Looking back on the century, the only real thought is: why didn’t we do this sooner? The technology we’re using – solar panels, windmills, and the like – were available in functional form a hundred years ago. But we treated them as novelties for a few decades – and it was in those decades that climate change gathered its final ferocity. Now we live in a low carbon world and it works just fine – except that there’s no way to refreeze the poles, or lower the sea level, or turn the temperature back down to a place where we can grow food with the ease of our ancestors. Timing is everything, and it hurts to think we blew it.”