That is true Matthew but then no carbon constraint scheme can ever achieve its intended outcome – unless you are talking levels lower than those of ice ages.
That is because the enhanced greenhouse effect from carbon dioxide addition is logarithmic – each doubling of CO2 results in the same additional effect, regardless of whether you are talking about doubling from 100-200 ppmv or 1,000-2,000 ppmv and each molecule added has less effect than the one before it.
If you want to double the effect then you need to increase to the square of the previous level. Twice the effect of ice age levels of 200 ppmv requires 2002 or 40,000 ppmv.
CO2 accounts for ~10% of Earth’s greenhouse effect and the IPCC’s basic calculations concur with that. By their formulae Earth is headed for 29 or 512 ppmv, that equates to 9 doublings from 1 so 9 x 3.7 W/m2 = 33.3 W/m2 – one-tenth of Trenberth et al‘s “Back Radiation” or greenhouse effect.
As most school kids know, or should do, Earth’s greenhouse effect is calculated at 33°C, making CO2 responsible for 3.3°C, or it will be at 512 ppmv.
You can see where this is going. For CO2 to deliver the “median guesstimate” of +3°C, doubling its past performance, requires the square of its atmospheric level. Even taken from its pre-industrial estimate of 278 ppmv that’s 2782 or 77,284 ppmv.
You see why we are unexcited about trivial changes in the level of this trace gas? And why we state that carbon constraint can’t work as advertised?
Warren, however, believes otherwise:
It’s time we stopped deluding ourselves in Australia that we have climate change policy pegged. We don’t. Climate change policy is global and generational. As we are discovering in real time, one of the greatest risks to effective climate change policy is the widening gap between what is technically possible and what is politically achievable.
Our haste to put a price on carbon was always going to lead to implementation problems. The European Union planned the introduction of its scheme over five years, with a 15-year phase-in period.
In Australia, we designed a hugely complex carbon pollution reduction scheme, abandoned it and then just introduced a carbon price – all in less than five years.
It is self-evident that our scheme is out of step with the rest of the world. That’s not a problem, providing we are honest with ourselves and move to fix inherent design flaws quickly in the interests of the scheme’s long-term viability.
One of those design flaws is the introduction of a $15 floor price from 2015 to 2018.
The global problem we are facing, based on best advice of the majority of scientists, is that there is only a limited amount of greenhouse gases that can be emitted before we trigger dangerous climate change. Deutsche Bank’s global head of energy research Mark Lewis says the true scarcity value of each of those remaining tonnes of greenhouse emissions is about $US100 a tonne. This means any price underneath that is a compromise. A subsidy. A soft start.
But imposing the true environmental cost up front is political and economic suicide.