Thursday, May 21, 2015

Where are the Bunnies - a Four Question Locator

It occurred to Eli that which side of the fence one sits on about climate change (sitting on the fence being quite not comfortable) can be summed up in two numbers:  The temperature anomaly over some period of time and the cost of not reaching that anomaly.  It has also occurred to many that the various descriptions of the positions are a bit slippery which is particularly favored by those trying a straddle.

For purposes of rough approximation, the temperature anomaly can be taken as a product of two numbers, the CO2 mixing ratio and the equilibrium climate sensitivity.  The cost is the difference between the cost of doing nothing and the cost of doing something.

Thus, this opinion pole for the bunnies to sit on.  There is no right answer, there are just opinions. It will be interesting to see if there really are groupings or just a single blob.  The poll is open to all

The current CO2 mixing ratio is 400 ppm and the CO2 equivalent mixing ratio in 2011 was 430 ppmV.  The IPCC WG3 predicts that (Page 11)
Without additional efforts to reduce GHG emissions beyond those in place today, emissions growth is expected to persist driven by growth in global population and economic activities. Baseline scenarios, those without additional mitigation, result in global mean surface temperature increases in 2100 from 3.7 °C to 4.8 °C compared to pre-industrial levels10 (median values; the range is 2.5 °C to 7.8 °C when including climate uncertainty, see Table SPM.1)11 (high confidence). The emission scenarios collected for this assessment represent full radiative forcing including GHGs, tropospheric ozone, aerosols and albedo change. Baseline scenarios (scenarios without explicit additional efforts to constrain emissions) exceed 450 parts per million (ppm) CO2eq by 2030 and reach CO2eq concentration levels between 750 and more than 1300 ppm CO2eq by 2100.
The IPCC AR5 puts the climate sensitivity at somewhere in the range between 1.5 and 4.5 C with a most probably value somewhere in the neighborhood of 2.7 K.

The cost of limiting global temperature anomaly change to 2 C is estimated at 0.06% global GDP per year, but depends on when one starts.  The cost of doing nothing is also subject to gremlins, but Grant McDermott at Stickman's Corral has summarized a bunch of estimates

So, bottom line, answer the four questions to generate your place on the climate change map.

Eli has voted.  (the point at the origin is an artifact)