1. Can we provide thermodynamic constraints for the long-term coupled evolution of the economy and the atmosphere? Tim Garrett University of Utah

2. SRES Emissions Scenarios out to 2100 CO 2 Emissions 2100 All scenarios are considered equally probable

3. Range of possible futures depends as much on societal trajectories as climate physics

4. Atmospheric CO 2 Perturbation (ppmv) But historically, the problem looks tightly constrained… R 2 =0.90

6. Cullenward et al. 2011 Climatic Change xkcd.com

7. Available potential energy density The atmosphere is an open thermodynamic system sunlight atmosphere dissipation to space

8. Available potential energy density …so is the global economy fuel civilization dissipation to space

9. A child grows because it dissipates less energy than it consumes Energy efficient consumption is central to a positive feedback driving growth

10. Wealth is a fiscal measure of our capacity to enable the consumptive flow of primary (potential) energy. This flow enables all civilization activities. The convergence of energetic and material flows is what we fiscally quantify as the real GDP. By growing civilization, convergence grows our capacity to consume by expanding access to new energy reservoirs. This is what we implicitly value as economic production or the GDP. POSITIVE FEEDBACK GDP ($/yr) fuel civilization dissipation to space

11. Energy consumption rate is global economic wealth Wealth is an accumulation of past real economic production. The GDP is a convergence of flows. Key point: is hypothesized to be a constant coefficient: the power of money Hypothesis is testable and falsifiable Current rate of energy consumption Wealth Power of money constant Past world real GDP

12. Hypothesis evaluation C = Global Wealth a = Global energy consumption rate a/C = Power per dollar Inflation-adjusted wealth is an implicit measure of the rate of energy consumption by civilization = 9.7 ± 0.3 mW per 1990 US dollar

13. IPCC: “Future greenhouse gas (GHG) emissions are the product of very complex dynamic systems, determined by driving forces such as demographic development, socio-economic development, and technological change. Their future evolution is highly uncertain.”

14. non-SRES global CO 2 Emissions Identity Current rate of energy consumption Wealth Power of money constant Past world real GDP

15. non-SRES global CO 2 Emissions Identity carbonization of energy supply wealth of civ. Emissions Energy consumption rates Without decarbonizing, emissions cannot be reduced without destruction of global wealth Current wealth is tied to the past history of real GDP, which cannot be destroyed Past real GDP

18. CThERM Multi-decadal coupled hindcasts Gross World Product ( trillions 1990 $/yr ) Hindcast initialized with current state in 1985 Dashed: observations Color: hindcasts Carbon Dioxide Concentrations Initialization

19. Forecasts to 2100 No switch from fossil fuels 3.7 - 8.3 ºC 1.9 - 4.4 ºC SRES Models get an unphysically high GDP per [CO 2 ] because they assume that energy consumption can be decoupled from the economy through efficiency gains Civilization divergence

20. Conclusions Civilization’s future is tied to its past consumption. Wealth, energy consumption and CO2 emissions are coupled through a constant Energy efficiency gains accelerate growth of wealth and CO2 emissions The negative feedback on emissions and wealth is resource depletion and environmental disasters. Shouldn’t SRES models appeal foremost to physics if they are to be coupled to GCMs?