Can we provide thermodynamic constraints for the long-term coupled

evolution of the economy and the atmosphere?

Tim Garrett

University of Utah

SRES Emissions Scenarios out to 2100C

O2 E

mis

sion

s

2100

All scenarios are considered equally probable

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

Atm

osph

eric

CO

2 P

ertu

rbat

ion

(ppm

v)

But historically, the problem looks tightly constrained…

R2=0.90

Cullenward et al. 2011Climatic Change

xkcd

.com

Available potential energy density

Material andenergetic flow

The atmosphere is an open thermodynamic system

sunlight

atmosphere

dissipation to space

Available potential energy density

Material andenergetic flow

…so is the global economy

fuel

civilization

dissipation to space

A child grows because it dissipates less energy than it consumesEnergy efficient consumption is central to a positive feedback driving growth

Wealth ($)

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

• 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

Hypothesis evaluation

C = Global Wealtha = Global energy consumption ratea/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

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.”

non-SRES global CO2 Emissions Identity

Current rate of energy consumption Wealth

Power of money constant

Past world real GDP

non-SRES global CO2 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

CThERM Multi-decadal coupled hindcasts

Gro

ss W

orld

Pro

duct

(t

rillio

ns

199

0 $

/yr)

Hindcast initialized with current state in 1985Dashed: observationsColor: hindcasts

Car

bon

Dio

xide

Con

cent

ratio

ns

Initialization

Forecasts to 2100 No switch from fossil fuels

3.7 - 8.3 ºC

1.9 - 4.4 ºCSRES Models get an unphysically high GDP per [CO2] because they assume that energy consumption can be decoupled from the economy through efficiency gains

Civ

iliza

tion

dive

rgen

ce

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?