Table 2.

Comparison of SRM and ERD approaches to climate mitigation^a.

Control Approach	Solar Radiation Management (SRM)	Exclusive Regulatory Decarbonization (ERD)
Time to modify	Months	Decades at best
Ability to handle uncertainties	Very great	Very limited by need for new international negotiations
Catastrophic changes	Capable of fully avoiding if rapid action taken	50% probability at best of achieving less than 2 °C increase using IPCC assumptionsb
Ocean acidification	No effect	Reduce w/difficulty, not solvec
Marginal cost/ton carbon equivalent	$0.02 to 0.10	$3,500 to achieve 2 °C w/50% probabilityd assuming high IPCC CSF and long CO2 residence times in atmosphere
Cumulative overall costs Development Control	(undiscounted to 2100) ∼$0.001 × 1012 ∼$0.090 × 1012	(undiscounted to 2100) ≫$0.45 × $1012e ∼$2300 × 1012f
Effectiveness	Demonstrated by major volcanic eruptions to be very high	Probably fairly low given low CSF and unwillingness of humans to reduce GHGs
Other environmental effects	Unknown and untested but likely	Some already evident like rainforest destruction from oil palm expansion
Participation needed	Government involvement desirable initially; not required	Mandatory actions by most governments, companies, and people

Sources:

^a.Based on Carlin [55], Table 1, which is based on Carlin [60], unless otherwise stated. IPCC assumptions used for ERD.

^b.Rive, et al. [56], Table 1. This assumes a goal of staying below a 2 °C temperature increase from pre-industrial levels in order to avoid dangerous climate changes as per European Union policy.

^c.See discussion in [55], Section II.B.3, pp. 734–735.

^d.Rive et al. [56], p. 385.

^e.Nova [59], p. 17 shows about $5 billion per year in the last few years for climate science and technology expenditures for the US alone. Other nations, particularly in Western Europe, have also had substantial expenditures. These expenditures have substantially increased under the Obama Administration, as shown in the Nova 2009 total, and would be very likely to be much higher if serious CO₂ emission reductions should be undertaken.

^f.Galiana and Green [57], p. 20.