Int. J. Environ. Res. Public Health 2011, 8 1016 because of the long time lag required to alter behavior and significantly change atmospheric GHG levels. Table 2. Comparison of SRM and ERD approaches to climate mitigationa. Control Approach Time to modify Ability to handle uncertainties Catastrophic changes Ocean acidification Marginal cost/ton carbon equivalent Solar Radiation Management (SRM) Months Very great Capable of fully avoiding if rapid action taken No effect $0.02 to 0.10 Exclusive Regulatory Decarbonization (ERD) Decades at best Very limited by need for new international negotiations 50% probability at best of achieving less than 2 °C increase using IPCC assumptionsb Reduce w/difficulty, not solvec $3,500 to achieve 2 °C w/50% probabilityd assuming high IPCC CSF and long CO2 residence times in atmosphere (undiscounted to 2100) >>$0.45 ×$1012e ~$2300 ×1012f Cumulative overall costs (undiscounted to 2100) Development ~$0.001 ×1012 Control ~$0.090 ×1012 Effectiveness Demonstrated by major volcanic Probably fairly low given low CSF and unwillingness eruptions to be very high of humans to reduce GHGs Other environmental Unknown and untested Some already evident like rainforest destruction from effects but likely oil palm expansion Participation needed Government involvement Mandatory actions by most governments, companies, desirable initially; not required 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. If 80% emissions reductions are to be achieved by 2050, as the Waxman-Markey bill in the US House of Representatives [7] proposed, taking account of population growth and increases in energy use since 1990, the reductions ―needed‖ per person would be almost 90% (see [55], p. 721). Given the rapid spread of new energy using technology such as computers, server farms, cell phones, and other electronic gadgets, this appears more than unlikely. In reality, most experience to date has been that in political jurisdictions where the most serious energy efficiency efforts have been made, the ―best‖ that has been achieved is that GHG emissions have been held steady because the emissions reductions have been balanced out by increases brought about by demand for increased use by increasing urban populations (see [55], pp. 721–725). Finally, as summarized in Table 2, stratospheric SRM would much more reliably achieve cooling at a small fraction of the huge costs of reducing GHG emissions.