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Efficacy of geoengineering to limit 21st century sea-level rise - PubMed

  • ️Fri Jan 01 2010

Efficacy of geoengineering to limit 21st century sea-level rise

J C Moore et al. Proc Natl Acad Sci U S A. 2010.

Abstract

Geoengineering has been proposed as a feasible way of mitigating anthropogenic climate change, especially increasing global temperatures in the 21st century. The two main geoengineering options are limiting incoming solar radiation, or modifying the carbon cycle. Here we examine the impact of five geoengineering approaches on sea level; SO(2) aerosol injection into the stratosphere, mirrors in space, afforestation, biochar, and bioenergy with carbon sequestration. Sea level responds mainly at centennial time scales to temperature change, and has been largely driven by anthropogenic forcing since 1850. Making use a model of sea-level rise as a function of time-varying climate forcing factors (solar radiation, volcanism, and greenhouse gas emissions) we find that sea-level rise by 2100 will likely be 30 cm higher than 2000 levels despite all but the most aggressive geoengineering under all except the most stringent greenhouse gas emissions scenarios. The least risky and most desirable way of limiting sea-level rise is bioenergy with carbon sequestration. However aerosol injection or a space mirror system reducing insolation at an accelerating rate of 1 W m(-2) per decade from now to 2100 could limit or reduce sea levels. Aerosol injection delivering a constant 4 W m(-2) reduction in radiative forcing (similar to a 1991 Pinatubo eruption every 18 months) could delay sea-level rise by 40-80 years. Aerosol injection appears to fail cost-benefit analysis unless it can be maintained continuously, and damage caused by the climate response to the aerosols is less than about 0.6% Global World Product.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.

Sea-level reconstruction based on fitting past sea level to forcings from (20) blue; (21) red; and (22) green and their average (heavy black line and gray shadow showing 5–95% confidence interval). Tide gauge observations (thin black and their confidence interval (pink shading). The inset shows detrended observed (black) and modeled response (purple) to the five volcanic eruptions (Pinatubo, 1991; El Chichón 1982; Agung, 1963; Santa Maria, 1902; and Colima, 1890) with annual smoothing, shading shows 5–95% confidence interval.

Fig. 2.
Fig. 2.

Radiative forcing observed since 2000 (12), and projected over the 21st century due to scenarios RCP8.5, (thick blue), RCP4.5, (thick black), and RCP3PD (thick magenta) (18), and several geoengineering options (thin lines). Radiation management schemes are shown by thin solid lines: space mirror (red lines—the steeper gradient is -1 W m-2 per decade from 2010 and the other ramping to -4 W m-2 by 2100); aerosol forcing is set to either a constant -1.56 W m-2 (the average forcing of a Pinatubo eruption every 4 years), or a -4 W m-2, (black lines). Carbon cycle alteration is shown by broken lines: afforestation, (blue dashed); biochar, (magenta dotted); BECS, (blue dotted); and a combination of BECS + afforestation + bichar, (black dotted).

Fig. 3.
Fig. 3.

Sea-level simulations (relative to mean sea level 1980 to 2000) using mean forcings from before 2000 and RCP scenarios (18) since 2001. The past is constrained by observed global sea level, post 2010 simulation with the RCP scenarios labeling the figure with no geoengineering (black); with the scenario plus a constant -1.56 W m-2 (blue); the scenario plus space mirror (from 0–-4 W m-2) linear ramp (red). Shadows represent 5–95% confidence bands in each simulation.

Fig. 4.
Fig. 4.

As Fig. 3 but the simulation with RCP RCP scenario + space mirror effective at a rising rate of 1 W m-2 per decade from 2010 to 2100, (red); and RCP scenario + constant -4 W m-2 reduction due to SO2 injection, (blue).

Fig. 5.
Fig. 5.

As Fig. 2 but the simulation with RCP scenario + BECS, (red); and RCP scenario + combined forcing (BECS + biochar + afforestation), (blue).

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