Carbonyl sulfide: No remedy for global warming

Abstract

The enhancement of the stratospheric aerosol layer caused by the eruption of Mt. Pinatubo (June 15, 1991), and the subsequent cooling of the earth's lower atmosphere [Dutton and Christy, 1992; Minnis et al., 1993] shows that stratospheric aerosols can have a strong effect on the earth's climate. This supports the notion that the intentional enhancement of the stratospheric aerosol layer through increased carbonyl sulfide (OCS) emissions might be an effective means for counteracting global warming. Through the use of a one‐dimensional photochemical model, we investigate what effect such a program might have on global average stratospheric ozone. In addition, we consider the impact of enhanced OCS emissions on rainwater acidity and on the overall health of both plants and animals. We find that while the warming produced by a single CO2 doubling (1 to 4°C) might be offset with ozone losses of less than 5%, any attempt to use carbonyl sulfide as a permanent solution to global warming could result in depletion of global average ozone by 30% or more. We estimate that in order to achieve cooling of 4°C rainwater pH would fall to between 3.5 and 3.8. Finally, a 4°C cooling at the surface will require that ambient near ground OCS levels rise to above 10 ppmv which is probably greater than the safe exposure limit for humans. Thus, enhanced OCS emissions do not provide an environmentally acceptable solution to the problem of global warming.

Kinetic Insights into Hydrogen Sulfide Delivery from Caged-Carbonyl Sulfide Isomeric Donor Platforms

“…61–62 In the global sulfur cycle, COS is generated from both abiotic sources, including volcanos, hot springs, and oceans, as well as biotic sources, including plants, soils, and biomass burning, 63 and is eventually oxidized to sulfur dioxide (SO 2 ) and sulfate (SO 4 2− ) in the atmosphere. 61,64 In mammalian systems, however, COS functions as a competent substrate for the ubiquitous enzyme carbonic anhydrase (CA), which results in rapid conversion to H 2 S ( k cat /K M for bovine carbonic anhydrase II: 2.2 × 10 4 M −1 s −1 ). 65–68 This property enables COS to serve as a H 2 S precursor and provides new avenues for H 2 S donor development based on COS-releasing motifs.…”

Climate engineering a review of aerosol approaches to changing the global energy balance

“…The primary source of this aerosol is the oxidation of carbonyl sulfide (OCS), emitted as a gas from the oceans. The enhancement of these OCS fluxes (e.g., as analyzed by Taubman and Kasting, 1995) might be considered as an alternative to direct delivery of stratospheric aerosol. Only a fraction of this gas reaches the stratosphere.…”

“…Only a fraction of this gas reaches the stratosphere. Evidently as much or more sulfur than is supplied to tropospheric aerosols would be required to supply the stratosphere with as much sulfate aerosol as provided by Pinatubo (Taubman and Kasting, 1995).…”

The oceanic cycle and global atmospheric budget of carbonyl sulfide

“…They also predicted a global surface cooling by about 0.1"K from such an increase, which is on the threshold of climatic significance. Taubman and Kasting (1995) have recently insisted that the intentional release of COS to the atmosphere is not an environmentally acceptable remedy for global warming caused increases in CO,. However, since present concentrations of COS and CS, (a COS precursor) are quite low, a small unintentional increase in the emission quantities by industrial activities could have a large effect on atmospheric concentrations, and hence climate.…”