Emissions of Water and Carbon Dioxide from Fossil-Fuel Combustion Contribute Directly to Ocean Mass and Volume Increases

Abstract:

The direct, non-climate, contribution of carbon dioxide and water emissions from fossil-fuel (FF) combustion to the volume and mass of the oceans has been omitted from estimates of sea-level rise (SLR) in IPCC reports. Following the method of Gornitz et al. (1997), H₂O emissions are estimated using carbon emissions from the Carbon Dioxide Information Analysis Center, along with typical carbon and hydrogen contents of FF.

Historic H₂O emissions from 1750 to 2010 amount to 430 ±50 PgH₂O, equivalent to 1.2 ±0.2 mmSLR. Sometime in this decade the volume of H₂O from historic FF combustion will exceed the volume of Lake Erie (480 km³). CO₂ dissolved in the ocean increases the seawater volume by 31-33 mL mol^-1 CO₂. From 1750 to 2010, 370 ±70 PgCO₂ from FF combustion has dissolved in the oceans, causing 0.7 ±0.2 mmSLR. Combined H₂O+CO₂emissions from FF have therefore added 1.9 ±0.4 mm to sea levels in the Industrial Era.

Combustion of FF in 2010 resulted in emissions of 32 PgCO₂ and 12 ±1 PgH₂O. SLR contributions for that year from FF emissions were 0.033 ±0.005 mm from H₂O and 0.011±0.003 mm from dissolved CO₂, a total rate of 0.044 ±0.008 mm yr^-1.

Emissions incorporated in socio-economic models underlying the RCP 8.5 and 2.6 scenarios are used along with concentration-driven CMIP5 Earth System Models results to estimate future sea-level rise from FF combustion. From 2010 to 2100, RCP8.5 and 2.6 models respectively produce 9 ±2 mmSLR and 5 ±1 mmSLR from FF H₂O+CO₂. For perspective, these amounts are larger than the modelled contributions from loss of glaciers in the Andes.

The direct contribution of FF emissions to SLR is small (1-2%) relative to current rates and projected estimates under RCP scenarios up to 2100. The magnitude is similar to SLR estimates from other minor sources such as the melting of floating ice, land-use emissions and produced water from oil operations, none of which are currently included in SLR assessments. As uncertainties in observations and contributions are reduced, small contribution factors, hitherto neglected, will become relatively more important in balancing the books.

Reference

Gornitz, V., C. Rosenzweig, and D. Hillel, 1997: Effects of anthropogenic intervention in the land hydrological cycle on global sea level rise. Global and Planetary Change, 14, 147-161. DOI: 10.1016/S0921-8181(96)00008-2