Monday, September 30, 2013

The oceans, on acid. And bacon.

The new IPCC report reminds that through the fits and starts of climate warming, we continue to steadily carbonate the ocean. From the Summary for Policymakers:

Measurements of CO2 partial pressure and pH from three stations
...atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification...
Ocean acidification is quantified by decreases in pH. The pH of ocean surface water has decreased by 0.1 since the beginning of the industrial era (high confidence), corresponding to a 26% increase in hydrogen ion concentration.

The chemical conditions are unlike anything that the vast majority of organisms living in the surface of the ocean have ever regularly experienced. The changes are predicted to continue:

Ensemble mean surface pH from suite of earth system models
Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will increase ocean acidification... Earth System Models project a global increase in ocean acidification for all RCP scenarios. The corresponding decrease in surface ocean pH by the end of 21st century is in the range of 0.06 to 0.07 for RCP2.6, 0.14 to 0.15 for RCP4.5, 0.20 to 0.21 for RCP6.0 and 0.30 to 0.32 for RCP8.5

The RCP2.6 scenario, one in which the world rapidly moves to limit carbon emissions, would likely avoid some of the worst damage to coral reefs and other marine ecosystems.

The RCP8.5 scenario, the current "business as usual", could be considered the "few corals" scenario. To use IPCC parlance, this would be stated with medium or high confidence.  Perhaps we should add bacon to this scenario. They say everything tastes better with bacon.

(with thanks to research assistant Matthew Wagstaff)

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