Ocean Acidification: Effect on Earth Radiation and Global Warming

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Clouds can affect the Earth radiation balance. Image by Godserv

Clouds can affect the Earth radiation balance. Image by Godserv

Ocean Acidity Effects

Dr. Katharina Six, one of the researchers involved in the study, explains to Decoded Science:

“We studied some sea water enclosures (mesocosms) to see if there was a connection between the acidity and the concentration of DMS. What we found was that for more acidic environment (i.e. lower pH), DMS content was lower. Lower DMS in the waters implies lower DMS in the atmosphere too; indeed, we could see that there was a correlation between these two quantities. In some areas heavily affected by ocean acidification, we saw an overall decrease of DMS flux into the atmosphere as high as 22 %.”

Radiation Energy Change

Dr. Six and her coworkers used these data to try to predict the effect that these lower DMS concentrations may have on the CCN and cloud formation, and consequently, on the Earth’s radiation balance. To do this, they performed some modeling studies, using a program (aerosol-climate model ECHAM5.5-HAM2) which simulates the chemistry and the physics of the aerosol in the atmosphere.

Our results showed that the global radiative forcing increases as a result of lower DMS concentration.” Dr. Six said “in the cases of medium sensitivity to DMS, an additional radiative forcing of 0.4 W m-2 was predicted. This corresponds to an increase in temperature of 0.23 – 0.48 oC.”

Connection with Global Warming?

According to Dr. Six:

These results highlight a very important point: ocean acidification, which is a consequence of increasing CO2 levels, might cause a considerable concentration change in a non-CO2 climate-relevant gas. This translates as a simple phenomenon – less clouds get formed, so more energy reaches the Earth – which has the potential to speed up global warming.

At the moment, this process and the effect on the atmosphere temperature are not considered in the projections of future climate change; however, this study suggests that it may have to be taken into account.

It is essential to perform more investigations in the field; it is important, for instance, to understand which marine species are more affected by acidic pH for DMS production, and if there are analogous phenomena which may have a similar effect on DMS production, but that have not been considered.

Does ocean acidification have the ability to affect the atmosphere, and even the entire globe? Fewer clouds may mean a hotter planet, and only further study will tell us how hot – and how soon.

Sources

Six, K.D. et al., Global warming amplified by reduced sulphur fluxes as a result of ocean acidification. (2013). Nature Climate Change, DOI: 10.1038/NCLIMATE1981. Accessed August 30, 2013.

Simo, S. et al., Coupled dynamics of dimethylsulfoniopropionate and dimethylsulfide cycling and the microbial food web in surface waters of the North Atlantic. (2002). Limnology and Oceanography, 47(1), 53-61. Accessed August 30, 2013.

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