Recent work on sea-level rise from a variety of approaches suggests a rise of 1-1.5 m by the end of this century. According to Dr.  John Moore: “If no geoengineering were done and using the latest estimates of plausible economic development pathways to 2100, sea level would rise between about 50 cm to 1 m. With reasonable geoengineering schemes sea level would still rise - by as little as 30 cm with modest greenhouse gas emissions, but up to 70 cm with high emissions.”

In the new article at the high repute scientific journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) John Moore and his colleagues evaluates several geoengineering schemes in terms of their ability to offset the estimated sea level increase.

According to the authors, the most effective course of action requires adopting two parallel strategies: converting to fuels that are derived from biomass, such as sugar cane and switchgrass; and capturing atmospheric CO2 and storing in geological reservoirs and in ecosystems that naturally process and sequester carbon.

Geoengineering has been proposed as an emergency treatment for climate change, though it remains highly controversial with huge scientific and international governance issues to be resolved. Schemes that aim to divert incoming solar radiation, such as placing giant mirrors in Earth orbit, or injecting sulfur dioxide particles into the atmosphere, may partially offset the projected increase but tend to be less economically viable and present greater risks of unintended consequences and its effects on ecosystems and the climate system are poorly understood.

Sea level rise is perhaps the most damaging repercussion of global warming, as 150 million people live less than one meter above current high tides (and these areas include some of the world's largest cities).

Is geoengineering the ‘Plan B’ for mankind?

Most scientists agree that carbon dioxide emissions caused by humans contribute greatly to global warming, and that these emissions need to be controlled if damaging future impacts such as sea-level rise are to be averted. But if we fail to do so, is there a 'Plan B'?

Scientists have proposed ways of 'geo-engineering' the Earth system to tackle global warming, thereby reducing its impact on both the main contributors of sea level rise: thermal expansion of ocean water and melting of glaciers and ice sheets.

In the article the researchers present simulations of 21st century global sea level resulting from both geoengineered reduction in solar insolation and modification of the atmospheric carbon reservoir. “We select examples of low cost methods - afforestation and sulphate aerosol injection, and much more expensive and ambitious projects - such as mirrors in space, and attempt to model reasonable scenarios of their development and effectiveness over the 21st century.“

Potential geoengineering options can be divided into two broad categories. Possibly the easiest to realize are those that rely on decreasing temperatures by blocking incoming solar radiation or increasing albedo, which would balance the radiative impact of increasing greenhouse gasses, though not address the chemical or biological consequences of greenhouse gasses. The second category of solutions addresses the temperature issue and the chemistry together by modifying - or seeking to reverse - the anthropogenic change in the global carbon cycle. In effect lowering the CO2 concentration of the atmosphere.

The researchers are John Moore (Beijing Normal University, and Arctic Centre at the University of Lapland), Svetlana Jevrejeva (National Oceanography Centre), and Aslak Grinsted (Copenhagen University).

Article:
J. C. Moore, S. Jevrejeva, and A. Grinsted, (2010) Efficacy of geoengineering to limit 21st century sea level rise, Proceeding of the National Academy of Sciences, doi/10.1073/pnas.1008153107
www.pnas.org/cgi/doi/10.1073/pnas.1008153107

Written elsewhere:
Nature News: Geoengineering won’t curb sea-level rise
Science/AAAS: Can Geoengineering Halt Sea-Level Rise?
BBC: Geoengineering 'not a solution' to sea-level rise
Scientific American: All-out geoengineering still would not stop sea level rise
News Scientist: Geoengineering won't undo sea level rises

UoL/Arctic Centre/AV