Geo-engineering doesn’t prevent at all the rise of the tides. Engineering on a global scale is not a solution, even in an emergency, to the climate damage caused by human activities. This is the conclusion reached by a team of British, Chinese and Danish researchers after a new study on the future of the Earth’s oceans. In their opinion there is no escape: sea levels will rise at least 30-70 cm by the end of 2100, even using the latest weather manipulation techniques. Substituting geo-engineering for the control of emissions would create an enormous risk for future generations, according to research published in the scientific journal Proceedings of the National Academy of Sciences.

The highest authority on climate change, the IPCC (Intergovernmental Panel on Climate Change) predicted that sea levels will be 20-60 cm higher by the end of this century. This is an estimate which many scientists now revise upwards, bringing it up to 1-1.5 meters.

It will be a problem “which will affect approximately 150 million people living in coastal areas, including some major cities on the planet”, says Svetlana Jevrejeva, of the National Oceanography Centre in Liverpool, England, co-author of the research. For instance, in China in the coming decades, millions of people will move towards the interior of the country.

Most scientists agree: in order to slow down the rise in sea level, we have to address the problem at its root – reducing emissions. But for the achievement of this result, it could be too late. Therefore alternative proposals emerged and led to a whole new branch in this research. The idea is to develop engineering techniques to manipulate the weather. There are proposals to “fertilize” the oceans with iron dust or stir deep waters for the growth of algae, as they would capture carbon dioxide. Other ideas include: launching a gigantic planetary sunshade in orbit, injecting huge amounts of sulphur into the atmosphere to simulate the effect of volcanic eruption, and generating a cloud of particles that can shield the solar radiation. Other ideas focus on farming systems which facilitate the settling of soil carbon (biochar as a way of converting organic material in coal).

However, the case requires circumspection, as Jevrejeva and colleagues say. They concluded a study on the impact which five geo-engineering techniques may have on sea level rise towards the end of the century:

By 2100 the sea will rise by 30-70 cm even with the use of any engineering technique, except in the case of using the most extreme methods and with the most stringent global emissions scenario.

A moderate or worse intermittent use of weather manipulation wouldn’t be very useful.For instance, the researchers explain that injecting into the stratosphere the same amount of sulphur dioxide that was produced in the volcanic eruption of Mount Pinatubo of 1991 (approximately 10 million tons of SO2), could postpone the sea level rise for 40-80 years. Instead, to keep the sea at the level it had in the late 90s, we should repeat this “artificial eruption” every 18 months.

However, this, note the researchers, wouldn’t block the acidification of the oceans, which is inevitable unless there is a radical cutback in emissions of carbon dioxide. Not to mention that it would be costly and could cause “side effects”, such as changes in rainfall patterns or the danger of damaging the ozone layer in the upper atmosphere. Another hypothesis was the launching of huge mirrors to reflect sunlight, another case of weather manipulation, but this has hidden costs and implies technological challenges that are, according to scholars, daunting, to say the least.

The only method which leaves some room for opportunity is the use of bio-fuels that, used in conjunction with reforestation and biochar, combined with strict emission reductions, could limit the seas rising to 20-40 cm. Briefly, we have to be careful with exorbitant and costly engineering projects, Jevrejeva warns:

We do not know how the planet could react to geo-engineering activities of such a wide range.

National Oceanography Centre