Any attempt to geoengineer our way out of the climate warming mess we’ve found ourselves in is going to take a massive balancing act of sea level rise and surface air temperatures before we see any progress.
“Basic physics and past observations suggest that reducing the net influx of solar energy will cool the Earth,” said Peter J. Irvine, graduate student, University of Bristol, UK, and participant in the Worldwide Universities Network Research Mobility Programme to Penn State. “However, surface air temperatures would respond much more quickly and sea levels will respond much more slowly.”
Geoengineering is the term used for mechanically changing the amount of sunlight that reaches the planet’s surface. Such techniques include placing reflective sheets in the atmosphere to reflect some of the sunlight, as well as placing aerosols in the upper atmosphere, reflecting the effects caused by volcanic eruptions.
“These solar radiation management approaches could be cheaper than reducing carbon dioxide emissions,” said Klaus Keller, associate professor of geosciences, Penn State. “But they are an imperfect substitute for reducing carbon dioxide emissions and carry considerable risks.”
However, their likely success is balanced entirely on how well they are implemented.
“Strategies designed to reverse sea-level rise differ from the strategies designed to limit the rate of temperature changes,” said Ryan Sriver, research associate in geosciences, Penn State.
A Balancing Act
The implementation of such geoengineering techniques comes with a lot of risk and requires a huge amount of balancing to reach the wished for end result.
For example, to stop or reverse the expected sea-level rise as a result of the melting polar ice caps, incoming solar radiation would have to be decreased rapidly. However, this approach would cause a rapid cooling. Try it the other way around though, with a more gradual approach, would minimize the risks of rapid cooling but would also allow for considerable sea-level rise while we wait.
But we can’t rely on the public to decide either, because those living near the coast are obviously going to be concerned more about sea-level rise than about the rate of surface temperature changes, but those living inland will feel the opposite way.
The researchers from the University of Bristol and Penn State used a model to analyse the tension that exists if one wants to control sea level rise and rats of surface temperature changes. They ran 120 scenarios on their model with differing combinations of solar radiation management (SRM), including one which had no SRM at all.
The authors note that their model includes many approximations, such as a lack of mechanistic representation of ice sheets and they acknowledge that they did not consider scenarios that combine solar radiation management and reducing carbon dioxide emissions.
Their report, published in the current issue of the journal Nature Climate Change, shows that the forcing required to stop sea level rise could cause a rapid cooling with a rate similar to the peak rate used in a scenario with no SRM.
“While abrupt cooling may sound like a good idea, it could be more damaging than the increasing temperatures caused by increasing carbon dioxide,” said Keller.
“The rate of cooling can be a problem if it exceeds the capacity of the plants and animals to adapt,” added Sriver.
A Long Term Commitment
Another consideration that must be taken into account with geoengineering is the burden of responsibility it places on future generations.
The researchers showed that “termination of solar radiation management was found to produce warming rates up to five times greater than the maximum rates under the business-as-usual scenario, whereas sea-level rise rates were only 30 percent higher.”
So in other words, if our children or our children’s-children want to avoid such harsh ramifications from terminating our decision to geoengineer our atmosphere, they must commit to a slow phase out over many decades.