Jul 01, 2016 5:40 PM GMT
https://www.project-syndicate.org/commentary/albedo-modification-research-and-development-by-david-keith-and-gernot-wagner-2016-06CAMBRIDGE – The last time the atmosphere held as much carbon dioxide as it does today was about three million years ago – a time when sea levels were 10-30 meters higher than they are now. Climate models have long struggled to duplicate those large fluctuations in sea levels – until now. Indeed, for the first time, a high-quality model of Antarctic ice and climate has been able to simulate these large swings. That is smart science, but it brings devastating news.
The new model shows that melting in Antarctica alone could increase global sea levels by as much as one meter (3.2 feet) by the end of this century – well above prior estimates. Worse, it suggests that even extraordinary success at cutting emissions would not save the West Antarctic Ice Sheet, locking in eventual sea-level increases of more than five meters. As little as one meter could put at risk entire cities, from Miami to Mumbai, and cause enormous economic disruption.
We need to turn down the heat – and fast. To this end, albedo modification – a kind of geoengineering intended to cool the planet by increasing the reflectivity of the earth’s atmosphere – holds tremendous promise.
Injecting synthetic aerosols that reflect sunlight into the stratosphere, for example, could help counter the warming caused by greenhouse gases. The mechanism is similar to wearing a white shirt in the summer: white reflects sunlight and cools what is underneath, whereas darker colors absorb sunlight and heat.
To be sure, even in the best-case scenario, solar geoengineering alone could not stabilize the world’s climate. For that, we must both stop pumping carbon pollution into the atmosphere and learn how to remove what is already there. That is why emissions cuts should receive the lion’s share of resources devoted to combating climate change.
But, as the recent study shows, emissions cuts alone cannot save the West Antarctic Ice Sheet and prevent a drastic sea-level rise. If they are pursued in conjunction with moderate albedo modification, however, there is a chance of halting rising temperatures, helping to keep the world under 1.5° Celsius above pre-industrial levels, the more ambitious target agreed at the Paris climate talks last December.