By Tan Copsey
A major study published today in the United Kingdom asks what role proposed geoengineering technologies could play in regulating the climate. Tan Copsey spoke to one of its contributors, Ken Caldeira.
As part of a series for chinadialogue that examines the environmental and political arguments around geoengineering, Tan Copsey spoke to Ken Caldeira, senior scientist at the Department of Global Ecology at the Carnegie Institution and a leading expert in “climate emergency response research”. Caldeira is a contributor to the study published today by the Royal Society, Geoengineering the Climate: Science, Governance and Uncertainty, which asks whether planetary-scale geoengineering schemes could play a role in preventing the worst effects of climate change.
Tan Copsey (TC): What geoengineering ideas do you think are being considered seriously by scientists?
Ken Caldeira (KC): I think it is useful to approach this question by asking what problems are we trying to solve. If we are trying to solve the problem of increasing climate risk and climate damage, then we need to consider transforming our energy system first. If we are concerned with catastrophic climate change, then that pushes us towards other techniques.
If we look at the IPCC [Intergovernmental Panel on Climate Change] predictions for global temperature over the century, in every scenario the world continues to warm. So the question is: if rainfall patterns shift such that we are no longer able to grow food properly for the world, or Greenland starts sliding into the sea, raising sea levels rapidly, or if methane starts catastrophically re-gassing from the Siberian frozen grounds, what would we do? This leads us to think about options that could be deployed very rapidly to cool the earth.
I think the leading candidate is to emulate what major volcanoes do, which is to put huge amounts of small particles into the stratosphere, where they can deflect sunlight back into space. We know this works, because after Mount Pinatubo erupted in 1991, the earth cooled about half a degree Celsius. It would have probably cooled three, four, or maybe five degrees had that amount of material been maintained in the stratosphere. While these are very risky types of things to do, I think that in a climate emergency situation we might have to deal with those risks.
There are other options that make some sense: one of them is the idea of whitening clouds by spraying sea water through the air. This forms tiny little salt particles that increase the whiteness of marine clouds [reflecting light back into space].
I think these are really the two options that have the most plausibility. Most other options are either too difficult or expensive – like the idea of putting satellites into space between the earth and the sun, which would be a huge and difficult engineering undertaking.
TC: Do you think that someone will need to deploy forms of geoengineering in our lifetime?
KC: I am uncertain about how bad climate change is going to be for humans. I think it is pretty clear that if you are a polar bear or a coral reef, your days are numbered unless we radically change our emission patterns very soon.
Climate change is clearly an issue for some ecosystems and it is probably an existential issue for some people who are already at the margins, where climate change could push them over the edge.