Playing God With the Climate
Geo-engineering—science fiction or a realistic hope for humanity’s future?
Man has upset the balance of the Earth’s climate. Should scientists use technology to change it back? High-profile academic and social critic Professor Clive Hamilton examines the push towards geoengineering
In recent times scientists have watched with mounting alarm as carbon dioxide concentrations—particularly boosted by explosive growth in China—have increased relentlessly. Just last year the World Bank warned that “we’re on track for a 4°C warmer world marked by extreme heatwaves, declining global food stocks, loss of ecosystems and biodiversity, and life-threatening sea level rise.”
Against this backdrop, scientists began to talk about responses to this potential climate emergency—and the idea of geoengineering was born.
More than 40 schemes have now been put forward, all of which would deliberately intervene in our climate system. And the idea is gaining traction, with Bill Gates committing several million dollars to finance research into geoengineering and Richard Branson promoting it as a response to climate change. Even top oil companies are quietly backing geoengineering studies, in anticipation of a shift in the political landscape.
So how can we engineer the climate? From manipulating the Earth’s cloud cover to changing the ocean’s chemical composition to blanketing the planet with a layer of sunlight-reflecting particles, there are plenty of theories out there. Some are grand in conception, some are prosaic; some are purely speculative, some are all too feasible. But they all tell us something interesting about how the Earth system works.
It would take decades before we could discover whether attempting to engineer the climate is glorious enterprise or ruinous folly, but in the meantime here’s a look at some of the surprising possibilities being suggested.
Redecorate in white
As the sea ice in the Arctic melts, the Earth loses some of its reflectivity— white ice is replaced by dark seawater which absorbs more heat. If a large area of the Earth’s surface could be whitened, then more of the sun’s warmth would be reflected back into space rather than absorbed. A number of schemes have been proposed, including painting roofs white, which is unlikely to make any significant difference globally.
What might be helpful, though, would be to cut down all of the forests in Siberia and Canada. While it is generally believed that more forests are a good thing because trees absorb carbon, boreal (northern) forests have a downside. Compared to the snowcovered forest floor beneath, the trees are dark and absorb more solar radiation. If they were felled the exposed ground would reflect a significantly greater proportion of incoming solar radiation and the Earth would therefore be cooler.
But if such a suggestion appears
outrageous, it is in part because matters are never so simple in the Earth system. Warming would cause snow on the denuded lands to melt, and the situation would end up worse than before the forests were cleared.
More promisingly perhaps, at least at a local scale, is the attempt to rescue Peruvian glaciers, whose disappearance is depriving the adjacent grasslands and their livestock of their water supply. Painting the newly dark mountains with a white slurry of water, sand and lime keeps them cooler and allows ice to form; at least that is the hope. (The World Bank is funding research.)
Put up a shield
Another idea is to reduce solar radiation before it gets to Earth. One proposal is to spray sulphur dioxide or sulphuric acid into the upper atmosphere to form tiny particles that would reflect an extra 1 to 2% of incoming solar radiation back into space, thereby cooling the planet.
The most likely delivery method is a fleet of customized high-flying aircraft fitted with tanks and spraying equipment, although a hose suspended in the sky is also being investigated. In effect, humans would be installing a radiative shield between the Earth and the sun, one that could be adjusted by those who control it to regulate the temperature of the planet.
How effective would such a solar filter be in suppressing warming? All the models indicate that if we reduced the amount of sunlight reaching the planet, the Earth would indeed cool fairly quickly and evenly, although with less effect at the poles. The models also show that rainfall would be returned some way towards pre-warming patterns. Crucially, the solar shield would do nothing to offset the acidification of the oceans due to carbon emissions.
But other scientists argue that the climate system is so complex that it is impossible to draw any firm conclusions about the effects of such a radical intervention in the Earth system.
Other studies indicate that the
Indian monsoon could be seriously disrupted, affecting food supplies for up to two billion people, although the disruption may be less than in a scenario of warming without the solar filter.
One problem with sulphate aerosol spraying—described as the “killer objection” — is that we can only get a good idea of how it would work by fullscale implementation. Even then we would need at least ten years of global climate data before we had enough information to separate out the effects of sulphate aerosol spraying from natural climate variability and, indeed, from the effects of human-induced climate change. The levels of omniscience and omnipotence required to make it work really would have us playing God.
To add to the risks, if after ten years, when we accumulated enough data to decide that our intervention was not a good idea, it may be impossible to terminate the solar shield.
Find a new orbit
In 1993, the esteemed journal Climatic Change published a novel scheme by the Indian physicist P.C. Jain to counter global warming. Professor Jain began by reminding us that the amount of solar radiation reaching the earth varies in inverse square to the distance of the Earth from the sun. He therefore proposed that the effects of global warming could be countered by increasing the radius of the Earth’s orbit around the sun—a sci-fi style idea that uses nuclear fusion. An
orbital expansion of 1 to 2% would do it, although one of the side effects would be to add 5.5 days to each year. He then calculated how much energy would be needed to bring about such a shift in the Earth’s celestial orbit. The answer is more than the amount of energy humans would consume over 100 billion billion years (the age of the universe is around 14 billion years).
Sink the culprits
When we dig up and burn fossil carbon we make use of its trapped energy; but the carbon atoms do not disappear. So where do they go? First they go into the atmosphere. Some are then soaked up by vegetation. Some sooner or later end up in the various layers of the oceans. The deep ocean has the capacity to absorb large amounts of carbon dioxide from the atmosphere, and it would help if we could get more carbon down there and hope that it stays.
But how do we get carbon to the deep ocean? The answer lies in what is known as the biological pump. Tiny marine plants known as phytoplankton grow by combining carbon dioxide, various minerals and sunlight to multiply into blooms. On death, gravity causes the plankton to sink.
The effectiveness of the biological pump depends on the suitability of conditions for marine life, including the availability of micronutrients, especially iron. If a shortage of iron is limiting plankton growth in an area of ocean, then perhaps the artificial addition of the missing ingredient can stimulate algal blooms.
Fertilizing some areas of ocean with iron slurry does indeed induce algal blooms. But it turns out that much of the carbon fixed in the phytoplankton does not find its way to the ocean floor but circulates in the surface waters, feeding the food chain, before being emitted as carbon dioxide back into the atmosphere.
And while iron fertilization stimulates biological productivity in one area, nutrient stealing can see it fall in others. As one expert said: “You might make some of the ocean greener by iron enrichment, but you’re going to make a lot of the ocean bluer.”