Clive Hamilton - Earthmasters: The Dawn of the Age of Climate Engineering

One of Australias leading thinkers, Clive Hamilton is author of the bestsellers Requiem for a Species, Affluenza and Growth Fetish. He is Vice-Chancellors Chair and Professor of Public Ethics at the Centre for Applied Philosophy and Public Ethics, Charles Sturt University.

I am in awe of what Clive Hamilton has done in Earthmasters. The man is a seer, not from dreams or mushrooms, but by force of an extraordinary intellect in full command of both climate science and geopolitical reality. More than merely an excellent treatment of the pros and cons of geoengineering schemes aimed at slowing climate change, Earthmasters examines the dawn of climate engineering as the perilous, ethically fraught final frontier in our species long drive to apply technology to control ever-more of the planet.
JAMES GUSTAVE SPETH, author of Red Sky at Morning: Americaand the Crisis of the Global Environment

Clive Hamilton is one of the worlds leading thinkers about the consequences and unsustainability of our hyper-consumption and materialism. His message is increasingly urgent and in Earthmasters, he clearly shows that we cannot expect megatechnological solutions to be problem-free when our ignorance of how the biosphere works is so great. The only thing we can manage is ourselves and we havent done a very good job of that.
DAVID SUZUKI, author of The Legacy

Sucking Carbon

The great carbon cycle

Geoengineering methods are typically divided into two types. Carbon dioxide removal methods aim to extract the gas from the atmosphere and deposit it somewhere safer; as we will see, they variously identify these storage options as the soil, vegetation, the oceans and back underground. They would work by manipulating one of the great natural processes that makes the Earth a dynamic evolving entity, the global carbon cycle, which continually exchanges carbon between the atmosphere, the oceans and the biosphere (and, much more slowly, the lithosphere). The second type, solar radiation management (considered in the next chapter), aims to cool the planet by reflecting a greater proportion of incoming radiation from the Sun back out to space. While carbon dioxide removal methods target the source of the malady too much carbon in the atmosphere solar radiation management methods target one of its symptoms: too much heat.

The usual distinction between geoengineering methods conceals as much as it reveals. Although all aim to alter the global climate, perhaps a more useful division would be between those that aim to intervene in the functioning of the Earth system as a whole, where the risks are greater, and more localized interventions that have only regional environmental impacts, where the costs of failure are lower. Nevertheless, the usual distinction also points to an important difference whether the intervention targets the disease or only a symptom of it and for that reason I stay with it in this and the next chapter to describe how they work. However, when it comes to the larger questions of geopolitics and ethics, and what climate engineering can tell us about humans in the twenty-first century, it will be more enlightening to focus on the system-altering technologies rather than localized ones.

Fossilized carbon is congealed solar energy, deposited millions of years ago when massive numbers of dead organisms were transformed by heat and pressure beneath layers of rock. When we extract fossil fuels from coal mines, oil wells and natural gas deposits, and burn them for their captured energy, the carbon atoms combine with oxygen and float into the atmosphere as carbon dioxide. By absorbing more heat near the Earths surface, the atmosphere enriched by carbon dioxide causes global warming. But then what happens to the carbon? As it circulates around the globe, some carbon dioxide is absorbed by land-based plants and microorganisms in the soil. Some is absorbed by the oceans. In fact, over the last decade or so the biosphere and the oceans have each absorbed a quarter of our emissions. But that is only the beginning of the story.

In the case of the terrestrial biosphere, vegetation and other life forms are in a constant flux of growth and decay. At times the flows do not balance each other out. In recent decades, the net amount of carbon stored in the Earths soils and vegetation has been gradually rising; despite continued deforestation in parts of the world, the take-up has been greater than the release. But this can only be temporary as there is a limit to the capacity of the biosphere to absorb carbon, a limit that will decline as more land is turned over to farming, as trace nutrients are depleted and as climate change advances. In future decades we cannot rely on the terrestrial biosphere to soak up much, if any, of our extra emissions; indeed, it may well become a net source of emissions. Growing trees is good, but it cannot save us from climate change.

So the capacity of the worlds oceans to absorb carbon dioxide is of decisive importance to the future climate. How does it work? Carbon dioxide from the air initially dissolves into the top layer of the ocean, more so in choppy turbulent seas. But the top layer is saturated and can absorb only as much carbon dioxide as is drawn down into the deep layers, layers that are not well mixed and so can take up more carbon dioxide. Cold water can absorb more carbon dioxide than warm water so the cold ocean layers of the high latitudes (towards the poles) do most of the work, even though they account for only 23 per cent of the Earths surface.

However, as more carbon dioxide is absorbed the surface layers of the oceans become more acidic (mixing carbon dioxide with water produces carbonic acid), slowing their ability to take up our carbon dioxide emissions. And as the globe warms so do ocean waters, further reducing their capacity to soak up more carbon. Nevertheless, over decades and centuries the atmosphere and oceans will continue to exchange carbon dioxide in a process of equilibration. So over the long term some 7075 per cent of this centurys carbon dioxide emissions will eventually be absorbed by the oceans, with some 2025 per cent remaining in the atmosphere. Some of the increased carbon dioxide stored in the atmosphere will stay there for many centuries, long after the last tonne of fossil carbon has been shovelled into the furnace of a coal-fired power plant. Over an even longer time-scale, the excess carbon dioxide very gradually penetrates the ocean depths, slowly drawing down the atmospheric content over thousands of years. Even so, 10 or 12 per cent of our fossil fuel emissions would persist in the atmosphere after 10,000 years.

Note: GtC = gigatonnes (billions of tonnes) of carbon. The land change is the sum of uptakes to land (+137 GtC) and cumulative emissions from land use change (153 GtC).
Sources: Pre-industrial stocks from C. Sabine et al., Current status and past trends of the global carbon cycle, in C. Field and M. Raupach (eds), The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World (Washington, DC: Island Press, 2004), pp. 1744. Changes in stocks from C. Le Quere et al., Trends in the sources and sinks of carbon dioxide,