A new book by David Hone, Chief Climate Change Adviser at Shell, takes the reader on a journey through the transition in the energy system that must be undertaken to address the climate change issue. The book, Putting the Genie Back: Solving the Climate and Energy Dilemma, deals with a wide range of topics, including carbon pricing, electric cars and solar power, and even ventures into areas such as the somewhat taboo subject of geo-engineering. What follows is an excerpt from the book where Hone discusses the geo-engineering solution.

In the days before computer models, climate lobbyists, climate sceptics, so called ‘warmists’ and catastrophists, there was an early and thoughtful introduction to and analysis of the issue of climate change by the science community, published within a longer report on the environment by the US government and issued under the signature of President Lyndon B. Johnson. It makes for fascinating reading.

This 1965 paper looked at the atmospheric build-up of carbon dioxide, the potential for further build-up by 2000 as fossil fuels continued to be consumed, expected temperature rises, and the possible impact this temperature rise would have on global sea levels as ice caps melted. It concluded that: . . . . the climatic changes that may be produced by the increased carbon dioxide content could be deleterious from the point of view of human beings.

Perhaps the most surprising aspect of the 1965 paper is the reference to a geoengineering solution the deliberate large-scale intervention in the Earth’s natural systems to counteract climate change. The conclusion to the section on carbon dioxide emissions goes on to say: The possibilities of deliberately bringing about countervailing climatic changes therefore need to be thoroughly explored. A change in the radiation balance in the opposite direction to that which might result from the increase of atmospheric carbon dioxide could be produced by raising the albedo, or reflectivity, of the earth. . . . .” 

Simplest solution

Nearly fifty years later, not a great deal has been done in response to this, although climate science has certainly advanced. Rather, the focus has been entirely on mitigation of emissions, with an increasing parallel focus on adaptation. The case for taking more drastic action through geo-engineering has waned, even as success in actually reducing emissions has been hard to come by.

There are good reasons for this. The climate system is chaotic, at least in the short term. Climate science is still struggling to fully understand and forecast shorter decadal trends, such as the apparent pause in surface temperature change in the first decade of this century. Although the physics of a geo-engineering solution may be understood in terms of the radiative balance, the shorter-term impact could be unpredictable and therefore potentially dangerous.

A modern container ship travelling from Shanghai to Southampton via the Suez Canal will eject about 30 tonnes of sulphur into the atmosphere, along with some 3,000 tonnes of carbon dioxide

Nevertheless, some scientific effort continues against the backdrop of political steps such as the Paris Agreement. The simplest of the geo-engineering solutions is already in existence, albeit not as an intentional means of managing the global temperature. Sulphur is being artificially pumped into the troposphere through the worldwide use of High Sulphur Fuel Oil (HSFO) in ships (and of course from other sources such as coal-fired power stations not fitted with scrubbers). The combustion of this fuel powers much of the world’s oceangoing fleet, with the sulphur being emitted through the ship’s funnel.

HSFO contains some 3.5% sulphur, so a modern container ship travelling from Shanghai to Southampton via the Suez Canal will eject about 30 tonnes of sulphur into the atmosphere, along with some 3,000 tonnes of carbon dioxide. The carbon dioxide adds to the growing accumulation of this gas in the atmosphere, but the sulphur remains in the atmosphere for just a few weeks in aerosol form before dropping out. Nevertheless, as a result of all the marine activity and other sources of sulphur, there is a net suspension of sulphur in the atmosphere above us. The result of this is that it cools the atmosphere by scattering incoming radiation, offsetting some of the warming impact of carbon dioxide and other greenhouse gases.

However, sulphur also has a negative effect in terms of local and regional air quality so the International Maritime Organization (IMO) has moved to limit sulphur in marine fuel. One analysis discusses the climate impact of the marine fuel sulphur specification being reduced globally to 0.5%. Whereas the global annual average cooling effect of shipping is currently some -0.6 W/m2 (compared to the current additional radiative forcing from post-industrial carbon dioxide now around 2 W/m2), this is shown to reduce to -0.3 W/m2 in the case of a global 0.5% sulphur specification – in other words, another 0.3 W/m2 of warming.

An indicative calculation has shown that a fleet of 150 aircraft injecting sulphur into the stratosphere on a continuous basis could potentially offset the warming associated with a doubling of carbon dioxide in the atmosphere

But the real issue is the potential role of sulphur in deliberately managing the global temperature as a possible geo-engineering solution. Trying to do this at sea level and injecting sulphur into the troposphere has far less impact than doing the same in the stratosphere. For the same amount of surface cooling, approximately one twentieth the amount of sulphur is required at 25,000 metres because the half-life of the aerosol suspension is some 18 months at that height, rather than a few weeks seen in the low atmosphere.

An indicative calculation has shown that a fleet of 150 aircraft injecting sulphur into the stratosphere on a continuous basis could potentially offset the warming associated with a doubling of carbon dioxide in the atmosphere. The cost of this is estimated to be no more than $10 billion per annum and perhaps quite a bit less.

Ocean acidification

But what of the implications of being able to manage atmospheric warming for an amount so small that even some individuals could undertake the experiment, or perhaps a group such as the small island states in defence of their territory? For major emitters this would be a paltry sum, far less than some of the direct mitigation options.

But if such a practice were undertaken, what then for the global endeavours to reduce emissions? Would we all give up trying? And while some amount of cooling might be achieved, phenomena such as ocean acidification would continue. Who should decide on such weighty issues and what if one nation or group of nations decided to conduct the practice unilaterally?

There are other geo-engineering options, but perhaps none as simple as the sulphur solution. At the other end of the spectrum are proposals to reflect sunlight before it reaches our earth. Suggested shade designs include a single-piece shade and a shade made by a great number of small objects. Most such proposals contemplate a blocking element at the Sun-Earth L1 Lagrange point.

A more predictable geo-engineering solution might be one that reverses the cause of our warming climate and begins to remove carbon dioxide from the atmosphere. As previously discussed, the application of carbon capture and storage and other negative emission technologies will be critical.

Editor’s Note

The above is an excerpt from David Hone’s forthcoming book Putting the Genie Back: Solving the Climate and Energy Dilemma.

David Hone is Chief Climate Change Adviser at Shell and author of the Shell Climate Change blog, published by Shell and also syndicated on the website of The Energy Collective.

He is a chemical engineer with 37 years of experience in the oil and gas industry. As a long-time climate commentator, his goal has always been to tackle the issue from a fact-based perspective, avoiding emotion and ideology.