Geoengineering the Climate

P R Wallis, January 2010

In the December 2009 Newsletter I wrote an article on "Our Restless Planet" describing the considerable changes which have occurred naturally. Some have been cyclical from orbital and eccentricity changes, causing a sequence of ice ages, modified by the movement of the continents on their tectonic plates. The latter are also responsible for volcanic eruptions, which spew out green-house gases and make the Earth habitable. Finally I mentioned the modern industrial green-house emissions which will warm the globe, with climate changes of a yet uncertain magnitude. I mentioned the possibility of "geoengineering" to ameliorate these if necessary and said that the Royal Society would be reporting shortly.

This report has now been published[1]. In his foreword the President Lord Rees accepts that our discharge of green-house gases is driving changes to the climate and the long-term consequences will be exceedingly threatening, especially if nations continue ‘business as usual' in the coming decades. He says that most nations now accept the need to shift to a low-carbon economy but warns that this may achieve too little, too late, and there could be a pressure to counteract the effects by geoengineering. The report aims to clarify the scientific and technical aspects of this, though far more detailed study would be needed before deployment could be considered.

The report classifies the many proposals into two types:

1. (CDR) which reduces the level in the atmosphere, allowing thermal infra-red radiation from the earth to escape more readily.
2. Solar radiation management (SRM) which reduces incoming short-wave (visible and UV) radiation reaching the earth, by deflecting sunlight or increasing the reflectivity (the albedo) of the atmosphere, clouds or the earth's surface.

The report regards CDR as theoretically preferable, as it aims to tackle the root cause. However it recognises that no proven CDR techniques are available yet. For example biomass combined with carbon sequestration is expensive and requires land which competes for agriculture and biofuels. Enhanced weathering involves major mining and energy costs and so far unknown environmental effects. Fertilisation of the ocean with iron is not yet understood. Capturing carbon dioxide from ambient air has potential but a high cost. On top of this, all CDR methods would be very slow, taking many decades and do not present an option for a rapid reduction of global temperature.

Turning to SRM, the aim would be to balance the global mean radiative forcing of 4W/m² that would arise from the doubling from pre-industrial levels of carbon dioxide in the atmosphere[2]. It is estimated that a solar reduction of about 2% would be required for space-based methods. For surface-based or cloud methods an increase in the earth's albedo from 0.31 to 0.32 would suffice, but mean rather large changes locally. Even if the global mean temperature is compensated correctly, there would be regional differences; for example the solar reduction would impact more greatly on low latitudes than high latitudes. Compensating for changes in precipitation might need a smaller reduction in insolation, but a great deal more needs to be done to understand the complexities of such changes.

Of the SRM techniques considered, the report assesses the surface albedo change as vastly expensive and doubtfully effective. Cloud albedo increase, by spraying salt for example, is judged feasible at moderate cost but could make big regional variation. The enhancement of the stratospheric sulphate layer is better known, as volcanic eruptions have demonstrated such cooling[3]. The cost of it is low so it must be considered as the most promising option. Significant research would be required to identify potential impacts on the hydrological cycle, stratospheric ozone and biosphere.

Space-based reflectors have the advantage that no direct changes are made to the earth's chemical environment, but the costs would be much higher than stratosphere aerosols. One form of space system places reflectors near[4] the Lagrangian L1 point, 1.5 M km from the earth towards the sun; it would present no obstruction for satellites or telescopes.

A characteristic of SRM is that once a system is emplaced, it would be very quick, achieving the cooling effect in a few years. Detailed modelling studies so far suggest that the resulting climate, though not matching the pre-industrial climate precisely, would be far less damaging than the uncorrected consequences of doubled carbon dioxide.

The report's overall view is that early and effective action should be taken to reduce the discharge of green-house gases, i.e. mitigation, and adapting to climate change. Internationally coordinated research and development is needed to clarify the feasibility and environmental impacts of the more promising geoengineering methods. If CDR methods can be demonstrated to be safe, effective, sustainable and affordable, they should be deployed alongside conventional mitigation as soon as they can be made available. SRM methods should not be applied unless there is a need to rapidly reduce or limit global temperatures and they should only be applied for a limited time.

Other views on the subject exist, of course. Green Peace objects to any research on geoengineering at all on the grounds that it might be used as an excuse to stop or delay mitigation. A recent article in Nature[5] argues conversely for early studies on SRM. They say that due to the carbon cycle's inertia even a massive programme of emission cuts and carbon dioxide removal will take many decades to slow warming discernibly. SRM is the only technique which could have a virtually immediate effect and could be a vital resource in case climate is more sensitive than expected. It is also cheap. We need to find out more about its effectiveness and risks soon and not leave it till an emergency.

PeterWallis

___________oOo__________

There can be no doubt that climate change is a real phenomenon. Throughout Earth's long history, the climate has constantly changed. The question is: to what degree are we, that is, mankind, contributing to the problem? It is becoming difficult to hold a rational debate on this subject, as there is now a firmly established ‘official view' that: climate change is caused by the industrial activities of mankind increasing carbon dioxide concentration to dangerous levels Q.E.D.. Politicians are now involved and anyone who dares to question this ‘official view' is in their minds, guilty of something akin to heresy, particularly when they can sense a fertile area for taxation. The media fueled as ever by sensationalism, prefers to predict impending disaster and the scientific community, ever eager to grab research grants has done itself no favours by ‘doctoring' some results to fit current theories and making predictions that have been shown to be totally false. What is required is an unbiased appraisal of the facts.

The problem with this contentious subject is that it tends to confuse, climate change, short term changes in weather patterns and atmospheric pollution. There is no doubt that we must concentrate on reducing the levels of atmospheric pollution as this can only be regarded as a benefit to all and the reduction of man made ‘greenhouse gases' may have some, as yet uncalculated effect on the changing climate but this effect pales into insignificance when compared to the major factors that are responsible for dramatic climate change on Earth. These are natural cyclic phenomena over which we have absolutely no control and we have not been studying them in detail for long enough to make accurate predictions. It should also be pointed out that despite the fact that meteorologists have at their disposal some of the most advanced computers on the planet, they still find it impossible to produce an accurate long-term weather forecast! In fact their daily predictions are often wide of the mark.

If our political masters wish us to take seriously the idea that anthropogenic CO₂is the main cause of climate change, then they should lead by example. They should formulate legislation to prevent the ever increasing light pollution in towns and countryside wasting energy illuminating empty public buildings and office blocks and tax aviation fuel to reduce unnecessary air travel. Aircraft pump CO₂ directly into the atmosphere which causes measurable change in local weather conditions. If we are to make substantial reductions in anthropogenic CO₂ then we will have to make a paradigm shift in our way of life. Many of the suggestions currently proposed are akin to merely rearranging the deck chairs on the Titanic.

Doug Daniels.

[1] "Geoengineering the Climate – science,governance and uncertainty", Sept 2009.

[2]IPCC 2007a

[3]o C.

[4] Slightly nearer the sun, to compensate for its light pressure.

[5] Keith D W, Parson E and Morgan M G "Research on global sun block needed now", Nature 28^th January 2010.

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