Solar radiation management (SRM) and geoengineering are not needed

SRM is perilous, as the consequnces of intervening in a highly complex system are unpredictable. Actual GHG emissions cuts can achieve more, faster, surer, cheaper and without the risk.

Solar radiation management, SRM, is a group of proposed geoengineering technologies that aim to reduce the inflow of solar energy, rather than to reduce global warming by reducing greenhouse gases. It aims to offset greenhouse warming by reducing the incidence and absorption of incoming solar (short-wave) radiation (often referred to as insolation). Solar radiation management (SRM) methods propose to do this by making the Earth more reflective, that is by increasing the planetary albedo, or by otherwise diverting incoming solar radiation. This provides a cooling effect to counteract the warming influence of increasing greenhouse gases.

The physics of SRM is, in principle, rather straightforward. A doubling of the atmospheric CO₂ concentration compared to the pre-industrial level would cause a warming of about 4 watts per m2.

This is a small number in relation to the 107 watts that is reflected, so if 111 watts were reflected instead, there would be no global warming.

The case for SRM is simple: by shading our planet from a small proportion of sunlight, global warming can be halted, even reversed, in some cases fast and in some cases possibly at low cost.

For obvious reasons global warming will hit hot regions disproportionately, which risks making SRM a North-South issue. A group of scientist claiming to be neutral about SRM recently accused the ETC group (an NGO critical of SRM) of “paternalism” in an opinion article for Nature headlined “Developing countries must lead on solar geoengineering research”.

A case could easily be made for the opposite view, that SRM is yet another way for the North to procrastinate and escape responsibility for emissions. As the Nature article points out, “most solar-geoengineering research is being done in the well-heeled universities of Europe and North America”. It could also be added that substantial funding comes not only from the rich countries but also from rich northern philanthropists. The main danger of northern paternalism towards the global south may not necessarily come from small NGOs.

Another line of argument for SRM, by Mike Muller at Witwatersrand University, South Africa, goes:
“Africa must look hard at uncomfortable options or face being left behind by other countries with fewer scruples.”

It is not clear whether Muller just means that the front-runner of a technology will reap the fruits compared to later adopters, or if he means that someone else will actually steal the rain before it reaches Africa.

What actually constitutes an SRM technology is neither theoretically nor empirically well defined, but the following are often mentioned.

Surface albedo methods include white roofs and brightening of human settlements, introducing more reflective crop varieties by selection or genetic engineering, the conversion of forests to grasslands, desert reflectors (mirrors) on an enormous scale, afforestation in deserts such as the Sahara to increase evapotranspiration, deforestation at high latitudes (where trees are much darker than snow cover), and spreading white sand on dark soil. Yet another method is making the oceans brighter with chemicals that create small bubbles in the water or, in a more limited way, just making the wakes of ships longer and brighter.

Cloud albedo enhancement means making the clouds whiter, by spraying salt water into them.

Stratospheric sulphur or the injection of other particles makes the high atmos-phere hazier, so more light is reflected back and less energy reaches the Earth surface. This takes place during very large volcanic eruptions such as Pinatubo in 1991, which lowered the temperature for some five years by at most 0.5 degrees C. The method was proposed by Budyko in 1974 and would mean injecting millions of tons of SO2 into the stratosphere, each year.

Space-based methods aim at putting lenses, mirrors or clouds of dust in space so as to deflect or diffuse solar radiation before it reaches Earth.

The Royal Society proposed four criteria for assessment of each geoengineeering technology:

1. Effectiveness: including confidence in the scientific and technological basis, technological feasibility, and the magnitude, spatial scale and uniformity of the effect achievable.
2. Timeliness: including the state of readiness for implementation (and the extent to which any necessary experiments and/or modelling has been completed), and the speed with which the intended effect (on climate change) would occur.
3. Safety: including the predictability and verifiability of the intended effects, the absence of predictable or unintended adverse side-effects and environmentalimpacts (especially effects on inherently unpredictable biological systems), and low potential for things to go wrong on a large scale.
4. Cost: of both deployment and operation, for a given desired effect (ie for CDR methods, cost per GtC, and for SRM methods, cost per W/m2) evaluated over century timescales (later also expressed as its inverse, ie affordability). In practice, the information available on costs is extremely tentative and incomplete, and only order-of-magnitude estimates are possible.

These criteria are still useful, but should be compared to a default, such as coal power replaced by wind, solar or efficiency.

Fossils-to-RE is effective, can be done fast, has very few safety issues, and is cheap.

It should also be noted that SRM must beat fossils-to-RE on all four criteria. It is not a question of weighted average. You cannot have it if it is cheap but dangerous, or if it is deemed to be effective, safe and timely, but costs much more than shutting down a coal power plant and building PV per tonne of CO2 avoided.
It is indeed hard to see how any proposed SRM technology could pass this screening process. Most of the SRMs are irresponsible and ill-founded, and not worthy of serious consideration.

However, highly respected scientists have argued for geoengineering either as a last resort or as a faster and more effective way to deal with warming than emission reductions.

Stephen Schneider 1996:
“Supposing a currently envisioned low-probability but high-consequence outcome really started to unfold in the decades ahead (for example, 5°C warming in this century) which I would characterize as having potential catastrophic implications for ecosys-tems... Under such a scenario, we would simply have to practice geo-engineering ...”

Paul Crutzen 2006:
“Reductions in CO2 and other greenhouse gas emissions are clearly the main priorities. However, this is a decades-long process and so far there is little reason to be optimistic.”

Lord Rees of Ludlow, President of the Royal Society in the foreword to the Society’s report on geoengineering in 2009:
“But if such reductions achieve too little, too late, there will surely be pressure to consider a ‘plan B’ – to seek ways to counteract the climatic effects of greenhouse gas emissions by ‘geoengineering’.”

The term geoengineering and the concept of solar radiation management go back to the early 1970s and to still earlier efforts at weather modification for military or other reasons.

This long history is important for two reasons. One predominant idea of the postwar decades was that scientists can predict and control anything, given enough resources. Another common belief was that economic growth inevitably leads to more CO₂ emissions.

Weather and climate modelling was first developed with the early computers in the 1940s and 1950s. The scientific community, having developed the atomic bomb and the hydrogen bomb, were clearly overconfident. John von Neumann, the computer pioneer who was dubbed “the smartest man on earth”, worked on weather modelling. He believed that there were two kinds of weather, stable and unstable, and that all that was needed was bigger computers:
“All processes that are stable we shall predict. All processes that are unstable we shall control.”

He imagined that we needed only to identify the points in space and time at which unstable processes originated, and then a few airplanes carrying smoke generators could fly to those points and introduce the appropriate small disturbances to make the unstable processes flip into the desired directions. “A central committee of com-puter experts and meteorologists would tell the airplanes where to go in order to make sure that no rain would fall on the Fourth of July picnic.”

In 1963, Edward Lorenz showed that predictability is very limited. If the input data is changed a tiny bit, the result (weather) can change completely.

Though weather and climate are not the same thing, they have similar flipping points. But Lorenz’s article went unnoticed for more than a decade.

Some people, especially those whose scientific roots stretch a long way back, still be-lieve we can control the weather or the climate.

Another aspect of this long history is that by the 1970s, much of the scientific community actually saw global warming as a potential menace, though the general public was unaware of it. Because the global warming theory was not corroborated by actual temperature data, there was not much sense of urgency.

At that time economic growth was seen as inextricably linked to primary energy growth, through growth in transport, electricity demand and industrial output. Some of this growth was expected to be met by nuclear power, including fast-breeder reactors and fusion power.

Wind power did not exist, solar photovoltaic was extremely expensive, other renewable energy looked limited (hydro, biomass) or not very good (solar thermal, geo-thermal, electric cars). Nobody considered radical efficiency improvement an option.

The conventional wisdom was that economic development would lead to very much increased CO2 emissions for a very long time. An eventual Peak Oil would be met with coal liquefaction and tar sands. This view was common in developed countries, the third world and the Soviet Union.

This mindset did not change fast.

Even though climate change entered the international political agenda in 1987, emissions largely kept climbing.

In 1997, the year of the Kyoto protocol, the renowned physicist Edward Teller and the chief physicist at Lawrence Livermore national laboratory claimed that actually cutting emissions would cost more than $100bn/year, whereas for less than one per cent of that cost, warming could be “obviated” by sending millions of tons of sulphate or alumina aerosols into the stratosphere.

The decoupling of growth and emissions was not very apparent by 2008–2009, when the Royal Society revived geoengineering, first with a theme journal issue on the subject in 2008, and then with a report entitled Geoengineering the climate: Science, governance and uncertainty in September 2009.

This in turn led in 2010 to the formation of the Solar Radiation Management Governance Initiative (SRMGI), “an international, NGO-driven project that seeks to expand the global conversation around the governance of SRM geoengineering research”.

SRMGI does “not take a position on how SRM should be governed or whether it should ever be used”, but it provides an important platform for those who want to keep SRM as an option. (Those who are opposed to geoengineering for whatever reason are not interested in expanding the global conversation about it.)

The idea that geoengineering would be easier and cheaper than reducing emissions was being questioned by 2010, but the strongest evidence for the viability of GHG cuts is even more recent.

It is a different world now compared to 2007. It is not only conceivable that substantial GHG reductions can take place. It is a fact.

This was achieved during a period of economic growth, and without trying very hard.

Even more noteworthy is that China, after a long period of dramatically growing CO₂ emissions, more or less stabilised its emissions in 2013–2017, with growth of just 0.3 per cent over four years.

This is not a question of low-hanging fruit, but of general, affordable methods with a very large remaining potential. For example, solar and wind are rolling out very fast, in richer and poorer countries:

Issues with Solar Radiation Management:

• SRM addresses the wrong problem. The problem with climate change is not just that the average global temperature is rising. Redistribution of local and regional weather patterns can be disastrous for people and nature even if it does not influence the global average. Increased droughts and deluges do not cancel each other out.
• SRM and other engineering is a Plan B, but a Plan B is not required if we focus on Plan A. There is now growing optimism that 2 degrees and 1.5 degrees can be achieved this way.
• SRM leaves a number of important issues unattended. The problems caused by burning fossil fuels are not limited to CO₂ warming. They include ocean acidification, acid rain, black carbon emissions, N₂O, tropospheric ozone and methane emissions from the fossil fuel cycle, nitrogen eutrophication (terrestrial and aquatic), and health problems due to emissions of particles and mercury. Real CO₂ reduction reduces all such problems, but SRM does not. Some of the problems can be reduced with technical fixes (de-sulphurisation etc.) but SRM itself does not solve them. No fix exists for ocean acidification.
• SRM expresses the notion that we have to find new solutions – a kind of Man-hattan Project or Apollo Project for the climate – rather than using available technology and policy measures, just more and faster.
• The notion that brand-new solutions are needed may be attractive to billionaires who want personal credit for saving the world, sometimes in tandem with a media that is drawn to individual heroes. But it is the less glamorous collective national and international effort that can do the job, as they represent far more knowledge, resources and tenacity.
• SRM shifts attention from real GHG cuts, which represent a faster, surer, safer and more permanent way to mitigate climate change.
• SRM creates false hope for the fossil fuel industry, and could delay its decline or transition.
• The modelling of chaotic systems will remain imperfect. Unforeseen conse-quences of human intervention in the climate and weather systems are to be expected.
• SRM increases international tensions, because it changes precipitation pat-terns, which may mean that there are winners and certainly losers. More rain, and better harvests in one country may lead to droughts in another country.
• SRM experiments and deployment could undermine the 1977 Environment Modification Convention.
• Allegations of foul play are hard to confirm or disprove. Accusations, justified or not, can cause diplomatic crises.
• SRM could be “weaponized”, for example in an effort to change battlefield conditions or to starve an enemy population.
• Some of the techniques discussed are not easily reversible, since a “termina-tion shock” – a sudden rapid warming – may take place if a measure such as stratospheric injection is discontinued for whatever reason (international con-flict, economic crisis).

Fredrik Lundberg