Geoengineering: why all the fuss?

The IPCC, in its wisdom, has decided to wade into another emerging controversy – this time over whether any form of ‘geoengineering’ might be acceptable to contain rising global temperatures. At a meeting in Peru last week, experts from all the working groups looked at the various ideas currently in circulation and how they might be treated in the upcoming Fifth Assessment Report.

The answer to any question often depends on the phrasing of the question itself, and for geoengineering it is no different. It seems perverse, in my view, to include – as the IPCC does – the removal of carbon dioxide from the atmosphere in the same basket as ‘solar radiation management’, which includes for example efforts to intentionally change the planet’s albedo by spraying sulphate aerosols into the stratosphere. By the former definition, you engage in geoengineering every time you plant a tree. Moreover, why not include the addition of CO2 to the atmosphere under the category of ‘geoengineering’? That would make us all geoengineers every time we start the car or switch on a light.

The irony is that such a use of the term would be technically quite correct: we do all take part in geoengineering on a daily basis, and not just by our collective effect on the planet’s carbon cycle. We have altered the nitrogen cycle by an even greater proportion, through the synthesis and use of nitrogenous fertilisers. One might also consider the anthropogenic transformation of the land surface to be geoengineering, of a very physical nature – in which case all the world’s farmers are also geoengineers. It is because we have made this enormous transformation that we can now be said to be living on a human engineered planet in a new geological era, the Anthropocene.

However, in the everyday sense of ‘geoengineering’ I think the discussion should be more limited, to planetary-scale artificial efforts to mitigate global warming. There are various of these in circulation, some more realistic than others. The addition of mirrors at the Lagrange point between the sun and the Earth would be prohibitively expensive – more so by far than simply getting rid of fossil fuel-combusting technologies and replacing them with zero-carbon ones. More realistic by far is ‘solar radiation management’ by the addition of sulphates to the upper atmosphere – what makes this one scary is that it would probably actually work, and be achievable at reasonable cost (0.5-2.5bn $ a year).

Some quite ambitious experiments are indeed already being proposed. Researchers in the rather hush-hush ‘SPICE’ project (Stratospheric Particle Injection for Climate Engineering) are apparently considering the feasibility of building a giant 1km-high chimney near their laboratory in Cambridge, but are nervous about the public reaction. (You can imagine the tabloid headlines as the boffins carry out their crazy James Bond-type experiment in the air.) Actually I am told that it will be more like a garden hose tethered to a helium balloon, and will only spray out water vapour, but I doubt that minor detail will trouble the tabloid hacks.

We know that sulphate aerosols injected into the stratosphere act to cool the troposphere below because the effect can be observed every time there is a big enough volcanic eruption. Temperatures dipped by several tenths of a degree following the Pinatubo eruption of 1991, for example. But the addition of aerosols does not simply cancel out warming. It makes sunlight more diffuse, which stimulates plant growth ($) through photosynthesis – in the years following large volcanic eruptions the growth rate of CO2 in the atmosphere tends to fall. It also tends to deplete ozone in the stratosphere, not directly but through stimulating the formation of ‘polar stratospheric clouds’ which are the main sites for ozone destruction in the polar springtimes.

Most seriously, perhaps, is that aerosol injection would also alter precipitation patterns ($). This would mean reduced evaporation and precipitation worldwide, with enhanced drying in the sub-tropics. So the price we might pay for a reduction in global warming would be reduced rainfall in some parts of the world. This effect on the hydrological cycle would produce winners and losers and probably makes the whole thing politically unfeasible – once someone (the UN?) is intentionally altering the planet’s temperature, every drought and harvest failure would be blamed on the geoengineers, despite the scientific challenges of pinning any single event on the aerosol injectors (which are, naturally, the same challenges we face in attributing specific events to climate change).

But there is a real issue here: the globe is already cooled by human-injected aerosols, perhaps by half a degree or more. These come from biomass burning, coal-fired power stations and suchlike, and are injected into the troposphere, where they cause health-threatening air pollution. As China and other polluted developing countries get richer, they will doubtless insist on cleaner air. So the current aerosol sunshade will certainly be removed in decades to come, boosting global warming still further. So why not shift the aerosols from the troposphere to the stratosphere, where no-one has to breathe them? I put this as a proposal to illustrate unwitting planetary management is no different from intentional planetary management – except for the politics.

So the problems of geoengineering come down most to governance. Human beings are already having a great deal of trouble – see my posts from UNFCCC meetings – deciding what we want the average temperature of this planet to be over the next century. The possibility of directly influencing the atmospheric sunshade introduces a new level of complexity. But it is an option which must be explored, even if only as an insurance policy in the event of some catastrophic climatic tipping point. So let the research continue – but let no-one be fooled – as Bjorn Lomborg recently was – that the ‘solar radiation management’ variant of geoengineering is an easy or cheap option as compared to boring everyday reduction in carbon emissions.


  1. Barry Woods

    As you describe.. there would be the inevitable – geo-engineering caused -extreme weather – accusations and cross border conflict because of it.

    For those political reasons, I cannot see any major geo-engineering would ever get the go-ahead.

  2. grayman

    Your thoughts on geoengineering are intriging, the former beingeveryday observation and the latter being possibly dangerous. The mere thought that we can actually control the climate of the earth boggles the mind, But IMO is a waste of resources that could be better spent on problems the world faces today, ie, clean water, malaria, hunger, shelter.

  3. David Bailey

    I am pretty doubtful about deliberate climate modification.

    1) We don’t really know if it is getting hotter, or by how much – a lot of the research is distorted in a variety of ways..

    2) It is by no means obvious to me that the temperature is optimal as it is. Maybe the temperatures of the Medieval Warm Period, when vines grew in the North of England, was better in lots of ways! Except for the thrill of skating on the Thames, I doubt if the period of the little ice age, was optimal!

    Maybe a little research into the feasibility of such tricks, might be prudent, but we hardly need to offset the few tenths of a degree of warming that is claimed so far!

  4. One Voice

    Weather or not is irrelevent at this point. In order for SRM programms to be effevtive, they would have to be 1- globally deployed (NATO countries are already doing such programs) and 2- already have started in order to gain desired effects, the process is accumulative and will take decades to reach the levels needed for stated intents. Current nano-particulates being discussed/used are of course aluminas, which are not only far cheaper and resourseful, but have 4 times the reflective surface area. They also have the useful prupose of becoming ionized (charged) and becoming the perfect medium HARRP signals to travel, if you beleive in such things. None of us have any clue, but all one needs to do is simply look up and observe.

    1. David Bailey

      The urgency that seems to be implied by your reply, seems a bit exaggerated when you look at the actual global temperature graph:

      These graphs were shown widely 10 years ago, when temperatures did seem to be increasing, but the curve has flattened a lot since then, and the up-to-date picture is less often displayed!

      Furthermore, if CO2 is causing significant warming, it is important to remember that the effect is logarithmic. That means you get the same effect each time you double CO2 concentration. It is really important to realise the difference between a linear effect – each ton of CO2 producing a fixed rise in temps – from a logarithmic effect, where there is a law of diminishing returns.

    2. scas

      I see someone mentioned Roy Spencer. Isn’t he the guy that produced the false temperature record and missed the orbital drift biased for 20 years without detecting his error? Yet he remains a contrarian in spite of his poor history. He even has Dr in his website name. What a pompous ass. And his connections to Big Tobacco. Then again, climate deniers cherry pick contrarian scientists and ignore real world observations.

      Spencer has received 657 000 from heartland institute. And we all know their history. Specter is also an expert for ICECAP, an organization that belives we must prepare for an ice age. He claims scientists need a problem in order to get funding. It looks like he is creating a controvery to get money. What a hypocrite. Spencer took part in Great Warming Swindle, a fraudulent an erroneous fake-umentary.

      Therefore “doctor” roy spencer is a climate denier shill.

    3. David Bailey

      Would you like to give me the correct up-to-date global temperature graph?

  5. Hector Balint

    It surprises me that the possibilities of industrial photosynthesis are seldom mentioned in this kind of discussion. As you point out, man succeeded in industrialising the nitrogen cycle. If the problem is too much CO2 common sense would suggest that the solution is to diminish it. Screwing around with the weather in order to try and change the climate would be desperate stuff. There are bombers that can fly at 70,000 feet so I don’t think we need to have the 20km vertical fire hoses at the ready, though it might be a way to recycle Lovelock and Rapley’s “ocean pipes”. They appear to have sunk without trace.

  6. Paul

    ‘So why not shift the aerosols from the troposphere to the stratosphere, where no-one has to breathe them?’

    Aerosols in the stratosphere promote ozone depletion:

  7. J Bowers

    So, you have a number of loans that you’re struggling to pay, so you take out another loan with no payments for six months to make the monthly payments on the existing loans. Problem is, six months go by…..

    And if the geoengineering does nothing to scrub the increased CO2 from the atmosphere, the phytoplankton and corals still take a big hit. I find normal engineering far more attractive, to get us off our addiction to fossil fuel combustion.

  8. scas

    The anti-geoengineering pundits are obviously in a form of denial. They refuse to believe that the arctic sea ice is almost gone, and that the East Siberian Arctic Shelf is now degassing 3.5 billion tons of methane per year, this will only increase and the ESAS holds 1600 GT. They assume emission reductions are enough and putting up windmills will somehow make things okay. This is false and suicidal thinking. We are locked in for more heating, and the Arctic merhane is in a state of positive feedback. According to Shakhova abrupt release of up to 50 Gt is possible. This would ruin our world and kill everyone from famine and heat. Marks estimate of only 0.5 degrees is wrong. It is most like 2-3 C, or 1-2 Watts per square metre.

    Some contrarian pundits like to point out the methane isn’t an issue based on David Archers model or some other obscure reference. Well, real life observations and the words of majority climate scientists matter, not the climate deniers false opinions or even the greens. All political group has religious beliefs. So I guess jamaes hansen and lovelock were right, but then most climate deniers have never bothered to read their books, because they are comfortable in their “belief” that the climate is not changing, and that if it is humans are not responsible, and that if we are, then climate will change as per IPCC politicized lower-bound models.

    Additional warning on the state of methane can be found at climateprogess, NSF, and multiple other climate science organizations.

    We should be developing geoengineering, synethic food, and nuclear power.
    And we need 80% emissions reductions.

    1. David Bailey

      Well I know I have posted this before, but maybe you didn’t see it. The North Pole sea ice was so thin a sub could surface there in 1958!

      Have a look, and tell me if researchers haven’t underestimated the natural variability of arctic ice a little.

      As I keep on saying, I very much support traditional Greenpeace values – stopping forest destruction, pollution (excluding CO2, which is essential for plant growth), arms proliferation, etc. I just think a lot of well meaning activists – which probably includes you – have been duped by a huge, well funded campaign focusing in the wrong direction.

  9. M

    One thing is that SRM should be considered in addition to, rather than in place of, mitigation. For one thing, SRM does not reduce ocean acidification. Plus, the more mitigation, the less SRM is needed, and the less SRM, the fewer unintended side effects…

  10. metro70

    You say the mitigation of the cooling aerosols will increase warming, but you don’t mention the research of Drew Shindell of NASA and others including James Hansen, that concludes that ~50% of the Arctic warming and melt is caused by black carbon [soot], that cuts down the albedo—it also is at least part of the cause of melting glaciers and permafrost.


    [ “We will have very little leverage over climate in the next couple of decades if we’re just looking at carbon dioxide,” Shindell said. “If we want to try to stop the Arctic summer sea ice from melting completely over the next few decades, we’re much better off looking at aerosols and ozone.”]

    They’ve testified to Congress on black carbon, calling for mitigation, but seem to get no help in that cause from other climate scientists.
    Why would that be?

    Are the AGW scientists only interested in mitigation that will result in more warming —–to bolster their AGW case?

    You speak of geo-engineering research in case of tipping points, but why don’t you get behind the push for this easier mitigation for quick result?

    Why are you and others not agitating for the major focus right now to be on this, to stop the melting of the Arctic ice—especially when so many warmists want us to be alarmed about the possibility and hazards of sea level rise.

    Melting ice has ~70 times more impact on sea level rise than does thermal expansion of the ocean, so it’s strange that AGW scientists are not all over the media etc about it.

    Meanwhile the burning of wood and other biomass in China, India, Indonesia and Brazil that generates the black carbon continues as we speak.

    This sort of disconnect , along with refusal to engage with sceptical scientists, is what fuels scepticism in the community.

    1. Mark Lynas (Post author)

      I completely agree that black carbon is a major issue, and I describe it in detail in my book. Absolutely it is one of the earliest and easiest potential ways to reduce the rate of global warming. It is also another reason why carbon offsets based on improved cookstoves in developing countries are a good idea for a whole host of reasons – BC and health, for instance, much more than CO2.

  11. MarkB

    “Actually I am told that it will be more like a garden hose tethered to a helium balloon, and will only spray out water vapour, but I doubt that minor detail will trouble the tabloid hacks.”

    Because only tabloid hacks would care?

  12. Robin Smith

    Treating symptoms in any way will not cure the disease. No matter what we do, if the force at the root is more powerful, it will always overwhelm any treatments, nothing will change. Wasted time.

    So when are we going to talk about root cause? See here for an idea as to what that might be:

    The Robin Smith Institute: Root cause of Climate Change


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