Atmospheric Sciences Editors' Vox

Good Night Sunshine: Geoengineering Solutions to Climate Change?

In order to limit global warming to Paris Agreement goal levels, climate engineering should be considered as a viable solution.

By and Guy Brasseur

The goal of last year’s Paris Agreement to limit global warming to 2C, if not 1.5C, are admirable, but it’s unlikely that this aspirational goal can be reached with voluntary greenhouse gas emission reductions alone. Already, we are nearing the 1.5C global warming level, with predictions for reaching 2C not far into the future. The implications of global warming are recognized widely, both in short-term events like coastal inundation and extreme weather, and long-term in the form of permanently shifting climate zones and higher sea level. The range of our actions, however, is not limited to greenhouse gas generation only.

Building on humanity’s remarkable history of engineering approaches to overcome challenges—from early use of fire to create stronger tools, to modern manufacturing and construction—climate engineering techniques should be included as viable solutions for reducing the impacts of global warming. Investigations of geoengineering approaches have been around for several decades, but have grown especially since the 2006 publication of Paul Crutzen’s essay on reducing solar influence, called “Albedo enhancement by stratospheric sulfur injections: A contribution to resolve a policy dilemma?”

Climate engineering takes two approaches: (1) Carbon dioxide removal (CDR), and (2) solar radiation management (SRM). CDR addresses the cause of climate warming by removing greenhouse gas from the atmosphere (“treat the illness”). SRM offsets the warming effects of greenhouse gases by allowing Earth to absorb less solar radiation (“treat the symptoms”). Reduction of greenhouse gas emissions, as proposed in the Paris Agreement, is desirable, but is not a prerequisite for climate engineering. Among the range of techniques, SRM, the focus of Crutzen’s essay, is the main source of professional and public anxiety and has mostly remained taboo. There are concerns about unintended consequences, local applications with global consequences, runaway effects, and even climate warfare.

Given that climate engineering remains highly controversial, a set of thoughtful research papers and scientific commentaries have been published on this topic in AGU’s open-access journal Earth’s Future, introduced by Boettcher and Schäfer (2017). The thematic set of papers entitled Crutzen +10: Reflecting upon 10 years of geoengineering research, examines the techniques and risks of climate engineering, from specific methodologies to sociopolitical dimensions. The contributions highlight our much improved understanding of the environmental, political, and societal risks and benefits of climate engineering, but they also recognize that the current state of our knowledge is insufficient for reliable deployment. Computer modeling and integrated assessments have advanced the positive and negative aspects of various techniques, allowing for an informed public debate and eventual decision-making. Some nations more than others are advancing this understanding and are considering some implementation. However, more extensive scientific efforts and social study that includes real-world, outdoor experimentation will be needed to adequately assess near-term deployments and their impact.

Climate engineering has unquestionable potential to limit global warming when coupled with currently available technologies, but the scientific, social and ethical dimensions of implementation are not sufficiently examined. Given the worldwide impact of most deployment approaches, planning should occur on a global scale, involving all nations, both rich and poor, and not be limited to a few technologically advanced, wealthy stakeholders. We know we must limit the impacts of global warming, but we also know that warming will continue for decades or centuries even with radical reductions in greenhouse gas emissions. This situation generates an urgent need to invest in research and impact analysis of climate engineering approaches. Judging by the resilience of today’s human society to global environmental change, ignoring the potential of climate engineering solutions does not seem prudent nor realistic.

—Ben van der Pluijm, Department of Earth & Environmental Sciences, University of Michigan; email: [email protected]; and Guy Brasseur, Max Planck Institute for Meteorology; National Center for Atmospheric Research; email: guy[email protected]

  • James Matkin

    There can be little doubt that solar geoengineering will have an impact on the climate just as volcanoes do. In the 70s some fear of global cooling also attributed to fossil fuel particles dubbed “global dimming.” It is a bad idea because the evidence of global warming today is natural and unstoppable as it is not driven by trace amounts of Co2 plant food. Think about it global warming has made civilization possible by melting the last ice age away so we could live and prosper. There is no climate crisis. Polar ice is stable – seas are not rising much – polar bears are thriving – islands are not sinking and deserts are greening. More Co2 is entirely beneficial.

    “A report on the State of the Climate in 2016 which is based exclusively on observations rather than climate models was published yesterday by the Global Warming Policy Foundation (GWPF). Video and full report follows.

    Compiled by Dr Ole Humlum, Professor of Physical Geography at the University Centre in Svalbard (Norway), the new climate survey is in sharp contrast to the habitual alarmism of other reports that are mainly based on computer modelling and climate predictions.

    ‬ Prof Humlum said: “There is little doubt that we are living in a warm period. However, there is also little doubt that current climate change is not abnormal and not outside the range of natural variations that might be expected.”

  • socalledbob

    Maybe we need more sunlight to increase photosynthesis. More sunlight could also alter rainfall patterns. What would be needed is another moon to extend daylight hours and reduce the need for night time lighting. I doubt enough a reflection from another moon would be enough to spur plants and alter rainfall. But it might be enough light to make people aware of the situation.
    Regardless a planned shutdown of aircraft for a certain period for both N America and Europe needs to be done soon to test for climate sensitivity.

    • Dustin Yunng

      an aircraft shutdown so the skies where I live in NC isnt blocked with chemtrails, shutting out the beautiful sunlight….

  • Bruce Melton

    It is very important to draw a distinction between geoengineering and climate pollution cleanup. atmospheric carbon dioxide removal is in no way, shape, or form geoengineering unless we classify all other pollution spill cleanup as geoengineering. There are major psychological implications of using language that describes climate pollution cleanup as geonengineering that have shown to create great concern about the feasibility of geoengineering as a broad class of solutions. Atmospheric carbon dioxide cleanup (removal) exhibits none of the traits that these concerns are founded from. Also, very important to the geoengineering discussion of emergency climate control action published after the above referenced Boettcher and Schäfer (2017) article went to press, Keith et al., Stratospheric solar geoengineering without ozone loss, PNAS, December 12, 2016, uses minute stratospheric calcium carbonate to increase upper atmosphere albedo in a process that increases, not decreases stratospheric ozone, abating concerns over sulfate albedo control pH impacts and ozone depletion.

  • Reid

    The only safe way to handle climate change is to adapt to it, not to attempt to engineer our way through it. That means changing our behavior: how and where we live. In addition to effects from current anthropogenic climate forcing, Earth is also near the peak of a 100,000 year natural temperature cycle. [Severinghaus, Wolff, and Brook (2010). Searching for the Oldest Ice. Eos, Vol 91 No 10, 5 October 2010.] In 5-, 10- or 50-thousand years the climate may be quite different, despite the present rate of warming, just as it was only 20-thousand years ago. Then in the future how do we reverse-engineer any changes we may force upon the climate system today? Geoengineering climate becomes an exercise in chasing our human tails around. We simply need to adapt.

  • Priscilla

    Interesting read, but seriously, bad choice of accompanying photo. There are so many out there who believe contrails or natural atmospheric optical effects such as parhelia and circumhorizontal arcs are dreaded “chemtrails” secretly deployed by the government. Using a photo like this immediately provides unfounded confirmation that their theories are correct – and maybe they are to some extent – but you really don’t want to introduce a newly publicized area of scientific research (ridiculous or not) by linking it to an already well-established conspiracy theory. We already have way too many people going around saying that lenticular clouds are created by the government to conceal UFOs.

  • Hartmut Heinrich

    “All nations must be involved.” OK, forget it. Anyhow, climate engineering is an excuse for doing little or nothing in reducing emissions of GHG. Nature and ist climate System is so komplex as we learn from climate modelling that better to keep hands off.

  • Hagen Marilia

    Are you proposing to disturb the stratosphere ? ANSWER THIS QUESTION FIRST:
    How the atmospheric layers are formed?
    WHAT ARE THE MECHANISMS? IONOSPHERE,ASTHENOSPHERE, Mesosphere, STRATOSPHERE…. are you proposing a instrument to just go there and dismiss something you have no idea? IS IT?

  • Dagmar Palmerova

    when we add the complete military psychotronic systems around our planet and the biowarfare programs, we might get finally to the core of this day/nightmare

  • Lorraine Surringer

    Geoengineering has been going on for years without informing the people or getting their agreement. It is the biggest crime against this planet and humanity in my opinion!
    In the UK we are all Vitamin D3 deficient due to lack of sun: rickets is back, immunity is massively affected so that cancer is now 1 in 2, auto-immune diseases and asthma are through the roof and dementia and mental health issues too!
    And there are as many people who don’t believe Al Gore’s ‘global warming’ hype as do! I honestly believe that geoengineering is the CAUSE of any climate change and not the cure that they are touting! 30,000 US Scientists signed the Oregon Petition denying global warming and in the UK scientists are not given a voice if they dispute it and have even been axed from the mainstream media for speaking out – eg Piers Corbyn, David Bellamy.
    They are poisoning the very air we breathe and we have no choice but to breathe!

    • socalledbob

      Worldwide average reduction of sunlight of 22% has been occurring since the 1960’s. It’s called global dimming or cooling. Particulates are obscuring the sun and altering rainfall patterns. Real time data can be found here:

  • flow ir in

    it is not even clear that there _is_ a climate problem, nor is it clear what the feedback value of CO2 is. Interfering at this stage, with no idea what it will do, is monstrously reckless.

    • Dustin Yunng

      It could be population control under the name of geoengineering….right, its all for the people…. we dont believe that!!!

    • Mitch_Ocean

      Perhaps you should read even a fraction of the literature before you comment. For your information, concern about potential impacts of fossil fuel CO2 as a policy problem were first brought forward to LBJ back in the 60’s. Given that current warming (transient not equilibrium) is about 1 deg C for less than 50% of a CO2 doubling, the likelihood that the feedback is small is infinitesimal. Your individual ignorance does not translate to a lack of knowledge.

      • flow ir in

        “concerns about potential” are not evidence of a climate problem. a Climate of alarmism, perhaps.

    • Romed Bucher

      it’s not even clear that water always runs downhill!

  • David Ball

    Funny that your pic of the proposed geoengineering program looks identical to the stuff floating over my house everyday for the last 8 years.

    • Awesome guy

      because they have been doing it for much longer than 8 years…

    • Colophon

      It’s a stock photo of a cirrus cloud. It’s pretty hard to illustrate something that is in the theoretical stages. Real SRM geoengineering wouldn’t make clouds – clouds actually increase global warming, so would not be useful at all!

  • Richard Bunce

    Classic, Climate Justice proponents claim to know enough about the Earth’s climate to destroy the hydrocarbon fuel based economy and all the social impacts and unintended consequences that will have but do not know enough about the Earth’s climate to employ geoengineering… of course this is really about Climate Justice proponents increasing government power and revenue and redistributing wealth not CO2 atmospheric concentration reduction.

    • Colophon

      It’s pretty clear that we need an alternative to the hydrocarbon based economy, because whether or not you believe in AGW, it is pretty obvious that we will run out of hydrocarbons.

      • Are Buntz

        Since you can make hydrocarbon fuels out of CO2 and H2O… no we will not.

        • Colophon

          Are you familiar with the concept of enthalpy? CO2 and H2O are the combustion products of hydrocarbons. You take hydrocarbons, you combust them, and you get lower-enthalpy products, with the difference being released as usable energy.

          Going back the other way you need to put the same amount of energy in. Converting CO2 and H2O into hydrocarbons requires energy input – you can’t get more back out than you put in!

          • Are Buntz

            Plenty of excess energy around from nuclear powered generation plants for instance, which is why the Navy is looking at this as a way to generate jet fuel on board it’s nuclear powered carriers. Hydrocarbon fuel is easy to store, transport, convert to usable energy in an ICE. Could even use it out in the middle of nowhere when wind turbine/solar panel generation exceeds demand to provide transportation fuels that are easy to store and transport.

            • Colophon

              That’s fair enough but it’s not an energy source, in the way that fossil fuels are. It’s a means of energy storage: you have to use another energy source to create the fuel. What I mean by the hydrocarbon economy is the use of fossil carbon. Once that runs out then we will be essentially recycling the carbon we already have, and we will need renewable energy sources to do that.

              And at the moment there’s certainly not enough “spare” capacity to do what you suggest: if there was then we wouldn’t need the fossil fuel in the first place! In the future then yes it could be viable but to my mind that is no longer a “hydrocarbon economy”; it’s a renewable energy economy using hydrocarbons as a storage method.

              • Are Buntz

                The hydrocarbon economy is the use of hydrocarbon fuels… whether produced in the earth over millions of years or in a plant in a few minutes. Particularly for transportation having hydrocarbon fuels will be important for a long time to come, at least pending another energy storage revolution.

                OK to think about it that way I suppose, although I doubt the CO2 hunters will not… and certainly storing renewable energy output when or where or how it may not be needed into a form where it can be easily stored, transported, and used in existing hydrocarbon systems.