8 ms·

Mitigating the risk of geoengineering

42 points by julianpye 10y ago

philipkglass 10y ago
Since we're past the point where emissions cuts alone can keep long term warming below 2 C, I do expect active geoengineering efforts later this century. Solar radiation management with aerosols is not a long term fix but could keep positive feedback effects damped while slower long term fixes (like emissions reduction plus accelerated silicate weathering) roll out. The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide, which is cheap to form via sulfur combustion and disperses excellently because it's a gas. Delayed oxidation reactions cause SO2 to form nuclei for aerosols. Even though calcium carbonate is also inexpensive, I don't think there is a comparably cheap/easy way to deliver a fluid precursor for it to the upper atmosphere. The closest I can think of is aerosolizing a calcium hydroxide solution that would carbonate in situ via reaction with atmospheric CO2... but calcium hydroxide is only slightly soluble in water. You'd need to lift a lot of extra water mass.
- marcosdumay 10y ago
  > The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide So, it just a matter of throwing tons of "dry sulfuric acid" on the atmosphere?
  - philipkglass 10y ago
    Sort of. One could release sulfur dioxide (or burn sulfur to form sulfur dioxide) at high altitude, or release slower-reacting sulfur species like carbonyl sulfide from surface locations. In any of these cases what will happen is that reactions with nitrogen oxides, ozone, light, atmospheric moisture, and other particles will ultimately convert the sulfur to sulfuric acid, which will then form additional particles of high reflectivity. It would somewhat increase the surface precipitation acid burden, similar to the acid rain that was a byproduct of 20th century industrialization, but most sulfur oxides that come from power plants or metal refining are flushed out of the lower atmosphere by precipitation. By directly or indirectly adding SO2 to the stratosphere instead of the troposphere, the ratio of reflection:acid content would be higher than that of incidentally produced waste-product SO2. (That's why we can't start cooling the planet just by removing sulfur controls from existing coal plants; most of that SO2 would produce acid rain accompanied by little additional sunlight reflection.)
- tbrownaw 10y ago
  past the point where emissions cuts alone can keep long term warming below 2 C Isn't that 2C supposed to have come from "just give me a damn number" rather than any analysis of likely impacts? I'm going to be very amused if we somehow stop any warming without reducing co2, and die off when all the shellfish keep dissolving.
  - philipkglass 10y ago
    Yes, it's a pretty arbitrary number: https://www.carbonbrief.org/two-degrees-the-history-of-climate-changes-speed-limit https://www.carbonbrief.org/two-degrees-the-history-of-clima... I don't think that "amused" would exactly be my reaction if we kill off all the wild shellfish :-/
neon_electro 10y ago
What do potential geoengineering efforts mean for homeowners and businesses with installed solar power generation?
- yarrel 10y ago
  My first thought was agriculture...
- wlesieutre 10y ago
  Relatively minor, nobody's talking about blocking 50% of the sunlight, more like 1-2%. Pretty straightforward for direct photovoltaic generation, but the wider consequences on the (very complicated) Earth system are hard to say. Would it affect wind patterns (and wind power generation as a result)? What about plants/animals/agriculture?
  - diggernet 10y ago
    And how do we undo it when we discover we don't like the side effects?
    - wlesieutre 10y ago
      More geoengineering! On the other hand, anthropogenic climate change is already going to screw all those things up, so it's not like avoiding geoengineering is necessarily the right choice either. Just need to understand the potential risks and benefits as well as possible before considering it.
      - diggernet 10y ago
        As someone who grew up hearing stories about the unintended environmental damage caused by many well-intended Corps of Engineers projects, geoengineering makes me cringe. Edit: I probably should have found a way to use "hubris" in that sentence...
        10y ago
cnp 10y ago
And people laugh at the chemtrail folks... All of this research is taking place right in the open.
codecamper 10y ago
another naive article, this time from Harvard, that fails to mention the term "ocean acidification". At some point krill cannot form their exoskeletons, bringing an abrupt end to whales and other sea creatures.
- curtis 10y ago
  I don't think it's reasonable to expect every article about global warming to mention "ocean acidification". Displacing fossil fuel power generation with nuclear power plants would certainly reduce ocean acidification, but nevertheless most of the nuclear power articles I've read neglect to mention this fact. There are other forms of climate engineering that would address C02 directly. One that's received a fair amount of press is "iron fertilization"[1]. I don't know, but my guess is that most people who talk about "solar geoengineering" (of any sort) probably think we're going to be doing solar geoengineering, iron fertilization, and probably multiple other forms of climate engineering at the same time. But not every article that discusses iron fertilization mentions sulfur dioxide, and not every article that talks about stratospheric sulfur dioxide mentions iron fertilization. [1] https://en.wikipedia.org/wiki/Iron_fertilization https://en.wikipedia.org/wiki/Iron_fertilization

42 points by julianpye 10y ago

Since we're past the point where emissions cuts alone can keep long term warming below 2 C, I do expect active geoengineering efforts later this century. Solar radiation management with aerosols is not a long term fix but could keep positive feedback effects damped while slower long term fixes (like emissions reduction plus accelerated silicate weathering) roll out. The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide, which is cheap to form via sulfur combustion and disperses excellently because it's a gas. Delayed oxidation reactions cause SO2 to form nuclei for aerosols. Even though calcium carbonate is also inexpensive, I don't think there is a comparably cheap/easy way to deliver a fluid precursor for it to the upper atmosphere. The closest I can think of is aerosolizing a calcium hydroxide solution that would carbonate in situ via reaction with atmospheric CO2... but calcium hydroxide is only slightly soluble in water. You'd need to lift a lot of extra water mass.

marcosdumay 10y ago
> The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide So, it just a matter of throwing tons of "dry sulfuric acid" on the atmosphere?
- philipkglass 10y ago
  Sort of. One could release sulfur dioxide (or burn sulfur to form sulfur dioxide) at high altitude, or release slower-reacting sulfur species like carbonyl sulfide from surface locations. In any of these cases what will happen is that reactions with nitrogen oxides, ozone, light, atmospheric moisture, and other particles will ultimately convert the sulfur to sulfuric acid, which will then form additional particles of high reflectivity. It would somewhat increase the surface precipitation acid burden, similar to the acid rain that was a byproduct of 20th century industrialization, but most sulfur oxides that come from power plants or metal refining are flushed out of the lower atmosphere by precipitation. By directly or indirectly adding SO2 to the stratosphere instead of the troposphere, the ratio of reflection:acid content would be higher than that of incidentally produced waste-product SO2. (That's why we can't start cooling the planet just by removing sulfur controls from existing coal plants; most of that SO2 would produce acid rain accompanied by little additional sunlight reflection.)
tbrownaw 10y ago
past the point where emissions cuts alone can keep long term warming below 2 C Isn't that 2C supposed to have come from "just give me a damn number" rather than any analysis of likely impacts? I'm going to be very amused if we somehow stop any warming without reducing co2, and die off when all the shellfish keep dissolving.
- philipkglass 10y ago
  Yes, it's a pretty arbitrary number: https://www.carbonbrief.org/two-degrees-the-history-of-climate-changes-speed-limit https://www.carbonbrief.org/two-degrees-the-history-of-clima... I don't think that "amused" would exactly be my reaction if we kill off all the wild shellfish :-/

neon_electro 10y ago

What do potential geoengineering efforts mean for homeowners and businesses with installed solar power generation?

yarrel 10y ago
My first thought was agriculture...
wlesieutre 10y ago
Relatively minor, nobody's talking about blocking 50% of the sunlight, more like 1-2%. Pretty straightforward for direct photovoltaic generation, but the wider consequences on the (very complicated) Earth system are hard to say. Would it affect wind patterns (and wind power generation as a result)? What about plants/animals/agriculture?
- diggernet 10y ago
  And how do we undo it when we discover we don't like the side effects?
  - wlesieutre 10y ago
    More geoengineering! On the other hand, anthropogenic climate change is already going to screw all those things up, so it's not like avoiding geoengineering is necessarily the right choice either. Just need to understand the potential risks and benefits as well as possible before considering it.
    - diggernet 10y ago
      As someone who grew up hearing stories about the unintended environmental damage caused by many well-intended Corps of Engineers projects, geoengineering makes me cringe. Edit: I probably should have found a way to use "hubris" in that sentence...
      - 10y ago

cnp 10y ago

And people laugh at the chemtrail folks... All of this research is taking place right in the open.

codecamper 10y ago

another naive article, this time from Harvard, that fails to mention the term "ocean acidification". At some point krill cannot form their exoskeletons, bringing an abrupt end to whales and other sea creatures.

curtis 10y ago
I don't think it's reasonable to expect every article about global warming to mention "ocean acidification". Displacing fossil fuel power generation with nuclear power plants would certainly reduce ocean acidification, but nevertheless most of the nuclear power articles I've read neglect to mention this fact. There are other forms of climate engineering that would address C02 directly. One that's received a fair amount of press is "iron fertilization"[1]. I don't know, but my guess is that most people who talk about "solar geoengineering" (of any sort) probably think we're going to be doing solar geoengineering, iron fertilization, and probably multiple other forms of climate engineering at the same time. But not every article that discusses iron fertilization mentions sulfur dioxide, and not every article that talks about stratospheric sulfur dioxide mentions iron fertilization. [1] https://en.wikipedia.org/wiki/Iron_fertilization https://en.wikipedia.org/wiki/Iron_fertilization