this is all good and well-known, but the cost of this commercial venture (as per the news) is way too high.
For a 2deg offset, the calculations show ~4 TgSO2 of injection per year which translates to ~ 40 Trillion dollars per year at a rate of $10 per gram of SO2. Cost estimates have gone through the roof into the stratosphere from a few billion dollars to trillions of dollars. Well, looks this is what commercialization would do. At this rate, the cost of stratospheric aerosol geoengineering could be similar to the cost of mitigation.... Bala On Wed, Dec 28, 2022 at 5:07 AM Andrew Lockley <[email protected]> wrote: > https://makesunsets.com/blogs/news/calculating-cooling > > > DECEMBER 27, 2022 > Share > Calculating Cooling > > How do we know how much cooling we're creating with our "clouds," and how > does this compare to warming from carbon dioxide emissions? > Fortunately, much smarter people have studied this for decades. Let's > review some of their work and calculate our climate cooling impact. > > Radiative Forcing? > > Radiative forcing is the key concept here. This is how much energy enters > the atmosphere vs. leaves it. An increase in radiative forcing leads to > warming, and a decrease causes cooling. Here's a more detailed explanation. > Measured in watts per square meter (W/m^2), we're over 3.1 W/m^2 of > increased radiative forcing since 1750. > > > Reflective Clouds > > How much reflectivity can we get from our clouds? Here's the summary we're > working from: > > > > This number isn't pulled from thin air. As the author explains: "This > sulfate efficacy value differs from that used in Smith and Wagner (2018) > (which considered only incoming radiation) and falls towards the center of > the values present across recent literature (Ferraro et al 2012, Pope et al > 2012, Kuebbeler et al 2012, Pitari et al 2014, Kleinschmitt et al 2017, Dai > et al 2018)." > > The key number here: > -.62 W/m2 radiative forcing created for a year by injecting 1 Tg of sulfur > > But, we're using SO2. So, SO2/S mass ratio means we get half as much > cooling per Tg: > -.62/2 = -.31 W/m2 radiative forcing per Tg SO2/year > > CO2's Warming > > How much does carbon dioxide warm the planet? I was surprised about the > uncertainty band here. IPCC says between .27 and .63 C per 1000 gigatons > co2: > > > > So: 1000 gigatons CO2 = +.45C > > Converting Units > > Now we've got all the information we need to do our math. First, a > conversion: temperature to radiative forcing. From the first table above, > .7C per W/m2 > > So, we'll convert our radiative forcing per Tg SO2 to temperature change: > -.31 W/m2 * .7C per w/m2 = -.217 C per Tg SO2/year > > Residence Time > > How long do these particles create cooling? 1-3 years. For our purposes, > we'll go with 2.1 years (although further particle optimization, higher > injection altitudes, and other changes may eventually result in much > greater residence time). > > So, 2.1 years particle life * -.217C per TG SO2/year = -.4557 C per Tg SO2 > launched for 1 year > > Putting It All Together > > So, how many grams of "cloud" to offset 1 ton of co2's warming impact for > a year? > 1000 gigatons co2 = +.45C > 1 Tg SO2 = -.4557C > 1000 gigatons co2 ~ 1 Tg SO2 > 1 gigaton = 1,000 Tg, so: > 1,000*1,000 = 1,000,000 Tg co2 = 1 Tg SO2 > dividing both sides by 1T: > 1,000,000 g co2 = 1 g SO2 > 1 metric ton = 1,000,000 g: > 1 metric ton co2 = 1 g SO2 > > So, with uncertainty bands on all of this, a gram offsets a ton: one gram > "cloud" offsets 1 ton of co2's warming impact for a year. > > Here's the spreadsheet I used to calculate this, with links to sources. > > There are arguments to compare this in different ways (joules, etc.); many > of these have strong merits. Because buyers of voluntary carbon credits are > focused on co2 equivalence, we've gone this route. > > As with all our work here, please let us know if you think we've made a > mistake and we'll correct! > > (image via Lexica) > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/CAJ3C-06OwAfeYPF%3DLwJ3X2nYdGvtq5gPj%3DNvRTGKnbO7sOR_hw%40mail.gmail.com > <https://groups.google.com/d/msgid/geoengineering/CAJ3C-06OwAfeYPF%3DLwJ3X2nYdGvtq5gPj%3DNvRTGKnbO7sOR_hw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- With Best Wishes, ------------------------------------------------------------------- G. Bala Professor Center for Atmospheric and Oceanic Sciences Indian Institute of Science Bangalore - 560 012 India Tel: +91 80 2293 3428; +91 80 2293 2505 Fax: +91 80 2360 0865; +91 80 2293 3425 Email: [email protected]; [email protected] Google Scholar <https://scholar.google.com/citations?user=eurjQPwAAAAJ> ------------------------------------------------------------------- -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAD7fhVmyf8gXFy48N_4VsUgf%2BF-CE1ar4mwQpVA9zhy7FNFyaA%40mail.gmail.com.
