Alan
It’s true that the hardware does not exist, but it is misleading to say that “the technology does not exist” because most people will interpret this as meaning that something cannot be done using standard commercial engineering practices.
Since we are talking aerospace, compare two examples:
·A new high-performance fire-fighting aircraft that could deliver 50 tons of water per pass.
·A hypersonic passenger aircraft with ram jet propulsion.
Neither exists today.
If you put together specs for the water bomber you could get multiple bids with performance guaranties from the big aircraft companies, and if someone (U.S. Forest service?) paid the bill you could reasonably expect that the aircraft be delivered and work more or less as expected.
Whereas, for the hypersonic passenger aircraft you could get companies to bid on engineering studies and test units, but not on a completed aircraft because no one knows how to do it, through the basic science is known.
I suspect most people would say that the technology “exists today” in the former case and not in the latter.
My recollection is that you have agreed with this clarification in previous discussions of this topic. Have you changed your mind?
Now, turning to geo. Some of the technology does exist in the sense that you could procure the hardware in a few years. This is true of the modified business jet’s in the Aurora report but it’s not true of other systems we looked at like the sky-hose or the airships.
Your comments about sulfur compounds ignore very large differences between the chemicals.
H2S is toxic at a few hundred ppm. The idea of using large quantities of it in an aircraft or in balloons (as proposed in your paper) seems to me highly implausible. The risks to operators and the public would be very large. That’s why we ignored that option in our paper.
H2SO4 is routinely handled in industry today, it’s one of the most common industrial chemicals.
We proposed transporting S to the stratosphere (low mass and very easy to manage) and converting to SO3 in situ. We talked to a leading firm that engineers H2SO4 plants about designing a conversion system suitable for an aircraft and concluded that it was plausible using current technology.
My view is that technology needed to begin putting sulfates in the stratosphere does exist today in the sense I have defined here. Of course some more speculative technology does not exist, but so what?
Here is what I say in “A case for engineering the climate” (forthcoming from MIT press and available for pre-order at
Amazon now, please excuse the self-promotion).
One could in principle use existing aircraft such as jet fighters, but modern business jets are more efficient and much cheaper. A stock Gulfstream G650, a top-of-the-line business jet, cruises at altitudes up to 50,000 feet. If a G650 were retrofitted with a low-bypass military engine such as the Pratt & Whitney F100, it could lift a payload of 13 tons to 60,000 feet, an altitude that would likely be adequate for the minimal deployment. A fleet of just twenty aircraft acquired within a few years at a cost of $1.5 billion should enable sufficient radiative forcing to produce large-scale climatic effects that were just barely detectable.
The requisite deployment technology does not exist as ready-to-go hardware today, but it could be supplied by any number of vendors using what the aerospace industry calls commercial off-the-shelf technology. We could build the deployment hardware far more quickly than we likely could develop the rest of the science, engineering, and governance required to begin deployment of geoengineering. In this sense that one can say that the technology exists today.
This is not an argument for or against immediate deployment. It is simply a statement of capability.
Do you stand behind the statements you made in the article?
Yours,
David