Respectfully, no, it is not “incorrect”. My contextual meaning of what I wrote “…too have any measurable effect…” was on the global climate. We are talking about (severe) climate change mitigation (on a global scale). Local efficacy of a given experiment is a good start but not an end point.
But let me start with some general responses to your comments, then look at the actual experiment (described in the linked to article)
First, you refer to various experimental efforts. Good, this is EXACTLY what I was talking about: Experiments (note that you mention “14 localised experiments”). Again, local is good for starters, but could be overwhelmed by global scale atmospherics and local, regional, and large-scale climate forcings, if scaled-up.
You wrote: "What is proposed are modelling studies, carefully gated experiments and sea trials that would give us progressively greater confidence that the net results were beneficial. "
Yes, of course, that is the purpose of such geoengineering (at whatever scale) experiments. You are echoing my original comment. Thank you for providing me with this (limited, special case) example.
The study (actually, an article referring to a research project near [similar conditions as] the Great Barrier Reef) you link to describes plans to ‘scale up’ the experiment (in 2021) to 3 times the original area (which is ‘one tenth’ of the planned area), with future plans (2022 and beyond) to scale-up (i.e., increase the area of impact) the experiment to ‘ten times’ the original area, which “should be able to brighten clouds across a 20-by-20-kilometre area.”
Now, all this experimenting clearly indicates the intent to cover a larger (and larger) area to achieve its desired impact. In this case, however, since it is targeted at protecting the Great Barrier Reef, there is a limit (total area of the Reef) to the scale of THIS particular experiment. I hope it works (but see my comment, later)
You also wrote: “The alternative to investigating which methods of climate intervention have positive potential is to let the current levels of GHG, further unavoidable emissions, and overbalancing tipping points take us into darkness.”
OK, no one here is arguing FOR the ‘alternative’.
and: "You cannot have the experimental data until you have done the particular experiment. "
Right. I agree. My previous comments comport with this assertion.
You wrote: “Why may not we have a mix of existing known and unknown challenges and prospective solutions by which to devise future XPrizes?”
I am not sure how one would design an XPrize around an ‘unknown’ challenge. The purpose of an XPrize is to find a ‘prospective’ solution (or several) to a (kn own) challenge. Certainly, a prospective solution can offer us a guide to a future XPrize (e.g., by revealing short-comings, flaws, constraints, etc.). If you wish, please provide an example of this ‘mix’ that you refer to.
AS FOR THE EXPERIMENT (Harrison et al):
Here are the key/essential nuggets of information:
[Description of the purpose and procedure for the proposed experiment]
’“Microscopic sea water droplets are sprayed into the air, evaporating leaving just nano-sized sea salt crystals which act as seeds for cloud droplets, brightening existing cloud and deflecting solar energy away from the reef waters when heat stress is at its maximum.
I will note that there are many different types of clouds (density, size of droplets, etc.) and not all are candidates for brightening (although sea salt as a ‘nucleating’ mechanism sounds promising to me, assuming an inherently higher refraction index of sea salt crystals). There is evidence that smaller droplets make for denser nucleation (of water vapor molecules) and which subsequently generate more pronounced cooling effects (Rosenfeld et al, 2019)
“In the future this technology might be able to be applied over the Great Barrier Reef to reduce the severity of coral bleaching during marine heat waves, cooling and shading the corals below.”
OK, that all sounds good and worth experimenting ‘on’. I would like to look deeper at the supporting prior research that buttresses this current effort.
[Description of the actual experiment]
“We tested the hypothesis at one-tenth of the scale we’re aiming for, using a drone in the atmosphere and a sampling vessel 5km away on the sea surface and showed how we can successfully create hundreds of trillion of these sea salt crystals per second which float up into the atmosphere to bolster the reflectivity of the existing clouds,” Dr Harrison said.
I do recognize the need for stimulating near-sea-surface clouds (which are the very type decreasing due to warming). However, my main concern here is with the phrase “float up into the atmosphere”. Obviously, you do NOT want these nano-scale sea salt particles (the mechanism of cloud nucleation) to float too high into the atmosphere (and/or disperse too widely into same), as this will impact (limit) the altitude, extent/size (reflective surface area of the clouds) and ‘solidity’ (density) of the cloud formation (thus the desired impact). And, the wider the area, the more larger scale (atmospheric) forces come into play
Lastly, I will note that this experiment (Harrison et al) is as much about cloud ‘seeding’ as it is about cloud ‘brightening’.