For the full text see page 30 of this pdf, but I will bring you some edited highlights.
Ocean-fertilisation poses an unknown but potentially serious threat to marine biodiversity, which plays an essential role in regulating the global carbon cycle, as well as putting fishing communities at risk.
Pity they didn't see episode 1 of Ways to Save the Planet which fertilised the top layer of ocean with deep water nutrients, causing a previously empty bit of ocean to fill with life. Remember that much of the Pacific is desert-like already in its lack of biodiversity. These wave-powered pumps, if they work in earnest, are a means to greatly increase biodiversity. It deserves better than knee-jerk opposition. There's more...
Er, how do you know the threat is major, if it is also unknown? We have a major and known threat of global warming, and that means - why do I feel like I am talking to a 4 year old here - it would be good to have a controllable system for global cooling.
Climate geo-engineering by increasing the earth’s albedo poses a major and unknown new threat to the climate system, to biodiversity and to people.
Sure, the future is unpredictable if we control the amount of cloud cover or its reflectivity to manage the global temperature. But here is the thing. The future is unpredicable full stop. And it is rather more predicatable if we deal with global warming than if we don't.
So, as I was saying, two new episodes. The first was about a design for a tethered high altitude helium balloon wind turbine. Strictly this is renewable energy rather than geo-engineering, but the ends are much the same. They built a scaled down prototype which worked after a fashion. It would take a full size prototype to test whether such a turbine would have the output predicted. If so, 9.5 million of them could generate all the world's electricity. They would need 2500 times the global annual production of helium, which might be an issue.
In the same niche, there's a video on TED, suggesting kites can be used to generate power.
The second new episode was on increasing the reflectivity of clouds - stratocumulus over oceans - by spraying micron-size droplets of sea water at them. As usual there were some problems. First they insisted on unmanned radio-controlled low carbon boats to deploy the equipment, and so went for the somewhat oddball Flettner rotor propulsion system. Plenty to build and test there, and it worked surprisingly well. It's not clear how much power the rotors would need, or where it would come from. There were solar panels on the CGI ships, which wouldn't be much good under cloud - but then if it is cloudy, the ship is already in the right place, right?
There was less success actually making the droplets small enough, but you can't have everything.
But what I thought was most telling about this episode was the objections. At the end of each episode a handful of experts - presumably - in lab coats are asked why the proposal is a bad idea or wouldn't work. Usually, they have given sound objections. 16 trillion lenses in space, are you kidding? But this time, they were stuck. All they had was vague objections to the principle of geo-engineering, much like the stuff from the Greens. But unlike blankets on icecaps, robot ships could be turned off at the first sign of trouble.
Unlike, indeed, a massive tree-planting operation, if that is done for geo-engineering purposes. Come on people, show some sense of perspective. I know you can hug a tree more easily than a robot ship, but that is no guide to how best to save the planet.