The value of manned space flight?

[Umbran]

I assumed "pumping energy into the oceans" to be a shorthand for "energy produced on Earth is not radiated into space".

Nope, it was literal. Because for anything else, we get into loss to space, which can be substantial.

...in which case energy from non-renewable sources eventually ends up in the environment as heat.

Well, mostly.

There may be a lag between when energy gets produced and when it eventually ends up in as waste heat, but even if the lag is of the order of decades or even hundred years, it doesn't significantly change the picture.

Picayune aside: Some chemicals we produce, and changes we make, effectively store energy for much longer than a hundred years. Some plastics, for example, don't oxidize on the decade-to-century timescale.

Heck, my suburban house is already over a century old.

 

[Umbran]

But there are ways other than the direct heat that we output, that can cause catastrophic climate change.

Yes, there are. Water vapor, carbon dioxide, methane, nitrous oxide, and flourinated gases are the main culprits we can put out.

While some of them are pound-for-pound worse than CO2, we'd have to work at it to make the others in quantity enough to be a bigger problem than our current CO2 emissions, which are huge.

The point is more that when we think "catastrophic", it is really about how fragile human systems are.

 

[The Firebird]

Yes, there are. Water vapor, carbon dioxide, methane, nitrous oxide, and flourinated gases are the main culprits we can put out.

While some of them are pound-for-pound worse than CO2, we'd have to work at it to make the others in quantity enough to be a bigger problem than our current CO2 emissions, which are huge.

The point is more that when we think "catastrophic", it is really about how fragile human systems are.

Methane in particular is concerning, because its short term effect is substantial and there is a lot locked up in permafrost. Some heating will release it and cause a powerful positive feedback on a short timescale.

 

[The Firebird]

My main reason for continuing to support crewed spaceflight is that it is really sexy PR for science. Which is itself a great thing - we need all the people excited about science that we can get. At a personal level, I think space flight and space science in gereral are exciting and fascinating, even when there is no immediately obviously application.

I wish humans got as excited about, say climate science and vaccine science, but our brains seem wired for novelty, not for slow, incremental, meticulous study and experiment. But at least a few people who get jazzed by science through the Artemis missions will go on to become scientists, and that's a good thing.

It always seemed to me much more the engineering that got people exciting than the science. Everyone has seen the pictures from Cassini, but not many could tell you about it's science objectives.

 

[The Firebird]

The Paris Agreement was trying to keep change down below 2C, really hoping for under 1.5C, because by about 3C, the impacts on society start becoming severe enough that our history does not give us a handle on the sociopolitical changes that would follow. Humans would be alive, but the existence of modern social order becomes... dicey?

Expect to see stratospheric aerosol injection or other geoengineering efforts before the civilization destroying stuff. Those have their own risks, which in many cases are substantial.