Is Netflix's Seaspiracy film right about fishing damaging oceans?

This is, in essence, the crux of the problem. With your level of education it shouldn't be at all difficult to find a resource that answers your questions. Instead you've sought out two comic strips and two extremely ideological sources.

The basics of climate change can be taught standing on one foot. Carbon dioxide absorbs IR radiation, while oxygen and nitrogen are transparent to it. There was an equilibrium between visible light hitting the earth, being absorbed, and being reemitted as IR. We've doubled the amount of CO2, so you would expect twice as much of that heat to be retained. Compare it to the surface of the moon, which is at the same distance from the sun as us, but is on average well below freezing. CO2 isn't the only factor, but we've changed the equilibrium by doubling it.

That's it. It's very, very simple. The reason it produces only yelling is because it's been said so many trillions of times that if you haven't seen it, it's because you're not looking. There's no sane counter-argument: more CO2 produces more heat. It couldn't not do so.

The economics of why that's a problem is more complicated, but we've spent so much effort fighting anti-science attempts to deny really basic, obvious, trivial chemistry that we don't get to the even slightly non-trivial parts. The slightly non-trivial parts are "Yes, if you raise the temperature 4 degrees F it's going to make a lot of marginally livable places unlivable, and many millions of people will die. Also, some of that carbon dioxide becomes carbonic acid when absorbed by the oceans, which isn't good for sea life. Also, you know that weather is a chaotic system, and changing the energy balance of it causes changes to what meta-stable parts do exist, requiring substantial changes to the lifestyles of people there."

Again, this has all been said thousands of times. If it helps to have somebody explain it to you, great. But you also know that I'm about to be overrun with Gish Gallopers trotting out repeated-refuted objections, and to a casual observer it's going to look like I can't keep up and therefore must be wrong. And the only way to decide for yourself is the one thing you don't want to do: as you say, you're not an expert and don't want to become one.

So I'm really not sure what to do, and I'm pretty sure I've just wasted my virtual breath. I really think that my second paragraph should have put an end to this, and you can imagine my frustration that it doesn't.

It's quite simple, and I'm surprised you have not heard this before (it's taught to school children where I live in the UK), but:

- We were alerted to a potential climate change issue by the melting of glaciers and sea ice amongst other things.

- If this continues such that large quantities of ice melts then this will cause large problems as low-lying cities (such as New Orleans) and even whole countries (such the Netherlands and Bangladesh) would be flooded.

- It is also predicted that such changes will disrupt global weather patterns and produce more extreme weather. I'm not 100% on the science behind this, but I think it has something to do with weather gradients.

- Thus scientists began to look for an explanation (such that they could predict if such warming would indeed continue). An increase in carbon dioxide and other "greenhouse gases" in the atmosphere were determined to be a likely cause as they are known to have an insulating effect (can be demonstrated in simple small scale experiments), and we have also been able to measure increasing levels in the atmosphere. And this was backed up by modelling (presumably of known solar influx with different concentrations of CO2 in the atmosphere).

- There is also a secondary effect: Ice being whiteish reflects a lot of the Sun's energy back away from the earth back out into space. But water and soil tend to absorb a lot more of that energy. Thus there is concern that a small global temperature rise which causes the amount of sea ice / glaciers lost to pass a threshold point could cause a runaway effect where global temperatures continue to rise despite no more CO2 being released.

- Hence the focus on reducing CO2 emissions, and doing so ASAP.

- Re: "my winter was cold, where is the warming (exaggerating that of course)"

Pretty much everywhere except the North American continent. See https://www.forbes.com/sites/startswithabang/2019/01/30/this...

Hyperbole is counterproductive in the realm of science, but in the realm of public opinion and policy-making on catastrophic unaddressed problems, I would argue it is a necessity.

There are levels. Individuals may need something that seems like "entertainment" to accept and make individual change.

Politicians need something else, eg science and studies, in order to conduct politics and change/form laws and regulation.

Both are needed.