Last year I bought a Ford Fusion plug-in hybrid. During the summer, it was great. Roughly 20 miles of range on electricity, and roughly 35 mpg for longer distances. The sweet spot seems to be between 65 and 80 degrees. At roughly 100 degrees, the car will run the gasoline engine to climate control the battery pack. At less than 40 degrees, the electric range ends up being about half. Below roughly 20 degrees, and the car will use the gasoline engine to run climate control in the cabin. Still working out way better than the old commuter car that it replaced (stopping for fuel about once per 4 weeks during typical driving, or when going out of town for a longer trip instead of once per week in the old commuter) but it's far from perfect. My experience in using a plug in hybrid gives me significant reservation about switching to BEV.
You said:
So which is it? Warming from atmosphere affecting the water or carbon added to the oceans?
It's both. Increasing carbon dioxide in the atmosphere increases the absorption of infrared light, which results in warmer temperatures that radiate mainly into the oceans. Increasing carbon dioxide in the atmosphere also increases the carbon content of rain, which precipitates mainly into the oceans increasing acidity. Both affect global patterns in different ways and both are unlikely to be friendly to our current mode of civilization.
I've heard that this wasn't an oversight, or perhaps was retconned into making sense, via the narrative that the run involves a loop around a black hole.
The logic here says that a black hole bends space around it, so a ship being able to navigate closer to the black hole means the run is made in a shorter distance than in a ship that has to stay farther away. Speed is a component in how close you can skirt a gravity well. In this scenario, the ability to reduce the distance of the run is in fact a noteworthy accomplishment, and Han is boasting about it.
If all else fails, immortality can always be assured by spectacular error. -- John Kenneth Galbraith