…would aliens decide to eliminate us because of “global warming”?
You’d think that a civilization with the ability to cross interplanetary distances would, when encountering this set of circumstances (humans, on Earth, burning fossil fuels), simply mock us for using such inefficient and diffuse sources of energy, and provide us with matter-conversion cells or zero-point energy modules or something suitably science-fictiony, scoring a tidy profit on the trade.
(What…why would you assume the aliens wouldn’t be capitalists…?)