Short answers, pulled from the story.
The greenhouse effect occurs when heat-trapping gases in a planet's atmosphere prevent heat from escaping to space, raising the surface temperature. On Earth, sunlight passes through greenhouse gases to warm the surface, which then emits longwave radiation that those gases mostly absorb, slowing the planet's cooling.
Joseph Fourier proposed the existence of the greenhouse effect as early as 1824, though he did not name it. Claude Pouillet strengthened the evidence in 1827 and 1838, Eunice Newton Foote demonstrated carbon dioxide's warming power in 1856, and John Tyndall measured the infrared absorption of gases from 1859 onward.
The greenhouse effect makes Earth's surface about 33 C warmer than it would otherwise be, raising the average to around 15 C. Measured as energy, it equals 159 W/m, or 40 percent of the longwave radiation that leaves the surface but never reaches space.
Venus reaches 735 K because its atmosphere is about 97% carbon dioxide and extremely dense, producing the strongest greenhouse effect in the inner Solar System. Mars holds about 70 times as much carbon dioxide as Earth but warms only about 6 K, because its atmosphere is thin and lacks water vapor.
Burning fossil fuels has raised atmospheric carbon dioxide and methane, producing about 1.2 C of global warming since the Industrial Revolution as of 2023. The global average surface temperature has been rising at 0.18 C per decade since 1981.
Greenhouse gases are those with asymmetrical molecules that absorb longwave radiation, including carbon dioxide and molecules with three or more atoms. Symmetrical gases such as nitrogen, oxygen, and argon are transparent to longwave radiation and make up more than 99% of the dry atmosphere without trapping heat.