The science of this fascinates me, even if it be used one way or the other in politics.
One odd exchange went like this:
Person 1: Well, the sun's energy output varies!
Person 2: Yeah, but it's only 5%.
And that was that. But 5% (aside from sounding scary rather than calming, but that's my math mind speaking) translates to about 13 extra degrees' worth of energy at around Earth's temperature.
There are lots of other factors, of course. For example, is this "extra 5%" of the same distribution, so to speak, as the first 273 K worth, w.r.t. the fractions of it reflected or absorbed? That kind of thing. The "13 degrees" above suggests it's roughly equivalent, which may not be the case.
In other words, if 99% of the additional 5% got reflected, whereas, say, 50% of the "first 273 K worth" was reflected, it wouldn't make much difference. But if the additional 5% was 99% absorbed, with the same fraction for the "first 273", it could be far more significant than "only" a 5% increase.