Ok, I see. So just so we're on the same page, for reference, the average surface temperature was thought to be 7.7 C in the last ice age. Converting both to Kel

Ok, I see. So just so we're on the same page, for reference, the average surface temperature was thought to be 7.7 C in the last ice age. Converting both to Kelvin to account for the arbitrary zero point of Celsius, the 20th century was a 2.2% temperature increase relative to the ice age. Does your math agree? I agree that a delta of 0.5 C is less dramatic than a delta of 6.2 C, but is your intuition in accordance with all that, and do you think percentage increases are useful here for building intuition? Where would you draw the line for "small" in terms of percentage change of temperature? I also calculate that the Earth is 30% warmer than Mars, but you might want to double check my math. Edit -- we could also consider that temperature is in most respects an exponential measure of physical quantities (E ~ e^kT). So the ratio increase in a physical quantity of interest (E2/E1) is already given, on a log scale, by an absolute temperature difference (T2 - T1).