All my life I’ve heard that the earth is actually closer to the sun in (northern hemisphere’s) winter. Does this mean that, on average, summers in the southern hemisphere are hotter than ours, due to the combination of direct rays of the sun and the closer distance? Or isn’t the closer distance that significant?
From this site, apparently summer’s are, on average, cooler in the southern hemisphere, due to the presence of much more water which reduces seasonal variations. I suppose this means the sun’s effect is minor comparatively if it’s measurable at all.
As for the sun: Perihelion is about 146 million km, and comes in early January; Aphelion is 152 million km, in early July.
That’s a distance variation of 4%, which implies a solar energy variation of 8%.
Wikipedia claims (and probably has a citation for) that winter in Antarctica is much worse than the North Polar winter. Because its actually a high plateau, not only is the Earth tilted away like Northern hemisphere but also the Earth is more distant, and there’s no water around.
We can’t separate just by looking, in any meaningful way, the effect of water, and the Earth’s tilt, and determine the effect of greater planetary distance on Southern hemisphere winter. I’m sure someone has written a detailed model. But we can’t just go and check for a Southern hemisphere place, in winter, that’s analogous to Northern hemisphere. The land-forms are just too different.
And a nominal equilibrium temperature difference of 2% (since power goes like the fourth power of temperature). 2% of 300 Kelvin is 6 degrees C or about 11 degrees Fahrenheit, which is quite a big effect. However, as pointed out by others, the southern hemispheres is geographically very different from the northern hemisphere.