Earth’s ‘wobbly’ orbital behaviors also drive climate changes, ice ages
Despite what many people believe, seasons on Earth are not determined by the nearness of the northern and summer hemispheres to the sun.“Seasons occur because in January, for instance, the North Pole points away from the sun, so the southern hemisphere gets more direct sunlight,” Wysession says. “Six months later, that will be reversed. In terms of climate change, this has an impact because land heats up much more quickly than water, five times more quickly. The northern hemisphere has most of the land on Earth; the southern has most of the water. On January 3 or 4 (it varies) the Earth is at its closest point to the sun (the perihelion), but because water heats up so slowly, it doesn’t make as much difference in temperature in the southern hemisphere as it otherwise might.“In the northern hemisphere summer, despite the Earth being farther away from the sun, land heats up much more quickly than the southern hemisphere’s water, and heats up about the same amount consistently. The two hemispheres end up buffering the climate swing, producing less severe winters than we would have otherwise.”
Stick around, though, if you like extremes. Wysession says that in the future, the Earth will be farther away from the sun in winter and closer to it in the summer, causing more severe temperature swings in these two seasons. This will happen about 12,000 years from now.
“Orbital parameters of Earth, the sun and moon and the planets have great effects on ice ages and other climatic changes,” he says. “Those major events are driven by very small changes in the planetary orbital functions.”