Although our planet is thought to have had about a 2:1 ratio of oceans to continents throughout its history, there was a period from about 2.4 to 2.1 billion years ago where the surface was 100% covered in ice: a Snowball Earth scenario. Could our planet, despite global warming, actually become cooler over the next 20,000 years? (NASA)

Ask Ethan: Will Earth’s Temperature Start Decreasing Over The Next 20,000 Years?

Sure, we’re warming now. But will this continue, or will natural factors change things?

According to our best understanding of Earth’s climate, the global average temperature has increased significantly over the past ~140 years: the amount of time for which a reliable, direct temperature record exists. It’s widely accepted that the driving force behind this increase is the human-caused emission of greenhouse gases such as CO2, which has increased in atmospheric concentration by about 50% from the pre-industrial levels that were present early in the 1700s. But humans aren’t the only entities that affect Earth’s climate; there are natural variations that occur in the Earth-Sun system. Will they cause Earth’s temperature to decrease in the relatively near future? That’s what Ian Graham wants to know, as he writes in to ask:

“I’m trying to get my head around the Earth’s axial tilt and the ramifications of the current 23.5 degree increase/decrease, and trying to understand Milankovitch’s theory. If the Perihelion is increasing and the earth warms as a result, ignoring the greenhouse effects of humans, what is the effect of both the Perihelion increase and the movement of earth away from the Sun? My thought is the Earth’s global…