Asked by tulleh to Alice, Andi, Bas, Daniel, Rhian on 11 Mar 2015. This question was also asked by miguel.
Keywords: ice age
This is a really good question! There are actually quite a few complications with the terminology, so let me start from there.
– From a glaciology point of view, an “ice age” is a period of time when we have ice sheets both in the northern and southern hemisphere. So technically, following this definition, we’re still in an ice age now, because there are ice sheets in Greenland and Antarctica. Within an ice age there are “glacial” and “interglacial” periods, and currently we are in an interglacial, which is basically the warm period within an ice age (and obviously the glacial is the cold period). In theory, it will take a long time (tens of millions of years) for the Earth to get completely out of the current ice age and be completely ice free everywhere.
– As a more general definition, people often talk about the “Ice Age” when what they really mean is the most recent glacial period (within the current ice age). The so called “Last Glacial Maximum” is the period with the maximum extent of ice sheets which normally ends a glacial period.
So I guess the question could be: when will the next glacial period start?
The answer is that we don’t actually know!
The main theories about ice ages and glacial/interglacial periods are based on the periodic changes in the Earth’s orbit and position with respect to the Sun, which determines how much solar radiation warms up the planet. These changes are regular and can be predicted quite well, but there are other mechanisms at play that we don’t fully understand. So we don’t actually know exactly what causes ice ages, and the glacial cycles within them. The main theories include a combination of incoming solar radiation, distance of the Earth from the Sun, ocean circulation, position and height of continents, composition of the atmosphere…this is actually really complicated and fascinating!
Another important point is the fact that at the moment the planet should still be in a cooling trend in terms of mean global temperatures, since technically we are still within an ice age (and the Earth probably won’t be fully ice free for a very long time!). But in reality, as you probably know, global temperatures are actually warming because of anthropogenic greenhouse gases emissions. Some scientists think that this might delay the next glacial period!
a long and excellent answer form Alice! 🙂
View all answered questions
Copyright Gallomanor, produced by Mangorolla CIC 2019