What Was Earth’s Temperature During Ice Age? Here’s Why Knowing It Matters Today

A team of researchers has determined how cold it really was during the ice age.

During the Last Glacial Maximum (LGM) 20,000 years ago, glaciers covered large parts of the planet including North and South America, Europe and Asia. It was a period that was studied extensively but scientists were not clear as to how cold it was then.

The researchers of a new study, published in the journal Nature, developed models that translate the data from ocean plankton fossils to sea-surface temperatures. Combining this data with climate models of the LGM, they were able to produce a "hindcast" of what the conditions were like at the time.

They found the average temperature during the LGM was 6 degrees Celsius (11 degrees Fahrenheit) cooler than that of today, with the places that experienced the most cooling being those in higher latitudes.

"In your own personal experience that might not sound like a big difference, but, in fact, it's a huge change," study co-author Jessica Tierney of the University of Arizona Department of Geosciences said in a news release.

It is important because it sheds light on how the planet reacts to carbon in the atmosphere. During the ice age, the carbon dioxide levels were at 180 parts per million (ppm) but today they are at 415 ppm, nearly double the carbon dioxode levels during the industrial revolution, which was at 280 ppm.

As the National Oceanic and Atmospheric Administration (NOAA) explains, the carbon dioxide levels today are higher than at any other point in the past 800,000 years and this is mostly because of the burning of fossil fuels.

According to the researchers, each time that atmospheric carbon doubles, there will be a 3.4 degree Celsius (6.1 degree Fahrenheit) increase in temperature.

"The Paris Agreement wanted to keep global warming to no larger than 2.7 F (1.5 C) over pre-industrial levels, but with carbon dioxide levels increasing the way they are, it would be extremely difficult to avoid more than 3.6 F (2 C) of warming," Tierney said. "We already have about 2 F (1.1 C) under our belt, but the less warm we get the better, because the Earth system really does respond to changes in carbon dioxide."

As a greenhouse gas, carbon dioxide absorbs and radiates heat. The greenhouse effect typically helps to keep the Earth warm so that annual global temperatures will not be below freezing. But the massive increase in atmospheric carbon dioxide significantly affects the Earth's temperature.

"Increases in atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance that is causing Earth's temperature to rise," the NOAA explains.

Having a clearer picture of the Earth's past climates can help us further understand how the Earth reacts or will react to the changes that are already happening today.