Climate scientists now know how cold it got during the last ice age

Scientists have calculated the average global temperature during the last ice age.

According to a new paper, published Wednesday in the journal Nature, the average temperature during the Last Glacial Maximum, LGM, which occurred roughly 20,000 years ago, was 46 degrees Fahrenheit.

During the 20th century, the average global temperature was a comparatively balmy 57 degrees Fahrenheit, 11 degrees warmer.

"In your own personal experience that might not sound like a big difference, but, in fact, it's a huge change," Jessica Tierney, an associate professor of geosciences at the University of Arizona, said in a news release.

Tierney and her colleagues analyzed paleoclimate signatures in ocean plankton fossils to map a range of sea-surface temperatures during the last ice age. Researchers fed their data into a model designed to simulate ancient weather patterns.

"What happens in a weather office is they measure the temperature, pressure, humidity and use these measurements to update a forecasting model and predict the weather," Tierney said. "Here, we use the Boulder, Colorado-based National Center for Atmospheric Research climate model to produce a hindcast of the LGM, and then we update this hindcast with the actual data to predict what the climate was like."

More precisely estimating ancient temperature changes can help climate scientists better understand the relationship between atmospheric carbon concentrations and climate change.

During the last ice age, carbon in the atmosphere measured around 180 parts per million. Today, carbon concentrations are greater than 415 parts per million

"If we can reconstruct past warm climates, then we can start to answer important questions about how the Earth reacts to really high carbon dioxide levels, and improve our understanding of what future climate change might hold," Tierney said.

Researchers used their model's predictions to map temperature changes during the LGM across Earth's continents.

"In North America and Europe, the most northern parts were covered in ice and were extremely cold. Even here in Arizona, there was big cooling," Tierney said. "But the biggest cooling was in high latitudes, such as the Arctic, where it was about 14 degrees Celsius -- 25 degrees Fahrenheit -- colder than today."

Researchers said they hope the work will help climate scientists better understand how human-caused climate change will affect Earth's poles in the coming.

"Climate models predict that the high latitudes will get warmer faster than low latitudes," Tierney said. "When you look at future projections, it gets really warm over the Arctic. That's referred to as polar amplification. Similarly, during the LGM, we find the reverse pattern. Higher latitudes are just more sensitive to climate change and will remain so going forward."

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Beyond the Ice Age

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