Was the climate equally warm in the past?

Reading the Past Through Proxies

Because thermometer records only stretch back to the 18th century, researchers reconstruct older climates from indirect evidence such as tree rings, pollen deposits, and glacial traces. For Scandinavia, these proxies reveal a climate that was never static over the past two millennia: a mild spell up to roughly 300 AD, a cooler era from about 300 to 800 AD—with the sixth century standing out as especially severe, probably due to volcanic activity and possibly echoed in the Fimbulwinter legend—then a warmer medieval interval, and finally the Little Ice Age, which lingered until the early 1900s. Across all these swings, temperatures generally moved within a band of about 1.5–2°C.

Why Glaciers Are Slow Witnesses

A glacier that looks about the same size today as it did 1,500 years ago does not prove the climate was the same. Ice masses react sluggishly to temperature shifts, so their extent reflects where the climate has been, not where it is now. The crucial question is which way the climate is heading and how fast. Fifteen centuries ago, the region was cooling down and would stay cold for a long time; today, it is heating up quickly.

A Departure From the Old Range

Since 1950, Scandinavia has warmed by roughly 1.5–2°C—the same span that once took centuries to unfold, now packed into a few decades. Globally, 2024 pushed warming past 1.5°C above pre-industrial levels. Humanity has moved outside the temperature envelope that shaped the last several thousand years, and glaciers everywhere are retreating because of human-driven warming. Given how slowly ice responds, what we have witnessed so far is only the start.

Melting Ice, Emerging History

Shrinking glaciers are also creating a new field of study: glacier archaeology. A reindeer trap found in Norway shows how receding ice is releasing long-frozen artifacts. More discoveries are likely, offering fresh insight into both human history and past climate—and adding to the debate about the future we are choosing.