8 February, 2018

The most comprehensive study of the variability of temperature globally is published this week in the journal Nature. It reveals the degree to which temperature fluctuations reduced from the last ice age to our current warm period and varied around the world.

The paper, led by Dr Kira Rehfeld, who is a postdoctoral fellow at the British Antarctic Survey and the Alfred Wegener Institute, is the first of its kind to investigate past climate variability from a global perspective. The team examined climate data, extracted from a network of marine and terrestrial samples, from nearly 100 research sites across the world. This data was then compared to the iconic Greenland ice cores, which are considered as the ‘gold standard’ high-resolution climate archive.

Trapped air bubbles within ice cores form an archive of past atmosphere and temperature.

By understanding natural climate changes that took place thousands of years ago, scientists can improve predictions for future change.

Examining the records from a large number of climate archives shows that climate becomes more stable after warming. In addition, the study demonstrates the phenomenon of major temperature fluctuations during glacial periods has varied from region to region. In the tropics, the range in temperature at the height of the last ice age was three times as intense as today, whereas the ice cores from Greenland indicate variations were 70 times as intense. The more intensive variations during glacial periods are due to the greater difference in temperature between the ice-covered Polar Regions and the tropics.

Lead author Dr Kira Rehfeld at British Antarctic Survey and the Alfred Wegener Institute, says:

“Looking ahead on multi centennial to millennial timescales our results point towards a reduction in climate variability, as the temperature difference between the poles and the equator decreases following further warming.

“It’s important for scientists to establish whether temperatures in a warm world, can experience sudden major fluctuations, on short and long timescales. Previously, it was assumed that temperature varied greatly during the last ice age (21,000 years ago), while the current warm period was largely characterised by small temperature variations. But now we see that the two states are more similar than we had thought, particularly in the tropics.

Global patterns of declining temperature variability from Last Glacial Maximum to Holocene by Kira Rehfeld, Thomas Münch, Sze Ling Ho and Thomas Laepple is published in Nature DOI: 10.1038/nature25454