The achievement of first author Kira Rehfeld and her colleagues: they have for the first time gathered and compared data from diverse climate archives and a total of 99 research sites. In the climate research community, ice cores are generally considered the gold standard, because their layers are highly consistent, unlike sediment layers from the seafloor, which are frequently marred by tectonic shifts, currents or marine organisms. The AWI researchers have devised mathematical methods that allow them to estimate the uncertainties and potential sources of error while assessing various paleoclimate archives, and to take these factors into account in their analyses. “As such, we can compare the sediment samples with the ice cores for various epochs in the planet’s history,” says Laepple.
The more intensive variations during glacial periods are due to the greater difference in temperature between the ice-covered polar regions and the Tropics, which produced a more dynamic exchange of warm and cold air masses. “If we then follow that idea to its logical conclusion, it tells us the variations will continue to lessen as global warming progresses,” says Rehfeld – simply because the difference in temperature between the warming North and the Tropics will decline. “However, our data covers timeframes spanning centuries and millennia – we can’t zoom in on just a handful of years, which means we can only draw indirect conclusions regarding the extreme events that shape weather,” explains climate researcher Rehfeld, who is currently pursuing research with the British Antarctic Survey (BAS).
Climate modellers had previously postulated the mechanism of reduced variability under warmer climatic conditions in 2014. Yet with their analysis, Rehfeld, Laepple and colleagues are the first to reinforce this theory with global climate data from the past. The AWI researchers describe their next endeavour as follows: “We plan to investigate in detail the changes in short-term variations in the past and their relation to long-term climate changes. To do so, we need reliable climate archives, and to improve our understanding of how they work.” Increasing the accuracy to a level at which paleo-archives can also reflect extreme events will likely be one of the greatest challenges for the years to come.