In order to better understand climate change, scientists need to grasp the complex interactions between the Earth's atmosphere, oceans, ice sheets, landmasses and biosphere. A new study by researchers from the University of Copenhagen's Niels Bohr Institute furthers our grasp of these interactions by shedding light on the numerous climate variations that the Earth has experienced up to five million years ago.
"You can look at the climate as fractals, that is, patterns or structures that repeat in smaller and smaller versions indefinitely," said Peter Ditlevsen, who participated in the research. "If you are talking about 100-year storms, are there then 100 years between them? Or do you suddenly find that there are three such storms over a short timespan? We have now investigated this."
The team analyzed numerous climate factors including temperature measurements over the last 150 years, ice core data from Greenland from the interglacial period 12,000 years ago and data from ocean sediment cores that date back five million years.
The analyses shed light on the natural variations in climate over a given period of time and how these variations are connected to the length of the time period. This relationship is common for fractals and can help us understand aspects of our modern climate and determine the relative size of climate events depending on their time period.
In addition, the team has discovered that there are differences in the fractal behavior of the ice age climate and the current warm interglacial climate.
"We can see that the climate during an ice age has much greater fluctuations than the climate during an interglacial period," Ditlevsen said. "There has been speculation that the reason could be astronomical variations, but we can now rule this out as the large fluctuation during the ice age behave in the same 'fractal' way as the other natural fluctuations across the globe."
The climate of the ice age is also revealed to be much more chaotic than during warm interglacial periods, a new climate characteristic that will help scientists better differentiate between natural and human-induced climate changes.
"We see that the ice age climate is what we call 'multifractal,' which is a characteristic that you see in very chaotic systems, while the interglacial climate is 'monofractal,'" Ditlevsen said. "This means that the ratio between the extremes in the climate over different time periods behaves like the ratio between the more normal ratios of different timescales."
The findings were published in the March 16 issue of Nature Communications.
