The summer and winter seasons of the last 11,000 years have been reconstructed in unprecedented detail, going back in time to the beginning of the Holocene, the era we currently live in: it was possible thanks to the information stored in ice cores collected in Antarctica, including the longest ever collected by American researchers, which reaches over 3 kilometers in length.
The result, published in the journal Nature, was obtained by an international group of researchers led by the University of Colorado at Boulder and also confirmed the theory elaborated about a century ago and which explains the beginning and end of the ice ages with small variations undergone by the Earth's orbit and the inclination of its axis with respect to the Sun.
“The research team's goal was to push the boundaries of what's possible a little further with regard to interpretations of past climate,” comments Tyler Jones, who led the study, “and for us this it meant trying to understand climate seasonally, from summer to winter, over many thousands of years.'
Furthermore, these detailed data also provide an important point of reference for those studying the impacts of man-made greenhouse gas emissions on our present and future climate: by knowing which planetary and seasonal cycles occur naturally and why, it is possible to better identify human influence on climate change.
The researchers examined an ice core more than 3 kilometers long, which holds data up to 68,000 years ago, analyzing in particular the concentrations of some water isotopes, i.e. elements that have the same number of protons but different numbers of neutrons.
This is an extremely difficult process, due to the high precision required, and which has been possible using high quality ice cores, very high resolution measurements and thanks to the progress made in the last 15 years on this type of analysis.
The resulting data shed new light on past temperatures and atmospheric circulation, including transitions between ice ages and warmer periods.
“Humans have an innate curiosity about how the world works and about what happened in the past,” Jones says, “because this can also help us understand what will happen in the future.”
According to the researchers, the next step will be to study and interpret other ice samples taken from other locations, such as Greenland, in order to better understand the climate variability of our planet.