In-depth analysis of climate data from the past 66 million years has provided a better understanding of the role of tipping points in global change and improved predictions of future climate.
The study of the tipping points climate, that is to say of the “critical thresholds” beyond which the climate system undergoes irreversible changes such as the collapse of ice sheets or the slowing of global ocean circulation, has highlighted how Our current climatic period shows distinctive and peculiar characteristics compared to past climatic eras.
This is what emerges from a research conducted by theNational Institute of Geophysics and Volcanology (INGV) in collaboration with other international research institutions and universities, recently published in the journal 'Scientific Reports'.
Throughout geological history, our planet has gone through very different climatic phases: from the periods “Hothouse” e “Warmhouse”, where temperatures were high and there were no polar ice caps, in the periods “Icehouse”, like the current one, in which the presence of ice at the poles regulates the global climate.
The results of the INGV-led study, obtained thanks to innovative and advanced mathematical tools for the analysis of climate variability able to detect precursor signals of critical transitions, they offer new perspectives on the stability of the Earth's climate and the risk of irreversible transitions, closely linked to ongoing climate change.
"Our work shows that climate tipping points do not manifest themselves with the same dynamics in different geological periods of the Earth. In particular, the current Icehouse period, characterized by glacial-interglacial cycles, presents distinctive characteristics compared to past eras, with crucial implications for understanding climate stability and ongoing change", explains Thomas Alberti, researcher at INGV and first author of the article.
“The current Icehouse is particularly sensitive to small disturbances, making it more vulnerable to human-induced climate change. The metrics used showed that approaching tipping points is accompanied by an increase in the persistence and intensity of extreme events, with implications for the future of the Earth's climate.”, keep it going Alberti.
The analyses conducted in the research have allowed us to distinguish between gradual and abrupt changes in the climate system, highlighting how, in the current phase ice house, climate fluctuations are more frequent and characterized by greater variability than in warmer eras.
“The results obtained suggest that our era is characterized by a more 'intermittent' behavior compared to the warm periods of the past, with more rapid transitions between different climate states”, he adds Fabio Florindo, President of INGV and co-author of the study. “This variability makes it even more difficult to accurately predict the evolution of our climate and requires special attention in the study of tipping points”.
The study of the different tipping points climate models highlight how their behavior depends on the underlying climate structure and the internal dynamics of the system: understanding these differences is essential to improve climate forecasts and identify thresholds beyond which climate change could become irreversible.
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Figure 1: Multi-scale bivariate analysis during warm periods (66–34 million years ago).
(A) Time series of CENOGRID paleoclimate data: oxygen (O) in blue and carbon (C) in red.
(B–D) Multi-scale indicators that relate the two signals:
- (B) Instant Size (d), a measure of the complexity of the system;
- (C) Extreme index (θ), which reflects the stability of the system (values close to 0 indicate more stable or persistent states);
- (D) Co-occurrence index, which shows how much the two signals are coupled in time (values close to 1 indicate stronger coupling).
The dashed vertical lines in panel (A) indicate the boundaries between different geological epochs, with some key events highlighted.
In panels (B–D), continuous, dotted vertical lines mark the Critical points (Tipping Points) identified by Rousseau et al. through a univariate analysis on O and C (for clarity, only those on C are labeled). The dashed and dotted white horizontal lines represent the main time scales of Milankovitch astronomical cyclicities: precession (~20.000 years), obliquity (~40.000 years) and eccentricity (~100.000 years).
Figure 2: Multi-scale bivariate analysis during cold periods (last 34 million years).
(A) Time series of CENOGRID paleoclimate data: oxygen (O) in blue and carbon (C) in red.
(B–D) Indicators that analyze the relationship between the two signals on different time scales:
- (B) Instant Size (d), which measures the complexity of the climate system at any given time;
- (C) Extreme index (θ), which reflects how stable or persistent the system is (values close to 0 indicate greater stability);
- (D) Co-occurrence index, which measures the level of synchronization between O and C (values close to 1 indicate a strong interdependence).
In panel (A), the dashed vertical lines mark the boundaries between geological epochs, while some major climatic events are highlighted at the time they occurred.
In panels (B–D), the solid and dashed vertical lines indicate the Critical points (Tipping Points) identified by Rousseau et al. with a separate analysis of each signal (only carbon signals are shown for clarity). The white dashed and dotted horizontal lines represent the main time scales of Milankovitch astronomical cyclicities: precession (~20.000 years), obliquity (~40.000 years) and eccentricity (~100.000 years).