New research shatters old assumptions about climate change

New mathematical modeling of the Atlantic meridional overturn – a system of ocean currents – shows greater complexity than previously thought.

An international team of scientists has warned against relying on nature providing clear “early warning” indicators of climate catastrophe, as new mathematical modeling reveals fascinating new aspects of the complexity of climate dynamics.

This suggests that the climate system may be more unpredictable than previously thought.

By modeling the Atlantic meridional overturning circulation, one of the major ocean current systems, the team, which included mathematicians from the University of Leicester, found that the stability of the system is much more complex than simple “on and off” states as previously assumed. The transformations between these countries may lead to major changes in the regional climate of the North Atlantic region, but they are far from the enormous effects of the transformation between qualitatively different countries.

But some of these small shifts may eventually escalate to cause a major shift between qualitatively different countries, with huge global climate impacts. Early warning signals may not be able to distinguish the severity of the next turning points. Like a Jenga block tower, removing some blocks may affect the stability of the system, but we cannot be sure which block will cause the entire system to collapse.

Professor Valerio Lucarini from the School of Mathematics and Computer Science, University of Leicester. Credit: University of Leicester

Publication and importance of results

Their findings were recently published in Advancement of science In a research paper conducted by the Niels Bohr Institute at the University of Copenhagen.

The Atlantic meridional overturning circulation is one of the most fundamental features of the climate system. It transports heat from low to high latitudes in the North Atlantic, so it helps create positive thermal anomalies in northern and western Europe and in the downwind North Atlantic region. A slowdown in blood circulation would lead to a relative cooling in this region.

Challenges in climate prediction

Predicting the behavior of our climate, such as that of the Atlantic meridional overturning circulation, is challenging because of its astonishing complexity. Scientists either need a model with the highest possible accuracy, or they try to understand its behavior using a less resource-intensive model that allows accurate statistical analysis.

Professor Valerio Lucarini, from the School of Mathematics and Computer Science at the University of Leicester, said: “Within each state, there are a large number of nearby states. Depending on where or what you are observing, you may find some indications that a collapse is approaching. But it is not clear whether this collapse will be contained in neighboring states or will lead to major disruptions because the indicators only reflect the local characteristics of the system.

“These states represent the different ways in which the Atlantic overturning circulation organizes itself on large scales, with major implications for global climate and especially at the regional level in the North Atlantic. Under some scenarios, the circulation could reach a 'tipping point' “The system is no longer stable and will collapse. Early warning indicators tell us that the system may be transitioning to another state, but we don't know how different it might be.”

“In a separate investigation, we saw something similar happen in paleoclimate records: when you change the time scale of interest — just like a magnifying glass — you can discover smaller and smaller distinct features that indicate competing modes of operation of global climate. “Paleoclimate records over the past 65 million years have allowed us The past year has provided a new explanation for the evolution of climate over that time period, revealing these multiple competing states.

“This study paves the way for looking at climate through the lens of statistical mechanics and complexity theory. It really stimulates a new view of climate, where you have to synthesize complex numerical simulations, observational evidence and theory into an inescapable mixture. You have to appreciate and embrace this complexity. There is no way Briefly, there is no free lunch in our understanding of climate, but we can learn a lot from it.

Reference: “Punctuated equilibrium analysis of Cenozoic climate evolution shows a hierarchy of abrupt transitions” by Denis Didier Rousseau, Witold Pajniewski, and Valerio Lucarini, 12 July 2023, Scientific reports.
doi: 10.1038/s41598-023-38454-6

Funding: Horizon 2020 Framework Programme, Danmarks Frie Forskningsfond, European Research Council