BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Metastability Properties of the Earth's Climate: a Multiscale View
 point - Prof Valerio Lucarini\, University of Leicester
DTSTART:20250509T150000Z
DTEND:20250509T160000Z
UID:TALK231325@talks.cam.ac.uk
CONTACT:Professor Grae Worster
DESCRIPTION:The ultralow frequency variability of the Earth's climate feat
 ures an interplay of typically long periods of stasis accompanied by criti
 cal transitions between qualitatively different regimes associated with me
 tastable states. Such transitions have often been accompanied by massive a
 nd rapid changes in the biosphere. Multiple transitions between the coexis
 ting warm and snowball climates  occurred more than 600 Mya and  eventuall
 y led to conditions favourable to the development of multicellular life. T
 he coexistence of such states is due to the instability associated with th
 e positive ice-albedo feedback\,  Yet\, this behaviour repeats itself acro
 ss a wide range of timescales\, spatial domains\, and physical processes. 
 Building on Hasselmann's program\, we propose here to interpret the time-e
 volution of the Earth system as a trajectory taking place in a dynamical l
 andscape\, whose multiscale features describe a hierarchy of metastable st
 ates and associated tipping points. We introduce the concept of climatic M
 elancholia states\, saddle embedded in the boundary between the basins of 
 attraction of the stable climates and explain under which conditions they 
 act as gateways of noise-induced transitions. Using a hierarchy of numeric
 al models\, we discuss in detail the dichotomy between warm and snowball c
 limate by bringing together the deterministic and stochastic viewpoint on 
 the related global stability properties. We then discuss the paleoclimatic
 ally-relevant case where multiple competing climatic states are present an
 d show the relevance of our angle for interpreting proxy data. Finally\, i
 f time allows\, we will present some very recent results suggesting that o
 ur viewpoint might explain some intriguing aspects of the dynamical featur
 es of the tipping points of the Atlantic Meridional Overturning Circulatio
 n.\n\nKey References\nV. Lucarini and T. Bodai\, Transitions across Melanc
 holia States in a Climate Model: Reconciling the Deterministic and Stochas
 tic Points of View\, Phys. Rev. Lett. 122\, 158701 (2019)\nG. Margazoglou 
 et al.\, Dynamical landscape and multistability of a climate model\, Proc.
  R. Soc. A.477 210019 (2021)\nV. Lucarini\, M.D. Chekroun\, Theoretical to
 ols for understanding the climate crisis from Hasselmann’s programme and
  beyond\, Nature Reviews Physics 5 (12)\, 744-765 (2023)\nD. D. Rousseau e
 t al.\, A punctuated equilibrium analysis of the climate evolution of ceno
 zoic exhibits a hierarchy of abrupt transitions. Sci Rep 13\, 11290 (2023)
 \nJ. Lohmann et al.\, Multistability and Intermediate Tipping of the Atlan
 tic Ocean Circulation\, Sci. Advances 10 DOI: 10.1126/sciadv.adi4253 (2024
 )\n
LOCATION:MR2
END:VEVENT
END:VCALENDAR