Analysis of Earth’s climate sensitivity: past, present & future

Abstract

Earth’s climate system is comprised of a complex web of interacting feedbacks, each operating on differing timescales and with varying spatial patterns. Our understanding of climate feedbacks inform quantitative estimates of climate sensitivity, which represents Earth’s response to changes in its energy balance. Despite decades of research, understanding of climate sensitivity is incomplete, and this directly affects our ability to predict future climate change and develop effective mitigation and adaptation strategies. This thesis uses probabilistic assessment to explore and quantify Earth’s climate feedbacks over multiple response timescales using multiple lines of evidence. Chapter 2 utilises an efficient earth system model with a Bayesian statistical framework to constrain Earth’s fast and multidecadal feedbacks. Chapter 3 estimates the magnitude and equilibrium response timescale of the ice sheet-albedo feedback using proxy evidence from the most recent deglaciation which then inform long term projections of future warming in Chapter 4. Chapter 4 also utilises a conceptual energy balance model to explore polar amplification and the latitudinal behaviour of the total climate feedback parameter under different mean climatic states, both warmer and colder than today. Together, these findings provide new insights into the evolving spatial and temporal behaviour of Earth’s feedbacks and help to develop understanding of climate sensitivity in the context of the past, present and future. This shall contribute towards the collective effort to predict and prepare for the future of our climate with the acknowledgement that Earth’s feedbacks are likely to amplify human-induced warming on multiple time horizons.

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Identifiers

ORCID for Alice Booth: orcid.org/0000-0003-2085-9376

ORCID for Philip Goodwin: orcid.org/0000-0002-2575-8948

ORCID for Toby Tyrrell: orcid.org/0000-0002-1002-1716

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