Early Eocene hyperthermals as carbon cycle tipping points?

Abstract

Gradual global warming might trigger the release of large amounts of carbon from natural reservoirs such as submarine methane hydrates and permafrost, exacerbating the effects of human-caused carbon emissions. These "tipping points" in the carbon cycle have the potential to greatly amplify global warming, yet they are not currently included in the projections of the Intergovernmental Panel on Climate Change (IPCC). In order to effectively limit global warming to less than 2 degrees Celsius, as outlined in the UN Paris Agreement, it is crucial to understand these potential tipping points. However, observational and historical data is not sufficient to fully understand the slow changes in the carbon cycle. Therefore, we will utilize the geological record to identify and quantify past carbon cycle tipping points in the Earth's system. The carbon cycle and climate perturbations of the early Eocene represent an ideal series of natural experiments. We employ a two-pronged approach built around climate reconstructions and carbon cycle modelling. First, we apply state of-the-art early-warning signal and causality time series analyses to newly generated and existing high-resolution datasets of early Eocene climate and carbon cycle change, with the aim of detecting carbon cycling tipping points in the geological record and disentangling forcings and feedbacks. Second, we aim to reproduce carbon cycle tipping points in the Earth System using a simple carbon cycle box model, tuned and validated using the geological record. This will provide important input for mechanistic projections of carbon cycle tipping points in the (distant) future.