Presence or absence of stabilizing Earth system feedbacks on different time scales.

The question of how Earth's climate is stabilized on geologic time scales is important for understanding Earth's history, long-term consequences of anthropogenic climate change, and planetary habitability. Here, we quantify the typical amplitude of past global temperature fluctuations on time scales from hundreds to tens of millions of years and use it to assess the presence or absence of long-term stabilizing feedbacks in the climate system. On time scales between 4 and 400 ka, fluctuations fail to grow with time scale, suggesting that stabilizing mechanisms like the hypothesized "weathering feedback" have exerted dominant control in this regime.

Rate-induced collapse in evolutionary systems.

Recent work has highlighted the possibility of 'rate-induced tipping', in which a system undergoes an abrupt transition when a perturbation exceeds a critical rate of change. Here, we argue that this is widely applicable to evolutionary systems: collapse, or extinction, may occur when external changes occur too fast for evolutionary adaptation to keep up. To bridge existing theoretical frameworks, we develop a minimal evolutionary-ecological model showing that rate-induced extinction and the established notion of 'evolutionary rescue' are fundamentally two sides of the same coin: the failure of one implies the other, and vice versa.

Asymmetry of extreme Cenozoic climate-carbon cycle events.

The history of Earth's climate and carbon cycle is preserved in deep-sea foraminiferal carbon and oxygen isotope records. Here, we show that the sub-million-year fluctuations in both records have exhibited negatively skewed non-Gaussian tails throughout much of the Cenozoic era (66 Ma to present), suggesting an intrinsic asymmetry that favors "hyperthermal-like" extreme events of abrupt global warming and oxidation of organic carbon. We show that this asymmetry is quantitatively consistent with a general mechanism of self-amplification that can be modeled using stochastic multiplicative noise.

The Balance of Nature: A Global Marine Perspective.

The ancient idea of the balance of nature continues to influence modern perspectives on global environmental change. Assumptions of stable biogeochemical steady states and linear responses to perturbation are widely employed in the interpretation of geochemical records. Here, we review the dynamics of the marine carbon cycle and its interactions with climate and life over geologic time, focusing on what the record of past changes can teach us about stability and instability in the Earth system.

Routes to global glaciation.

Theory and observation suggest that Earth and Earth-like planets can undergo runaway low-latitude glaciation when changes in solar heating or in the carbon cycle exceed a critical threshold. Here, we use a simple dynamical-system representation of the ice-albedo feedback and the carbonate-silicate cycle to show that glaciation is also triggered when solar heating changes faster than a critical rate. Such 'rate-induced glaciations' remain accessible far from the outer edge of the habitable zone, because the warm climate state retains long-term stability.