Seafloor weathering and the oxygen isotope ratio in seawater: Insight from whole-rock δ18O and carbonate δ18O and Δ47 from the Troodos ophiolite

International audienc

Evolution of the global carbon cycle and climate regulation on Earth

The existence of stabilizing feedbacks within Earth's climate system is generally thought to be necessary for the persistence of liquid water and life. Over the course of Earth's history, Earth's atmospheric composition appears to have adjusted to the gradual increase in solar luminosity, resulting in persistently habitable surface temperatures. With limited exceptions, the Earth system has been observed to recover rapidly from pulsed climatic perturbations. Carbon dioxide (CO₂) regulation via negative feedbacks within the coupled global carbon‐silica cycles are classically viewed as the main processes giving rise to climate stability on Earth. Here we review the long‐term global carbon cycle budget, and how the processes modulating Earth's climate system have evolved over time. Specifically, we focus on the relative roles that shifts in carbon sources and sinks have played in driving long‐term changes in atmospheric pCO₂. We make the case that marine processes are an important component of the canonical silicate weathering feedback, and have played a much more important role in CO₂ regulation than traditionally imagined. Notably, geochemical evidence indicate that the weathering of marine sediments and off‐axis basalt alteration act as major carbon sinks. However, this sink was potentially dampened during Earth's early history when oceans had higher levels of dissolved silicon (Si), iron (Fe), and magnesium (Mg), and instead likely fostered more extensive carbon recycling within the ocean‐atmosphere system via reverse weathering—that in turn acted to elevate ocean‐atmosphere CO₂ levels

Risk Sensitivity and Terrorism

One enduring question about terrorism is why individuals choose to join terrorist groups. Past studies have shown that terrorists are not always poor, and they can in fact come from more privileged groups in society. Risk sensitivity and prospect theory are approaches that can help explain some of the anomalies. They suggest that two types of group are likely to supply members for terrorist organizations in disproportionate numbers. One group consists of those who face a loss of status or position due to ongoing changes in society. A second group consists of those who have an opportunity to gain a major advance in status or position. Both groups are thus more likely or more willing to take risks such as joining dissident terrorists – either to maintain their position or to improve it. An analysis of the situation of Palestinian nationalists, nationalists in Northern Ireland and the Tamils in Sri Lanka provides support for the idea that sensitivity to risk can be an important factor in explaining the willingness of individuals to join terrorist groups

Mapping out the Great Irish Famine in fiction, 1847–1870: imperial counternarratives

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