Tropical forcing of Circumpolar Deep Water Inflow and outlet glacier thinning in the Amundsen Sea Embayment, West Antarctica

Outlet glaciers draining the Antarctic ice sheet into the Amundsen Sea Embayment (ASE) have accelerated in recent decades, most likely as a result of increased melting of their ice-shelf termini by warm Circumpolar Deep Water (CDW). An ocean model forced with climate reanalysis data shows that, beginning in the early 1990s, an increase in westerly wind stress near the continental shelf edge drove an increase in CDWinflow onto the shelf. The change in local wind stress occurred predominantly in fall and early winter, associated with anomalous high sea-level pressure (SLP) to the north of the ASE and an increase in sea surface temperature (SST) in the central tropical Pacific. The SLP change is associated with geopotential height anomalies in the middle and upper troposphere, characteristic of a stationary Rossby wave response to tropical SST forcing, rather than with changes in the zonally symmetric circulation. Tropical Pacific warming similar to that of the 1990s occurred in the 1940s, and thus is a candidate for initiating the current period of ASE glacier retreat

A Simple Model for Trading Climate Risk

Short term climate events such as the sea surface temperature anomaly known as El Niño are financial risk sources leading to incomplete markets. To make such risk tradable, we use a market model in which a climate index provides an extra investment option. Given one possible market price of risk each agent can maximize the exponential utility from three sources of income: capital market, additional security, and individual risk exposure. Under an equilibrium condition the market price of risk is uniquely determined by a backward stochastic differential equation. We translate these stochastic equations into semi-linear partial differential equations for the simulation of which numerical schemes are available. We choose two simple models for sea surface temperature, and with ENSO risk exposed fisher and farmer and a non-exposed bank three toy agents. By simulating their optimal investment into the climate index we obtain first insight into the dynamics of the market. Zusammenfassung Klimaereignisse auf einer kurzen Zeitskala, wie die Anomalie der Oberflächentemperatur im Ozean, bekannt als El Niño, sind finanzielle Risikoquellen, die zu unvollständigen Märkten führen. Um so ein Risiko handelbar zu machen, nutzen wir ein Marktmodell, in dem ein Klimaindex eine zusätzliche Investitionsmöglichkeit schafft. Zu einem gegebenen Marktpreis des Risikos kann jeder Händler seinen exponentiellen Nutzen aus drei Einkommensquellen maximieren: dem Kapitalmarkt, der zusätzlichen Anlagemöglichkeit und der individuellen Risikoexposition. Unter einer Gleichgewichtsbedingung wird der Marktpreis des Klimarisikos durch eine stochastische Rückwärtsgleichung eindeutig bestimmt. Diese stochastischen Gleichungen übertragen wir in semilineare partielle Differentialgleichungen, für die numerische Lösungsmethoden vorhanden sind. Wir wählen zwei einfache Modelle für die Meeresoberflächentemperatur. Dann betrachten wir einen Fischer und einen Farmer, die El Niño- Risiko ausgesetzt sind, sowie eine Bank, die diesem Risiko nicht ausgesetzt ist. Durch Simulation ihrer optimalen Investitionen in den Klimaindex erhalten wir einen ersten Einblick in die Dynamik dieses Marktes

Radically rethinking agriculture for the 21st century. Perspective

Population growth, arable land and fresh water limits, and climate change have profound implications for the ability of agriculture to meet this century's demands for food, feed, fiber, and fuel while reducing the environmental impact of their production. Success depends on the acceptance and use of contemporary molecular techniques, as well as the increasing development of farming systems that use saline water and integrate nutrient flows