Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

The ocean is the main source of thermal inertia in the climate system. Ocean heat uptake during recent decades has been quantified using ocean temperature measurements. However, these estimates all use the same imperfect ocean dataset and share additional uncertainty due to sparse coverage, especially before 2007. Here, we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2) – levels of which increase as the ocean warms and releases gases – as a whole ocean thermometer. We show that the ocean gained 1.29 ± 0.79 × 1022 Joules of heat per year between 1991 and 2016, equivalent to a planetary energy imbalance of 0.80 ± 0.49 W watts per square metre of Earth’s surface. We also find that the ocean-warming effect that led to the outgassing of O2 and CO2 can be isolated from the direct effects of anthropogenic emissions and CO2 sinks. Our result – which relies on high-precision O2 atmospheric measurements dating back to 1991 – leverages an integrative Earth system approach and provides much needed independent confirmation of heat uptake estimated from ocean data

Sulphate and nitrate concentrations in snow from South Greenland 1895-1978

An understanding of the phenomenon of acid rain requires the identification of the sources of the species affecting the pH of rainwater, both natural and anthropogenic, and their temporal and spatial development. The scant data concerning the historical development of the acidity in precipitation are from urban regions or their vicinity, where local effects dominate and obscure the hemispherical pattern1. The Greenland ice sheet allows us to trace the evolution of the acid rain in a remote location that is free from local effects. Sulphuric and nitric acids are the two species that dominate the acidity in precipitation (2–4). We report here measurements of [SO42−] and [NO3−] in firn samples spanning the period 1895–1978. Samples, each covering 1 yr, were taken from a 70-m core drilled at Dye 3, South Greenland; [NO3−] and [SO42−] both increased by a factor of ˜2 during the period. By comparing the recent concentrations of nitrate and sulphate with those resulting from natural sources, we conclude that anthropogenic emissions of the precursors (NOx, SO2) had already surpassed natural sources in the late 1950s

Phase lag of Antarctic and Greenland temperature in the Last Glacial and link between CO2 variations and Heinrich events

Proceedings of the 6th international conference on paleoceanography [ICP IV] held august 23-28, 1998 in Lisbon, Portugal. ISBN: 978-0-306-46293-1; 443 p

Iridium-catalysed arylation of C-H bonds enabled by oxidatively induced reductive elimination

Direct arylation of C-H bonds is in principle a powerful way of preparing value-added molecules that contain carbon-aryl fragments. Unfortunately, currently available synthetic methods are not sufficiently effective to be practical alternatives to conventional cross-coupling reactions. We propose that the main problem lies in the late portion of the catalytic cycle where reductive elimination gives the desired carbon-aryl bond. Accordingly, we have developed a strategy where the Ir(III) centre of the key intermediate is first oxidized to Ir(IV). Density functional theory calculations indicate that the barrier to reductive elimination is reduced by nearly 19 kcal mol-1 for this oxidized complex compared with that of its Ir(III) counterpart. Various experiments confirm this prediction, affording a new methodology capable of directly arylating C-H bonds at room temperature with a broad substrate scope and in good yields. This work highlights how the oxidation states of intermediates can be targeted deliberately to catalyse an otherwise impossible reaction. ©2018 Macmillan Publishers Limited, part of Springer Nature. (c) All rights reserve