Cement production is a source of CO2. Analysis of carbonation — a process that sequesters CO2 during the lifetime of cement — suggests that between 1930 and 2013, it has offset 43% of CO2 emissions from cement production globally. The image shows conveyors at a concrete manufacturing plant in southern California, USA.

Letter p880

IMAGE: STEVEN J. DAVIS

COVER DESIGN: TULSI VORALIA

The late Palaeozoic was marked by a series of glacial–interglacial cycles. Geochemical and fossil data suggest a role for terrestrial vegetation–carbon cycle feedbacks in the climate response to orbital forcing. The image shows a modern tree fern, Cyathea australis, which was grown in simulated Carboniferous glacial atmospheres of 400 ppm CO2 and 24% O2. The image was produced as a silver-print, photogenic drawing re-enacting old 18th century photographic processes.

Letter p824; News & Views p803

IMAGE: © SIOBHAN MCDONALD;

REPHOTOGRAPHED DIGITALLY BY VINCENT HOBAN

COVER DESIGN: TULSI VORALIA

Landfalling typhoons can cause great damage in east and southeast Asian countries. An analysis of bias-corrected datasets reveals that the proportion of the strongest landfalling typhoons has at least doubled over the past decades. The image shows cloud top temperatures of Super Typhoon Nepartak on July 7 of 2016 as it was approaching Taiwan.

Letter p753

IMAGE: NASA GODDARD MODIS RAPID RESPONSE

COVER DESIGN: TULSI VORALIA

Atmospheric CO2 concentrations rose during the last deglaciation, but the carbon sources are unclear. Climate and carbon cycle simulations suggest that permafrost melting was the main source of carbon between 17,500 and 15,000 years ago. The image shows small streams of summertime meltwater in Kobbefjord, southwest Greenland.

Letter p683; News & Views p648

IMAGE: JAKOB SIEVERS, AARHUS UNIVERSITY, DENMARK

COVER DESIGN: TULSI VORALIA

Earth’s crust diverges and extends along mid-ocean ridges. Analyses of gravity and seismic data from the equatorial Atlantic show that propagation of ridge segments can compress the crust and create sufficient uplift to create small islands. The image shows the St Peter and St Paul islets in the equatorial Atlantic. The islets are composed of highly deformed mantle rocks that were uplifted through transpressive stresses.

Letter p619

IMAGE: RICHARD RASMUSSEN - GREEN PLANET STUDIOS

COVER DESIGN: TULSI VORALIA

Freshwater release from melting polar ice could weaken the Atlantic overturning circulation. Eddy-resolving ocean simulations reveal that the freshening has not yet significantly affected meridional overturning, but an effect may emerge soon. The image shows a snapshot of ocean currents and sea ice in a high-resolution model of the North Atlantic Ocean, nested in a global ocean/sea-ice model.

Letter p523; News & Views p479

IMAGE: E. BEHRENS/GEOMAR

COVER DESIGN: TULSI VORALIA

The global transport and fate of semivolatile aromatic hydrocarbons and their relevance for the carbon cycle are poorly quantified. Global measurements in paired atmospheric and ocean samples suggest that air–sea fluxes are substantial. The image shows research vessel Hespérides during the Malaspina 2010 expedition.

Letter p438; News & Views p415

IMAGE: JOAN COSTA – CSIC

COVER DESIGN: TULSI VORALIA

Climate changes are projected to be particularly pronounced in the Arctic. Field data from a manipulation experiment suggest that emission of volatile organic compounds in the Arctic tundra is extremely sensitive to changes in climate. Whereas higher temperatures increase emissions, more clouds would lead to a decrease, complicating prediction of future emissions. The image shows tundra heath in autumn colours in low Arctic Greenland.

Letter p349

IMAGE: FRIDA LINDWALL

COVER DESIGN: TULSI VORALIA

The polygonal patterns in permafrost regions are caused by the formation of ice wedges. Observations of polygon evolution reveal that rapid ice-wedge melting has occurred across the Arctic since 1950, altering tundra hydrology. Polygonal tundra of Alaskan North Slope near Barrow photographed from a small research airplane measuring methane fluxes from air.

Article p312

IMAGE: GEORGE BURBA, LI-COR BIOSCIENCES/UNIVERSITY OF NEBRASKA-LINCOLN

COVER DESIGN: TULSI VORALIA

The formation of Earth’s continental crust is unclear. A review of the geochemical composition of crust formed above subduction zones across the globe suggests that subduction and relamination of buoyant magmatic rocks play an important role. The image shows the McMillan Spires in the North Cascades National Park of Washington State; they are composed of the Skagit Gneiss that crystallized at a depth of about 40 km, near the base of the continental crust, and has a composition similar to that of average continental crust.

Review Article p197

IMAGE: JOHN SCURLOCK

COVER DESIGN: TULSI VORALIA

Streamflow is a mixture of precipitation of various ages. Oxygen isotope data suggest that a third of global river discharge is sourced from rainfall within the past few months, which accounts for less than 0.1% of global groundwater. The image shows a reach of the Iris Burn River in Fiordland, New Zealand in February 2015.

Letter p126

IMAGE: GLENN JASECHKO

COVER DESIGN: ALEX WING

In active mountain belts, erosion is driven by bedrock landsliding. River water chemistry in New Zealand's Southern Alps suggests that stochastic mass wasting processes also enhance chemical weathering in such environments. The image shows water with extensive algal growth seeping from the base of a landslide deposit at Chenyoulan River, Taiwan in November 2013.

Letter p42

IMAGE: ROBERT EMBERSON

COVER DESIGN: DAVID SHAND AND ALEX WING