Volume 7 Issue 9, September 2014

Water availability and use are inherently regional concerns. However, a global-scale approach to evaluating strategies to reduce water stress can help maximize mitigation.

Particles of smoke from natural and human-made fires absorb sunlight and contribute to global warming. Laboratory experiments suggest that smoke is often more absorbing than current numerical models of global climate assume.

Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

In 2004, a phase transition was discovered in the most abundant lower-mantle mineral. A decade of focused experiments, computations and seismic imaging stimulated by this discovery has revealed previously unknown complexities in Earth's deep mantle.

The topography of the Earth's surface can be read as an archive of past climatic and tectonic upheavals. Field data reveal how a bedrock gorge may be erased within a human lifetime, taking with it the evidence of a major earthquake.

The release of large quantities of methane from ocean sediments might affect global climate change. The discovery of expansive methane seeps along the US Atlantic margin provides an ideal test bed for such a marine methane–climate connection.

The Arctic has warmed more than twice as fast as the global average. A literature synthesis discusses mechanisms how the associated decline in sea ice and snow cover could potentially alter mid-latitude weather, but uncertainties are profound.

How the atmosphere, hydrosphere and surface materials interacted on early Mars is poorly understood. Oxygen isotopic composition of zircon grains in a martian meteorite reveals a prolonged history of exchange between martian regolith and atmosphere.

The levels of aerosols in the atmosphere affect cloud reflectivity and the Earth’s radiative balance. A comprehensive analysis of satellite observations shows that thermodynamics and precipitation govern cloud responses to aerosols.

Atmospheric aerosols can exert an important influence on Earth’s climate. Combustion chamber experiments reveal that the absorption properties of brown carbon aerosols from biomass burning are linked to their black carbon content.

Global mean surface warming has been slow over the past 15 years. An analysis of climate simulations suggests that the low warming rate can be explained by an unusual phase of El Niño/Southern Oscillation and solar and aerosol variability.

Methane emissions from the sea floor affect ocean chemistry and can reach the atmosphere. Observations from the northern US Atlantic margin reveal about 570 gas plumes at water depths between 50 and 1,700 m.

Variations in solar activity have been linked to centennial to decadal-scale interglacial climate fluctuations. A ¹⁰Be-based reconstruction of solar activity from the Last Glacial Maximum indicates a similar Sun–climate link operated during glacial conditions.

The Cretaceous/Palaeogene mass extinction caused ecosystem upheaval. Fish abundance data from the Tethys Sea and the Pacific Ocean indicate heterogeneity in the extinction and recovery, with greater resilience in the Pacific.

Increased oxygen availability in the Cambrian oceans supported the evolution of animals that mixed the seafloor sediments. Numerical modelling suggests the development of a feedback loop between bioturbation, phosphorus burial and oxygen levels.

Large earthquakes can trigger seismicity in remote regions. Analysis of seismic data from Antarctica reveals ice quakes coincident with passing seismic waves from the 2010 Chile earthquake, suggesting that the ice sheet is sensitive to such triggers.

Narrow river gorges are often short-lived features. Images of a bedrock gorge in Taiwan, which was carved after 1999, reveal rapid widening where the upstream floodplain meets the gorge, an erosional front that propagates downstream as the gorge is erased.