Reviews & Analysis

Abrupt climate changes during the last glacial period affected most of the Northern Hemisphere. Greenland ice core data suggest that for the penultimate abrupt warming event, climate change was nearly synchronous at high and low latitudes.

Ethanol has been heralded as a cleaner fuel for cars than gasoline. An analysis of air quality data suggests that a switch from ethanol to gasoline use in São Paulo in response to changing prices led unexpectedly to lower local levels of ozone pollution.

Record-breaking heatwaves in 2003 and 2010 surprised both the public and experts. Observations provide new insights into how temperatures escalated to unprecedented values through the interaction of boundary-layer dynamics and land surface drying.

Carbon loss from subducting slabs is thought to be insufficient to balance carbon dioxide emissions at arc volcanoes. Analyses of ancient subducted rocks in Greece suggest that fluid dissolution of slab carbonate can help solve this carbon-cycle conundrum.

A dense early atmosphere has been invoked to explain the strong greenhouse effect inferred for early Mars. Yet an analysis of the smallest impact craters suggests that the atmospheric pressure on Mars 3.6 billion years ago was surprisingly low.

Ocean island lavas have complex geochemical signatures. Numerical simulations suggest that these signatures may reflect the entrainment and transport to Earth's surface of both primordial material and recycled oceanic crust by deeply rooted mantle plumes.

Oxygen-producing photosynthesis must have evolved before the pervasive oxidation of the atmosphere around 2.4 billion years ago, but how long before is unclear. Geochemical analyses of ancient sedimentary rocks now suggest that cyanobacteria generated oxygen at least 3 billion years ago.

The tropical belt has become wider over the past decades, but climate models fall short of capturing the full rate of the expansion. The latest analysis of climate simulations suggests that a long-term swing of the Pacific Decadal Oscillation is the main missing cause from the coupled climate models.

The climate regimes of monsoon regions and deserts are connected. Satellite data and numerical experiments reveal that an increase in dust aerosol loading over the Arabian Sea and West Asia can lead to enhanced summer monsoon rainfall over central India on timescales of days to weeks.

As Mercury's interior cools and its massive iron core freezes, its surface feels the squeeze. A comprehensive global census of compressional deformation features indicates that Mercury has shrunk by at least 5 km in radius over the past 4 billion years.

The age of the oldest Jack Hills zircons — Earth's oldest minerals — is contentious. Atomic-scale mapping of the distribution of radiogenic isotopes within a Jack Hills zircon confirms that the oldest known continental crust formed just after the Earth–Moon system.

The end-Permian extinction decimated marine life on an unprecedented scale. However, an analysis of the lifestyles of the surviving genera shows that very little functional diversity was lost at the sea floor.

Despite reports of no trends in snow- and rainfall, rivers in the northwest USA have run lower and lower in recent decades. A closer look at high- and low-altitude precipitation suggests that observational networks have missed a decline in mountain rain and snow that can explain the discrepancy.

Global mean surface temperatures have not risen much over the past 15 years, despite continuing greenhouse gas emissions. An attempt to explain the warming slow-down with Arctic data gaps is only a small step towards reconciling observed and expected warming.

Little is known about the presence of high-latitude sea ice before 2.6 million years ago. A reanalysis of marine sediments from the Arctic Ocean indicates an intermittent presence of perennial sea ice as early as 44 million years ago.

Wind systems determine the transport pathways of air pollutants such as ozone. Simulations with a chemistry-climate model suggest that decadal shifts in atmospheric circulation have helped shape season-specific trends in surface ozone levels in Hawaii since the 1990s.

A slowing Atlantic overturning circulation during the last deglacial warming caused abrupt cooling in the Northern Hemisphere. Lake sediment records suggest that hydrological change in Europe lagged the temperature drop by almost 200 years.

Volcanic plumes can be hazardous to aircraft. A correlation between plume height and ground deformation during an eruption of Grímsvötn Volcano, Iceland, allows us to peer into the properties of the magma chamber and may improve eruption forecasts.