Reviews & Analysis

Seafloor vents spewing mineral-rich plumes of hydrothermal fluid — termed black smokers — can persist at mid-ocean ridges for decades or longer. Earthquake data indicate that ongoing magma injection may determine their locations.

Some components of the climate system continue to adjust long after atmospheric greenhouse-gas levels have stopped changing. A coupled climate–vegetation model shows that forests can be committed to die-back or expansion before change is observed.

Understanding millennial-scale climate variability provides context for present and future climate change. It now emerges that temperatures were spatially and seasonally more heterogeneous over the past 1,000 years than previously thought.

Large and rapid global sea-level changes indicate that polar ice sheets may have ephemerally existed during the Cretaceous greenhouse climate. Two oxygen isotopic studies provide evidence for and against this conclusion.

Ammonia is a significant atmospheric pollutant whose global distribution is poorly understood. Satellite measurements highlight ammonia hotspots across the globe and indicate that current inventories may underestimate emissions in the Northern Hemisphere.

Global mean sea-level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades. A review of the latest work shows that global mean sea-level rise is unlikely to exceed one metre over the twenty-first century, but regional departures from this global mean could reach several decimetres.

A widespread biotic turnover occurred around the time of the Sturtian glaciation. Microfossil analyses show that one regional extinction pre-dates the glacial advance, challenging the more severe models for glacial effects in the Neoproterozoic era.

Millions of people in southern Asia rely on arsenic-contaminated groundwater to live. Massive water withdrawals through wells may be increasing the problem by drawing arsenic-mobilizing substances into shallow aquifers and arsenic-contaminated shallow groundwaters into deeper aquifers.

Ice clouds significantly affect the Earth's radiative forcing, but which particles lie at the core of the ice crystals is a matter of debate. In-flight spectroscopy suggests that biogenic materials contribute to ice formation in clouds.

The lack of strong splitting of seismic shear waves below central Nevada is in marked contrast to the surrounding region. Seismic data and numerical experiments suggest that a skinny, cylindrical drip of lithosphere may be to blame.

The complex three-dimensional structure of the Earth's solid inner core reveals how it has grown through time. Numerical simulations of the solidification process suggest that part of this structure has resulted from recent tectonic activity.

Remnants of the Laurentide ice sheet lasted until about 7,000 years ago. Climate simulations show that they caused the multimillennial delay between maximum early Holocene solar radiation and temperatures evident in Northern Hemisphere proxy records.

The myriad bodies that occur in the Solar System show a wide range of physical properties. Exploration by spacecraft during the past four decades has shown that volcanism — a major mechanism by which internal heat is transported to the surface — is common on many of these bodies.

Iron can stimulate productivity in many regions of the world ocean, but only if it exists in a readily dissolvable form. Chemical analyses of typical aerosol particles show that the mineralogy of iron-containing particles largely determines their solubility.

Atmospheric deposition of nitrogen can, but does not always, speed up the sequestration of carbon in trees and forest soil. This complexity may arise from the spatial variations in each of the three mechanisms by which nitrogen affects carbon storage.

Climate model simulations do not perfectly match observations of Arctic sea-ice decline. Nevertheless, by combining models, observations and physical reasoning, it can be predicted that September sea ice is likely to vanish before the end of the twenty-first century.