Progress Article

Marine macroalgae are dominant primary producers in coastal zones. A review of the published literature suggests that macroalgae may play an important role in carbon sequestration.

The Palaeocene–Eocene Thermal Maximum was associated with a massive release of carbon. Marine sediments suggest a temporary deepening of the calcite compensation depth, indicating extensive silicate weatheringin the aftermath of the event.

Sea surface temperatures have varied over the past 2,000 years. A synthesis of surface-temperature reconstructions shows ocean surface cooling from ad 1 to 1800, with much of the trend from 800 to 1800 driven by volcanic eruptions.

Slow earthquakes have recently been discovered on the shallow parts of some subduction zones. A review of the conditions under which these quakes form reveals that they could be common in most subduction zones globally.

Glaciers and polar ice sheets store and release a small but important pool of organic carbon. The changing climate is making glaciers an increasingly important driver of carbon dynamics in aquatic ecosystems.

The amount of carbon stored in peats exceeds that stored in vegetation. A synthesis of the literature suggests that smouldering fires in peatlands could become more common as the climate warms, and release old carbon to the air.

The removal of trace gases from the troposphere is, in most cases, initialized by reactions with hydroxyl radicals. An evaluation of this process (sometimes termed self-cleansing) using existing observations from environments with different atmospheric compositions suggests that it runs at maximum efficiency.

The Indonesian seas provide the only connection between ocean basins in the tropics. A review of observational data and model results concludes that vertical mixing determines the physical properties of water in the Indonesian throughflow.

Giant ore deposits are priority targets for mining companies. A review of the characteristics of several giant porphyry and epithermal deposits worldwide suggests that they formed from ordinary processes that were fortuitously operating at maximum efficiency.

About 4 billion years ago, the terrestrial planets were bombarded by asteroids following an orbital shake-up of the outer Solar System. Lunar samples, planetary cratering records and dynamical models piece together an increasingly coherent view of this bombardment interval.

A 500,000-year-long period of warmth in the middle Eocene was marked by high atmospheric carbon dioxide concentrations and prolonged dissolution of carbonate in the deep oceans. Numerical simulations attempting to capture these features identify gaps in our understanding of the causes of this and similar perturbations.

Temperature change over the past 2,000 years has shown pronounced regional variability. An assessment of all available continental temperature reconstructions shows a clear twentieth century warming trend, but no evidence of a coherent Little Ice Age or Medieval Warm Period.

Glacial ice covers around 10% of the Earth's continents. A review of the literature suggests that microbes living on glaciers and ice sheets are an integral part of both the glacial environment and the Earth's ecosystem.

Climate change is governed by changes to the global energy balance. A synthesis of the latest observations suggests that more longwave radiation is received at the Earth's surface than previously thought, and that more precipitation is generated.

The beginning of the Holocene interglacial was marked by ice-sheet melting and sea-level rise. A review of sea level and climate records identifies two sea-level jumps associated with the final drainage of glacial Lake Agassiz, and links them to an abrupt cooling event.

The growth of the smallest atmospheric particles to sizes at which they may act as seeds for cloud droplets is a key step linking aerosols to clouds and climate. A synthesis of research indicates that the mechanisms controlling this growth depend on the size of the growing particle.

Hydrothermal vents in the sea floor release large volumes of hot, metal-rich fluids into the deep ocean. Mounting evidence suggests that organic compounds bind to and stabilize metals in hydrothermal fluids, thereby increasing metal flux to the open ocean.

Soils are the main terrestrial reservoir of nutrients such as nitrogen and phosphorus, and of organic carbon. Data synthesis reveals that soil erosion can result in lateral fluxes of these nutrients at comparable magnitudes to those induced by fertilizer application and crop removal.

Arsenic levels in shallow groundwater in the Bengal Basin exceed thresholds for safe drinking water. Groundwater modelling indicates that deep wells that reach safe water below 150 m could remain safe for centuries if used for domestic water only, whereas the intensive use of deep groundwater for irrigation could contaminate this resource within decades.

Carbon dioxide uptake by the terrestrial biosphere has the potential to mitigate fossil fuel emissions. Comprehensive estimates of Europe's greenhouse-gas balance suggest that any uptake of carbon dioxide by the terrestrial biosphere is offset by methane and nitrous oxide emissions.