Articles in 2015

Martian gullies have been seen as evidence for past surface water runoff. However, numerical modelling now suggests that accumulation and sublimation of carbon dioxide ice, rather than overland flow of liquid water, may be driving modern gully formation.

Subduction zone earthquakes can be followed by aseismic slip. Analysis of fault slip in northern Peru reveals transient aseismic slip that lasted for seven months and released more than 1,000% of the energy expelled by the quake that preceded it.

Gullies on Mars have been linked to possible flowing water, but are most active when seasonal CO₂ ice is defrosting. Numerical modelling suggests that CO₂ ice sublimation can induce debris flows consistent with observations of martian gullies.

Sea level rose rapidly during Meltwater Pulse 1A, about 14,500 years ago. A reassessment of sea-level rise and isostatic adjustment suggests sea level rose roughly 8 to 15 m in total, with 0 to 10 m derived from the Antarctic ice sheets.

El Niño events tend to suppress Atlantic hurricane activity. Simulations with high-resolution climate models show that the efficiency of this suppression mechanism varies with the flavour of the El Niño event.

Clear evidence for subduction-induced metamorphism, and thus the operation of plate tectonics on the ancient Earth has been lacking. Theoretical calculations indicate that we may have been looking for something that cannot exist.

An absence in the ancient geological record of blueschist metamorphic rocks has been taken as evidence against early subduction. Thermodynamic calculations now suggest that blueschist rocks could not have formed on a younger, hotter Earth.

Aquatic ecosystems are important sources of the greenhouse gas nitrous oxide. Measurements of nitrous oxide concentrations from 321 rivers, lakes and ponds in Canada reveal that some boreal aquatic systems can act as net nitrous oxide sinks.

Plate tectonic motions can influence biological systems. Numerical modelling of the topographic evolution of New Zealand, combined with fish phylogenetic analyses suggest mountain growth directly influenced biological diversification.

The frequency and amplitude of the El Niño/Southern Oscillation varied during the Holocene. A comparison of proxy records and model simulations suggests that any link between orbital forcing and this variability is either complex or non-existent.

Some climate change impacts rise fast with little warming, and then taper off. To avoid diminishing incentives to reduce emissions and inadvertently slipping into a lower-welfare world, mitigation policy needs to be ambitious early on.

As the world's leaders are negotiating climate change mitigation in Paris, a strong El Niño brings the warmest year on record. After a decade and a half of slow warming and slow policy progress, 2015 may bring an acceleration of both.

The structure of atmospheric aerosol particles affects their reactivity and growth rates. Measurements of aerosol properties over the Amazon rainforest indicate that organic particles above tropical rainforests are simple liquid drops.

In the absence of an enforceable set of commitments to reduce greenhouse gas emissions, concerned citizens may want to supplement international agreements on climate change. We suggest that litigation could have an important role to play.

During the last deglaciation, the Indian summer monsoon failed during periods of cooling in the North Atlantic. Sediment records suggest that the concomitant cooling of the surface of the Arabian Sea contributed to the monsoon weakening.

The physical state of atmospheric particulate matter affects its growth and reactivity, which can affect climate. Measurements of particle rebound reveal that particulate matter over the Amazon forest is usually liquid during wet and dry seasons.

Many governments agreed to limit global mean temperature change to below 2 °C, yet this level has not been assessed scientifically. A synthesis of the literature suggests that temperature is the best available target quantity, but a safe level is uncertain.

Jupiter’s banded cloud layer contains enigmatic jets and vortices. Numerical simulations show that both features originate at depth in giant planet atmospheres, with vortices developing in areas of upwelling to shallow layers.