Increased delivery of phosphorus to the Late Ordovician ocean from volcanism helps explain widespread cooling and eutrophication-driven extinctions, as shown by a biogeochemical model incorporating volcanic ash and carbon isotope records. The photograph shows Selenopeltis fossils, a genus of spiny trilobite that became extinct in the Late Ordovician — along with 85% of species of marine organisms. Locality: Mecissi-Alnif, Morocco. Photograph taken in the Oxford University Museum of Natural History.

See Longman et al.

Reorganized ocean circulation during Late Ordovician cooling altered oxygenation through the water column, leading to widespread extinctions, according to anoxia reconstructions using the I/Ca proxy and Earth system modelling. The image shows Late Ordovician limestones investigated in this study from Vauréal Canyon, Anticosti Island, eastern Canada.

See Pohl et al.

Greenland’s peripheral low-lying glaciers and ice caps are currently losing mass, but during the past two millennia may have responded to warming by growing larger. This image shows a helicopter slinging a load of ice cores off the 2,000-metre summit of the Nuussuaq Peninsula ice cap, coastal west Greenland.

See Osman et al.

Emission controls avoided some 870,000 deaths in China between 2002 and 2017 but further air quality improvements need energy–climate policies and changed economic structure, according to index decomposition analysis and chemical transport models. The image shows a view in 2014 of the Forbidden City, Beijing, a palace complex designed by the architect Kuai Xiang during the Ming dynasty.

See Geng et al.

Vorticity gradient force balance explains the location and number of circumpolar cyclones at Jupiter’s poles, and the absence of circumpolar cyclones on Saturn, according to calculations. The image shows Jupiter's south pole, created using data from the JunoCam imager on NASA's Juno spacecraft.

See Gavriel and Kaspi

Forestation of rainfed agricultural land in Europe triggers substantial local and downwind precipitation changes, according to results from an observation-based continental-scale statistical model. The image shows an aerial view of a farmland in Chao da Ribeira, Madeira, Portugal.

See Meier et al.

New particle formation is a major source of cloud condensation nuclei, important in the rapidly changing Antarctic climate. The image shows an aerial view of the Research Vessel Hesperides sampling ship-borne data on nucleation of biogenic particles from sulfuric acid and amines along the west coast of Graham Land, West Antarctica.

See Brean et al.

The transition between the locked and slipping parts of the southern Cascadia megathrust has a low porosity, suggesting it has a ductile rheology that would limit the size of large earthquakes. This image shows dead trees in the Ghost Forest at Oregon’s Neskowin Beach, United States, an area buried beneath mud and debris following the Cascadia earthquake in 1700.

See Guo et al..

Weathering of deep bedrock through snowmelt-driven water table fluctuations within hillslopes releases reactive nitrogen into the subsurface, which contributes to the flux of nitrous oxide to the hydrosphere and atmosphere. The image shows an aerial view of the East River, central Colorado, United States, flowing through a mountainous watershed underlain by Cretaceous marine shale.

See Wan et al.

Reduced planetary albedo due to fewer low clouds on early Earth could explain some 40% of the required forcing to offset the faint young Sun, according to global climate model experiments.

See Goldblatt et al.

The CO mixing ratio in Mars’s atmosphere increases towards the poles because of downward transport of CO from the upper atmosphere, according to an analysis of data from the ExoMars Trace Gas Orbiter. This image shows an area in Melas Chasma (Valles Marineris, Mars) taken by the Colour and Stereo Surface Imaging System on-board the European Space Agency’s Trace Gas Orbiter mission. The colour composite has been manipulated to emphasize the spectral diversity of landforms and sediments on the surface.

See Olsen et al.

Newly formed biogenic particles in the Himalaya increase free-tropospheric background aerosol concentration by a factor of up to two. The image shows the Pyramid International Observatory, a research station from which observations were taken for this study, located at 5,050 metres above sea level (a.s.l.) at the base of the Nepali side of Mount Everest (also known as Sagarmatha or Chomolungma). The mountain behind the station is Pumori, at 7,161 m a.s.l.

See Bianchi et al.