Volume 8 Issue 2, February 2015

Soil contains aged organic carbon that can be hundreds or thousands of years old. Human disturbance in small and large watersheds is mobilizing some of this fossil carbon from soils to aquatic systems.

The Sahara was more humid and habitable thousands of years ago. Reconstructions of North African hydroclimate show that the onset of aridity started in the north, with the monsoon rains weakening progressively later at lower latitudes.

In the first decades of the twentieth century, the Earth warmed rapidly. A coral-based climate proxy record of westerly winds over the equatorial Pacific suggests that wind strength and warming rate were linked, as they are today.

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.

Earth’s nitrogen isotopic composition has been linked to an unknown primordial reservoir. Macroscopic analyses of mineral inclusions in meteorites suggest that ices in the Sun’s protoplanetary disk could be the source of Earth’s nitrogen.

The atmospheric circulation controls the regional expression of global climate change. An analysis of aquaplanet climate simulations suggests that the radiative effects of clouds and water vapour are key to the circulation response to global warming.

Carbon dioxide emissions from lakes contribute to the continental carbon balance. Water chemistry analyses of reservoirs in Spain suggest that carbonate weathering causes CO₂ supersaturation in lakes above a threshold alkalinity.

Most dissolved organic carbon in rivers originates from young carbon in soils and vegetation. A global radiocarbon data set suggests that human disturbance is also introducing aged carbon to rivers and to active carbon cycling.

Global temperatures rose quickly between 1910 and 1940. A reconstruction based on corals suggests that the Pacific trade winds were weak during this period of rapid warming, but strengthened as warming slowed in the following decades.

Holocene temperature trends in the Arctic are unclear. An isotope record from ice wedges in Siberia suggests that winters have warmed since the mid-Holocene, whereas summer temperatures have cooled.

Earth’s initial oxygenation took several hundred million years. Experiments and geochemical modelling suggest that early photosynthetic marine microbes may have been repeatedly stressed by Fe(II) delivered by submarine volcanism.

The Tibetan Plateau is extending. Numerical simulations suggest that regional-scale extension is caused by gravitational collapse of the plateau, whereas rapid extension in the south is caused by underthrusting of the Indian slab.

The spatial pattern of climate change is uncertain. Analyses of a simple model suggest that uncertainty in tropical feedbacks induces a global response, but the impact of uncertainty in polar feedbacks tends to be limited to the region.

During the early to mid-Holocene, Africa was more humid than today. Precipitation reconstructions from across Africa suggest that the termination of humidity was spatially variable, moving towards progressively lower latitudes.

Seismic tremors can be used to distinguish plate boundaries. Analysis of tremors occurring deep beneath the San Andreas Fault may identify the boundary between the North American Plate and the preserved remnant of a subducted slab.

The 2011 Tohoku-oki earthquake released stress within a subduction zone. Analysis of seismic data shows that stresses returned to pre-quake levels within a few years, implying that large quakes could occur more often than previously thought.