STABLE-ISOTOPE ratios of carbon in soils or lake sediments1–3 and of oxygen and
hydrogen in peats4, 5 have been found to reflect past moisture variations and hence to …

A DECADE ago, Lovelock and Whitfield1 raised the question of how much longer the
biosphere can survive on Earth. They pointed out that, despite the current fossil-fuel induced …

Abstract About 850,000 years ago, the period of the glacial cycles changed from 41,000 to
100,000 years. This mid-Pleistocene climate transition has been attributed to global cooling …

BACKGROUND Humans are altering the planet, including long-term global geologic
processes, at an increasing rate. Any formal recognition of an Anthropocene epoch in the …

Many aspects of the carbon cycle can be assessed from temporal changes in the 13C/12C
ratio of oceanic bicarbonate. 13C/12C can temporarily rise when large amounts of 13C …

BUBBLES of ancient air in polar ice cores have revealed that the atmospheric concentration
of CO2 during the Last Glacial Maximum was 180–200 ppmv, substantially lower than the …

A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been
identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River …

The carbon balance of terrestrial ecosystems is particularly sensitive to climatic changes in
autumn and spring,,,, with spring and autumn temperatures over northern latitudes having …

Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate
change and millennial-scale temperature variability. Its concentrations over the past 650,000 …

Increased storage of carbon in the oceans has been proposed as a mechanism to explain
lower concentrations of atmospheric carbon dioxide during ice ages; however, unequivocal …