Reconstructions of ancient atmospheric carbon dioxide (CO2) variations help us better understand how the global carbon cycle and climate are linked. We compared CO2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere.

The concentration of atmospheric carbon dioxide decreased between
45 million and 25 million years ago, a trend accompanied by glaciation at the poles. Modelling results suggest when and where the ice closed in.

Carbon dioxide emissions from fossil fuels and cement manufacturing are rising faster than the worst-case scenario drawn up by the Intergovernmental Panel on Climate Change (IPCC). According to the latest worldwide carbon budget, released by the Global Carbon Project, CO2 levels rose by 3.5% a year between 2000 and 2007, compared with 2.7% as calculated by the IPCC.

Delegates to a recent IMO working group meeting were unable to make progress toward an agreement to reduce emissions of greenhouse gases from international shipping.