1824Jean Baptist Joseph Fouriercalculates that the Earth is about 33°C warmer than it should be given its distance from the sun and hypothesised that this was due to properties of the Earth’s atmosphere

1859John Tyndalltests the warming properties of carbon dioxide and finds a reduction in the heat energy (infrared radiation) passing through a test tube containing small amounts of CO2 – thus demonstrating the heat-trapping properties of this gas

1896Svante Arrheniuscalculates that a 40% decrease or increase in atmospheric CO2 might cool or warm the world sufficiently to trigger glacial advances or retreats

1938Guy Callendarcalculates that a doubling of atmospheric CO2 would result in a roughly 2°C rise in average global temperature

1957Roger Revelledemonstrated that the particular chemistry of sea water prevents it from absorbing all of the excess CO2 emitted through human activities – and that most of the additional CO2 will return to the atmosphere and contribute to warming

1950s and 1960sCharles Keelingbegins measuring CO2 in the atmosphere at Mauna Loa in Hawaii, finding that there are seasonal changes due to uptake and release of CO2 in the Northern Hemisphere’s forests, but that the atmospheric concentration was rising steadily