The Amazing History of Global-Warming Science 
John Tyndall, an English scientist in the forefront of the ice-age debate of the 1800’s, wondered how the climate could have changed so much. He suspected the atmosphere, which was known to have the ability to trap the sun’s heat. Working in his laboratory, in 1859 he found the most important greenhouse gas was water vapor (H₂O), but that carbon dioxide (CO₂) was also effective.

In 1896 Arrhenius completed a laborious numerical computation which suggested that cutting the amount of CO₂ in the atmosphere by half could lower the temperature in Europe some 4-5°C (roughly 7-9°F) — that is, to an ice age level.

In the 1990’s French and Russian scientists extracted a mile and a half deep ice core from Antarctica. Analysis by an international team found that over the four ice-age cycles in the last 400,000 years, CO₂ dropped in step with the temperature but only by about one third, not one half. That could easily be because other greenhouse gases changed with CO₂. This is either confirmation of the 1896 prediction, or an amazing coincidence.