| 1800–70 The levels of CO2 in the atmosphere are 290 ppm. |
| 1824 Jean-Baptiste Joseph Fourier, a French mathematician and physicist, calculates that the Earth would be much colder without its protective atmosphere. |
| 1827 Jean-Baptiste Joseph Fourier presents his theory about the Earth’s warming. At this time many believe warming is a positive thing. |
| 1859 John Tyndall, an Irish physicist, discovers that some gases exist in the atmosphere that block infrared radiation. He presents the concept that changes in the concentration of atmospheric gases could cause the climate to change. |
| 1894 Beginning of the industrial pollution of the environment. |
| 1913–14 Svante Arrhenius discovers the greenhouse effect and predicts that the Earth’s atmosphere will continue to warm. He predicts that the atmosphere will not reach dangerous levels for thousands of years, so his theory is not received with any urgency. |
| 1920–25 Texas and the Persian Gulf bring productive oil wells into operation, which begins the world’s dependency on a relatively inexpensive form of energy. |
| 1934 The worst dust storm of the dust bowl occurs in the United States on what historians would later call Black Sunday. Dust storms are a product of drought and soil erosion. |
| 1945 The U.S. Office of Naval Research begins supporting many fields of science, including those that deal with climate change issues. |
| 1949–50 Guy S. Callendar, a British steam engineer and inventor, propounds the theory that the greenhouse effect is linked to human actions and will cause problems. No one takes him too seriously, but scientists do begin to develop new ways to measure climate. |
| 1950–70 Technological developments enable increased awareness about global warming and the enhanced greenhouse effect. Studies confirm a steadily rising CO2 level. The public begins to notice and becomes concerned with air pollution issues. |
| 1958 U.S. scientist Charles David Keeling of the Scripps Institution of Oceanography detects a yearly rise in atmospheric CO2. He begins collecting continuous CO2 readings at an observatory on Mauna Loa, Hawaii. The results became known as the famous Keeling Curve. |
| 1963 Studies show that water vapour plays a significant part in making the climate sensitive to changes in CO2 levels. |
| 1968 Studies reveal the potential collapse of the Antarctic ice sheet, which would raise sea levels to dangerous heights, causing damage to places worldwide. |
Labels: Environmental History