James Croll

In the mid-19th century, a handful of geologists began to speculate that certain geological features could be attributed to glacial erosion. The main question was: how could Earth have been cold enough for an extended period? James Croll, the son of a stone mason and raised on a farm, had limited formal education but became fascinated with philosophy and science after discovering a magazine at age 11.

Eventually, he obtained a caretaker position at the Andersonian College and Museum in Glasgow, where he gained access to a wealth of scientific resources. His groundbreaking paper in 1864 proposed that the Earth’s orbit fluctuated over centuries, leading to prolonged periods of cold. Croll theorized that increased polar ice would result in lower temperatures, creating a feedback loop where colder conditions would lead to even colder temperatures until the Earth’s orbit shifted closer to the sun.

His hypotheses were crucial for geologists, earning him recognition from contemporaries like Charles Lyell and Charles Darwin. His major work, Climate and Time, published in 1875, solidified his standing as a prominent figure in climate science.

The second video, HAARP: Watch out for this conspiracy theory on climate change by FRANCE 24 English, discusses the various conspiracy theories surrounding climate change and their implications.

John Tyndall

While Croll was developing his theories, John Tyndall, an Irish scientist and mountaineer, was examining how different gases absorbed radiant heat. He discovered that water vapor and carbon dioxide were particularly effective at trapping heat, confirming a concept first introduced by Joseph Fourier in 1820 about the "greenhouse effect."

A Pair of Swedes

Svante Arrhenius, another influential figure, calculated in 1896 that halving atmospheric CO2 could lower temperatures by 4ºC to 5ºC. His colleague, Arvid Hogbom, recognized that industrial emissions were contributing significant amounts of CO2, leading Arrhenius to posit that doubling CO2 levels could raise temperatures by 5ºC to 6ºC.

Guy Stewart Callendar

In 1938, Guy Stewart Callendar revisited Arrhenius' earlier work, analyzing historical temperature data and CO2 levels. He noticed a correlation, suggesting that increased CO2 would elevate temperatures. Despite his findings, many scientists remained focused on explaining past climate changes rather than addressing the potential future impacts of rising CO2 levels.

Kaplan and Plass

After World War II, interest in atmospheric science surged, particularly regarding infrared absorption. Theoretical physicist Lewis D. Kaplan confirmed that CO2 in the upper atmosphere had a more pronounced impact than at lower altitudes. Gilbert N. Plass expanded on these ideas in 1956, estimating that a doubling of CO2 could result in a 3ºC to 4ºC rise in temperatures.

Hans Suess and Roger Revelle

Research by chemists Hans Suess and Roger Revelle unveiled that the oceans were not absorbing as much man-made CO2 as previously thought. They established that while the upper ocean layers absorbed CO2, they also released it back into the atmosphere, complicating the overall picture.

Charles David Keeling

To address these uncertainties, Keeling developed precise measurement techniques for CO2 levels in the atmosphere, leading to the establishment of a baseline for future comparisons. His findings confirmed that CO2 levels were increasing at a rate inconsistent with the idea that oceans were absorbing most emissions.

As the evidence mounted, the scientific community began to recognize the urgent need to understand the interactions between CO2 and the biosphere, setting the stage for more comprehensive climate models.