Was global warming first proposed by astronomers?

Author | Zhou Yihao

Review | Zheng Chengzhuo

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On December 1, 2023, Dubai held the United Nations Climate Change Dubai Conference (COP28). COP is an annual climate conference attended by almost all countries, where representatives from various countries negotiate global goals to address climate change. But what many people don’t know is that some important studies on climate change were originally proposed by a group of astronomers.

Venus photographed by Mariner 10 probe | Source: NASA

The story began in the 1950s and 1960s, when American astronomer Cornell Mayer and others discovered that Venus was a strong radio source, which meant it was very hot, which was unexpected, but no one could explain it well at the time. Later, some astronomers realized that the chemical composition of a planet's atmosphere had a decisive influence on its climate, and American astronomer Carl Sagan proposed that the dense carbon dioxide in Venus' atmosphere caused a runaway greenhouse effect, causing its surface temperature to reach 460 degrees Celsius.

Regarding Venus' unusually hot surface and strong radio brightness, Dr. James Hansen, a scientist working at NASA's Goddard Institute for Space Studies at the time, not only agreed with the role of greenhouse gases in maintaining the hot temperature on the surface of Venus, but also boldly hypothesized that the real source of this heat might be thermal energy deep inside Venus, rather than sunlight.

James Hansen | Source: scicolloq.gsfc.nasa.gov

In May and August 1978, NASA launched two Venus probes, Pioneer 12 and Pioneer 13. On December 4 of the same year, Pioneer 12 entered orbit around Venus; in November of the same year, Pioneer 13 released four probes, which entered the atmosphere of Venus on December 9. Hansen worked with other scientists to use the data obtained by these probes to reveal how the runaway greenhouse effect on Venus was formed: the heat from the sun was absorbed by the surface of Venus and then locked by greenhouse gases in the atmosphere, forming a persistent and powerful greenhouse effect. At the same time, this discovery made Hansen look back at our home, the Earth.

Pioneer-Venus Probe (Pioneer 12 on the right, Pioneer 13 on the left) | Image source: NASA

Hansen built a computer climate model and used it to predict what would happen to the Earth's climate if greenhouse gases continued to accumulate. He compared these models with the Earth's ancient climate record and found that during the last ice age, large amounts of carbon dioxide and methane emissions were associated with significant increases in temperature. He also collected a large amount of climate data from the 20th and 19th centuries to understand how global temperatures changed, and then compared them with the predictions of the computer models, which matched closely within the margin of error. He also made accurate predictions about the temporary drop in Earth's temperatures caused by the eruption of Mount Pinatubo in the Philippines in 1991. Because of these studies, he became a leading figure in trying to convince the world to take global warming seriously.

Cover of the Chinese version of "Environmental Storm: Climate Disasters and Human Opportunities" | Source: Amazon

With his fruitful research results and extensive public influence, Hansen was awarded a series of important awards from the American Physical Society, the American Meteorological Society, and the American Geophysical Union, and was elected as a member of the National Academy of Sciences in 1996. During the Copenhagen Climate Conference in 2009, Hansen published a new book, "Environmental Storm: Climate Disasters and Human Opportunities", which fully demonstrated the hazards of global warming and called on mankind to cherish the last chance to save itself.

References

[1] Chen Le, Zhang Shaobing, Yu Jinfei. Venus: A window to understand the early Earth[J]. Reviews of Earth and Planetary Physics, 2022, 53(01): 66-84.

[2] Venus was still habitable 700 million years ago: the temperature on the planet was between 20-50 degrees Celsius [J]. East China Science and Technology, 2019, (10): 76-77.

[3] Yin Huaiqin. High temperature on Venus and global warming[J]. Knowledge is power, 2013, (07): 50-53.

[4]Bullock AM ,Grinspoon HD . Global Climate Change on Venus [J]. Scientific American, 2003, 13 20-27.

[5]GRP. Planetary science. Climate change on Venus. [J]. Nature, 2001, 412 (6842): 36-7.

[6]Pioneer Venus project, wikipedia, https://en.m.wikipedia.org/wiki/Pioneer_Venus_project

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