Nearly two centuries after it was discovered that gases in the Earth’s atmosphere help warm the planet’s surface, a public poll has found that more than half of Americans believe climate change poses a “critical threat” to people. vital interests of the country, an increase of 10 percentage points from a June 2017 poll and six points from March 2019. American public resistance to the science of climate change and the behavioral changes needed to combat it has been particularly persistent relative to much of the rest of the world; but over the past few decades a number of events and discoveries have helped to heighten the importance of the issue. Here is a selection of some key developments.
1. First evidence
The Keeling Curve tracks changes in CO2 concentration in the Earth’s atmosphere using data from a research station on Mauna Loa in Hawaii.
Encyclopedia Britannica/UIG/Getty Images
The scientific justification for global warming was established in the 19th century. Joseph Fourier discovered in 1824 that the Earth would be colder without an atmosphere. John Tyndall determined in 1859 that carbon dioxide and water vapor block infrared radiation and that an increase in their atmospheric composition could induce warming. And in 1896, Svante Arrhenius published the first calculation of how much warming would be created by increasing levels of carbon dioxide in the atmosphere.
But not before the second half of the 20and century, updated scientific assessments began to enter the public consciousness, albeit slowly at first. In 1958, Ralph Keeling began plotting CO2 levels in the atmosphere from the summit of Mauna Loa in Hawaii, producing the famous Keeling Curve, which is updated daily. (When it started, CO2 levels in the atmosphere were 313 parts per million (ppm); in 2022, they were around 420 ppm.)
In 1965, scientists from the President’s Scientific Advisory Committee of the United States first expressed concerns about greenhouse warming, saying that the continued release of CO2 into the atmosphere would “almost certainly cause significant changes” and “could be deleterious from the point of view of human beings”. .” And in 1983, back-to-back reports from the National Academy of Sciences and the Environmental Protection Agency sounded the alarm about rising greenhouse gas levels, the report from the EPA warning that “substantial increases in global warming may occur sooner than most of us would.” like to believe. »
2. Jim Hansen testifies
In the wake of the EPA and NAS reports, and other mounting evidence that greenhouse warming is real, Congress has held a number of hearings on the issue and invited expert testimony. exteriors. The most impactful came on June 23, 1988 when, on a hot day in Washington, D.C., James Hansen of NASA’s Goddard Institute for Space Studies told senators that “Earth is warmer in 1988 than in any moment in the history of instrumental music. measurements”, and that there was “only a 1% chance of an accidental warming of this magnitude… The greenhouse effect has been detected, and it is modifying our climate now”. the New York Times said Hansen’s testimony “sounded the alarm with such authority and force that the issue of an overheating world suddenly rose to the forefront of public concern”.
Scroll to continue
3. “An Inconvenient Truth”
Clockwise from bottom left Davis Guggenheim, director and producers Laurie David, Lawrence Bender and Scott Burns, posing next to an on-screen image of Al Gore from their documentary ” An Inconvenient Truth”.
Mel Melcon/Los Angeles Times via Getty Images
After his landslide defeat in the 2000 U.S. presidential election, Al Gore, who launched the first congressional hearing on global warming in 1981, began presenting a slide show on the science and politics of climate change, which the producer Laurie David and director David Guggenheim turned into documentary An inconvenient truth. The documentary, generally hailed by scientists for its accuracy, has increased awareness of global warming and the will to act to prevent it (even as it has helped to accentuate a growing partisan divide on the issue). It grossed over $50 million worldwide at the box office and won the Academy Award for Best Documentary Feature in 2007. That same year, Gore shared the Nobel Peace Prize with the Intergovernmental Panel on climate change.
4. Hurricanes Katrina and Sandy
Scientists have long predicted that a major consequence of global warming will be an increase in the quantity and severity of extreme weather events, and a series of them in the 21st century has highlighted the potential real impacts of climate change. In 2005, Hurricane Katrina flooded 80% of New Orleans and killed approximately 1,800 people. Although it is not possible to say that climate change directly caused the storm, a study concluded that the increase in ocean temperatures and sea levels likely exacerbated the damage it caused. . Similarly, rising sea levels almost certainly accentuated the storm surge from Superstorm Sandy, which hit the coast from northern Maryland to Manhattan in 2012. A 2021 study concluded that climate change was responsible of at least $8 billion in damage from the storm.
5. Wildfires
Claire Cowie watches over her horses as a fire approaches near Canberra, Australia, February 2020.
Brook Mitchell/Getty Images
From the Amazon to Australia to the American West, in 2020 the world has caught fire and climate change has played a significant role. The southern Amazon has seen nearly 600,000 individual fires, 25 of them larger than 190 square miles, while about 28% of the Pantanal – a floodplain region along the borders of Brazil, Bolivia and Paraguay – burned. That same year, and again in 2021, fires raging across Siberia sent a cloud of smoke to the North Pole.
Australia’s massive wildfires have captured the world’s attention and affected more than 3 million animals, creating “one of the worst wildlife disasters in modern history”. And with the western United States in the grip of its worst drought in more than 1,200 years, a series of wildfires have scorched more than four million acres of California. The scientific evidence was unequivocal: more than half of the acres burned each year in the western United States can be attributed to climate change, with the number of dry, hot and windy fall days in California having more than doubled since then. the 1980s.
Studies have shown that the number of fires in the Sierra Nevada could increase by 20% or more by the 2040s, and that the total area burned could increase by around 25% or more – further evidence that the signs harbingers of global warming have not only increased in recent decades, they are destined to do so even more in the future.
