Without climate change, we couldn’t inhabit the Earth as we do today. The greenhouse effect, by which gases in a planet’s atmosphere increase the heat of that planet’s surface, “makes life on Earth possible.” So says Carl Sagan in the video above. He adds that without it, the temperature would be about 30 degrees centigrade cooler: “That’s well below the freezing point of water everywhere on the planet. The oceans would be solid.” A little of the climate change induced by the greenhouse effect, then, is a good thing, but “here we are pouring enormous quantities of CO2 and these other gases into the atmosphere every year, with hardly any concern about its long-term and global consequences.”
It’s fair to say that the level of concern has increased since Sagan spoke these words in 1985, when “climate change” wasn’t yet a household term. But even then, his audience was Congress, and his fifteen-minute address, preserved by C‑SPAN, remains a succinct and persuasive case for more research into the phenomenon as well as strategies and action to mitigate it.
What audiences would expect less from Sagan, who just five years earlier had hosted the hit PBS television series Cosmos, based on his book of the same name. Its broadcast made contagious his enthusiasm for scientific inquiry in general and the nature of the planets in particular. Who could forget, for example, his introduction to the “thoroughly nasty place” that is Venus, research into whose atmosphere Sagan had conducted in the early 1960s?
Venus is “the nearest planet — a planet of about the same mass, radius, density, as the Earth,” Sagan tells Congress, but it has a “surface temperature about 470 degrees centigrade, 900 Fahrenheit.” The reason? “A massive greenhouse effect in which carbon dioxide plays the major role.” As for our planet, estimates then held that, without changes in the rates of fossil fuel-burning and “infrared-absorbing” gases released into the atmosphere, there will be “a several-centigrade-degree temperature increase” on average “by the middle to the end of the next century.” Given the potential effects of such a rise, “if we don’t do the right thing now, there are very serious problems that our children and grandchildren will have to face.” It’s impossible to know how many listeners these words convinced at the time, though they certainly seem to have stuck with a young senator in the room by the name of Al Gore.
You can whole video here: Greenhouse Effect, Senate Environment and Public Works Committee, December 10, 1985 (Carl Sagan)
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