Yes, humans are causing climate change. And we've known for 40 years. The certainty is not new or surprising.

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None of this should surprise us.
NASA
▼ Climate change is real, and humans are causing it. Thanks to forty years of satellite data, scientists are certain of those two facts. More than that, though, experts have been clear on the inevitability of climate change—and outspoken about it—for four decades, as a new paper documents. The comment, publishedin the journalNature Climate Changeearlier this week, celebrates the 40th anniversaries of three key pieces of climate science that contribute to modern certainty about anthropogenic climate change: the beginning of satellite temperature measurements in late 1978 and the 1979 publications of a report and a paper that shaped how scientists looked for human fingerprints in the climate signal.
“It’s about taking a trip down memory lane and trying to understand, ‘how did we get here?’” says paper author Benjamin Santer, a climatologist at the Lawrence Livermore National Laboratory. “In taking that trip down memory lane, it turns out that the events of 1979 were important… and were related.”
Satellites above
The paper links these three historic anniversaries, but it started with the satellite data. “We now have forty complete years of satellite-based estimates of global scale changes in the temperature of the atmosphere,” Santer says. “And that seemed important.”
Santer’s group at Livermore “has been looking at satellite temperature data for a long time now,” he says. “The beautiful thing about satellite data is global coverage,” he says. It’s allowed scientists to find hard evidence of warming that can’t be explained by anything but human agency.
In the process of thinking about writing a paper on the forty years of satellite data, he says, “it also became clear that there were other 40th anniversaries that were important and not unrelated to the forty years of satellite temperature data.” The global satellite information allowed scientists like him to apply the insights of 1979—that anthropogenic warming can be predicted using physics, and that studying climate change requires global data—to finding what’s known as the anthropogenic climate signal.
Compare the climate signal to the melody of a song, says Dagomar Degroot, an environmental historian at Georgetown University. Each point of data—each month, year, or decade of weather of weather, for example—is a note. “The notes may dance around the melody,” he says, but they still make a central tune you can hum. “In the same way, weather may fluctuate from year to year, but it’s possible to detect the (climactic) trends.”
The Charney report (▪ ▪ ▪)

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