Twenty-eight years ago today, on June 23, 1988, a man sat at a table in front of a microphone in a very ordinary hearing room at the Capitol in Washington, D.C. and gave a speech. Normally this kind of thing is not a cause for historical interest; after all, Congress, when it’s in session, has hearings day in and day out on all manner of subjects, and most of it can hardly be called world-changing. But this particular speech was. The man speaking was James Hansen, head of NASA’s Goddard Institute for Space Studies in New York, and he was facing a panel of the U.S. Senate Committee on Energy and Natural Resources. His message: science had determined that the climate of Earth was warming due to high levels of CO2 in the atmosphere, caused mostly by human activity, and he described some of the consequences. In the last 28 years we’ve come to know those consequences all too well: ice melting, sea level rise, droughts, extreme weather and superstorms, and even large-scale die-offs of life and ecosystems, such as coral reefs. Hansen’s testimony on that day in 1988 has often been boiled down to a single gloomy statement: “Global warming has begun.”

While it probably will not be, Hansen’s testimony certainly deserves to go down as one of the most important public speeches given in the last half-century. There is no doubt now, 28 years after he said these words, that climate change is the most important event facing the world at the present time. And his warnings have proven to be prophetic. We now know, both from even more advanced computer modeling than existed in 1988 and our direct observation since 1988, what climate change is doing to our planet. Still, Hansen’s speech accomplished a great deal. Historians have already begun to credit his testimony with putting anthropogenic global warming on the public agenda in a way it had not been before. The attention drawn to the issue has not receded. That same year, 1988, two United Nations organizations came together to create the Intergovernmental Panel on Climate Change (IPCC), the key world watchdog of climate science, which has since issued numerous comprehensive reports on what scientists the world over–including Hansen himself–are now saying about the causes, pace and effects of climate change. Hansen was not the first to warn the world of climate change, but he definitely accomplished a lot.

This educational science show, run on network TV in 1958, was an early public warning on anthropogenic climate change. The issue did not get public traction until the 1980s, however.

Humanity has known about climate change for a long time. Beginning in the late 19th century, scientists in various fields were building on each other’s work and moving, unknowingly at first, toward an understanding of how the atmosphere and hydrosphere worked. The greenhouse effect, the physical process of global warming, was discovered in the 1890s, but it took several more decades and a lot of scientific observation to conclude that the high levels of carbon dioxide emitted by industrial processes was in fact changing our climate–and that it was not a natural process. Some far-sighted scientists began sounding the alarm as early as the 1950s. But, despite all the research going on behind the scenes, it took 30 more years for climate change to hit the public agenda. Hansen was the guy who did it.

James Hansen did not drop off the radar screen after his famous 1988 testimony. Since then, in fact, he’s been at the forefront of climate science and climate change activism, arguing persuasively that more needs to be done, and much more quickly, to prepare for consequences that are coming much sooner and may be much worse than he and his colleagues could have foreseen less than 30 years ago. Indeed Hansen was recently in the news this year, 2016, as co-author of a new scientific paper that should be deeply alarming to everyone. He made a video summary of his findings, and I embed it below–I’ve run it a few other times on this blog in the past few months, but it’s so important that it needs to be widely shared. Hansen is not an alarmist. He’s a realist. These things are happening, and they’re happening now. The problem is so much worse today than it was in 1988, and as a society we’ve done comparatively little to reverse it.

James Hansen’s latest findings, presented in this video, are shocking. There is no other way to characterize it. What more do you need to take action on climate change now?

In my view, James Hansen is a genuine American hero. He is a public intellectual who has used his intelligence and his training to alert us to the most serious problem we face as a global society, and he’s worked tirelessly to advocate solutions to help us deal with it. He’s accomplished a tremendous amount in his 30+ years in science and activism, but history will probably always remember him first and foremost, sitting at that table in a conference room on a very hot day in 1988, telling us about our future. Few soothsayers in history have ever been as prescient as James Hansen. Probably few others ever will.

The header image of James Hansen is in the public domain. I am not the uploader of the YouTube clips embedded here.