More than three decades ago, a collection of scientists assembled by the United Nations first warned that humans were fueling a dangerous greenhouse effect and that if the world didn’t act collectively and deliberately to slow Earth’s warming, there could be “profound consequences” for people and nature alike.

The scientists were right.

On Monday, that same body — the Intergovernmental Panel on Climate Change — described how humans have altered the environment at an “unprecedented” pace and detailed how catastrophic impacts lie ahead unless the world rapidly and dramatically cuts greenhouse gas reductions.

The landmark report states that there is no remaining scientific doubt that humans are fueling climate change. That much is “unequivocal.” The only real uncertainty that remains, its authors say, is whether the world can muster the will to stave off a darker future than the one it already has carved in stone.

The sprawling assessment, compiled by 234 authors relying on more than 14,000 studies from around the globe, bluntly lays out for policymakers and the public the most up-to-date understanding of the physical science on climate change. Released amid a summer of deadly fires, floods and heat waves, it arrives less than three months before a critical summit this November in Scotland, where world leaders face mounting pressure to move more urgently to slow the Earth’s warming.

U.N. Secretary General António Guterres called the findings “a code red for humanity” and said societies must find ways to embrace the transformational changes necessary to limit warming as much as possible. “We owe this to the entire human family,” he said in a statement. “There is no time for delay and no room for excuses.”

But so far, the collective effort to slow climate change has proved gravely insufficient. Instead of the sort of emission cuts that scientists say must happen, global greenhouse gas pollution is still growing. Countries have failed to meet the targets they set under the 2015 Paris climate accord, and even the bolder pledges some nations recently have embraced still leave the world on a perilous path.

Most people don’t realize how much Northern Europe depends on the Gulf Stream to keep the climate moderate there. Look at a map, the UK, Germany and France are as far north as Labrador and Newfoundland. Without the Stream, Europe would return to Ice Age conditions. Of course, global warming would continue as the tropics continued to heat up. The boundary, the Intertropical Convergence Zone, would migrate south, and the weather there would become unstable and chaotic.

The good news is that sea level rise would probably be reversed. If it went on long enough, large portions of the continental shelves would be exposed and shallow water marine ecosystems would collapse: coral reefs, mangrove coasts, tidal biomes, the kelp forests. The world and life would survive, but the planet would look very different. And humanity could fall back on a more sustainable economy: hunter-gathering and slash-and-burn agriculture.