LOS ANGELES – In 2001, a team of international scientists projected that during the next 100 years, the planet’s inhabitants would witness higher maximum temperatures, more hot days and heat waves, an increase in the risk of forest fires and “substantially degraded air quality” in large metropolitan areas as a result of climate change.

In just the past month, nearly two decades after the third U.N. Intergovernmental Panel on Climate Change report was issued, heat records were busted across California, more than 3 million acres of land burned, and in major metropolitan areas, such as Los Angeles and San Francisco, air pollution has skyrocketed.

“This shouldn’t come as a surprise to anyone,” said Michael Gerrard, director of the Sabin Center for Climate Change Law at Columbia University. “Maybe we underestimated the magnitude and speed” at which these events would occur, he said, but “we’ve seen this long freight train barreling down on us for decades, and now the locomotive is on top of us, with no caboose in sight.”

In a matter of weeks, California has experienced six of the 20 largest wildfires in modern history and toppled all-time temperature records from the desert to the coast. Millions are suffering from some of the worst air quality in years due to heat-triggered smog and fire smoke. A sooty plume has blanketed most of the West Coast, blotting out the sun and threatening people’s lungs during a deadly pandemic.

California is being pushed to extremes. And the record heat, fires and pollution all have one thing in common: They were made worse by climate change. Their convergence is perhaps the strongest signal yet that the calamity climate scientists have warned of for years isn’t far off in the future; it is here today and can no longer be ignored.

“What we’ve been seeing in California are some of the clearest events where we can say this is climate change — that climate change has clearly made this worse,” said Zeke Hausfather, a climate scientist at the Breakthrough Institute, an Oakland, Calif.-based think tank. “People who have lived in California for 30, 40 years are saying this is unprecedented, it has never been this hot, it has never been this smoky in all the years I’ve lived here.”

Unprecedented, yes. But not unexpected. Since the 1980s, government and oil industry scientists have been anticipating the events that have transpired across the state this past month.

As one 1988 internal Shell Oil Co. document noted, “by the time the global warming becomes detectable it could be too late to take effective countermeasures to reduce the effects or even to stabilize the situation.”

“I’m only sorry that in 1989, I could not get an audience for what I wanted to communicate,” said Jim Hansen, a retired NASA researcher and early climate change scientist, of testimony he made to Congress.

Each of the extremes Californians are living through right now is fueled, at least in part, by the planet’s gradual warming, which is accelerating as greenhouse gas emissions continue to rise, scientists say.