James Hansen's Latest Warning

James Hansen first warned Congress about global warming in 1988. Pushker Kharecha is a climate scientist and longtime collaborator. They’re not activists waving signs — they’re the people who’ve spent decades knee-deep in the data, building the models, measuring the planet’s fever. And in their latest paper, they’re saying the fever’s far worse than the official diagnosis.

The planet isn’t warming by the “moderate” amount the UN’s climate panel still projects. It’s far more sensitive to carbon pollution — likely about 4.5°C for a doubling of CO₂, not 3°C. That difference sounds small. It’s not. It’s the difference between dangerous and catastrophic. And we’re already seeing the system kick into self-reinforcing overdrive: clouds that once cooled the Earth are thinning, reflecting less sunlight, letting in nearly twice as much extra heat as all the world’s coal plants produce in a year.

For decades, industrial pollution (e.g. sulfur from ships) masked some of this warming by bouncing sunlight back to space. Now we’ve cleaned up the air a bit. The masking effect is vanishing. The heat is roaring through. That’s why temperatures are jumping faster than expected. About 0.3°C per decade now, compared to 0.18°C just a few decades ago.

The Worst-Case Scenario

If Hansen’s numbers are right, here’s the ugly math in plain English:

• We’re already at about 1.6°C of warming.
• With current policies, we blow past 2°C in little more than a decade.
• By late century, we’re staring down 4°C or more — a world where ice sheets collapse, oceans rise by meters, coastal cities are drowned, food systems break under heat and drought, and mass migration isn’t a crisis, it’s the norm.

And remember: 4°C is the global average. Over land, and especially in the interiors of continents, including life-giving breadbaskets, that’s more like 6–8°C. Whole regions become literally unlivable and ungrowable.

This is physics. More heat in the system changes everything, storms, rainfall, agriculture, ecosystems, economies, politics. And with the planet warming faster than models predicted, “later this century” is rapidly becoming “within our lifetimes.”

Bottom Line

The 1.5°C Paris target? “Deader than a doornail,” Hansen says. Even 2°C is wishful thinking without radical action. The worst and most probable case is that we keep going as we are, triggering total collapse.

But the message in plain terms? We are running out of time faster than we think, because the danger was underestimated from the start.

What You Need to Know

1. Climate sensitivity is far higher than official estimates.
2. The planet is absorbing far more solar energy than before.
3. Cloud feedback is a big driver.
4. Aerosol cooling has been masking more warming than thought.
5. The 1.5°C target is already impossible.
6. Warming is accelerating faster than models predicted.
7. Major climate tipping points could be closer than thought.
8. The science community may be under-communicating the danger.

If you want the deep dive (numbers, charts, evidence) read their full paper: