We’ve been accidentally cooling the planet — and it’s about to stop | Humans’ fossil fuel burning has cooled the planet while warming it — presenting problems for the future.

It is the Sulfer thing. Sulfer Dioxide was shading the planet and making clouds more reflective, cooling the earth and we're fairly uncertain by how much.

Even though the article doesn't say it outright, the obvious conclusion is that we should have stopped using fossil fuels decades ago. And even if stop now we don't know how much more warming we'd do without the sulfer dioxide. Which shouldn't be added to the atmosphere because it would kill an outrageous amount of people.