My science book says the greenhouse effect keeps Earth warm enough for life, but the news always talks about it like a disaster. Which is it?
The natural greenhouse effect is good: gases such as carbon dioxide and water vapour trap heat and keep Earth’s average temperature around 15 °C instead of about −18 °C. The problem is the extra effect from burning fossil fuels, which adds more CO₂ and traps more heat. That enhanced greenhouse effect is what drives today’s global warming.
Accepted answer
Both are true, at different scales. The natural greenhouse effect is essential - without it, Earth's average temperature would be far below freezing. The problem in the news is the enhanced greenhouse effect: human activities like burning fossil fuels have added extra CO₂ and methane, trapping more heat than before and raising global temperatures beyond what's natural.