They analyze long-term data from ice cores, tree rings, ocean sediments, and satellites. Current changes—like the rapid rise in CO₂ since the Industrial Revolution—are too abrupt to be explained by natural cycles alone.

The carbon budget is the maximum amount of CO₂ humanity can emit to limit warming to a target (e.g., 1.5°C). We’ve already used most of it. Exceeding it increases the risk of tipping points.

These are processes that can amplify (positive feedback) or dampen (negative feedback) climate effects. For example, melting ice reduces reflection, absorbing more heat and causing more melting.

Thresholds in Earth’s systems—like the Amazon rainforest or polar ice caps—beyond which changes become irreversible. Crossing them could trigger global chain reactions.

Mitigation reduces or prevents emissions (like renewable energy). Adaptation means adjusting to impacts (like sea walls or drought-resistant crops).