Contributions to historical climate change have varied substantially among nations. These differences reflect underlying inequalities in wealth and development, and pose a fundamental challenge to the implementation of a globally equitable climate mitigation strategy. This Letter presents a new way to quantify historical inequalities among nations using carbon and climate debts, defined as the amount by which national climate contributions have exceeded a hypothetical equal per-capita share over time.

Extinction events typically represent extended processes of decline that cannot be reconstructed using short-term studies. Long-term archives are necessary to determine past baselines and the extent of human-caused biodiversity change, but the capacity of historical datasets to provide predictive power for conservation must be assessed within a robust analytical framework.

On Aug 31, 1665, Samuel Pepys noted dolefully in his diary: “Thus this month ends, with great sadness upon the public through the greatness of the plague, everywhere through the Kingdom almost. Every day sadder news of its increase. In the City died this week 7496; and of them 6102 of the plague.