The document outlines a discussion on designing a flexible and durable 2015 climate change agreement. It discusses that a durable agreement would remain ambitious and fair in response to future changes. It explores structuring the agreement with a core political document and annexes. The use of flexible metrics like emissions intensity by some parties is proposed to increase responsiveness to external factors and make contributions more durable over time. The document poses questions about interpreting durability and structuring the agreement to be durable.