The OECD's climate change expert group emphasizes the importance of tracking climate finance to improve accountability and learning, necessitating clear definitions and key performance indicators for effective programming. Different countries face challenges with varying monitoring frameworks and the intricacies of private sector finance tracking, while estimating impacts can differ based on the scale and timing of activities. Key indicators like USD/t CO2 are crucial for measuring cost-effectiveness, but the complexity of various climate activities can make reporting burdensome and necessitates careful verification to avoid double counting.