The aviation industry continues to contribute to anthropogenic climate change. Recent studies have shown that the total radiative forcing from aviation is around three times higher than that from CO₂ alone. To account for the full effect of aviation, climate metrics are needed, which equate the environmental impact of various emissions and effects. However, there is currently no consensus on which climate metric should be used in aviation policy. This thesis systematically analyses existing climate metrics by: 1) comparing the responses to simple emission profiles; 2) investigating the sensitivity to changes in high-level aircraft design variables; 3) using a Monte Carlo simulation to determine inherent biases in metric calculation methods; and 4) evaluating the ability of climate metrics to estimate CO₂-equivalent emissions. It is concluded that the Average Temperature Response (ATR) is the most appropriate climate metric for aviation climate policy. However, it is found that the time horizon remains a subjective choice that must be chosen carefully depending on the climate objective. The GWP*, a newly proposed climate metric, is concluded not to be suitable as a climate metric because of its high variability and secondary time horizon. Nevertheless, it is recommended to investigate the potential of using the GWP* as a Micro Climate Model to further climatic understanding.