A complete rethink is needed on how greenhouse gas emissions are quantified for national reporting

The 2015 Conference of the Parties (COP21) in Paris has for the first time agreed that both developed and developing countries need to reduce greenhouse gas (GHG) emissions to maintain a global average temperature ‘well below’ 2 °C and aim to limit the increase to less than 1.5 °C above pre-industrial temperatures. This requires more ambitious emission reduction targets and an increased level of cooperation and transparency between countries. With the start of the second Kyoto Commitment period in 2013, and the 2015 Paris Agreement, it is, therefore, timely to reconsider how GHG emissions are determined and verified. The policy agenda is currently centered on GHG emission estimates from bottom-up inventories. This includes annual national reporting of GHG emissions (e.g. to the United Nations Framework Convention on Climate Change (UNFCCC) and defining emission reduction targets. However, bottom-up emission estimates rely on highly uncertain and, in some cases, sparse input data and poorly characterized emission factors.In order to enhance accuracy, cost-efficiency and transparency of the process to assess progress towards the national emissions reduction targets, we call for a rethink of the current reliance on ‘bottom-up’ inventories for reporting national and global anthropogenic GHG emissions.