Staying within the limit of the Paris Agreement of 1.5 °C global warming requires closing the global 2030 ambition and action gap arising from insufficient current policies and contributions. This background paper documents the methodology and criteria for assessing multilateral initiatives of the G20 countries in four policy fields. In four steps and with the use of twelve criteria and further indicators the paper provides a toolkit to select and analyse existing multilateral initiatives, identify their strengths, weaknesses and gaps and derive proposals for improved or additional initiatives to foster global climate action.