Coordinating Lead Authors (CLA), Lead Authors (LA) and Review Editors (RE) are selected by the relevant Working Group Bureau from the nominations received. Further experts who have not been nominated by governments can be invited to fill gaps in expertise.

The composition of the group of Coordinating Lead Authors, Lead Authors and Review Editors reflects the need to aim for a range of views, expertise and geographical representation, ensuring appropriate representation of experts from developing and developed countries and countries with economies in transition.