This focus issue of Environmental Research Letters is a collection of research articles, invited by David Keith, University of Calgary, and Ken Caldeira, Carnegie Institution, that present and evaluate different methods for engineering the Earth's climate. Not only do the letters in this issue highlight various methods of climate engineering but they also detail the arguments for and against climate engineering as a concept.

Focus on Climate Engineering: Intentional Intervention in the Climate System Contents

Modification of cirrus clouds to reduce global warming
David L Mitchell and William Finnegan

Climate engineering and the risk of rapid climate change
Andrew Ross and H Damon Matthews

Researching geoengineering: should not or could not?
Martin Bunzl

Of mongooses and mitigation: ecological analogues to geoengineering
H Damon Matthews and Sarah E Turner

Toward ethical norms and institutions for climate engineering research
David R Morrow, Robert E Kopp and Michael Oppenheimer

On the possible use of geoengineering to moderate specific climate change impacts
Michael C MacCracken

This focus issue is not yet complete, there are still letters at press and in review.