Correspondence to the supplementary opinions on alternative cooling technologies in hot climate.

At present, air conditioning (AC) is the most effective means for the cooling of indoor space. However, its increased global use is problematic for various reasons. This is a correspondence to the supplementary opinion provided by Dr. Bin Yang, Dr. Stefano Schiavon, and Dr. Faming Wang to our paper titled "Challenges of using air conditioning in an increasingly hot climate." The paper explored the challenges linked to increased AC use and discusses more sustainable alternatives. The supplementary opinion provides a great technical complement to our paper. However, there is a need for a more holistic view both when it comes to combining various solutions and involving various levels in society.

Challenges of using air conditioning in an increasingly hot climate.

At present, air conditioning (AC) is the most effective means for the cooling of indoor space. However, its increased global use is problematic for various reasons. This paper explores the challenges linked to increased AC use and discusses more sustainable alternatives. A literature review was conducted applying a transdisciplinary approach. It was further complemented by examples from cities in hot climates. To analyse the findings, an analytical framework was developed which considers four societal levels-individual, community, city, and national. The main challenges identified from the literature review are as follows: environmental, organisational, socio-economical, biophysical and behavioural. The paper also identifies several measures that could be taken to reduce the fast growth of AC use. However, due to the complex nature of the problem, there is no single solution to provide sustainable cooling. Alternative solutions were categorised in three broad categories: climate-sensitive urban planning and building design, alternative cooling technologies, and climate-sensitive attitudes and behaviour. The main findings concern the problems arising from leaving the responsibility to come up with cooling solutions entirely to the individual, and how different societal levels can work towards more sustainable cooling options. It is concluded that there is a need for a more holistic view both when it comes to combining various solutions as well as involving various levels in society.