A review of bottom-up and top-down emission estimates of hydrofluorocarbons (HFCs) in different parts of the world

Hannah Flerlage*, Guus J.M. Velders, Jacob de Boer

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Hydrofluorocarbons (HFCs) are widespread alternatives for the ozone-depleting substances chlorofluorocarbons and hydrochlorofluorocarbons. They are used mainly as refrigerants or as foam-blowing agents. HFCs do not deplete the ozone layer, but they are very potent greenhouse gases, already contributing to global warming. Since 2019 HFCs are regulated under the Kigali Amendment to the Montreal Protocol, which demands reliable emission estimates to monitor the phase-down. Quantification of emissions is performed with two methods: bottom-up from product inventories or data on chemical sales; or top-down, inferred from atmospheric measurements by inverse modelling or interspecies correlation. Here, we review and compare the two methods and give an overview of HFC emissions from different parts of the world. Emission estimates reported by the different methods vary considerably. HFC emissions of developed countries (Annex I) are reported to the United Nations Framework Convention on Climate Change. These bottom-up estimates add up to only half of global emissions estimated from atmospheric data. Several studies with regional top-down estimates have shown that this gap is not owed to large-scale underreporting of emissions from developed countries, but mostly due to emissions from developing countries (non-Annex I). China accounts for a large fraction of the emissions causing the gap, but not entirely. Bottom-up and top-down estimations of emissions from other developing countries that could identify other large emitters are largely unavailable. Especially South America, West-, Central- and East-Africa, India, the Arabian Peninsula and Northern Australia are not well covered by measurement stations that could provide atmospheric data for top-down estimates.

Original languageEnglish
Article number131208
Early online date14 Jun 2021
Publication statusPublished - Nov 2021

Bibliographical note

Funding Information:
Following the protocol, the phase-out of ozone-depleting CFCs was finalized in 2010 and the phase-out of the less, but still ozone-depleting HCFCs will be virtually completed in 2020 for non-Article 5 (“developed”) countries and 2030 for Article 5 (“developing”) countries, with only small amounts allowed afterwards for servicing ( Ozone Secretariat, 2018 ). Article 5 countries under the Montreal protocol are those parties eligible to receive financial support from the Multilateral Fund, while non-Article 5 countries contribute to financial support, following the principles of responsibility and ability to act.

Publisher Copyright:
© 2021 The Authors

Copyright 2021 Elsevier B.V., All rights reserved.


  • Bottom-up estimation
  • Emission verifications
  • Global warming
  • Hydrofluorocarbons (HFCs)
  • Hydrofluoroolefines (HFOs)
  • Top-down estimation


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