Process-evaluation of forest aerosol-cloud-climate feedback shows clear evidence from observations and large uncertainty in models

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Blichner, Sara M. ; Yli-Juuti, Taina ; Mielonen, Tero ; Poehlker, Christopher ; Holopainen, Eemeli ; Heikkinen, Liine ; Mohr, Claudia ; Artaxo, Paulo ; Carbone, Samara ; Meller, Bruno Backes ; Dias-Junior, Cleo Quaresma ; Kulmala, Markku ; Petaejae, Tuukka ; Scott, Catherine E. ; Svenhag, Carl ; Nieradzik, Lars ; Sporre, Moa ; Partridge, Daniel G. ; Tovazzi, Emanuele ; Virtanen, Annele ; Kokkola, Harri ; Riipinen, Ilona

• Document type: Journal article
• Source: NATURE COMMUNICATIONS; v. 15, n. 1, p. 12-pg., 2024-02-07.

Abstract

Natural aerosol feedbacks are expected to become more important in the future, as anthropogenic aerosol emissions decrease due to air quality policy. One such feedback is initiated by the increase in biogenic volatile organic compound (BVOC) emissions with higher temperatures, leading to higher secondary organic aerosol (SOA) production and a cooling of the surface via impacts on cloud radiative properties. Motivated by the considerable spread in feedback strength in Earth System Models (ESMs), we here use two long-term observational datasets from boreal and tropical forests, together with satellite data, for a process-based evaluation of the BVOC-aerosol-cloud feedback in four ESMs. The model evaluation shows that the weakest modelled feedback estimates can likely be excluded, but highlights compensating errors making it difficult to draw conclusions of the strongest estimates. Overall, the method of evaluating along process chains shows promise in pin-pointing sources of uncertainty and constraining modelled aerosol feedbacks. This study shows that trees are likely to change clouds in the future and reveals that climate models struggle to accurately represent the relevant processes of aerosol-cloud-climate interactions over forests. (AU)

• FAPESP's process: 20/15405-0 - Formation mechanisms and impacts of nanoparticles over Amazon atmosphere
• Grantee: Bruno Backes Meller
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/17047-0 - Aerosol and clouds life cycles in Amazonia: biogenic emissions, biomass burning and impacts on ecosystem
• Grantee: Paulo Eduardo Artaxo Netto
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants