Health & Environmental Research Online (HERO)


Print Feedback Export to File
1668631 
Journal Article 
Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone 
Allen, RJ; Sherwood, SC; Norris, JR; Zender, CS 
2012 
Nature
ISSN: 0028-0836
EISSN: 1476-4687 
485 
7398 
350-354 
English 
Observational analyses have shown the width of the tropical belt increasing in recent decades as the world has warmed. This expansion is important because it is associated with shifts in large-scale atmospheric circulation and major climate zones. Although recent studies have attributed tropical expansion in the Southern Hemisphere to ozone depletion, the drivers of Northern Hemisphere expansion are not well known and the expansion has not so far been reproduced by climate models. Here we use a climate model with detailed aerosol physics to show that increases in heterogeneous warming agents--including black carbon aerosols and tropospheric ozone--are noticeably better than greenhouse gases at driving expansion, and can account for the observed summertime maximum in tropical expansion. Mechanistically, atmospheric heating from black carbon and tropospheric ozone has occurred at the mid-latitudes, generating a poleward shift of the tropospheric jet, thereby relocating the main division between tropical and temperate air masses. Although we still underestimate tropical expansion, the true aerosol forcing is poorly known and could also be underestimated. Thus, although the insensitivity of models needs further investigation, black carbon and tropospheric ozone, both of which are strongly influenced by human activities, are the most likely causes of observed Northern Hemisphere tropical expansion. 
NAAQS
• ISA-Ozone (2020 Final Project Page)
     Literature Search Results
     Literature Search - Included
          Citation Mapping
               Climate
     Title-Abstract Screening (SWIFT-AS) - Included
          Title-Abstract Screening (SWIFT-AS) - Included
     Full-Text Screening Included
          Full-Text Screening Included
     Included in ISA First Draft
          Integrated Synthesis
          Appendix 9
     Included in ISA Final Draft
          Integrated Synthesis
          Appendix 9
          Preface