What NFPA-listed chemical compound has the most potential to contribute to global warming?
select ?ent where { ?ent wdt:P31 wd:Q11173 . ?ent wdt:P2565 ?obj . ?ent wdt:P4952 wd:Q51139288 } ORDER BY DESC(?obj)LIMIT 5 
chemical compound: Q11173 nfpa 704: standard system for the identification of the hazards of materials for emergency response: Q51139288