unite nations unite state decision withdraw landmark paris climate agreement major disappointment global efforts reduce greenhouse gas emissions promote global security u.n. spokesman stephane dujarric say thursday u.n. secretary-general antonio guterres remain confident cities state businesses within unite state along countries continue demonstrate vision leadership work low-carbon resilient economic growth create quality job market 21st century prosperity dujarric say say crucial unite state remain leader environmental issue guterres look forward engage u.s. government build sustainable future grandchildren depend u.n. say u.s. withdrawal paris deal 'major disappointment