[Didjeridust]

Googla litt, og utan å gå heilt inn i det eg fann kan eg iallehøve koma med desse:
http://www.iied.org/human-settlement...them-solutions
http://www.reuters.com/article/idUSTRE48O9V120080925
Desse syner til ei studie gjort av Dodman og Satterthwaite som konkluderer med at talet er mykje mindre

Det er fleire andre treff som hevdar 80%, m.a. denne
http://www.grist.org/article/facts
men eg greier ikkje finna noko vitskapleg referanse til opphavet til det talet

Frå denne: http://www.australianreview.net/dige.../07/jones.html kan eg sitera:
"[T]here is considerable debate on the overall contribution of cities to global warming. Sánchez-Rodríguez and colleagues (2005) have a negative view. They blame cities’ high consumption, unsustainable land use management and poorly designed transport systems for generating a significant proportion of the world’s greenhouse gas emissions and for contributing disproportionately to climate change. Their view is that it is the interactions between human activities in urban areas and the environment that continue to have a negative impact on global environmental change."
Her vert og Dodman/Satterthwaite sine innvendingar nemnd