* World’s richest emit about half of Earth’s carbon
* Tracking the wealthy could break climate impasse
* New method would follow individual greenhouse emissions
By Deborah Zabarenko, Environment Correspondent
WASHINGTON, July 6 (Reuters) – To fairly divide the climate change fight between rich and poor, a new study suggests basing targets for emission cuts on the number of wealthy people, who are also the biggest greenhouse gas emitters, in a country.