Scientists said on Wednesday they had found evidence that carbon monoxide levels are falling over the eastern United States - evidence that efforts to curb pollution and global warning are working.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/study-shows-carbon-monoxide-down-over-us-east
[2] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-change