Carbon dioxide levels have increased by 31% over the past 250 years, reaching a concentration unseen on the planet in 420 000 years and perhaps as far back as 20 million years, according to the report.
(Carbon dioxide levels; have increased; by 31%; T:over the past 250 years; reaching a concentration unseen on the planet in 420 000 years and perhaps as far back as 20 million years) (Carbon dioxide levels; reaching; a concentration unseen on the planet; T:in 420 000 years and perhaps as far back as 20 million years)
Carbon dioxide levels Carbon dioxide levels
have increased reaching
by 31% T:over the past 250 years reaching a concentration unseen on the planet in 420 000 years and perhaps as far back as 20 million years
a concentration unseen on the planet T:in 420 000 years and perhaps as far back as 20 million years