![Global warming threatens the food supply of polar bears. [Photo:VCG]](http://img3.zhytuku.meldingcloud.com/images/zhycms_chinaplus/20181211/a7695be4-e13f-4b54-9ae7-2d314708f8d2.jpg?x-oss-process=image/resize,w_650)
A new study shows that by 2030 Earth’s climate will be comparable to that of the mid-Pliocene warm period of three million years ago if global warming continues unchecked.
The study, published Monday in the journal Proceedings of the National Academy of Sciences, found that it has taken humans less than 200 years to reverse the trend towards global cooling, which has been taking place for millions of years.
![The ability of green sea turtles to reproduce is under threat from global warming. [Photo:VCG]](http://img0.zhytuku.meldingcloud.com/images/zhycms_chinaplus/20181211/6e0bac4c-8360-4b50-a3f3-6a22b2e9f5a8.jpg?x-oss-process=image/resize,w_650)
It says that if greenhouse gas emissions aren’t curbed, by 2150 the planet’s climate would return to that of the Eocene period 50 million years ago, when the mean annual global temperature stood at around 30 degrees Celsius.
![The rapid loss of ice in the polar regions caused by global arming is putting at risk the ability of seals to establish dens to shelter their newborns. [Photo:VCG]](http://img1.zhytuku.meldingcloud.com/images/zhycms_chinaplus/20181211/e78d50a6-b292-4a18-a82e-0018e7b410e5.jpg?x-oss-process=image/resize,w_650)
