John H. Mercer (19 October 1922 – 3 July 1987) was a British glaciologist, chiefly known for his theoretical work on, and field studies of Antarctic ice streams, especially in the Transantarctic Mountains and in West Antarctica.
In 1978, in the science magazine Nature, Mercer pointed out that "green-house" warming from burning fossil fuel could have the same effect during the present interglacial.
After Mercer published his paper suggesting that the West Antarctic ice sheet could collapse in response to warming, he struggled to get funding.
Many climate scientists censor their own work to avoid losing funding, especially regarding prospects for limiting warming to 2 °C above pre-industrial temperatures.
He was a Research Scholar from 1954 to 1956 at the Australian National University in Canberra, where he studied land use and population in western Samoa.