The risk is that the rate will accelerate markedly. If emissions continue unchecked, then the temperature at the earth’s surface could soon resemble a past epoch called the Pliocene, when a great deal of ice melted and the ocean rose something like 80 feet compared to today. A recent study found that burning all the fossil fuels in the ground would fully melt the polar ice sheets, raising the sea level by more than 160 feet over an unknown period.