Underground temperatures reveal changing climate

Subsurface temperatures contain a clue not only about recent temperature history but also about trends and changes in temperature in the future. A borehole temperature profile of central Iceland has provided data on some 50,000 years of climate change. Boreholes in other parts of the world that were examined showed that most total temperature changes took place around 1750, during the beginning of the Industrial Revolution. These temperature changes observed through geothermal archives imply that the earth's temperature responds to a host of diverse factors.