Heat radiates outwards from the Earth's molten core to the surface of the planet.
Global warming is the term for a rise in atmospheric temperatures, caused by the burning of fossil fuels such as oil, coal and gas. These act as an invisible blanket in the atmosphere, storing up the heat from the Sun rather than letting it radiate back into space. Climatologists say there has already been a perceptible warming, especially in the last quarter of the 20th century, and expect the trend to accelerate in the coming decades. The result, they say, will be a partial warming of the polar ice caps and a rise in sea levels, because the volume of seawater will expand with the gradual rise in temperature. However, climatology is a new science that especially lacks historical data.