Al Gore, Nobel Laureate, speaking with Conan O'Brien.

"People think about geothermal energy - when they think
about it at all - in terms of the hot water bubbling up in some
places, but two kilometers or so down in most places there are
these incredibly hot rocks, 'cause the interior of the earth is
extremely hot, several million degrees..."

http://newsbusters.org/blogs/noel-sheppard/2009/11/18/
al-gore-earths-interior-extremely-hot-several-million-degrees

Truth is:

"It is approximately 4000°C at the centre of the Earth. To put
this in context:

1. The centre of the Sun is approximately 15 million°C
2. The surface of the Sun is 5500°C
3. Iron melts at 1535°C (when at atmospheric pressure)
4. Water boils at 100°C (when at atmospheric pressure)
5. Human skin is comfortable with temperatures up to about
60°C
6. The highest temperature recorded on the Earth's surface
is 58°C (Libya 1922)"

http://www.physlink.com/Education/askExperts/ae621.cfm