'Polar amplification' is a term that describes the more rapid rise in temperature in the Arctic and Antarctic than other places on the planet. Scientists say several reasons play a role in the phenomenon. One is that melting ice reduces surface reflectivity (albedo), causing a vicious circle of more heat absorption and further melt. Another is that heat from the tropics is increasingly transported to the poles via shifting ocean currents and wind patterns. Rising water vapor levels also trap heat that in the past would have been reflected back into space.