The past four years have seen important developments in understanding the thermal structure of the Earth. Temperatures in the Earth's core are still uncertain because of large differences in extrapolated melting temperatures from different laboratories and because of the uncertain effects of alloying components. For the mantle, major progress has been made in determining lateral temperature differences from improved seismic imaging of velocity variations and discontinuity depths. Numerical simulations of mantle convection are increasingly approaching the complexity of the Earth's mantle and suggest that the mantle can exist in intermediate states between whole mantle and layered convection.
Acknowledgments. We appreciate the comments of C. Bina and an anonymous reviewer.