Data may be the most significant driver of value and growth in the 21st century. Andy Karsner, senior strategist and “Space Cowboy” at X, explains the massive challenge humans face in accounting for the energy consumption of exponential data growth. The most important clean energy innovation of the 21st century, he suggests, will be to increase the thermal efficiency of semiconductors. Karsner stresses the importance of being as vigilant about data-center design as we are about building codes and vehicle engines.