Tracking Earth’s Energy Budget and Climate
Norman G. Loeb, NASA Langley Research Center
Climate is determined by how much of the sun’s energy the Earth absorbs and how much energy Earth sheds through emission of thermal infrared radiation. The distribution of radiant energy within the climate system gives rise to atmospheric and oceanic circulations and sets an upper limit on global mean precipitation. A stable climate requires a balance between absorbed solar and outgoing thermal infrared radiation. Continued increases in concentrations of well-mixed greenhouse gases in the atmosphere and the long time-scales time required for the ocean, cryosphere, and land to come to thermal equilibrium with those increases has led to a net gain of energy by Earth. Most of this excess energy (about 90%) warms the ocean, with the remainder heating the land, melting snow and ice, and warming the atmosphere. Earth’s energy imbalance is responsible for unprecedented changes in surface temperature, sea level, precipitation patterns and extreme weather.
Tracking and understanding changes in Earth’s energy budget and climate requires an observing system that monitors the relevant components of the climate system and sophisticated models that account for interactions amongst Earth’s subsystems in response to natural and anthropogenic climate forcings. This lecture will provide a general overview of the current state-of-the-art in Earth energy budget observation and climate modeling, present science highlights from recent research involving NASA satellites and other data and discuss the scientific challenges ahead in this critical area of research.