The earth’s energy imbalance is the difference between the amount of solar energy absorbed by the earth and the amount of energy the planet radiates back into space as heat. If the imbalance is positive, that is, if more energy is coming in than going out, then the earth will get warmer over time. If the imbalance is negative, then the planet will get cooler.
The energy imbalance is driven by so-called climate forcings. Some of them are natural, such as changes in the Sun’s brightness and volcanic eruptions. Others are man-made, such as the greenhouse gases we generate that trap heat in the atmosphere and human-made aerosols, which reflect sunlight and have a cooling effect. The actual energy imbalance is around 1% at this time.
Measuring the energy imbalance is no simple matter. Measuring the incoming energy is relatively straightforward, but measuring how much energy is going back out is a tricky business.
Last year, a satellite called the RAVAN CubeSat (which stands for Radiometer Assessment using Vertically Aligned Nanotubes) was launched into low-Earth orbit to test new technologies to help measure the earth’s radiation imbalance. The satellite uses two technologies that have never before been used on a spacecraft: carbon nanotubes that absorb outbound radiation and a gallium phase change blackbody for calibration.
The satellite has been in operation since January and it is working well. The ultimate plan is to orbit a constellation of many CubeSats to provide 24/7 coverage of the energy leaving our planet.
The energy imbalance is a direct measurement of the forces driving global warming. Being able to keep track of it on an ongoing basis seems like a very good idea.
Photo, posted March 4, 2015, courtesy of Kevin Gill via Flickr.