Earth’s energy budget accounts for the balance between the energy that the Earth receives from the Sun and the energy that the Earth radiates back into outer space. Smaller energy sources, such as Earth’s internal heat, that are taken into consideration, but make a tiny contribution compared to solar energy. The energy budget also accounts for how energy moves through the climate system.
The Sun heats the equatorial tropics more than the polar regions, received solar irradiance is unevenly distributed. As the energy seeks equilibrium across the planet, it drives interactions in Earth’s climate system, i.e., Earth’s water, ice, atmosphere, rocky crust, and all living things. The result is Earth’s climate.
Earth’s energy budget depends on many factors, such as atmospheric aerosols, greenhouse gases, the planet’s surface albedo (reflectivity), clouds, vegetation, land use patterns, and more. When the incoming and outgoing energy fluxes are in balance, Earth is in radiative equilibrium and the climate system will be relatively stable. Global warming occurs when earth receives more energy than it gives back to space, and global cooling takes place when the outgoing energy is greater.
Researchers have found that Earth’s energy imbalance approximately doubled during the 14-year period. The doubling of the energy imbalance is the topic of a recent study, the results of which were published in Geophysical Research Letters.
Scientists at NASA and NOAA compared data from two independent measurements. NASA’s Clouds and the Earth’s Radiant Energy System (CERES) suite of satellite sensors measure how much energy enters and leaves Earth’s system. In addition, data from a global array of ocean floats, called Argo, enable an accurate estimate of the rate at which the world’s oceans are heating up. Since approximately 90 per cent of the excess energy from an energy imbalance ends up in the ocean, the overall trends of incoming and outgoing radiation should broadly agree with changes in ocean heat content.
Increases in emissions of greenhouse gases such as carbon dioxide and methane due to human activity trap heat in the atmosphere, capturing outgoing radiation that would otherwise escape into space. The warming drives other changes, such as snow and ice melt and increased water vapour and cloud changes that can further enhance the warming. Earth’s energy imbalance is the net effect of all these factors. In order to determine the primary factors driving the imbalance, the investigators used a method that looked at changes in clouds, water vapour, combined contributors from trace gases and the output of light from the Sun, surface albedo (the amount of light reflected by the Earth’s surface), tiny atmospheric particles called aerosols, and changes in surface and atmospheric temperature distributions.