NASA: Earth’s energy imbalance has doubled since 2006

  • The Earth’s climate depends on the amount of radiative energy from the Sun that is absorbed and the amount of thermal infrared radiation emitted by the Earth.
  • A positive energy imbalance means the Earth system is gaining energy, causing the planet to warm up.
  • New research has shown that the energy imbalance more than doubled between 2005 and 2019.

The researchers found that Earth’s energy imbalance approximately doubled over the 14-year period from 2005 to 2019.

Earth’s climate is determined by a delicate balance between the amount of radiant energy from the Sun absorbed in the atmosphere and at the surface and the amount of thermal infrared radiation that the Earth emits into space. A positive energy imbalance means the Earth system is gaining energy, causing the planet to warm up. The doubling of the energy imbalance is the subject of a recent study, the results of which have been published on June 15 in Geophysical research letters.

Comparison of one-year overlapping estimates at 6-month intervals of the annual net energy flux at the top of the atmosphere of CERES (solid orange line) and an observational in situ estimate of energy absorption.

Image: NASA / Tim Marvel

Scientists from NASA and NOAA compared data from two independent measurements. NASA’s Clouds and the Earth’s Radiant Energy System (CERES) satellite sensor suite measures the amount of energy entering and leaving the Earth system. Additionally, data from a global network of oceanic floats, called Argo, allow an accurate estimate of the rate at which the world’s oceans are warming. Since about 90 percent of the excess energy from energy imbalance ends up in the ocean, overall trends in incoming and outgoing radiation should broadly be consistent with changes in ocean heat content.

“The two very independent ways of looking at the changes in Earth’s energy imbalance agree very, very well, and they both show this very big trend, which gives us a lot of confidence that what we are seeing is a real phenomenon and not just an instrumental artefact, ”said Norman Loeb, lead author of the study and CERES principal investigator at NASA’s Langley Research Center in Hampton, Va.“ The trends we found were quite alarming. in a sense.”

Increased emissions of greenhouse gases such as carbon dioxide and methane due to human activity traps heat in the atmosphere, capturing outgoing radiation that would otherwise escape into space. Warming causes other changes, such as melting snow and ice, as well as increased water vapor and changes in clouds, which can further increase warming. The earth’s energy imbalance is the net effect of all of these factors. In order to determine the main factors causing the imbalance, investigators used a method that examined changes in clouds, water vapor, the combined contributions of trace gases and the output of sunlight, the surface albedo (the amount of light reflected from the Earth’s surface), tiny particles in the air called aerosols, and changes in the distribution of temperatures on the surface and in the atmosphere.

The study reveals that the doubling of the imbalance is in part the result of an increase in greenhouse gases due to human activity, also known as anthropogenic forcing, as well as an increase in the vapor d water trapping more of the outgoing longwave radiation, further contributing to the Earth’s energy imbalance. In addition, the associated decrease in clouds and sea ice results in greater absorption of solar energy.

The researchers also found that a shift of the Pacific Decadal Oscillation (PDO) from a cold phase to a warm phase likely played a major role in intensifying the energy imbalance. The PDO is a model of climate variability in the Pacific. Its footprint includes a huge wedge of water in the eastern Pacific that goes through cold and hot phases. This natural internal variability of the Earth system can have dramatic effects on weather and climate. An extremely hot PDO phase that started around 2014 and continued until 2020 caused a widespread reduction in cloud cover over the ocean and a corresponding increase in absorption of solar radiation.

“It’s probably a mix of anthropogenic forcing and internal variability,” Loeb said. “And during that time, they both cause warming, resulting in a pretty big change in the Earth’s energy imbalance. The magnitude of the increase is unprecedented.”

Loeb warns that the study is only a snapshot of long-term climate change, and that it is not possible to predict with certainty what the next few decades might look like for a balanced energy budget. Earth. The study concludes, however, that unless the rate of heat uptake decreases, greater climate change than what is already happening is to be expected.

“The lengthening and complementarity of the Argo and CERES recordings have enabled us both to pinpoint the Earth’s energy imbalance with increasing precision, and to study its variations and trends with increasing insight, over time. time. Said Gregory Johnson, study co-author and physical oceanographer at the National Oceanic and Atmospheric Administration’s Pacific Marine Environment Laboratory in Seattle, Washington. “Observing the magnitude and variations of this energy imbalance is essential to understanding Earth’s climate change. “



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