Earth has a budget, an energy budget. Our planet is constantly trying to balance the flow of energy in and out of the Earth system. But human activities are throwing that out of balance, causing our planet to heat up in response.
Radiative energy enters the Earth system from sunlight that shines on our planet. Some of this energy is reflected off the Earth’s surface or in the atmosphere and returns to space. The rest is absorbed, warms the planet, and is then emitted as thermal radiation energy in the same way that black asphalt heats up and radiates heat on a sunny day. Eventually, this energy is also directed into space, but some of it is reabsorbed by clouds and greenhouse gases in the atmosphere. The absorbed energy can also be emitted towards Earth, where it will further heat the surface.
Adding more components that absorb radiation, such as greenhouse gases, or removing those that reflect it, such as aerosols, disrupts Earth’s energy balance and causes Earth to absorb more energy instead of escaping into space. This is called radiative forcing and it is the dominant way that human activities are affecting the climate.
Climate modeling predicts that human activities are causing the release of greenhouse gases and aerosols that are affecting the Earth’s energy budget. Now a NASA study has confirmed these predictions with direct observations for the first time: Radiative forcings are increasing due to human actions, affecting the planet’s energy balance, and ultimately causing climate change. The article was published online on March 25, 2021 in the magazine Geophysical Research Letters.
“This is the first calculation of the Earth’s total radiative forcing using global observations, taking into account the effects of aerosols and greenhouse gases,” said Ryan Kramer, first author of the paper and researcher at the Goddard Space Flight Center of NASA in Greenbelt, Maryland. and the University of Maryland, Baltimore County. “It is direct evidence that human activities are causing changes in the Earth’s energy budget.”
NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project studies radiation flux in the upper part of Earth’s atmosphere. A number of CERES instruments have continuously flown on satellites since 1997. Each measures how much energy enters the Earth system and how much goes out, giving the overall net change in radiation. These data, in combination with other data sources, such as ocean heat measurements, show that there is an energy imbalance on our planet.
“But it doesn’t tell us what factors are causing changes in the energy balance,” Kramer said.
This study used a new technique to analyze how much of the total energy change is caused by humans. The researchers calculated how much of the imbalance was caused by fluctuations in factors that often occur naturally, such as water vapor, clouds, temperature, and surface albedo (essentially the brightness or reflectivity of the Earth’s surface). For example, the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite measures water vapor in Earth’s atmosphere. Water vapor absorbs energy in the form of heat, so changes in water vapor will affect the amount of energy that eventually leaves the Earth system. The researchers calculated the energy change caused by each of these natural factors and then subtracted the values from the total. The remaining portion is the radiative forcing.
The team found that human activities have caused radiative forcing on Earth to increase by about 0.5 watts per square meter between 2003 and 2018. The increase is mainly due to greenhouse gas emissions from elements such as the generation of energy, transportation and industrial manufacturing. Reduced reflective sprays are also contributing to the imbalance.
The new technique is computationally faster than previous model-based methods, allowing researchers to monitor radiative forcing in near real time. The method could be used to track how human emissions are affecting the climate, monitor how well various mitigation efforts are working, and evaluate models to predict future changes in climate.
“Creating a direct record of radiative forcing calculated from observations will allow us to assess how well climate models can simulate these forcings,” said Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies (GISS) in New York City. York. “This will allow us to make more confident projections about how the climate will change in the future.”
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Ryan J. Kramer et al. Observational evidence of an increase in global radiative forcing, Geophysical Research Letters (2021). DOI: 10.1029 / 2020GL091585
Provided by NASA’s Goddard Space Flight Center
Citation: Direct Observations Confirm Humans Are Unbalancing Earth’s Energy Budget (2021, March 26) Retrieved March 26, 2021 from https://phys.org/news/2021-03-humans-earth- energy.html
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