Feature image: A satellite looks down at the surface of Earth. Image from Unsplash
Authors: N. G. Loeb, G. C. Johnson, T. J. Thorsen, J. M. Lyman, F. G. Rose, and S. Kato
At the most fundamental level, what causes climate change? Simply put, climate change is a symptom of an energy imbalance with more energy coming into Earth’s atmosphere than is able to go out. This imbalance drives changes in our climate system that scientists around the world study, including warming temperatures, rising sea levels, melting glaciers, and coral reef bleaching. Using two different kinds of observational data, a recent study has found evidence that the energy imbalance is increasing, which suggests climate change will only worsen.
To study a topic as large as Earth’s energy budget, you need global data about two of the largest constituents of Earth’s biosphere: the atmosphere and ocean. In their paper published in Geophysical Research Letters, Loeb and coauthors used a combination of satellite data and data collected from Argo floats, which are robotic sensors that float on the surface of the ocean. Data from the ocean is important because about 90% of the excess energy from Earth’s energy imbalance gets stored there. If the energy imbalance is getting larger, ocean data should show higher levels of heat storage.
In 2016, the authors calculated the Earth’s energy imbalance to be about 0.70 Watts per square meter (W m-2). Within this 2021 publication, they have updated the calculations to include data up to mid-2019, and their estimate of the imbalance increased to 0.77 W m-2. Looking at the change in the energy imbalance over time from 2005 to 2019, both the satellite and Argo float data suggest that the imbalance is increasing at a rate of about 0.46 W m-2 per decade. The agreement between these two data sources confirm that the trend is not likely due to errors with the data measurements. The question now is, what is causing the imbalance to grow larger?
There are many factors that contribute to Earth’s energy budget, including the levels of greenhouse gases in the atmosphere, cloud coverage, aerosol emissions, and the amount of incoming solar radiation reflected by the Earth, known as albedo. By studying changes to these values over time, the authors concluded that the greatest contributors to the growing energy imbalance are increasing greenhouse gases and water vapor in the atmosphere, changes in cloud coverage, and changes in Earth’s albedo, mainly related to the melting of polar ice.
Not all of the factors that influence Earth’s energy imbalance are caused by human activities; however, many of them are. Human civilization continues to burn fossil fuels, adding more greenhouse gases and aerosols to the atmosphere which contributes to the changes in cloud coverage and albedo. This study by Loeb et al. proves that humans are causing Earth’s energy imbalance to increase over time, which will further intensify the devastating impacts of climate change. With the recent deadly floods, heat waves, and forest fires impacting people all over the world, we must learn to adapt to climate change and hopefully transition as quickly as possible away from using fossil fuels as energy sources.
Throwing Earth Off Balance: Evidence Grows that Our Planet is Heating Up Faster than in the Past by Alyssa Stansfield is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.