Earth’s Energy Imbalance, Causes, Trends, Measurement, Importance

The State of the Global Climate Report 2025 has, for the first time, included Earth’s Energy Imbalance as one of the key climate indicators. The Earth’s energy imbalance is a key climate indicator that measures how fast the heat trapped by anthropogenic emissions of greenhouse gases is accumulating in the climate system.

What is Earth’s Energy Imbalance?

Earth’s Energy Imbalance (EEI) is a fundamental measure of the Earth’s climate energy budget.

• The Earth’s energy imbalance (EEI) is the difference between the amount of energy the Earth receives from the Sun (incoming solar radiation minus reflected solar radiation) and the amount of energy the Earth radiates back into space (outgoing long-wave radiation).
• If the amount of incoming radiation exceeds the amount of outgoing radiation (for example, due to the greenhouse effect), the EEI is “positive“, meaning the Earth is gaining energy, mostly in the form of heat. 
• If more energy escapes the Earth than is received (for example, after large volcanic eruptions), the EEI is “negative“, meaning the Earth is losing energy and cooling.

Measurement of Earth’s Energy Imbalance

The Earth’s Energy Imbalance can be measured in two main ways, combining both observational data and direct radiation measurements.

• Earth Heat Inventory (1960-present): This method combines separate estimates of heat stored in the ocean, land and atmosphere, as well as the energy needed to melt ice. This hybrid approach integrates the Global Climate Observing System (satellite and in situ) data, reanalyses and climate models. A preliminary estimate of the inventory can be made using the observed ocean heat content.

• Direct Satellite Measurements (2000-present): This method involves direct measurement of incoming solar radiation and outgoing long-wave radiation at the top of the atmosphere. It provides a direct assessment of Earth’s radiation balance and allows continuous monitoring of changes in the energy budget.

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Trends in Earth’s Energy Imbalance

Due to increasing concentrations of greenhouse gases, the EEI has become increasingly positive over time, and the accumulation of surplus energy has led to warming of the climate. Approximately 91% of the surplus energy has been absorbed by the ocean, 5% by the continents, 3% by the cryosphere and 1% by the atmosphere. 

• In 2025, the observed Earth’s Energy Imbalance reached the highest value since records began in 1960.
• Since 1960, heat has been continuously accumulating in the Earth system, including the ocean, atmosphere, land and frozen regions, due to a growing imbalance in the Earth’s energy budget.
• The total amount of heat stored on Earth is not only increasing but is accelerating over time.
• The rate of increase of EEI based on ocean heat content was about 0.13 ± 0.03 W m⁻² per decade during 1960-2025.
• The increase remained relatively stable across periods such as 1970-2025, 1980–2025 and 1990-2025.
• A higher rate of increase was observed during 2001-2025 at about 0.30 ± 0.1 W m⁻² per decade.
• Satellite-based measurements for 2001-2025 show an even higher rate of increase at 0.44 ± 0.13 W m⁻² per decade.
• Satellite estimates and ocean heat content estimates are consistent within the margin of error where they overlap.
• The increase in EEI is linked to rising concentrations of greenhouse gases and reductions in aerosol emissions.
• It is also associated with increased absorption of solar radiation due to decreased reflection by clouds and sea ice.
• A decrease in outgoing long-wave radiation due to increases in trace gases and water vapour further contributes to the rising imbalance.

Causes of Rising Earth’s Energy Imbalance

Human activities are the primary drivers of the increasing imbalance.

• Rising greenhouse gas concentrations reduce the amount of heat radiated back into space.
• Aerosol changes and air pollution influence cloud formation and radiative balance.
• Reduction in sea ice and snow cover lowers Earth’s reflectivity, increasing heat absorption.
• Changes in outgoing long-wave radiation due to increased water vapour and trace gases intensify warming.

Earth’s Energy Imbalance Significance

Earth’s Energy Imbalance (EEI) is a critical indicator for understanding and predicting climate change.

• It provides a direct measure of how fast the Earth system is gaining heat.
• It helps in understanding global warming trends across oceans, land, atmosphere, and ice simultaneously.
• It improves the accuracy of climate models and future climate projections.
• It acts as an early warning indicator of accelerating climate change.