Albedo is the reflection of sunlight back into space, mainly from bright surfaces such as clouds, snow, ice and atmospheric particles, providing an essential planetary cooling shield.
However, a 2021 NASA study found that the excess of incoming sunlight over outgoing radiation, known as Earth’s energy imbalance, has doubled since 2005. Satellite data reported in this study shows our planet now reflects 1.7 percent less sunlight than 20 years ago, and the decline is speeding up, amplifying global warming.
An international Albedo Accord is needed to reverse the darkening of the world, making sunlight reflection a key climate strategy.
Albedo loss causes about four times more immediate warming than carbon dioxide emissions, according to “Global Warming in the Pipeline,” a 2023 article by James Hansen and colleagues.
With more solar heat entering the Earth system, sunlight that used to be reflected safely back to space is now heating the oceans, land and air. Hansen’s analysis shows that albedo loss is not a subtle background shift — it’s becoming a dominant driver of global warming.
Tropical marine clouds contribute one-fifth of Earth's albedo. But as oceans warm, these clouds are evaporating by about 1.5 percent per decade, taking their reflectivity with them.
Loss of clouds drives a dangerous feedback loop: As warming vaporizes clouds, more solar radiation reaches the planet's surface, evaporating more water. This increases water vapor, a powerful greenhouse gas. More water vapor, combined with less cloud cover, causes further warming and worsens extreme weather.
A hotter world gets darker; a darker world gets hotter. Albedo is the awakening climate giant.
Carbon emission reduction alone cannot prevent climate tipping points, which are already activating at 1.5 degrees Celsius warming, such as the loss of coral reefs, ice and permafrost. Without a brighter Earth, these cascading effects will be unstoppable.
Concerted action to restore albedo could become a fast, safe, economic and acceptable strategy to slow warming, buying time to manage the longer-term problem of greenhouse gases.
Yet albedo remains almost entirely absent from climate strategies under the Paris Accord. The failure to prioritise albedo means governments are claiming to fight climate change while ignoring the most urgent and effective lever available to reduce heat.
To focus only on greenhouse gas emissions, while critically important for long-term climate stability, neglects the urgent and growing heating from albedo loss. Emission cuts, even augmented by greenhouse gas removal, do nothing to prevent warming from the loss of ocean clouds and polar ice. Climate policy requires a strategic pivot.
An Albedo Accord could help address this problem.
The successful Montreal Protocol brought nations together to phase out ozone-depleting substances. A similar international focus on Earth’s protective cooling shield of sunlight reflection could coordinate research, development and governance of albedo-restoring methods, as the most effective strategy to slow global warming.
We must protect the “albedo layer” just as we repaired the planet’s ozone layer.
Climate researchers have proposed technologies including marine cloud brightening, stratospheric aerosols, surface mirrors, sea ice thickening and ocean nanobubbles to reflect more sunlight and reduce near-term heat.
Some of these methods could be one thousand times better value for money than emission reduction in their cooling impact, according to estimates by the Royal Society.
Of course, such interventions come with serious responsibilities. They must be based on solid science, effective governance, public engagement and robust equity safeguards, with risks and benefits well understood. The geopolitical implications are profound.
In addition to environmental protection, action to restore albedo can provide benefits for climate stability, national interest and strategic advantage. Like the Montreal Protocol, an Albedo Accord can succeed only with public trust, global collaboration and transparency under international law.
A brighter Earth won’t solve every problem, but without it, every other climate effort will fall short. The sleeping giant of albedo is the climate system’s protective shield. Albedo restoration must now become a global priority.
Robert Tulip is an independent climate researcher based in Australia, affiliated with the Healthy Planet Action Coalition. Valerie Abrecht helped to write this article.
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