Among commonly-cited climate change contributors, such as carbon dioxide, and their corresponding cousins within organic chemistry, is another pollutant: microplastics, the millimetre-scale pollutant particles.
More than marine litter
Microplastics are formed either deliberately (such as microbeads once used in cosmetics) or through the slow breakdown of larger plastic items under sunlight and physical wear. We understand how they spread through both ocean currents and ecological cycles.
But new research from the Middle East and China makes clear is that their influence extendds into the fundamental systems that regulate Earth’s climate.
The oceans are our planet’s greatest climate ally. They absorb around a quarter of humanity’s carbon dioxide emissions and produce most of the oxygen we breathe. This buffering role depends on finely balanced biological and chemical processes. Microplastics interfere with many of them.
Disrupting the ocean’s carbon pump
At the heart of the issue lies the biological carbon pump. Tiny marine plants known as phytoplankton absorb carbon dioxide through photosynthesis. When they are eaten—or when they die—the carbon they contain can sink into the deep ocean, effectively locking it away for centuries.
Microplastics interfere with this process in several ways. Floating near the surface, they reduce light penetration, making photosynthesis less efficient. Laboratory and field studies show that phytoplankton exposed to microplastics often grow more slowly and absorb less carbon. Zooplankton, which normally graze on phytoplankton and help move carbon down the food chain, frequently ingest plastic instead, reducing their feeding efficiency and altering the flow of carbon through marine ecosystems.
The cumulative effect is subtle but worrying: less carbon being captured and stored by the ocean, and more remaining in the atmosphere to drive warming .
Tiny plastics, real heat
Microplastics may also contribute to warming more directly. Many plastics float at the ocean surface, where they interact with sunlight. Darker particles absorb heat, potentially causing localised warming in surface waters. In polar regions, microplastics trapped in snow and ice can reduce reflectivity (albedo), meaning more solar energy is absorbed rather than reflected back into space. This accelerates melting—another feedback loop climate scientists know all too well.
Even sand temperatures are affected. Experiments show that beaches containing higher levels of microplastics warm more quickly. For temperature-sensitive species such as marine turtles, this can skew sex ratios and threaten long-term population survival—a reminder that climate impacts often begin with ecology.
The plastisphere: a microbial wildcard
One of the paper’s most intriguing insights concerns the plastisphere: the communities of microbes that colonise plastic particles. These miniature ecosystems are biologically active. Some of the microbes living on microplastics release greenhouse gases such as carbon dioxide, methane and nitrous oxide as plastics degrade.
This matters because plastic pollution is increasing rapidly, and these emissions, while small individually, scale up with volume. The research makes it clear that microplastics are not chemically inert passengers in the ocean—they are active participants in biogeochemical cycles that influence climate .
Acidifying the oceans, weakening resilience
As plastics break down, they leach organic compounds that can lower seawater pH, contributing to ocean acidification. Acidification weakens coral reefs, shell-forming organisms and entire food webs. It also reduces the resilience of so-called “blue carbon” ecosystems such as mangroves and seagrass meadows—natural carbon sinks that protect coastlines and store vast amounts of carbon.
In other words, microplastics do not just add a new climate stress; they undermine the very systems that help us cope with climate change.
Why this matters
For those already engaged in climate action, the message is not that microplastics suddenly eclipse fossil fuels as a driver of warming. Rather, they reveal how interconnected environmental crises have become. Plastic pollution, climate change, biodiversity loss and human health are no longer separate policy silos—they are facets of the same planetary problem.
The paper also frames microplastics through the lens of the UN Sustainable Development Goals and human rights. Clean water, food security, health, climate stability and a safe environment are all compromised by unchecked plastic pollution. Climate-conscious citizens are therefore right to see plastic reduction not as a lifestyle issue, but as a structural climate intervention.
An emerging threat we can still curb
Perhaps the most important conclusion is this: the climate impacts of microplastics are still emerging. Their effects are currently modest compared with greenhouse gas emissions from energy and industry, but they are growing—and they are persistent.
Unlike carbon dioxide, which can in principle be drawn down, plastics fragment and accumulate. Every plastic item ever produced still exists in some form. That gives today’s policy decisions unusual weight.
Reducing single-use plastics, redesigning materials, improving waste management and accelerating a genuinely circular economy would cut pollution and protect the climate systems we rely on. Addressing microplastics is not a distraction from climate action; it is part of finishing the job properly.
For a readership already attuned to climate complexity, this research offers a sobering but empowering insight: some of the most consequential climate solutions may begin not in the atmosphere, but in the everyday materials we choose to produce, use and discard.
Source
From pollution to ocean warming: The climate impacts of marine microplastics, Journal of Hazardous Materials: Plastics, 2025-12-08
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