Choking the Carbon Pump: The invisible link between micro plastics and climate change

From inhibiting photosynthesis to disrupting the ocean’s carbon pump, micro plastics are no longer just a waste problem—they are a climate catalyst.

Climate change and micro plastic pollution share a common feature. Neither of them are problems, they are both predicaments. Calling something a problem implies that there is a solution that can make it go away. That’s not the case for climate change or micro plastics, they are both worsening situations with impacts that will continue to grow for the foreseeable future, whatever our best intensions.

It’s more than two separate predicaments though, as there is growing evidence that micro plastics can also effect climate change by influencing the various mechanisms that cause the changes we’re seeing and even lead to increased emissions and radiative forcing.

Firstly, what are micro plastics and why the fuss?

Plastics are totally integrated into our lives. From the moment you wake, lifting your head from a foam pillow, brushing your teeth with a plastic brush with paste from a plastic tube, washing yourself with soap from a plastic dispenser, then put on cloths made with a high proportion of plastic. Breakfast, your coffee, all wrapped in plastic, then jumping into you car, sitting on plastic seats gripping the plastic steering wheel, and so the day goes on…

While the extensive permeation of plastics has provided substantial benefits to society, their environmental footprint across the entire life cycle has become a growing concern. Every year, as much as 12 million tonnes of inadequately managed plastic waste enter the environment, with approximately 40% comprising of single-use plastics. Projections show that plastic production could triple within 35 years.

The issue is obvious - what did we expect when we started using a disposable material that doesn’t decompose? When we started replacing all other materials, even those in our cloths, with something that doesn’t biodegrade? Were we not expecting a growing mountain of waste and debris? Perhaps we were, but maybe not the fact that they would fragment down and infiltrate every nook and cranny of the planet.

Micro plastic sources, pathways and sinks. Image from Asim Nawab et al.

Micro plastics (MPs) are technically plastic particles between 1μm and 5mm in size (Nano plastics are smaller than 1μm in size - but for the purposes of this article, MPs include these smaller particles too). There are primary MPs, manufactured deliberately for specific purposes such as hygiene creams, which often find themselves washed into the environment. Secondary MPs, on the other hand, form when larger plastic items break down into smaller fragments under the influence of sunlight, wind, and mechanical erosion. Have you retrieved older plastic items from the back of a cupboard and found them brittle, sticky or even falling apart? I’ve had to wrap my 20 year old Bose headphones’ head strap in tape as the foam and cover were disintegrating, I’ve had to clean sunglass arms with alcohol wipes to remove the sticky layer and so on. Most people would throw them away and replace them, but that only makes matters worse.

Whenever a bit of plastic breaks in two, it increases the surface area of the original piece. As it falls apart into chunks, the chunks then become easier to break down as more surface is exposed to the sun, air and further mechanical erosion. Micro plastic creation is therefore an exponential process which is why its growing so quickly in every conceivable environment. Its estimated that now, the rate of secondary micro-plastic creation is faster than new primary production, since the plastic from the 1950’s is still out there multiplying like a virulent bacteria in an Earth sized petri dish.

Just pop a fleece, leggings or polyester cloths into the tumble drier then look at the lint filter to see how many tiny strands and plastic dust particles are collected. That’s just the bits you can see, that were trapped and that didn’t wear off or your skin didn’t absorb while you were wearing them.

To make matters worse, chemicals used within the plastics to alter their properties leach out as toxic pollutants such as terephthalates (e.g., di(2-ethylhexyl) terephthalate (DEHT)), and adipates, which also include flame retardants, stabilisers, and antioxidants. When they seep into different systems, they can contaminate the environment. Toxic pollutants, including organochlorine pesticides, poly-chlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), and heavy metals (e.g. lead, copper, zinc, and silver), then adsorb on the surfaces of MPs in the environment. The formation of microbial biofilms on MPs adds another layer of complexity to their ecological impact. Plastic waste can facilitate the spread of vector-borne diseases such as dengue, malaria, and Zika, risks that may intensify under rising temperatures and changing environmental conditions. MPs act as carriers for bacteria from rivers to oceans, altering microbial communities and posing ecological risks through biosecurity and elemental cycling.

I won’t dwell much on the health implications or on how much of your brain is filled with plastic just now (its more by weight than all the iron in your blood and has increased by 49% in just the last 8 years), or what it’s doing to the health of ecosystems from the air, plants, animals (including us and our food), the soils, the rivers, the oceans etc. You can look into this yourself if you have the stomach and I’ll just concentrate on the climate impacts.

I can recommend this excellent interview on Planet Critical for more on plastics in general though.

Unknown unknowns

One of the problems with MPs is that it’s so new a phenomena that too little research has been done to understand the situation, let alone make prognosis about the future. Much more has been carried out in the health sector, but this is also very new. While studies are showing direct correlation between amounts of accumulation and stroke risk, dementia, heart conditions etc. nobody really knows how bad it will get or when it will become a population wide issue across all ages. It may be that 1% of your brain weight will be plastic within 10 years - is that good, bad, cognitively debilitating, fatal or not a problem? We just don’t know. I’m betting against good though.

The same is true with the climate influences. Since they are in every system, how do they influence atmospheric moisture holding, cloud formation, soil moisture content, plant growth, nutrient fixing, carbon storage, ice melt, algal growth, ocean acidification? Studies are only now starting to look into the issue.

Micro plastics and the climate system

Unusually for an article on climate change, here there are more remaining questions than studies to report on, but the evidence is starting to emerge as studies are peer reviewed and published. Here’s what we know so far:

Micro plastics in the air

A recent study developed a semi-autonomous microanalytical system to quantify atmospheric plastic particles and their movements including airborne, dust-fall, rain, snow, and dust re-suspension, in two major Chinese megacities, Guangzhou and Xi’an.¹ The sensitivity of the equipment allowed them to detect particles as small as 200nm, far smaller than earlier methods. The results showed that concentrations were orders of magnitude higher than expected or detected through earlier techniques.

In another study just published, a team in the UK compared MP population in rural, suburban and city locations and surprisingly, found that concentrations were actually higher in rural locations, especially for smaller particles, as trees affected air flow and acted as traps allowing the particles to settle² Since particles can float in the air for weeks, they can travel for thousands of miles and permeate even the most remote corners of the planet. So the issue is real then.

Depending on their size and shape, they have a radiative effect which influence the Earth’s Energy Imbalance. They do this by scattering the light and reducing the Earth’s albedo directly. The amount is tiny so far, but measurable at 0.005%. But that’s still 0.02W/m² of additional energy accumulating in the Earth’s system, about 1.4% of the total energy imbalance.

That’s the direct influence, but indirectly the influence is likely to be much higher, since MPs also affect cloud physics with the potential to influence the formation of clouds and their brightness. Because of their hydrophobic nature, atmospheric plastics were often regarded as in-active cloud condensation nuclei and active ice-nucleating particles. Intriguingly, physical and chemical changes on surface defect, roughness, and mixing states of plastics through weathering and atmospheric aging processes, favour both their cloud condensation nuclei and ice-nucleating abilities. Effects will be different in varying atmospheric conditions as well as the size and chemical profile of the particles involved. This makes it complex to model but something that needs to be worked on as a priority. Clouds formed on MPs larger in size than natural aerosols will be dimmer and rain out faster than natural clouds. This reduces their albedo and longevity. It also influences local weather and moisture transport.

Image from Tafeng Hu et al.

The Chinese study quantified the flux of MPs moving through snow, rain, gravity and also re-suspension. MPs carried by air flows will of course allow them to travel far from their source and enter the soil and hydrological systems over a wide area.

When MPs rain or fall out and land on snow, ice or even sand, they can reduce the albedo of those surface, increasing the heat absorption. This would accelerate ice melt in much the same way as black carbon does. It’s even been suggested that MPs in sand could effect sex ratios and fitness in sand laying reptiles such as turtles and crocodiles.

Plants and primary productivity

Plants are impregnated by MPs both via water through their roots and also through air pollution through their leaves. From a climate perspective, we are interested to see if this has any effect on the photosynthesis process which could effect carbon absorption and sequestration from the atmosphere.

A significant paper published last year looked into just this question, drawing on 157 previous studies.³ They found that current MP exposure levels lead to a global reduction in photosynthesis of 7 to 12% in terrestrial plants, marine algae, and fresh-water algae. The cause of the drop is that MP exposure reduces the chlorophyll content of photoautotrophs by 11 to 13%.

Again, analysis is complex due to the wide range of plants and ecosystems involved, but it’s fair to say there are no carbon absorbing ecosystems that are benefitting from this pollution. The paper concentrates on food production and concludes that we are currently losing 59.1MT of rice a year, 75.9Mt of wheat a year, and 108.8Mt of Maize as a result of MP pollution. This just scratches the surface of how much less carbon is being absorbed by photosynthesis globally though, and therefore how much less of our carbon emissions are being sequestered. This could explain some of the observed reduction in natural CO₂ absorption since 2008 and the increasing rate of carbon dioxide accumulation in the atmosphere despite some increases in global greening area.

Another important question is rate. If plants have on average lost ~11% of their photosynthesis potential in the last couple of decades, but the rate of MP growth is exponential, what happens next? Could they lose another 11% over the next decade or is there a ceiling? What other damage is being done to the plants that make them more susceptible to disease, water stress or insect attack? Climate models assume substantial natural absorption of carbon through plants in the future, but don’t take any of this into account.

The study also included algal photosynthesis which has also reduced through MP pollution. Marine algae by up to 11% and freshwater algae by up to 18%. This will affect water oxygenation and potentially lead to more anaerobic microbial blooms which can emit methane, obviously a powerful greenhouse gas. It would also be worth studying effects on mangrove swamps, wetlands, kelp and sea grass colonies since they are often heralded as climate solutions, but are also natural traps for MPs washed from the land.

Micro plastics in the ocean

Other than direct, rain or snow fall out of MPs into the ocean from the air, rivers are an obvious source. A recent study from Germany provides a clue as to the scale of the global flow. A study of the River Rhine using litter traps for a full year estimates 3,000 to 4,700 tonnes of >25mm litter flows into the North Sea every year.⁴ 70% of the individual pieces were plastic totalling 446-697 tonnes in weight (up to 280 times greater than previous estimates). This is macro plastics, so the volume of MPs could be significantly higher.

Once the litter makes it into the oceans, further issues arise. Plastics make up a significant portion of marine debris, ranging from 60% to 80% of the total, and nearly 90% of waste observed floating in oceans and seas. An international paper published this year describes the various climate impacts of MPs in the oceans following a review of 57 papers published since 2015.⁵

The presence of MPs decreases the ocean’s ability to sink carbon. To start with the decomposition of MPs in the oceans actually releases greenhouse gases into the atmosphere including CO₂ and methane. These can also remain in the water increasing rates of ocean acidification. This inhibits the growth of carbonate forming plankton which are responsible for a great deal of carbon storage through their lifecycle.

Sources, pathways and climate related impacts of micro plastics. Image from Asim Nawab et al.

MPs inhibit photosynthesis in a number of ways. As already mentioned they reduce the chlorophyl content of algae, but they also reflect and scatter some incoming sunlight, reducing the light available to both algae and phytoplankton. Photosynthesis also relies on other nutrients being available including iron, phosphorus and nitrogen. Microbes that grow on MPs form films, known as plastispheres, can interrupt these nutrient cycles affecting their availability. These microbe communities also interfere with gas exchange with the atmosphere as well as other biogeochemical processes within the sea-surface micro-layer.

A study published late last year investigated the breakdown of MPs under UV sunlight and found that all the types tested leached Dissolved Organic Compounds (DOM) into the water, forming a chemical plume around the particles.⁶ The process sharply increases with exposure to sunlight, which given many particles exist in the surface layers of the ocean speeds up the release of these chemicals. The changing chemical mixtures released by MPs could affect aquatic ecosystems in multiple ways. MPs DOM is largely made up of small, biologically accessible molecules that may stimulate or suppress microbial growth, disrupt nutrient cycles, or interact with metals and other pollutants.

Zooplankton feed on phytoplankton and are an important part of the carbon pump which moves carbon from the surface to long term storage in the depths. Through their lifecycle, their faecal matter and their corpses, along with phytoplankton corpses, sink to the abyss, taking their carbon with them. Zooplankton are unfortunately now mistaking MPs for food and ingesting them. This affects their health but can also make both their faecal matter and bodies more buoyant, slowing down the flow of marine snow to the depths. Fish feeding on the zooplankton are therefore also ingesting MPs indirectly and so on up the food chain, including to humans.

A new study by the Oceanographic Center of the Balearic Islands and the Plymouth Marine Laboratory confirms this hypothesis.⁷ They took zooplankton from the western English Channel south of Plymouth and then examined their behaviour with MPs in the laboratory. Zooplankton not only routinely ingested MPs of different types, they remained in their gut for 40 minutes on average.

By combining these measurements with realistic estimates of copepod abundance in the western English Channel—one of the most highly studied bodies of water in the world—the team calculated that copepods could be driving micro plastic fluxes on the order of about 271 particles per cubic meter of seawater per day, in that region. Since fish routinely feed on the plankton, they are inevitably entering the base of the food web as well as being processed through faecal pellets.

Conclusions

Micro plastics are now distributed across the entire planet in every location and ecosystem. Their population is expanding exponentially, no only as global plastic production continues to increase, with predictions of a tripling within 35 years, but as old plastic degrades and breaks down in the environment.

Micro plastics constitute a serious predicament not only for ecosystem, plant, animal and human health, they are also accelerating the rate of climate change by interfering with radiative forcing and the carbon cycle. They have an emerging fingerprint in everything from albedo to ocean carbon storage and from photosynthesis rates to cloud properties. They are however a new phenomena and as such are not included in climate models or projections, yet have been shown to have significant effects in important areas. A decline in photosynthesis of 11% is not a rounding error.

There are a high number of unknowns, not just in terms of specific actions and forces, but also in interconnections and feedback loops. For example when micro plastics accelerate warming through albedo and lower carbon sinking, which then changes ocean currents, which then redistributes micro plastics providing further effect changes… This is obviously an area of planetary and climate science that needs a lot more work and media attention beyond just the health implications.

The world knows there is an issue but, just as with climate action in general, is being too slow to address it. The usual regressive countries, that climate policy has been hampered by, blocked action in recent UN negotiations, notably Saudi Arabia, Russia and the US. Vested interests and the might of the petrochemical industry, and their bought-and-paid-for politicians, hampering attempts to address it.

When it comes to micro plastics, like climate change, humanity is beginning to realise that it is stuck in an oubliette of it’s own making. Whether the health and ecological impacts will do more harm, more quickly, than the climate implications is anyones’ guess. What is starting to be realised is the scale of the predicament and the unwillingness of society and geopolitics to address it.

1. Tafeng Hu et al. ,Abundance of microplastics and nanoplastics in urban atmosphere.Sci. Adv.12,eadz7779(2026). DOI:10.1126/sciadv.adz7779

2. Gbotemi A. Adediran, Victoria Taylor, Alexandra Howard, Paul G. Whitehead, Jocelyne M.R. Hughes, Microplastics in the air: Weather and polymer influences on deposition trends across a rural–urban gradient, Environmental Pollution, Volume 388, 2026, 127388, ISSN 0269-7491, https://doi.org/10.1016/j.envpol.2025.127388.

(https://www.sciencedirect.com/science/article/pii/S0269749125017622)

3. R. Zhu et al. A global estimate of multiecosystem photosynthesis losses under microplastic pollution, Proc. Natl. Acad. Sci. U.S.A. 122 (11) e2423957122, https://doi.org/10.1073/pnas.2423957122 (2025).

4. Gnann, N., Höreth, K., Schweigert, N. et al. The river Rhine transports around 4,000 tonnes of macrolitter towards the North Sea each year. Commun. Sustain. 1, 5 (2026). https://doi.org/10.1038/s44458-025-00007-5

5. Asim Nawab et al. From pollution to ocean warming: The climate impacts of marine microplastics, Journal of Hazardous Materials: Plastics, Volume 2, 2026, 100032, ISSN 3051-0600, https://doi.org/10.1016/j.hazmp.2025.100032.

(https://www.sciencedirect.com/science/article/pii/S3051060025000320)

6. Liu S, Zelang X, Ma C, Li Z, Wang X, et al. 2025. Molecular-level insights into derivation dynamics of microplastic-derived dissolved organic matter. New Contaminants 1: e016 doi: 10.48130/newcontam-0025-0016

7. Valentina Fagiano et al. Real-time visualization reveals copepod mediated microplastic flux, Journal of Hazardous Materials, Volume 500, 2025, 140551, ISSN 0304-3894, https://doi.org/10.1016/j.jhazmat.2025.140551.

(https://www.sciencedirect.com/science/article/pii/S0304389425034715)