Plastic particles cool the climate (slightly)

In contrast to plastic pollution in the oceans or on land, the presence of microscopic plastic particles in the atmosphere has only recently been brought into focus. “We now know that microplastics can be found even in the most remote places in the air,” says Laura Revell, professor of atmospheric chemistry at the University of Canterbury. The particles are very small and have a low density, so they are easily carried over long distances by the wind. Then the microplastics from the seas end up in the atmosphere via evaporation. We’re seeing a kind of global plastic cycle emerge.

back to space

Those microplastics in the air seem to have an impact on the climate. Earth absorbs energy from sunlight, but also reflects some of it back into space. Revell explains that atmospheric particles, such as dust or soot, affect the effect of sunlight. Such particles have a cooling effect on the climate because they reflect sunlight and sunlight that in this way does not reach the Earth’s surface and is therefore not absorbed. For example, during large volcanic eruptions, ash particles block sunlight, causing global cooling. We see this phenomenon in microplastics in the atmosphere.

But that’s only part of the story. At the same time, Revell said, the plastic particles in the air are heating up the atmosphere. The cooling effect appears to be dominant, but due to their chemical structure, microplastics also absorb heat and send some of the sunlight that is reflected back by the Earth toward the surface. In this way they contribute to the warming of the atmosphere, in the same way that greenhouse gases contribute.

Color makes the difference

Examining the impact of microplastics on climate contains a number of important uncertainties. Revell explains that the color of plastic particles, for example, was not taken into account. We started from pure, uncolored polymers. The color changes the interaction with visible and infrared light. This is not in our model, but we suspect it would significantly enhance the warming effect.

Despite the uncertainties in the models, it appears that microplastics have a cooling effect on the climate, albeit to a very limited extent. But the amount of plastic that has ended up in the environment in the past 70 years is enormous, and it is increasing day by day. The effect of microplastics in the atmosphere may increase. And that’s not a good thing, Revell is quick to clarify.