As agricultural greenhouses proliferate, researchers are finding that their reflective roofs are having a cooling effect. Some experts see this as an unintended experiment with lessons for cooling cities, but others point to the environmental damage that greenhouses can cause.

By Fred Pearce. June 20, 2024

The world is awash with greenhouses growing fresh vegetables year-round for health-conscious urbanites. There are so many of them that in places their plastic and glass roofs are reflecting sufficient solar radiation to cool local temperatures — even as surrounding areas warm due to climate change.

The extent of this accidental climate engineering is becoming ever more apparent as analysis of satellite images dramatically increases estimates of the area of the planet swathed in greenhouses. From southern Spain to northeast China and the Rift Valley in East Africa to Mexico, millions of acres of former scrub and marginal farmland are being replaced by glistening reflective surfaces.

The intensive agricultural methods employed within greenhouses may often damage local environments by overtaxing water supplies and polluting rivers and soils with nutrients, pesticides, and plastic waste. But the influence of these seas of plastic on local temperatures can be even more dramatic — and often beneficial. They increase the albedo, or reflectivity, of the land surface, typically by around a tenth, and so reduce solar heating of the lower atmosphere.

In a greenhouse-intense area of southern Spain, researchers found an average cooling of 1.3 degrees F over 23 years. 

Click here to read the full article https://e360.yale.edu/features/greenhouses-cooling