There are two other important factors. One is albedo, or the reflectivity of the planet’s surface. Arctic sea ice bounces sunlight right back up to space, for example. Tropical forests have a low albedo–they absorb heat instead of reflect it. That’s counteracted to some extent, though, by chemicals that trees produce. These aerosol particles (think of the “smoke” of the Great Smoky Mountains) both reflect sunlight and help high-albedo clouds form.
Forests are a powerful, troubled ally in the struggle against climate change. They soak in 29% of the carbon dioxide humanity emits every year–a feat that has kept temperatures from spiking higher than the 1.1°C that they already have. But tropical deforestation gnaws away at this benefit, pushing CO₂ levels higher.
This binary model–carbon in, carbon out–frames many debates about land management in climate policies. It may be too simple, according to a new study in the journal Frontiers in Forests and Global Change. That’s because it leaves out other critical but overlooked effects that have an important, perhaps 0.5°C cooling effect on the global climate, a monumental figure given that every 0.1°C matters. Uncurbed deforestation puts this benefit in jeopardy, too.
“Clearly, the value of climate stabilization by tropical forests is under-valued,” Lawrence said.
Source: Bloomberg
