Excerpt:
"Broad leaf tees emit up to 600 million metric tons of isoprene each year, but no one thought it mattered much. For obvious reasons it is made near the ground, and it’s quite reactive and doesn’t last long. During daylight it’s destroyed within hours. So the experts didn’t think the isoprene could help seed clouds in the upper atmosphere. But there is still quite a lot of isoprene left in a rainforest at night, and tropical storms suck it up “like a vacuum cleaner” and pump it up and spray it out some 8 to 15 kilometers above the trees. Then powerful winds can take these molecules thousands of kilometers away.

When the sun rises, hydroxyl radicals start reacting with the isoprene again, but the reactions are quite different in the cold upper troposphere. And lightning may have left some nitrous oxides floating around too. This combination ends up making a lot of the seed particles that generate clouds in the tropics. It’s almost like the forests want to create more rain…

To put some perspective on this, isoprene is the most abundant non-methane hydrocarbon emitted into the atmosphere.

As Jasper Kirkby at CERN says — this is big:

Isoprene represents a vast source of biogenic particles in both the present-day and pre-industrial atmospheres that is currently missing in atmospheric chemistry and climate models.”

Until now, isoprene’s ability to form new particles has been considered negligible.

But climate models have also been estimating aerosols in the atmosphere for hundreds of years, and they didn’t realize trees made so much aerosol than they thought. This is so big, it may change the sacred “climate sensitivity” of the whole Earth:

“This new source of biogenic particles in the upper troposphere may impact estimates of Earth’s climate sensitivity, since it implies that more aerosol particles were produced in the pristine pre-industrial atmosphere than previously thought,” adds Kirkby. “However, until our findings have been evaluated in global climate models, it’s not possible to quantify the effect.”

Another possibility is that if forests of broadleaf trees turn out to be seriously helpful at seeding clouds, presumably that means the last few centuries of deforestation might have reduced cloud cover on Earth, which would have allowed much more sunlight in to heat the planet. If that’s true, it’s just one more climate forcing the modelers didn’t know about. It’s one more thing that warmed the planet which we blamed on carbon dioxide, but were wrong about. And it’s yet another feedback. More CO2 makes more forest grow, which may seed more clouds."