The pre-industrial atmosphere contained more particles, and so brighter clouds, than we previously thought. This is the latest finding of the CLOUD experiment, a collaboration between around 80 scientists at the CERN particle physics lab near Geneva. It changes our understanding of what was in the atmosphere before humans began adding pollution – and what it might be like again in the future. Most cloud droplets need tiny airborne particles to act as “seeds” for their formation and growth. If a cloud has more of these seeds, and therefore more droplets, it will appear brighter and reflect away more sunlight from the Earth’s surface. This in turn can cool the climate. Therefore understanding the number and size of particles in the atmosphere is vital to predicting not only how bright and reflective the planet’s clouds are, but what global temperatures will be. Today, around half of these particles come from natural sources. That includes dust from the ground, volcanoes, wildfires that make soot, or sea spray that evaporates midair leaving behind tiny specs of salt in the atmosphere. Many airborne particles also result from us burning fossil fuels. The CLOUD experiment at CERN also recently discovered that gases emitted by trees can stick together to make new seeds for clouds in the atmosphere – without needing any help from other pollutants as was previously thought. Scientists had thought that the cloud seeds needed sulphuric acid (often mixed with other compounds) or iodine molecules to stick together to initiate the process. The new follow-up study suggests that even today trees produce a large fraction of cloud seeds over the cleanest forested parts of the world. https://theconversation.com/trees-a...and-cooling-the-climate-than-we-thought-66713 Full study: http://www.pnas.org/content/early/2016/10/05/1602360113.full
Interesting . Not all clouds are the same and so not all seeding particles will generate same cloud formation
If the cloud forms during the day. If it forms during the night, it will block re-radiation of infrared, warming the climate. Hence the difficulty in modeling cloud formation contribution to climate.
An interesting side note. When a tree becomes infested with caterpillars it defends itself by producing tannin at random. Caterpillars can adjust to the tannin, but having to switch digestive properties back and forth uses a lot of energy and inhibits the growth of the caterpillar. So far so good. But remarkably, trees in the vicinity which have no infestation, also start producing tannin. Researchers suspect that certain chemicals may be transmitted by air, which can be read by other trees in the vicinity. Question: Is it possible that this "cloud" may be also be responsible for a form of communication between the trees themselves?
