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from the overcast-with-a-chance-of-light-wood dept.
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.
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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.In our new follow-up study, published in PNAS, we worked with other CLOUD scientists to simulate this process in the atmosphere. Our work suggests that even today trees produce a large fraction of cloud seeds over the cleanest forested parts of the world.
More trees means more clouds, which means cooler Earth.
(Score: 2) by Arik on Wednesday October 12 2016, @04:02AM
Because if it was more than an assumption dozens of you would have bombarded me with links to a proper observation, or demonstration. It's not. It's an assumption built into their models.
"Off the top of my head, I can think of some good reasons to think that more CO2 does not necessarily mean increased plant growth:"
Nice shift of the goal posts. You first try to raise it to the level of observable fact, without citation, then suddenly you're talking about simply being able to imagine reasons why it might be true. No one questioned that we can think of lots of reasons it might be true. We can also think of lots of reasons it might be false. What's needed is disciplined observation and experimentation to determine where the truth lies, not more people passing off their personal opinion as scientific fact.
"1. Humans are wrecking plant growth with slash-and-burn agriculture and other forms of habitat destruction faster than the higher CO2 can have its effect."
Do you have any proof of that? Slash and burn has decreased steadily for decades, as has agricultural land use in general, so it seems unlikely you are correct here.
"2. Higher concentration of CO2 in the atmosphere = higher temperatures (this has been demonstrated repeatedly in lab experiments, there's no guessing about that), which means that areas closer to the equator can become too warm for the plants currently there. In other words, the shift is towards the poles, not towards more plants."
Very unlikely. In the past Earth has actually been a hothouse more often than an iceball (it's an iceball currently.) Hothouse periods see tremendous vegetative growth all the way from the tropics to the poles. A true hothouse earth, should it come, would be a very challenging transition for humans but I think we can be quite sure that the plants will continue scrubbing carbon with or without us.
"3. Plants need more than CO2, they also need water. If the water is scarce, then a burst of plant growth will be limited by the water, and in fact there's a real risk of desertification."
And desertification is more often associated with cooling periods than heating periods. You should look up on the Saharan Pump.
If laughter is the best medicine, who are the best doctors?