Re: Global warming is predicted by the laws of thermodynamics
"Plant a trillion trees over the next few decades"
That's impossible.
Land area of the earth is 150 million square kilometres. 1 trillion trees is about 7000 trees per square kilometre, or about 81 trees per linear kilometre, or one tree every 12m.
12m spacing between each tree doesn't feel wrong but still feels quite dense for mature trees (that need to be self sustaining and not managed as cash crops). And that's assuming we cover every bit of land with a tree every 12m - every desert, every Antarctic ice field, every mountain peak, every exposed piece of rock. Remove all habitations to make room for the trillion trees. If only 10% of land can support trees, then the density is a tree every 4 cm. Impossible.
The trillion trees isn't too far off though. Global carbon dioxide emissions from fossil fuels are at about 35bn tonnes per year. A fully grown tree absorbs about 25kg of carbon dioxide per year (very variable according to species, location etc). That works out to about 0.14 trillion mature trees.
Carbon capture by tree planting is not a long term solution by itself. Eventually the carbon comes back out as the trees die and decompose. In fact it may make things worse as a tree absorbs carbon dioxide as it grows but emits methane as it dies - methane being about 21 times more potent a greenhouse gas than carbon dioxide. And this happens every year as trees grow leaves which then fall and rot.
It's got me wondering how much of that 25kg of carbon dioxide absorbed by a mature tree every year comes straight back out as leaves decay and rot. Even if only about 1kg of methane is emitted by rotting leaves, then it achieves nothing in terms of carbon reduction.