Warning kind of depressing but not really
An archeology dig on Pandora revealed a preserved piece of bark, with strange etchings on it the that no one could read, until today, when a novice made a small mistake that happened to crack the code.
My name is Tsa'chak and I was tasked with the recording of the history of Pandora. When this was written, what had made Pandora was so long ago that not even the eldest of the elders', elders', elders remembered anyone who had lived through these events.
Pandora was not always known as Pandora, it was actually called Earth, populated with the un-evolved Na'vi called Humans, smaller, softer, but with greater technological advances. The funniest thing is that the great technology actually brought the death of the planet. The closest planet with a viable ecosystem for human life was Kepler-452b, 1,400 light-years away in the constellation Cygnus. Some humans went there before Earth started to collapse, and we had wondered how they faired, before our issues became so pressing.
Earth was apparently very beautiful, with lots of water, and a plentiful of land, but humans got to greedy, hungry for these rocks called coal, old trees that had been buried for thousands of years, deep in the ground. The then burnt it, using it for energy in metal beasts, to boil water to make steam to move them. When coal wasn't enough, they found something called oil, a liquid substance that they would then burn, creating gasoline and diesel, burning them to power even bigger beasts.
Every step along that process was emitting this invisible gasses called Carbon Dioxide (CO2), going into the air. This was bad because there was this thing called The Greenhouse Effect (GhE), that protected Earth from these harmful rays form the sun, invisible waves that would kill a human is they didn't get reflected off of the thin barrier around Earth. That barrier also let some less harmful rays through, those that would be absorbed or bounced off of the ground, and hit the barrier and either was reflected back down or escaped back into space, and so on until they were all absorbed or flying away into empty space and other planets. This had the benefit of using the rays to heat up the planet so they could live there and not die from being to cold.
The CO2 emissions were slowly building up in the atmosphere, trapping more and more heat in it, heating up the Earth. When the Earth was created it when through a few periods of extreme cold, called Ice Ages, where a percentage of Earth's water froze, trapping little pockets of air for later. That frozen water was called glaciers, some big enough to cover entire continents. Those glaciers were then melting at an extreme rate, due to the extra heat trapped in the Earth's atmosphere.
The emissions went unnoticed for years as the different different techniques were developed, and more and more people accepted it as a constant and didn't think that it had any repercussions. By the time the people noticed something was wrong and what was causing it, it was too late, half because the emissions only affected the planet fifty years after they were emitted, and half because there were many wealthy people it charge of big groups, companies I think they were called, that made their money off the product of the emissions, so they fought so they would be able to continue making more money off the people who bought their product.
Those glaciers I told you about were one of Earth's protections, thousands of years old air bubbles trapped in the ice, waiting to be released in hope of stabilizing the atmosphere once again. Sadly Earth, Eywa, God, the human's deity, I guess, underestimated how much damage the humans could do as quite obviously, their plan didn't work, for if it had then I wouldn't be here would I.
At first the humans thought that they could fix this mistakenly called detrimental greenhouse effect that correctly became called global warming that became global climate change. They tried to then warn the people of what was truly happening, but the people were too happy with their current ways, in love with how easy it was for them. When the general populace saw what was happening, they changed, but only minor things that didn't really matter. Then when they saw how bad it was, it was ways to escape what others had done, because it couldn't be them who had did that. The rich and semi-rich all funded space programs to accelerate there growth, so all of them would be accepted for the settlement program and wouldn't have to risk it on a 'dieing' Earth.
Those left behind were die-hard scientists and the poorer classes, left behind to survive on their own for an undetermined amount of time. They decided to build a great building to house all of them that they called the Hall. It worked until the atmosphere changed to predominantly CO2. The humans then couldn't breath, and started to die. The ones alive made a system to convert the carbon away and make oxygen inside the Hall. It was all well then until the people started to get uneasy, restless to go out and see how the world changed. The few remaining scientist took the last few years of their lives then to make serum to convert human lungs and organs, to what are now Na'vi lungs and organs, although they didn't know that then, that operate on CO2 or oxygen instead of only the latter. Some of the people that wished to live outside of the Hall were then injected with the serum and put under observation. The only visible difference it made was that the exposure to a CO2 atmosphere caused their red blood cells to change into blue or purple blood cells.
Since their serum was a success the scientists the gave it to all of the Hall's residents, who all left the Hall for the first and last times of their lives. The world they then faced was drastically different, with flora, plant life, and fauna, animal life, having took over the once great cities, creating dense jungles of highly evolved life forms globe wide, the Pandora we know now. As they settled disputes came and the groups of different minded split and went in their own ways, settling as the many clans of Pandora. Our bodies then slowly changed and adapted through generations to the new environment and to different tasks. That is how this happen, and why we are here now. To whomever finds this have peace of mind knowing that we survived with a second chance at life on the planet we had almost destroyed. Tsa'chak out.