Humanity's hubris once again leads to disaster, but this time we can't recover.
The already thawing permafrost in Siberia unveils unfathomable amounts of fossil fuels. The influx of resources not only led to intense amounts of pollution and carbon emissions, but economic opportunity. The shadowy games of politics ramp up with many elites taking advantage of the situations to line their pockets. Their game is ruthless with the players tearing at each others throats and blackmailing, assassinating, or exposing each other to gain power. It isn't only the hidden rulers of the world that this effects, but the people as well. The political strife also opens the doors for wars on scales never seen before, although no nuclear weapons were utilized on an apocalyptic scale.
Ordinary citizens are subject to harsh conditions working to extract resources. Labor is often exploited in undeveloped or autocratic countries with little human rights laws. Slavery of ethnic groups and human trafficking are also utilized to provide labor. The horrendous conditions of labor camps and slums are hotbeds for disease. Diseases such as dysentery, trench foot, e. coli, and many many others made a return all across the world regardless of a country's economic status. Furthermore, bioengineering has created diseases that affect crops, livestock, and humans. Diseases held in the permafrost and polar ice are also released as well.
Massive earthquakes and other extreme weather also occur more frequently and those who survive are forced to live in the wild as cities are even more unsafe than they already were. The wild isn't safe either as wildfires sweep across the world. Acid rain is also common, though not harmful to humans directly, it erodes the soil and causes duststorms and mudslides.
Acid rain also carries nutrients into the ocean, causing harmful red tides that make the seas look like blood, most marine life dies due to this. Freshwater has its own issues as well as many fresh water sources have dried up. The ones that still exist are filled with industrial waste and toxic to all life. Things somehow manage to get worse as the amount of pollutants in the air forms thick black clouds that block out the sun and decimate most plant life.
At this point, the last humans are nomadic hunter-gatherers wandering in a post apocalyptic wasteland. They know things won't ever get better but still try and survive, it seems as though humanity will leave this earth without a trace left of our story. All is not lost though as historians before the extinction gathered the pieces of human history and put complete records inside of a near indestructible, airtight time capsule and buried them in every nation and shot them into space. The accomplishments of humanity will be buried with us.
The extinction is over but the world isn't healing just yet.
The last humans have been picked off by starvation, dehydration, and the elements, except for one. The last Homo Sapien, a man named Adam, wanders the earth alone with his dog. He has grown old for his time, living into his fourties. His life would soon be over as he has the privilege of dying of old age. He sits outside of his hut with his dog by his side. He looks at himself and realizes how wonderful his life was despite its many hardships. He looks at the world around him and marvels at how everything in the world fits together and how its all made perfectly. He lies down and falls asleep, but he never wakes up. He will lie in the same place he lived and died in, no creature shall feast on him, his hound made sure of that. From dust he was made, and to dust he will return.
With Adam's death, humanity is given a proper sendoff and the sun will dawn on a new era.