In the early 1970s, scientists warned of the consequences of climate change. Greenhouse effect, polar ice melt, droughts, dying forests and storms. But these warnings were dismissed as scaremongering or ignored.
Even at the beginning of the 21st century, when climate forecasts came in even earlier than predicted, politicians were still reluctant to accept the danger. Not even hundreds of thousands of protesting pupils and students were able to persuade the powerful to give in with their demonstrations.
They only reacted as the consequences of climate change could no longer be denied and it was already too late to change anything. The world was heading for the abyss. The ice of the polar caps had melted and the earth was heating up even more due to the disappearance of reflection surfaces. The temperatures rose so high that large parts of the world were no longer habitable, as people would cook alive during the day.
To the equator behind the 46th degree of latitude over the summer months no life was possible and over the 40th degree of latitude every day was deadly. The few habitable areas, which offered still acceptable temperatures, were further shortened by the risen sea level and so the world population remained only about 20-25% of their original habitat.
Overpopulation, famine and misery were the consequences. The remaining governments of the earth joined together to form a global emergency government and mankind saw only one way to escape from the Hothouse Earth. To found colonies on other planets...