Global Climate Catastrophe

The Global Climate Catastrophe was an environmental change that occurred from 1820 to 1885 UD.

Origins
The climate catastrophe truly started after the industrial revolution, like in most cases. However, the catastrophe really picked up after the Third World War. By then, the population was aware of climate change, rising sea levels, deforestation etc. However during the war, several nukes hit some polar cities and permafrost methane pockets, causing massive explosions. The resulting nuclear winter managed to stabilise the climate for a few years, however the methane and carbon dioxide levels increased. After it ended, temperatures soared.

Catalyst
On 1820.05 23rd UD, an expanse of methane pockets exploded due to rising heat. This caused a chain reaction, leading to portions of the Northern Ice Shelf to collapse and melt. The explosions measured from 20 to 100 megatons. In the next few years, temperatures rose to over 5 degrees since the start of the industrial revolution. Over 2 billion people died indirectly from drought, famine and natural disasters.

The Rising
On 1827.06 10th, the biggest methane explosion happened, melting a large portion of the ice cap. Within 2 days, a massive tsunami caused by the collapsing ice cap and melting water flooded all areas of the world below 15 meters from the sea. Over 50 million people drowned and large portions of cities were left abandoned and flooded.

Solutions
Faced with the desperate situation, the Unified Nations passed on the controversial ultimate order. The Unified Nations would hold semi authority of all nations in the world in an attempt to save all life on Terun. Within the next 20 years, funding went to science and research. Projects like the "Wall of life", which surrounded Cities with huge walls to prevent flooding, "revitalise" which saw cloned, extinct animals return and "Trees" which sucked carbon dioxide from the atmosphere. In 1840, the environment finally started to heal, with fossil fuels replaced by fusion reactors or other renewable energy. After the climate stabilised enough, efforts were made to reclaim back cities and clear the damage caused by the Third World War. Finally, in 1885, the Unified Nations dissolved, with its main objective completed had returned control of nations back. By then the world only had 3 nations left, with many nations combining and merging.

Legacy
The success story of Terun was later found out to have occurred on many other planets. However, with the dissolution of Unified Nations, the three remaining nations became locked in rivalry and eventually war.