The climate catastrophe
When the people of the 24th century look back on the 21st century, they always come to the same conclusion: there has been a lot of talk, a lot of decisions, and yet nothing has been done. The people of the 21st century staggered into the great catastrophe with their eyes wide open - but this was not the 3rd World War that people had feared so much in the 20th century: it was the climate catastrophe.
By the 24th century, glaciers and poles had melted, sea levels had risen by almost 100 metres and the average temperature had risen by 10°C. In the beginning, the people of Old Earth still tried to protect their land with dikes and floodwalls against the rising tides, but in many places the struggle was in vain - or at some point simply no longer affordable. Entire nations sank into the seas.
Flora and fauna capitulated to the rapidly rising temperatures with their hot, drought-inducing summers and stormy winters. A great mass extinction changed the face of the earth and conventional agriculture collapsed: Food prices skyrocketed and real meat quickly became a luxury product that only a small class of wealthy citizens could even afford.
Conflicts seethed across the globe, over land and over resources, especially water. Refugees poured in en masse, sometimes aimlessly, sometimes with the major industrial nations as their destination.
The collapse of the EU
Among the first victims of the climate catastrophe was the European Union. If it had already been plunged into a "refugee crisis" in the early 21st century, that was nothing compared to the refugee crises that followed. Refugees stormed wave after wave against the Union's borders and finally broke them. South and East no longer wanted to serve as a protective wall for Central Europe - especially since they didn't get enough money from Brussels anyway.
Following Britain's example, one country after the other left the EU, starting with Italy and Hungary, until finally only France, Germany, Austria, Belgium and Poland remained in the Union - Denmark and the Netherlands had already become part of the North Sea.
The period of disintegration was by no means orderly: Everywhere there was unrest among the discontented population, violence and crime boiled over and the masses of refugees broke the camel's back in many places. While national parliaments were still arguing about the limits of humanity, thousands died of hunger and disease in the reception camps or collapsed from exhaustion while they were shooed from one country to the next - because they could not be helped, did not want to be helped or were used as political leverage.
The disintegration of the European Union meant that trade relations and customs duties were not regulated, so that food shipments did not reach their destinations, went mouldy in the ports or trucks were looted by desperate people.
France and Germany were visibly losing their place on the world stage and found themselves unable to do anything about it. By the middle of the 22nd century, Europe had already become a marginal note in history, while the powder keg of the Middle East exploded and the USA broke up.
It was not until the 23rd century that the remnants of the EU began to consolidate again under German-Polish initiative and a new union was formed, joined by the Scandinavian countries, which soon became the tone-setters of the North European Union (NEU).
But while Central Europe had previously been largely spared the great wars of the modern era, the Northern European Union had to face a war with the Slavic Federation shortly after its founding, who saw the renewed union of European states as a threat to their interests.
The not-so-United States of America
In the United States of America, the plutocracy of corporations and the super-rich gained the upper hand during the first half of the 21st century, transforming the country into a technocratic paradise - for the few. The gap between rich and poor almost nowhere widened as much as in the USA. The discontented masses became increasingly restless and uprisings and outright rebellions became more frequent. When it became known that a handful of AIs owned more than 90% of the real estate and economic assets, civil wars broke out all over the US. The country descended into anarchy and the unity of the states crumbled. For a few decades, the USA still existed formally on paper, then it dissolved without a sound.
While some former federal states were able to moult into stable nations of their own, others fell into the hands of technocratic corporations and others remained in a state of anarchy. Some northern states found refuge in annexation to Canada.
A supposed winner
As climate change progressed, Russia opened up the vast expanses of Siberia, so the Russian Federation was long seen as the winner of the new era. But Russia was also quickly engulfed by ethnic and social conflicts. It took over 100 years of countless civil wars until a new federation, the "Slavic Federation", took its place - and promptly found itself in conflict with the superpower Pan-Asia.
The Slavic-Asian War led to the loss of most of the eastern territories of former Russia. With the Peace of Shanghai, the new eastern border of the Slavic Federation was drawn in the Siberian Sea after a war that resulted in losses for both sides. But peace was far from in sight: tensions with Turkey led to several Slavic-Turkish wars, and in the mid-23rd century the Slavic Federation saw itself threatened by a strengthened Europe. It tried to dissolve the new unity of the Northern European Union with war.
The Big Bang
If there was such a thing as a third world war, it was the war in the Middle East. While the sparks in this powder keg were flying throughout the 21st century and countless wars had been waged between changing alliances and with and against rebellious groups, the big bang that generations had feared occurred in the 22nd century.
Islamic forces united the states of the Arabian Peninsula with Egypt to form a new caliphate and war with Israel was inevitable. Later, no one knew whether it was really an Israeli atomic bomb that hit Mecca, because some voices claimed it was actually an Iranian or possibly even a Texan one. However, the Israeli-Arab war was the first war since the Second World War to be fought with the use of nuclear weapons. And the fire of this war raged and spread. Soon North Africa, Turkey, Iran and even India were involved, while European and especially American mercenaries joined in on all sides of the war. Some mercenaries even revived the medieval crusade mentality under the battle term of the "New Crusade", fighting Israelis and Muslims and repeatedly proclaiming tiny "Holy States" that did not last long.
In the end, a fundamentalist "Islamic Caliphate" emerged victorious from the ashes of this war. But it could not assert its claim to leadership over all Muslims: Iran promptly named a counter-caliph and Turkey, a strict Muslim state since the second half of the 21st century, also rejected both caliphs and disputed their legitimacy.
A loser of hearts
In the 21st century, India was well on its way to becoming the new global superpower, but the climate catastrophe broke the neck of the populous subcontinent. Worse still, India was caught in the maelstrom of the Middle East war and threatened to break up. This was the opportunity for the Pan-Asian People's Republic and Polystralia to gain influence over India; which stabilised India as a nation, but almost pushed the civil war-torn country off the world stage.
The Red Dragon rises
By the early 21st century, the People's Republic of China had become a world power, outranking the old world powers. With a mixture of economic pressure, diplomatic finesse and strategic warfare, China gained increasing influence for its neighbouring countries and soon reformed itself as the "Pan-Asian People's Republic". Not only through military successes, especially in the wars with the Slavic Federation, but also by coping with the consequences of climate catastrophes, Pan-Asia became one of the most stable states on earth and won its place as the strongest economic power on earth and the engine of technological progress. Achievements that still endured in the 24th century.
The thousand faces of the South
The climate catastrophe and the fear of Panasia welded Australia and the Pacific island states together into a new power: The Commonwealth of the Pacific, commonly referred to as "Polystalia". Although more of a middle power, Polystalia formed an important counterweight to the power of the Pan-Asian People's Republic.
The cradle of Mankind
The climate catastrophe intensified the wars, civil wars and rebellions on the black continent and caused millions of people to seek their salvation in flight. Already exploited and marginalised in the 20th century, the nations of Africa threatened to break apart altogether under the changed conditions, but the catastrophe awakened calls for unity unprecedented in history. Finally, in the 22nd century, the African People's Republic came into being, fought for with the blood of hundreds of thousands, built from the ruins of wars with the economic help of Pan-Asia and more or less dependent on big brother for that very reason.
The Maple Empire
Although the climate catastrophe also had negative consequences for Canada, it can be seen as one of the few beneficiaries of climate change. Rising temperatures changed the face of Canada, but it also became a safe haven for millions of emigrants from the old "West". When the USA finally disintegrated and some former northern states joined Canada, the "Commonwealth of the Atlantic" was formed, which soon included the numerous British islands - after all, the British monarch was still the head of state and people felt somehow responsible; even if Britain was rather a backwater province of the powerful North American confederation.
Order and Progress
The climate catastrophe also changed the landscapes of South America and fuelled conflicts that, since the middle of the 21st century, have increasingly resulted in open warfare, incited and supported by changing powers from other continents pursuing their own goals. Historians today like to speak of the Hundred Years' War, which held South America in its spell and from which Brazil emerged as a nuclear and great power - where Brazil got its nuclear arsenal could never be clarified. As a counterweight to the strong Brazil, the South American Alliance was formed as a union of the splinter states of the 20th century.
The new Leage of Nations
The United Nations was the ailing old man of the 21st century and was already dying when the Middle East war broke out in the middle of the 21st century and dealt it a death blow. For many decades, the idea of an international forum for international understanding was history, a pious dream of a few idealists. It would take until the end of the 22nd century for the New League of Nations to be founded in Shanghai; derided by many at first as a means for Panasia to expand its hegemonic position, the beginnings of this League of Nations were bumpy. However, as Panasia supported the members of the New League of Nations economically and technologically, membership soon became attractive to many and by the middle of the 23rd century, the majority of Earthly states were represented in the New League of Nations and even some artificial intelligences and large corporations were accepted as members on an equal footing.
Although at first the New League of Nations really served to enforce pan-Asian policies, it soon developed a momentum of its own, bringing together humanity that had been battered by wars and climate. By the end of the 23rd century, the New League of Nations had increasingly developed into a global government that was more capable of action and enforcement than its predecessor, although Old Earth was still far from being governed by a real world government.
An important project of the New World Federation was the New Ascension, which gave humanity a new perspective by looking into space. In the past centuries, national and international space projects had been undertaken again and again, but the difficult circumstances on Old Earth had always nipped longer-term ventures in the bud. More than one mission to colonise Mars had failed in the past and the Red Planet had become the grave of forgotten astronauts. But with the New Ascension Space Association, which took national and private space projects under its umbrella, everything was to change. As early as the mid-23rd century, NASA succeeded in establishing permanent colonies on Earth's moon, and by the end of the century, Olympus Town, a colony on Mars, had become so successful that NASA even moved its headquarters there in the early 24th century.
NASA had originated as a project of the New League of Nations, but it increasingly became a member of the League in its own right, managing to excite and inspire humanity and also becoming a significant factor economically by tapping into resources in space.
So significant, in fact, that NASA was able to embark on what was perhaps humanity's greatest project: The colonisation of a planet in another solar system.
What we left behind
The world the colonists left behind was far from perfect. Nor was it the united humanity that many an early 21st century dreamer would have dreamt of. But it was a world that, against all odds, had not perished. Humanity had survived the catastrophes it had brought upon itself. With the Pan-Asian People's Republic, the Commonwealth of the Atlantic, Brazil and, last but not least, NASA, there were four dominant great powers. With the Northern European Union, the Iranian Caliphate, India, the Commonwealth of the Pacific and the Korean-Japanese Economic Union, there were five emerging middle powers, and with the African People's Republic and the Slavic Federation, two emerging powers. But also a multitude of failed states and disconnected nations, some in the stranglehold of smouldering civil wars, others in the hands of corporations.
Yes, humanity had survived, but the majority of the 12 billion people on Old Earth lived in poverty. For wars and technological progress had accomplished one thing above all: they had wiped out the middle class almost all over the planet and widened the gap between rich and poor to such an extent that they were no longer two classes, but estates. Presumably, one does not do the matter an injustice if one says that henceforth there were two human races: The poor and the rich.
An Age of Wonders
Nuclear fusion, advanced artificial intelligence, synthetic humans (androids), virtual realities - despite all the disasters that had befallen Old Earth, it was a world of wonders. Advances in medicine, especially in genetics, had transformed the rich segments of the population into a new type of human that lived longer and was superior to biological humans thanks to genetic optimisation. A small caste of rich, optimised people lived at the expense of billions of underclass people and "outcasts" who struggled for daily survival in the slums of the megacities.