Over the 20th century technology has pushed forward in many fields. As there were huge investments needed the public campaigns to support new technology without much further reflection of potential consequences have pulled many western societies into risky technologies. Except the Club of Rome there were very few to question the naïve beliefs that technological change will make societies rich and potentially even more equal. The recent report “Climate Inequality Report 2023: Unequal Contributions to Climate Change” has debunked both of these claims. More flying across the planet, particularly short city hopping, has allowed few persons to reap the benefits of the jet-set world, but contributed to climate change in excessive quantities. This is a fact when we compare major world regions among each other as well as within each country. It has to be the wealthy countries that have to shoulder the biggest share of the costs. It has to be the wealthy that pay higher contributions for their pollution. Society has to reign in technology more than ever before. Moreover, we still have to get the income and pollution distribution organised in a better way. It is not only an implementation challenge, but the major question of the 21st century to repair the damage largely caused throughout the 20th century. 
20th Century
The 20th century has told us many lessons. History does not repeat itself, but it appears that new variants of old themes keep coming back. Slowly passing the century like a movie in decades instead of episodes, we witness socio-emotional tides. The first decade, the 00s intensify the beginning of urban planning and social revolutions. The 10s show the arousal and subsequent extinction of masses of people in trenches. The 20s were described as the Carefree Twenties. In the 30s we observed the rising tides of fascist organisations followed shortly afterwards by the disastrous 40s. After the Shoah and the World War the 50s were fabulous viewed from the U.S. and Western Europe. The 60s propagated sex, drugs and rock n’ roll spreading across continents. The wild 70s became almost inescapable through the continued rise of mass media. The 80s were depicted as the colourful 80s as the 2 previous decades had set the scene for psychedelic colours. The 1990s have been coined as the gay 90s by some. Coming out as a gay person became easier and Western societies more sensitive and open to diversity. The back cover of the recent publication by Aurélien Bellanger “Le vingtième siècle” (The 20th century) speaks of the book as “roman polyphonique virtuose”. I look back on the 20th century as “polyphone” in many respects. It would be an illusion to believe we can only keep the nice sounding harmonies without the tensions or dissonances. 