I'm assuming that no big wars happen in the 20th century that necessitate the development of nuclear bombs. What made countries lean to bioweapons anyway?Nuclear weapons do not exist on the scale we are familiar with. Perhaps you can imagine much smaller yields, much bigger bombs.
The real WMDs are the highly developed chemical and biological weapons that most great powers own.
Speaking of nuclear, which forms of energy production are the most popular right now? I can imagine renewables being on top of the scene due to climate change being a greater issue.
Also, if I may ask, how did the climate get even worse than it did compared to OTL?