1% is massive if that 1% is where most people currently live (like in Australia). And 1% is likely to be an underestimate - there are studies suggesting up to 600 million people being forced to relocate within the next century (based purely on rising sea levels - not sure what studies there are around forced relocation due to drought and extreme heat).

https://www.researchgate.net/figure/The-percentage-impacts-o... suggests it could be lot more than 1% too.