20,084,122 people. That's comparable to the population of the country of my birth, Australia, which is slightly higher at 23,401,892.
A variation of this sign has been seen at pro wrestling events over the years, stating that 'if (X Wrestler) wins, we riot'. This version of the sign prophesizes strife that could occur should the climate crisis not be tackled. The result should the world not move be grave for human rights.