According to The Telegraph, the box asks users to ‘start using your full name on YouTube’.
Users are not obliged to accept the suggestion, but if they decline they will have to tell Google why they don't want to use their real name, they report.
Google said it began implementing the change last month to give users ‘the option’ to use their Google+ identity on YouTube.
According to the report, if users do choose to link their accounts they will have the option to review their past comments and disassociate themselves with anything they find embarrassing.