8a.nu makes it hard to impossible for you to access and export YOUR data (scorecard). Luckily there is an independent passionate climber who got jack of this and has built a service to export his scorecard from 8a.nu into a CSV file. He has made it freely available for everybody in the Google Chrome webstore:
Sometimes undocumented changes of 8a.nu result in erroneous behaviour of this export tool. Please try a forum or wait for the passionate climber to update his tool.