Can you batch-change all authors in the CP?
There's currently no way to do so natively in the CP, but there is a round-about way to do it using a CSV file with a pair of indispensable plugins from Bob Olde Hampsink:

Import
Export

Do the export/import 2-step

Use the Export plugin to spit out just the Title and Author from the section you want. Open up the resulting CSV file in whatever editor you want, you don't necessary have to use Excel or OpenOffice in this case since it's just text.

Do a find/replace on the author with the new author. Save the file.

Open up in the Import plugin, and again, tell it what section you want and to replace the data. On the next screen, confirm Title and Author are already selected for you. Title should be checked as how to match up the data. Run the import.


You're basically telling the plugin to leave everything alone except to replace the Author and use the Title (which we exported before) as the source.
Rinse and repeat with as many sections you have.