AFAIK the footer height dynamically changes based on its content. If there’s only 1 line of text, the footer area uses ~75px I’d say. If that’s still too much, a custom CSS plugin or Nirvana’s CSS editor is your friend. The used div’s in its CSS are footer2, footer2-inside and/or site-copyright and add height=EnterAmountOfPixelsYouDesire.
DISCLAIMER: I’m no CSS expert, so fiddle on your own risk 😉