Create variable inside preprocess_page and have it accessible in preprocess_block() ?

Inside my preprocess_page.inc file I have created my preprocess_page() function which obtains the node ID of the currently viewed page.

I need to pass / or have this node ID value accessible inside my preprocess_block() method. Is there a simple way to do this without the use of $GLOBALS?

I figure I could use the drupal variable_set set method but those DB access calls would be serious overhead.

thanks.