Do you have quite a few pages which you want to remove from Google index without using the page removal tool for each URL? According to Google’s John Mueller, you can attempt 404 and noindex all pages which you want to remove before submitting a temporary sitemap to Google. According to him, this might speed up the process.
In a Google Webmaster Help thread, Mueller wrote, “One way to speed this up could be to submit a temporary sitemap file listing these URLs with the last modification date (eg, when you changed them to 404 or added a noindex), so that we know to recrawl & reprocess them.” “This is something you’d just want to do for a limited time (maybe a few months), and then remove, so that you don’t end up in the long run with a sitemap file that’s not needed by your site,”.
Therefore, if you want to remove a lot of pages within a short time period, you can try this method. Other search experts are however not sure how quick the page removal process will be. It might take a few days, weeks or even months to remove all the URLs.