CO2 can add an unpleasant prickle to real ale, though this is usually only evident when top pressure is used. Real Ale is normally hand-pumped. The former is OK, the latter may not be. Real Ale is usually drawn by handpump from the barrel because there is insufficient pressure in it to propel the beer from inside. Hence, the beautiful sight of a set of ornamental handpumps sprouting from the bar of many British pubs.
Electric pumps are fine too, as long as they draw the beer from the cask.
Many Real Ales are dry-hopped. Unfiltered, naturally carbonated beer completes its fermentation in the bottle, and forms sediment. Next, hold the glass up to your nose and take a good sniff - enjoy the blend of hop and malt aroma. Make a note of the beer if you like it - so you can ask for it by name at the pub, restaurant or beer store. Finally, talk to someone about what you have just seen, smelled, tasted and felt - share your experience.