If you visit Google website right now, and if you click on "Google", you will enjoy some animations and then if you click again, that will lead you to a page where you can see the top trending topics on Google in the year 2014.
You can check the trending topics by country or just see it globally and the top 5 globally trending topics on Google for the year 2014 were as follow:
1. Robin Williams
2. World Cup
4. Malaysia Airlines
5. ALS Ice Bucket Challenge