Ridesharing helps reduce your emissions!
If you drive a sole-occupancy vehicle you pay 100% of the costs and are responsible for 100% of the emissions.
If you instead have just one passenger riding shotgun your costs and emissions are reduced to 50% per person! It is so powerful yet so simple to do!
Even if you don't regularly commute anywhere, use an online system (like http://www.jayride.co.nz in New Zealand) to share any one-off trips you make. You'll have fun meeting new people, save money and help the environment!