Think of all the buses in all the cities, in the world right now. Chicago, New York, San Francisco, Paris, Hong Kong. THOUSANDS of them. If everybody rode their bike instead, yes, it would make a difference. Just you? Not so much.

Basically, switching from using a bus to a bike does indeed have a real effect on the environment, but this is only seen if the majority of people using buses for transportation switch to using bikes to get around.

If 1 person decides they will change the environment by driving to work on the bike, they might boost their self confidence, but they will only change a small portion of the effects of carbon emission if they drive the bike for maybe hundreds of years. Riding the bike for 1 week is useless, unless stated as above, many people decide to change their ways and all chip in to save the environment.

Of course. While one person riding a bike instead of taking the bus is not a huge impact, every little bit helps. Your weight is no longer on a bus so the engine doesn't work as hard to move you from point A to point B.

This would result in a slight emissions reduction from the bus. The biggest impact would be if others followed your lead. If many people opted for the bike option over the bus option, there would be a huge reduction in bus emissions. A side benefit is that biking is much healthier than riding a bus.

Yes, if applied on a large scale. In the next 20-30 years we might see a much larger "bike population" in detriments of cars; for faster travelling there will be special trains available and also commercial airlines.