Challenges
AKA Global Warming, this has been a problem due to pollution of the atmosphere
What is Climate Change
Instead of using a car, you could do this, but it is a bit slower
What is walking
Can be caused by human actions, such as manure in water, fertilizer run off, emissions from cars, etc.
What is Pollution
Greenhouse gasses in the atmosphere trap the sun's heat, causing global warming
What is the Greenhouse Effect