The document discusses the rise in the number of cars from 1900 to 1997 and how cars impact the environment. It notes that while cars increased from 4,192 in 1900 to over 600 million in 1997, they contribute to greenhouse gas emissions and global warming. The document explores potential solutions like more fuel-efficient vehicles, hybrid cars, electric cars powered by clean energy sources like batteries or hydrogen fuel cells, and solar-powered cars. It provides sources for further information on cars and the environment.