二氧化碳的含量比以往上升了许多英语怎么说

The concentraation of carbon dioxide has been increasing, comparing with the past.

Possible solution:
1. to control the CO2 emission from plants and exceeding a certain amount may be charged.
2. to grow more green plants.
3. to discover new clean fuels to replace those comprise carbons.
4. reducing the use of vehicles, especially private cars