carbon cycle

例句：

1. 1. Carbon dioxide is a major greenhouse gas that contributes to global warming.
   二氧化碳是一种主要的温室气体，对全球变暖有贡献。
2. 2.The carbon cycle plays a crucial role in the Earth's climate system.
   碳循环在地球的气候系统中起着至关重要的作用。
3. 3. Carbon sequestration is an important strategy for reducing greenhouse gas emissions.
   碳封存是减少温室气体排放的重要策略。