20वीं सदी की शुरुआत से पृथ्वी के तीव्र जलवायु परिवर्तन का मुख्य कारण किसे माना जाता है?

Prolonged exposure to extreme cold temperatures may result in tissue damage known as frostbite, which is categorized as a:

In the context of ecosystem energy dynamics, which of the following expressions correctly defines Net Primary Productivity (NPP)?