Final answer:
The 1997 Kyoto Protocol's main goal was to reduce greenhouse gas emissions in an effort to combat global warming. As an international treaty, it set legal obligations for participating countries, though not all key nations ratified it, challenging its overall efficacy.
Step-by-step explanation:
The main goal of the 1997 Kyoto Protocol was b) Reducing greenhouse gas emissions. Developed under the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol was an international treaty that aimed to combat global warming by imposing legal obligations on participating countries to reduce their emissions of greenhouse gases. Global warming is a significant concern for biodiversity and human societies, and since emissions do not adhere to national borders, international cooperation is crucial. Although the Kyoto Protocol was a milestone in international efforts to address climate change, enforcing it proved challenging as some key countries like the United States and China did not ratify the treaty. As a result, while some countries exceeded their reduction goals, the collective international effort to curb greenhouse gas emissions still requires significant progress.