Copenhagen is making significant strides towards its ambitious goal of becoming carbon-neutral by 2025, having already reduced emissions by 75% since 2005. The city promotes innovative concepts like CopenHill, a ski slope atop a waste-to-energy plant, symbolizing its commitment to reducing greenhouse gas emissions. However, the city may not meet its target by the original deadline, with hopes now set for 2026 or later due to dependence on state aid. Meanwhile, the global focus on sustainable transport systems is shifting towards walkability, aiming to reduce emissions and promote healthier communities through efficient urban design. Air pollution remains a critical health threat, with PM2.5 and ground-level ozone being major contributors to respiratory diseases and other health issues. Cities like Zhenjiang and Qingdao in China are also leading renewable energy initiatives, emphasizing biomass and zero-carbon developments to combat climate change and improve air quality.