Global warming and climate change have been a growing worldwide concern. Six sources, i.e., transportation, power, buildings, industry, agriculture and forestry, and land use, have been identified as major contributors to the rise of global carbon dioxide (CO2). The mobile industry is seen as a potential enabler to reduce greenhouse gases contributed by these six sources provided that appropriate measures are implemented. On the other hand, the mobile industry itself will also contribute to CO2 emission through network operations, mobile equipments, etc. To meet the requirement of low-carbon economy development, it is necessary to reduce the operation expenditure or energy consumption of mobile networks, while maintaining acceptable quality of service. This conference will explore and explain the scope and challenges of designing, building, and deploying GreenNets. In this regard, the conference aims to establish a forum to bring together research professionals from diverse fields including green mobile networks, system architectures, networking & communication protocols, applications, test-bed and prototype, traffic balance and energy-efficient cooperation transmission, system and application issues related to GreeNets.