Climate change and sustainable development for cities

Abstract

Under the current background of global warming, extreme weather and climate events, such as heavy precipitation and heat wave events, have increased in most land areas of the world. Meanwhile, in cities, the intensity and frequency of heat waves and heavy precipitation events have further increased as the urban climate has additionally been affected by rapid land surface change, enhanced anthropogenic heat release, and massive aerosol emissions. These enhanced aerosol emissions also deteriorate the air quality, often causing severe air quality problems in cities. The added urbanization effect on global and regional climate change has imposed increasingly serious impacts on the dense population, heavy traffic, vast infrastructure, and economic assets of urban areas. China has experienced much faster warming than the global average from the late of 20st century, especially since 1990. The average warming rate in the seven largest cities (Shanghai, Beijing, Tianjin, Shenzhen, Guangzhou, Wuhan and Chongqing) is higher than the average for China as a whole during the most recent 60 years. The number of hot days with maximum surface air temperatures over 35°C has increased markedly since 1990. In the past two decades, many cities, such as Beijing, Jinan, and Chongqing have experienced extremely heavy precipitation events, causing dozens of fatalities. During the past 50 years, severe air pollution conditions have frequently occurred in many cities over eastern China. In South China, the Huanghe-Huaihe River Basin and North China, increasing trends in the number of haze days are evident. Influenced by global warming, cities in low-lying coastal areas are highly susceptible to sea level rise and the related impacts of sea water encroachment, especially during tropical cyclone and storm surge periods. In cities in northern China and inland areas, climate change-related drought frequently significantly impacts water resources and ecosystem services. In recent years, the issue of urban climate change has received considerable attention in China. Many climate change adaptation strategies have been put into action in cities. Also, urban areas account for about 75% of energy-related CO2 emissions worldwide, and thus play a dominant role in the mitigation of global greenhouse gases. Meanwhile, increased urban climate change and its impacts greatly challenge the social, economic and ecological sustainable development of China's cities. In 2015, the United Nations adopted the 2030 Agenda for Sustainable Development, at the heart of which are 17 Sustainable Development Goals (SDGs). Goal 11, on making cities and human settlements inclusive, safe, resilient and sustainable, directly targets dealing with the challenges brought by urbanization. Many other goals, such as Goal 13 on taking urgent action to combat climate change and its impacts, Goal 3 on ensuring healthy lives and promoting wellbeing, Goal 6 on ensuring access to water and sanitation, and Goal 15 on protecting, restoring and promoting the sustainable use of terrestrial ecosystems, are all related to tackling climate change issues from the perspectives of human security and health, more resilient economies, and ecosystems. Obviously, implementation of these United Nations SDGs brings immediate impetus and new opportunities for climate change responses in cities. In the future, the impacts of global climate change and urbanization are expected to further increase. Cities will face more serious and complicated climate change risks to human health, economic development, and ecosystem services as our expectation of more hazards, higher exposure and vulnerability unfolds. For China, climate change and sustainable development in cities is an extremely prominent issue. However, systematic studies on climate change in cities are very limited, especially in terms of the interactions and mechanisms between global/regional climate change and urbanization processes, high-resolution climate change projections under the consideration of future urban development pathways, impact and risk assessments of climate change in combination with high exposure and vulnerability, and a portfolio of response options and measures for climate change in cities. Effective climate change actions rely on understanding the complexity and uncertainties of future climate change and related risks in cities. Under the framework of sustainable development, following related national green development strategies and polices, taking advantages of science, technology, finance and governance in cities, to actively tackle urban climate change issues, such as enhanced adaptation and mitigation measures, properly selecting development pathways will greatly enhance climate resilience in cities. A series of national actions, such as implementing "low carbon cities" and "sponge cities", and the "Action Plan on Prevention and Control of Atmospheric Pollution", will have co-benefits for climate change responses and sustainable development in cities.