Climate change and cities are deeply connected. Cities are one of the greatest contributors and likely best opportunities for addressing climate change.[2] Cities are also one of the most vulnerable parts of the human society to the effects of climate change,[3] and likely one of the most important solutions for reducing the environmental impact of humans.[4][2][3] The UN projects that 68% of the world population will live in urban areas by 2050.[5] In the year 2016, 31 mega-cities reported having at least 10 million in their population, 8 of which surpassed 20 million people.[6] However, secondary cities - small to medium size cities (500,000 to 1 million) are rapidly increasing in number and are some of the fastest growing urbanizing areas in the world further contributing to climate change impacts.[7] Cities have a significant influence on construction and transportation—two of the key contributors to global warming emissions.[8] Moreover, because of processes that create climate conflict and climate refugees, city areas are expected to grow during the next several decades, stressing infrastructure and concentrating more impoverished peoples in cities.[9][10]
In the most recent past, increasing urbanization has also been proposed as a phenomenon that has a reducing effect on the global rate of carbon emission primarily because with urbanization comes technical prowess which can help drive sustainability.[15] Lists of high impact climate change solutions tend to include city-focused solutions; for example, Project Drawdown recommends several major urban investments, including improved bicycle infrastructure,[16] building retrofitting,[17]district heating,[18] public transit,[19] and walkable cities as important solutions.[20]
Because of this, the international community has formed coalitions of cities (such as the C40 Cities Climate Leadership Group and ICLEI) and policy goals, such as Sustainable Development Goal 11 ("sustainable cities and communities"), to activate and focus attention on these solutions. Currently, in 2022, there is a deterioration in the progress of the goal. There is limited progress on making cities and human settlements more appropriate to live in Sub-Saharan Africa, Latin America and the Caribbean and the Pacific Island countries. There is fair progress in Central and Southern Asia and Eastern and South-Eastern Asian. However, it has been achieved in Developed countries.[21]
^Bazaz, Amir; Bertoldi, Paolo; Buckeridge, Marcos; Cartwright, Anton; de Coninck, Heleen; Engelbrecht, Francois; Jacob, Daniela; Hourcade, Jean-Charles; Klaus, Ian; de Kleijne, Kiane; Lwasa, Shauib; Markgraf, Claire; Newman, Peter; Revi, Aromar; Rogelj, Joeri; Schultz, Seth; Shindell, Drew; Singh, Chandni; Solecki, William; Steg, Linda; Waisman, Henri (2018). Summary for Urban Policymakers – What the IPCC Special Report on 1.5C Means for Cities. Indian Institute for Human Settlements (Report). doi:10.24943/scpm.2018. Archived from the original on 15 January 2023. Retrieved 11 November 2020.
^Wang, Yuan; Zhang, Xiang; Kubota, Jumpei; Zhu, Xiaodong; Lu, Genfa (1 August 2015). "A semi-parametric panel data analysis on the urbanization-carbon emissions nexus for OECD countries". Renewable and Sustainable Energy Reviews. 48: 704–709. Bibcode:2015RSERv..48..704W. doi:10.1016/j.rser.2015.04.046.