14 2 Climate Science – “Our climate is our future” Prof. Panmao Zhai also emphasised the impact of climate change on cities around the world: • As global surface temperature increases, warming is expected larger over land and in the Arctic and amplified in cities. • Heavy rainfall events are more intense and more frequent in a warming world, and runoff is amplified by urbanisation. • Low-lying islands and coastal areas are facing accelerating sea level rise, where once per century extreme sea level rise is expected to occur annually. The increasing extreme sea level will increase coastal flooding with the potential risk for widespread mortality and damage to housing, transportation, and energy infrastructure. • Most cities will experience increase of local temperatures of 1.5-2ºC earlier than other areas; and cities are the main sources of climate forcers. FIGURE 2.5 Global sea level from satellite altimetry since 1993 100 90 80 70 60 50 40 30 20 10 0 mm 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 2019 2021 2023 Year Satellite altimetry Average trend: 3.33+/-0.4mm/year 4.5mm/year Jan 2013 -Jan 2022 2.1mm/year Jan 1993 -Jan 2002 2.9mm/year Jan 2003 -Dec 2012 Panmao Zhai, IPCC FIGURE 2.6 Past trends in global surface air temperature (1958-2018) with cities reporting significant temperature increases *Urban Warming refers to the difference between local urban temperature change and surrounding warming. Prof. Zhai ended his presentation with a hopeful note – “Our climate is our future”. He emphasized that cities are the sites of innovation. Cities are where mitigation and adaptation plans are reimagined and implemented in the pursuit of the UN Sustainable Development Goals; and that the global community knows what it had to do with cities playing a central role in how societies adapt to a changing climate and to decarbonize.