Floods, Urbanization, and Climate Change in China
On 3 September 2020, the State Council Information Office held a regular policy briefing regarding the arrangements that were made at the recent executive meeting of the State Council for flood prevention, disaster relief and post-disaster recovery. Zhou Xuewen, secretary general of the National Flood Control and Drought Relief Command Headquarters, deputy minister of Emergency Management and deputy minister of Water Resources, indicated that since 1998, China has suffered the most severe floods. 751 rivers in 25 provincial regions have experienced floods with major rivers and lakes like the Yangtze River, Yellow River and Lake Taihu visited by 18 numbered floods. China has received 555.6 millimeters of precipitation, almost 10.6 percent more than the average over the past five years. This year's precipitation is the second worst since 1961, exceeded only by 1998 Flood.
The wide-ranging, long-lasting floods have affected 70.4 million people in 28 provincial regions, which increased 17 percent from the five-year average. Direct economic losses caused by the disasters have increased by 27 percent from the five-year average to almost 214 billion yuan ($31.3 billion). However, the death toll or missing in floods decreased 49.8 percent from the five-year average to 271. About 4.7 million people have been evacuated, 47.3 percent more than the average of the past five years. The Ministry of Emergency Management and the Ministry of Finance have distributed almost 1.5 billion yuan of disaster relief funds and about 195,000 disaster-relief materials have also been dispatched to the affected regions.
Sichuan province was particularly seriously affected, for example Leshan City and Jintang County of Chengdu City. Generally speaking, the quality of flood control facilities in many cities is inferior. One of the main problems is rapid urbanization. In 2010, Chen Weizhong, an expert of irrigation, pointed out that the rainfall could not go down through hard surfaced road to become underground water. Due to rapid urbanization, rivers, streams, ponds, and farmland have been occupied and destroyed, which has limited the capacity to channel floodwater.
On 24 August 2020, China Meteorological Administration issued Blue Book on Climate Change in China 2020, which provided the latest monitoring information on the climate change status in China and the whole world from the aspects of atmosphere, hydrosphere, cryosphere, terrestrial biosphere and driving factors of climate change.
The Blue Book indicates that many key indicators of the climate system are taking on accelerating changes. China, as a region susceptible to climate change, is confronted with more extreme climate conditions, pronounced regional differences of precipitation changes, and more days of rainstorm. It boasts a bettering ecological climate but faces more unstable conditions in terms of regional ecological environment.
The global average temperature in 2019 is 1.1℃ higher than that of pre-industrial levels, ranking second since the complete meteorological observation on record. Since the 1980s, every consecutive decade has witnessed warmer conditions compared with the previous one. In 2019, land surface temperature on average in Asia came second since the beginning of the 20th century. From 1951 to 2019, annual average temperature in China had risen by 0.24℃ per decade, with the rate dramatically higher than the global average level in the same period.
From 1961 to 2019, annual average precipitation in China is on mild increase, with more extreme heavy rain events and more days of rainstorm. Precipitation changes in all regions take on noticeable differences. From 1870 to 2019, average global sea surface temperature has notably risen. In 2019, global average sea level is accelerating its rise. The sea level change in coastal regions of China is on volatile rise. The rate is higher than the global average level in the same period. From 1960 to 2019, global mountain glaciers are in melting and retreating condition. The year 2019 is the most intense year of global glacier melt since 1960.
In 2018, the Intergovernmental Panel on Climate Change (IPCC) issued a special report on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways. The scientists remarked that there was emerging evidence of human influence on global atmospheric moisture content and precipitation. According to the Clausius-Clapeyron relationship, the saturation vapor pressure increased approximately exponentially with temperature. It was physically plausible that relative humidity would remain roughly constant under climate change. This meant that specific humidity increased about 7% for a one degree increase in temperature in the current climate.
In 2010, Chen Weizhong warned that in the expansion of urbanization, the cities have reduced their capacity to control floodwaters. Same or lesser volume of rainfalls would lead to more serious consequences. In summary, rapid urbanization makes floods worse. Thus, de-urbanization/de-industrialization is one of the key solutions to deal with climate change and serious floods.
Let the mischief-maker undo the mischief.
1. Hou Liqiang, “Despite floods, casualties half 5-year average”, China Daily, 4 September 2020.
2. “Blue Book on Climate Change in China 2020 rolled out”, China Meteorological News Press, 28 August 2020.
3. “Changes in Climate Extremes and their Impacts on the Natural Physical Environment”, IPCC, https://www.ipcc.ch/site/assets/uploads/2018/03/SREX-Chap3_FINAL-1.pdf