Just half a degree Celsius less warming would save economic losses of Chinese railway infrastructure by approximately $0.63 billion per year, according to a collaborative research team from Beijing Normal University and the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.
The study was published in Transportation Research Part D.
The researchers found that the rainfall-induced disaster risk of railway infrastructure has increased with increasing extreme rainfall days from 1981 to 2016.
Limiting global warming to the Paris Agreement target of 1.5°C instead of 2.0°C would significantly reduce the disaster susceptibility of Chinese railway infrastructure to extreme precipitation, according to LIU Kai, the first author of the study. LIU is an associated professor at the Academy of Disaster Reduction and Emergency Management, Beijing Normal University.
"Flood disaster can inundate the railway track, cause failures of the subgrade and track structure. Based on our statistics, a total of 975 historical railway rainfall-induced disasters was reported from 1981 to 2016," LIU said.
The team used a random forest (RF) machine-learning model to calculate the disaster susceptibility and quantify the relationship between susceptibility and precipitation change.
"We found a remarkable increase in the disaster susceptibility of railway lines along the Yangtze River valley." Said LIU. "The disaster susceptibility has increased by 30% during the period 1999-2016 relative to that in 1981-1998."
LIU and her team, in collaboration with Dr. ZHOU Tianjun, a professor from IAP, combined CMIP5, an archive of comprehensive climate models, with socio-economic projections to investigate future climate changes and the accompanying impacts.
The researchers specifically examined extreme precipitation changes under RCP4.5 and RCP8.5 scenarios over three time periods including near term (2020-2039), mid-term (2040-2059), and long term (2080-2099). RCP4.5 and 8.5 scenarios represent a possible range of radiative forcing values in the year 2100 relative to pre-industrial values (+4.5 and +8.5 W/m2, respectively).
They found that 32.0% and 45.0% of land area will be exposed to an increase in the annual average extreme rainfall days of more than 0.5 days by 2050 and 2090 under RCP8.5. The proportion of railway infrastructure with high disaster susceptibility is projected to increase from the baseline period level (1981-1998) of 1.1% to 4.5% by 2050 and up to 12% by 2090 under RCP8.5.
"We extended the projection to the changes in the proportions of railway lines at high risk for specific levels of 1.5°C, 2°C, and 3°C global warming and measure the benefits of mitigation by calculating the avoided impact. The avoided impact, or railway exposure to high disaster susceptibility, would be 90% and 391% if warming was limited to 1.5°C compared to the impact for 2°C and 3°C warming under RCP8.5, respectively," said Prof. ZHOU, the co-author of the study.
Under RCP8.5, with a global average temperature increase of 1.5°C, the direct damage and repair cost could increase to an annual amount of $1.47 billion. With 2°C warming, the damage doubles, and the loss grows to $2.10 billion.
"This study quantifies the influence of the climate change with its associated rainfall change on railway infrastructures in China. The design of newly planned high-speed railway lines should incorporate climate change effects," LIU said.
