Extreme weather events, such as heavy rainfall, flooding and heatwaves, have been described as the “new normal” for China.
The country lost almost 12bn yuan ($1.65bn) due to heavy rainfall and floods in April – “the worst in 10 years”. In June, dozens of people were killed and some 33 rivers in China “exceeded warning levels”. The floods in Guilin, capital city of Guangxi province, were the largest in the area since 1998.
It has been less than a year since the Beijing meteorological service recorded 745mm of rain in just five days during July 2023 – roughly the same amount the city usually receives in the whole month.
The province surrounding Beijing, Hebei, also had heavy rainfall at the same time. In July 2023, the county of Lincheng recorded more than one metre of rain, twice its annual average.
In July 2021, Hebei’s neighbouring province Henan had a “one-in-a-thousand-year” rainstorm.
While China has issued more policies to improve its emergency response system and infrastructure, the increasing number of extreme weather events continues to pose challenges.
In this Q&A, Carbon Brief looks at the reasons for China’s recent floods, how the country is adapting and whether it will need to re-examine and future-proof its flood defence systems.
- What are the reasons behind the recent floods?
- What role does human-caused climate change play?
- How is China adapting to increasingly frequent flooding?
- How effective are these measures?
- What can China learn from other cities?
What are the reasons behind the recent floods?
There are various factors behind the frequent heavy rain and flooding in recent years.
Dr Oliver Wing, honorary research fellow at the school of geographical sciences, University of Bristol, tells Carbon Brief that “on the whole, we expect a warming world to be a wetter world due to the Clausius-Clapeyron relationship”.
This relationship dictates that the air can generally hold around 7% more moisture for every 1C of temperature rise, meaning rainfall is likely to be heavier in a warmer climate.
Wing notes that “for sub-daily rainfall, we are seeing even greater scaling than this relationship would suggest. This makes surface water flooding in cities [more likely] due to short-duration, intense, localised rainfall increase”.
In addition, he says, “warming is inducing a rise in sea levels in most places, meaning storm surges have a higher baseline from which to inflict damage”.
In China, “higher than normal temperatures” were behind frequent heavy rainfall in southern coastal provinces, such as Guangdong and Guangxi, since April, says Zheng Zhihai, chief forecaster at the National Climate Centre of the China Meteorological Administration (CMA), and reported in China Daily.
Zheng adds that the El Niño-Southern Oscillation – a natural climate cycle that entered its warmer El Niño phase in mid-2023 – was partly to blame because it raised sea surface temperatures and directed vast amounts of water vapour from the South China Sea and the Bay of Bengal towards southern China.
Dr Faith Chan, head of the school of geographical sciences at the University of Nottingham Ningbo China, tells Carbon Brief that the rainfall pattern in Guangdong during this April was quite similar to the intensive rainstorm on 6-8 September in 2023 after Typhoon Haikui.
Specifically, the intense rainfalls were generated by the low-pressure moist current from the south-east and south Asian monsoon pattern crashing into another low-pressure rain belt from the Philippines and the west Pacific.
Typhoon Haikui had hit Hong Kong with the worst storm in 140 years and caused some of the heaviest rains in the provinces of Guangdong and Fujian.
While these intense rainstorms, in a meteorological sense, are not unusual, they are happening more closely to one another owing to the warming world, Chan says.
Large-scale heavy rainstorms typically occur three times on average in April – the onset of a monsoon season. But, this year, China has been battered by at least eight regional extreme rain events in the month alone, all happening in quick succession.
River floods are commonly seen in the affected regions, such as Chongqing and Hunan. Identifying the causes can be more complicated for river floods in general, says Wing:
“There are many modulating factors. Drier soils in a warming world may enable the land to absorb the increased rainfall, thereby mitigating any flood hazard increase. Many floods are not driven by intense rainfall, but are driven by snowmelt or low-intensity, long-duration rain falling on saturated soils. For this reason, it is not reasonable to extrapolate that increased rainfall in a warming world will lead to increased fluvial flooding.”
Chan says natural reasons “of course” enhanced the wetness, “but human-induced climate change led to the greenhouse effect and caused sea temperature to rise, which caused more storms and low-pressure rain belts. That is a fact”.
Wing agrees that “the thermodynamic impact” of human-led climate change increases the rainfall associated with storms. But, he adds:
“What we do not understand well is how anthropogenic climate change has altered the dynamics of the climate system, and where and how this either compounds or dampens the thermodynamic response.”
What role does human-caused climate change play?
Many studies have found that warmer sea surface temperatures are supercharging high-impact, back-to-back extreme rains.
The sixth assessment report (AR6) from the UN’s Intergovernmental Panel on Climate Change (IPCC) also says that human-induced climate change caused by greenhouse gas emissions contributes to ocean warming and “is likely the main driver of the observed global-scale intensification of heavy precipitation over land regions”.
In east and central Asia, under 1.5C of global warming, extreme annual daily rainfall (Rx1) and five-day accumulated rainfall (Rx5) events are projected to increase by 28% and 15%, respectively, relative to 1971-2000, according to AR6.
Similarly, it says that in China’s urban agglomerations, “an increase in global warming from 1.5C to 2C is likely to increase the intensity of total precipitation of very wet days 1.8 times and double maximum five-day precipitation”.
Prof Yang Chen of the Chinese Academy of Meteorological Sciences at the CMA tells Carbon Brief that human-caused intensification of heavy rainfall over China had been even larger than expected. He explains:
“Human-caused intensification of heavy precipitation over monsoonal China is markedly larger than expected from increases in atmospheric moisture due to warming, because of stronger feedback between latent heat releases and ascending motion within wetter storms in a warmer climate.”
Such feedback, he adds, is particularly evident in eastern China compared to other regions of similar latitudes.
A recent study in Nature also anticipates storm activity over China to become more frequent and intense as a result of warming. By the end of the 21st century, the annual average frequency of tropical cyclones on the east coast of China is anticipated to increase by 16% compared to the present day, according to the study.
Apart from climate change that is caused by human activities, poorly designed and constructed cities, as well as subsidence – caused by groundwater extraction, the weight of buildings as result of urban growth, urban transportation systems and mining activities – could also amplify floods.
Dr Kevin Smiley, assistant professor from the department of sociology of Louisiana State University tells Carbon Brief:
“Climate change is increasing the severity and frequency of extreme weather. Extra rainfall induced by climate change can be the difference between a building’s parking lot hosting puddles on a rainy day compared to floodwaters crossing the threshold of the building and causing thousands of dollars of damages.
“It’s always important to remember: climate change is anthropogenic, so this increased risk also has human-caused roots.”
How is China adapting to increasingly frequent flooding?
China has built a number of large water projects to prevent flooding, such as the south-north water transfer projects in the Yangtze river that was launched in 2002.
In the most recent “national water network construction planning outline” published by the State Council – China’s top administrative authority, the equivalent of central government – constructing “national water networks” by 2035 is among the “backbones” of future flood prevention.
The “backbones” in the document also include large hard-engineered structures on the main rivers, such as embankments, flood gates and channelised river networks, to mitigate flood risks.
Meanwhile, a study published in the journal Ocean & Coastal Management found that “nature-based solutions” have also become popular in China. The restoration and conservation of freshwater swamps, mangroves and wetlands along coastlines and river mouths are being used to provide a buffer for tidal and storm surges.
They include the Chongming Island wetland in Shanghai (Yangtze delta) and the Futian and Mai Po wetlands in Shenzhen Bay (Pearl River delta).
Another concept proposed in the planning document is to “accelerate smart development” by using the internet, data and technology to monitor and prevent floods.
The capital Beijing has incorporated data from high-definition cameras, as well as telescopes, radar maps and satellite cloud images to provide real-time hazard updates, which has improved emergency response times.
Ningbo, a port city on China’s east coast, has worked with mobile companies to analyse big data and disseminate information.
The Ministry of Emergency Management said these measures have reduced the number of deaths and missing people as a result of natural disasters by 54% over 2018-22, compared to 2013-17. The death toll continued to fall in 2023 but the number of destroyed buildings and direct economic losses rose by 97% and 13%, respectively, compared with 2018-22 levels.
In 2015, the sponge city programme (SCP) concept was written into a policy document of the Ministry of Housing and Urban-Rural Development. It was promoted across the country and 30 major cities, such as Wuhan (home to 11 million people) and Zhengzhou (home to 10 million people), were chosen to be the pilot cities.
Those sponge cities are designed to collect, purify and re-use at least 70% of the floodwaters through “green-blue facilities”, such as green roofs, permeable pavements and stormwater parks, in urban areas. The overall system was meant to resolve the issues of urban heating, freshwater scarcity and flooding all at once.
China has improved its recovery process too. In Ningbo, for example, flood victims were able to access financial compensation within an hour, using an improved online documentation process during Typhoon In-Fa in 2021.
How effective are these measures?
Chan tells Carbon Brief that China has “done very well in terms of preparation, response and recovery for flood and drought hazards” – the two most destructive types of natural disasters.
“As a global south country,” he says, referring to China as a developing country, “China has done quite well with the SCP [sponge cities programme] and the ecologically enhanced solutions for addressing climate change”.
However, Wing argues that nature-based solutions, such as SCP, can “get saturated quickly” and so “there’s a risk of their role being overstated”. He continues:
“These types of interventions are most effective for rainfall events which occur relatively regularly at low intensities. They will be quickly overwhelmed during the very intense, rare rainfall events (whose probabilities are changing rapidly in a warming world) that cause the most damage and suffering.”
In 2021, a “historically rare” rain and flood, that affected more than 14 million people and killed 398 in Zhengzhou, a showcase sponge city, highlighted the limitations of the SCP in the face of climate change.
SCP is designed to only withstand one-in-30-year rain events, says the Nature study. On top of that, it can create a false sense of security, which encourages more people to move to high-risk areas, leading to an increase in population and assets in exposed areas that require ever-increasing protection in a cycle referred to as a “levee effect”, says Chan.
The levee effect refers to the paradox whereby the construction of a flood-defence levee leads to a lowered perception of flood risks and a greater likelihood of property owners investing in their property, increasing the potential damages should the levee breach.
The effect, according to the Nature paper, is a key challenge in the densely populated Yellow River delta and Pearl River areas, which both face high risks of flooding.
Smiley says:
“Risk is realised when social vulnerabilities intersect with hazards. Vulnerabilities are social. Flood impacts are greater when social vulnerabilities are greater…Social vulnerabilities are uneven. A household with some wealth and good insurance can recover from a flooding event much faster and more successfully than a household living paycheck-to-paycheck.”
The Chinese government has allocated more than one trillion yuan ($138bn) – via a special government bond – to support the vulnerable citizens and reconstruction of areas hit by natural disasters in March this year. More than half of the funds are used for “the construction of water conservancy projects like flood control,” reported state media outlet the Global Times.
But the delivery of financial support has been questioned in the past. When Typhoon Doksuri hit China in 2023, only $2bn out of roughly $25bn in aggregate losses were underwritten, according to global reinsurer Munich Re.
In addition, the construction of those sponge cities has already cost China 1.5-1.8bn yuan ($210-250m) between 2015 and 2018. And maintenance will make this bill even larger.
The authors of the Nature paper suggest that the government should work on integrating fragmented “grey infrastructure” – built structures such as drains, pipework and pumping stations – into existing green-blue facilities, but should not rely on engineered infrastructure alone.
Dr Lele Shu, a researcher at the northwest institute of eco-environment and resources, Chinese Academy of Sciences, tells the Intellectual magazine that “the [impact of] heavy rain at the current rate cannot be mitigated through traditional engineered approaches alone”.
“Everytime there is heavy rain, the damage it causes will make headlines primarily because there are too many people living in the city,” adds Shu.
The lack of coordination between regional governments and municipalities in flood prone areas also often led to fragmented approaches to disaster management.
In the case of the Yangtze and Pearl deltas, there is a lack of delta-wide plans that “systematically zone land and prioritise investments within one unified hydrological system”, the Nature study adds.
Dr Zheng Yan, a researcher at the Research Institute of Eco-civilisation, China Academy of Social Sciences, noted in the aftermath of the 2023 Beijing flood that government bodies often look after their own jurisdiction and aim only to move the problem and divert the floods quickly, which piled pressure on cities in downstream areas.
Smiley says:
“Floodwaters don’t care about human-created boundaries by municipality, district or province. Effective urban design in one locality may lessen flood risk there, but indirectly increase risk elsewhere. Thinking collectively while centering justice means providing spatially extensive and locally attuned solutions that help all recover effectively instead of exacerbating inequalities.”
What can China learn from other cities?
As flooding is a challenge faced by cities across the world, there is a plethora of ideas and technologies that China can draw on.
The Nature paper suggests that the Yangtze and Pearl deltas, for example, could learn from the Ganges-Brahmaputra-Meghna delta and the Mekong delta to “improve their responses to regional challenges such as subsidence and erosion, by using and aligning with the underlying dynamics of the deltas that are rapidly changing in response to climate change and anthropogenic activities”.
Building a resilient society that is “proactive and forward-looking, with adequate capabilities to limit detrimental flooding impacts and timely return to the pre-disaster state” is also advocated by the paper.
Rotterdam, a Dutch delta city of 600,000 people that is surrounded by water on four sides, has built water storage facilities, such as an underground parking garage with a basin the size of four Olympic swimming pools. It has also installed green roofs and facades to absorb rainwater.
Japan has built an intricate network of concrete tunnels and vaults about 14 storeys beneath the Saitama prefecture in the outskirts of Tokyo, Japan’s capital city, that can hold more than 1,000 Olympic pools of rainwater.
Both cities’ underground flood diversion facilities are often used as a prime example of a viable flood defence system for urban cities on the frontline of climate change.
Hong Kong has a similar underground stormwater storage system beneath the sport pitches of the Happy Valley Racecourse, designed to withstand once-in-50-years flood events.
However, Chan says it is difficult to compare flood mitigation measures as each city is very different in terms of geography, demographic, densities and topography.
He tells Carbon Brief:
“But in my opinion, China’s megacities should think about using underground spaces to store the sudden extreme discharge from super intensive rainstorms…Tokyo and Rotterdam are quite wise (in that regard) for using their underground spaces.”
The post Q&A: How China is adapting to increasingly frequent flooding appeared first on Carbon Brief.
Q&A: How China is adapting to increasingly frequent flooding
Claver Gatete is Executive Secretary of the UN Economic Commission for Africa. Jason Veysey is Energy Modeling Program Director and Senior Scientist at the Stockholm Environment Institute. Lisa Sachs is Director of the Columbia Center on Sustainable Investment at Columbia University.
The case for global energy transition has rarely been clearer. The closure of the Strait of Hormuz earlier this year exposed the cost of unplanned, fossil-dependent systems, while the falling cost of renewables, the rising penetration of electric vehicles, and the growing value of demand flexibility have made the direction of travel obvious. The benefits of a clean, secure, integrated system are no longer in dispute. What remains unclear is how to build it.
Countries around the world have called for faster renewable energy deployment and alternative energy arrangements. A secure, affordable, resilient, decarbonised system requires specific investments in specific places in a specific sequence, optimised across sectors and borders. But very few governments have the analytical foundation to translate those imperatives into investment.
The two instruments that are supposed to determine investment priorities for decarbonisation – Nationally Determined Contributions (NDCs) and country platforms – cannot answer the most basic question facing any country undertaking an energy transition: what should the energy system look like?
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To close this gap, every country needs a bankable, economy-wide optimisation model for its energy system. A model is not a plan, but it can help answer the critical question of what the future energy system should look like. It shows how optimal scenarios vary as assumptions and policies are adjusted, calculates investment requirements and sequencing, and quantifies how system costs are affected by assumptions, policies, and exogenous variables like trade policy and financing terms.
Tool for efficient investment
Optimisation is a simplified way of simulating an energy system, but it can be an extremely powerful tool for moving energy planning from reactive (how do we manage the disparate actions in the energy system?) to intentional (what energy system underpins our national objectives?). A model can show how optimal scenarios vary as assumptions and policies are adjusted, and how investment requirements are quantified and sequenced.
Optimisation models can treat the energy system and the sectors it serves as an integrated whole, optimising across sectors and projects in ways that can be mutually reinforcing. If considered independently, growth in industrial demand, transport electrification, and digital infrastructure can add stress to the energy system. But an optimised plan can arrange these and other changes in an efficient, synergistic way.
Two to tango: How governments can unlock private investment for national climate goals
New load can be added where low-cost power is available; industrial customers can ensure the viability of investments in energy supply; electric vehicle charging policy can smooth load curves and reduce costs for all consumers.
Additionally, optimisation modeling can also change the financeability of investments. Taken alone, each project faces uncertainty about the rest of the system, which raises the cost of capital and causes projects to stall or unwind after contracts are signed. A coherent, optimised plan makes visible the coordination that private capital would otherwise have to bet on: identified offtake, sequenced and committed transmission, contracted power supply, and so on.
What COP31 and COP32 should do
The upcoming COPs in Turkey and Ethiopia can shift the center of gravity of international climate cooperation from fragmented commitments to planning. Three moves are urgently needed.
First, optimised, economy-wide, long-term energy system planning must be the foundation on which any meaningful NDC, country platform, or finance commitment rests. NDCs are typically drafted by environment or single-line ministries, with limited cross-sectoral input from ministries of energy, finance, and planning. They contain targets, derived from sectoral strategies or national commitments, not from an analytically grounded picture of what the energy system should look like and what investments would make it work. Country platforms are generally a portfolio of investments assembled from existing project pipelines, rather than derived from a system-level analysis of what an optimised, decarbonised energy system would require.
Second, recognise regions as a key planning unit. Modern integrated energy systems are inherently regional. Renewable endowments are unevenly distributed; balancing variable supply across borders lowers aggregate cost, reduces redundant backup capacity, and unlocks economies of scale no individual nation can achieve. Many energy investments in Southeast Asia, East Africa, Southern Africa and Central Asia may only be financeable in a regional context. Assessing domestic infrastructure without regional optimisation perpetuates the perception that decarbonisation is more expensive than it is.
COP31 leaders unveil global targets, with spotlight on electrification
Third, finance the planning capacity. A coordinated commitment by multilateral development banks, bilateral donors, and philanthropic partners to help every region and its constituent countries develop and maintain their own modelling capability, with open-source tools and regional analytical hubs, would close the most consequential gap in the current architecture. The cost is small relative to current spending on country platforms, failed project preparation, and misallocated infrastructure investment.
This includes supporting regional institutions such as the ASEAN Centre for Energy, the African Energy Commission, regional power pools, and the Latin American and Caribbean Energy Organization to determine what optimised regional systems require. Country-by-country pledging, repeated at every COP, will not deliver what meaningfully integrated systems can.
The 2026 energy crisis made the cost of unplanned, fossil-dependent systems newly visible. That window of clarity will close. The international community should seize the moment to build the planning foundation that has been missing for thirty years, rather than commissioning another round of NDCs or pledges, striving for outcomes neither was designed to deliver.
The post Every country needs a model to help optimise its energy transition appeared first on Climate Home News.
Every country needs a model to help optimise its energy transition
The world is currently experiencing what is expected to become the strongest El Niño on record – dubbed a “super El Niño” by many.
El Niño is the warm phase of a recurring climate pattern in the tropical Pacific that releases heat from the ocean into the atmosphere.
This temporarily raises global temperatures and reshapes rainfall and extreme weather around the world – impacting the lives of billions of people.
The current El Niño event began in June and is expected to last into 2027.
El Niño is part of a wider climate pattern called the El Niño-Southern Oscillation (ENSO) cycle.
The ENSO cycle also has a cool phase, known as La Niña, as well as a “neutral” phase. El Niño and La Niña events typically last between nine and 12 months, but can go on longer.
Below, Carbon Brief explains how the ENSO cycle works, its impacts on extreme weather and global temperatures and why this El Niño event is projected to be the most intense since records began.
The post Explainer: How the ‘super El Niño’ will reshape the world’s weather appeared first on Carbon Brief.
https://interactive.carbonbrief.org/el-nino-explainer/index.html
The second-largest reservoir in the US reached a record-low water height on Saturday – just days after the country’s largest reservoir broke its own record.
Both Lake Mead and Lake Powell are located on the Colorado River.
They provide water for populations across seven US states in the south-western US, with around 40 million people getting some or all of their municipal water from the Colorado River.
The river also provides water for around 5.5m acres (22,258 square kilometres) of farmland across Colorado, Arizona, California and the other states in the river basin.
Experts tell Carbon Brief that climate change, population growth and over-consumption are all contributing to the current record-low levels of the reservoirs.
Record lows
At full capacity, Lakes Mead and Powell can hold a combined 68 cubic kilometres of water – enough to supply all household consumption in the contiguous US for nearly 1.5 years. However, the water level in both reservoirs has been declining for decades.
The chart below shows the water level of Lake Mead, in metres above mean sea level. The reservoir, which began to fill in 1935 following the construction of the Hoover Dam, has a “full pool” maximum capacity of 347.60 metres. The water level in Lake Mead reached a record low of 317.11 metres on 7 August.
The following chart shows the water level of Lake Powell, in metres above mean sea level. Lake Powell’s full-pool level is 1,127.76 metres.
While the reservoir reached its maximum capacity several times in the 1980s, it has not done so since. On 15 August, the water level in Lake Powell was recorded at a new record-low of 1,072.87 metres.
Both reservoirs have continued to decline in the days since breaking their respective records. The downward trend will largely continue in both lakes until next spring, when the snowpack in the mountains of the Upper Colorado River Basin begins to melt, says Dr Jack Schmidt, a senior research scientist at Utah State University’s Center for Colorado River Studies. He tells Carbon Brief:
“The big dilemma of the moment is that we’re only in the middle of August, and we have no assurance of what the coming winter will be. The only thing we can be sure of is that we will be depleting overall total basin reservoir storage from now until, roughly, early April.”
Compounding factors
The record lows across the two reservoirs are the result of several compounding factors, experts tell Carbon Brief.
Since the turn of the 20th century, the amount of water flowing along the Upper Colorado River has declined by about 20%. Research suggests that half of this decline can be attributed to human-induced climate change.
Most of the river’s streamflow comes from the snowpack of the Upper Colorado River Basin, which stretches across five western US states but is primarily located in Colorado and Utah.
This region has been gripped by a historic “megadrought” for more than a quarter of a century. Nearly half of the megadrought’s intensity over 2000-18 is attributable to climate change, according to a 2020 study.
At the same time, the increasing population in the US south-west has put added pressure on the Colorado River’s water supply. The number of people obtaining some or all of their water from the Colorado system has grown by 15 million (around 60%) since 1992.
Schmidt tells Carbon Brief:
“There’s an ultimate cause of the present water crisis, and there’s a proximate cause. The ultimate cause is a warming climate, a warming planet and a pretty clear correlation between warming conditions and decreased runoff in the Colorado River Basin.
“The proximate cause is that in this messy democratic republic of ours, big policy decisions that match the variability of the climate occur painfully slowly – with intense political negotiations – and only incrementally.”
On 31 July, the US Bureau of Reclamation, which manages water resources in the western US, released an environmental impact statement on its proposed post-2026 strategy for managing Lakes Powell and Mead. The strategy itself has not been released yet.
Schmidt notes that the statement does appear to give the Bureau flexibility to “respond to crisis” by reducing the delivery of water to several states. However, he adds:
“They acknowledge it won’t work if we just stay critically dry, and of course every climate model for the 21st century, especially with a continually warming planet, says that that’s exactly what’s going to happen.”
The post Analysis: The two largest reservoirs in the US have hit record-low levels appeared first on Carbon Brief.
Analysis: The two largest reservoirs in the US have hit record-low levels
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