Top 20 Cities with Billions at Risk from Climate Change

2005 assets at risk: $84.6 billion
2070 est. assets at risk: $581.7 billion
2005 population at risk: 407,000
2070 est. population at risk: 794,000

A 600-mile "hotspot" along the U.S. Atlantic coast, from Boston to Cape Hatteras, North Carolina, is experiencing sea-level rise at a rate three to four times greater than the global average, according to a study last month in the journal, Nature Climate Change.

Risks to Virginia Beach and the southeast Atlantic coast are detailed in the 2009 government report Global Climate Change Impacts in the United States: "The intensity of Atlantic hurricanes is likely to increase during this century with higher peak wind speeds, rainfall intensity, and storm surge height and strength. Even with no increase in hurricane intensity, coastal inundation and shoreline retreat would increase as sea-level rise accelerates, which is one of the most certain and most costly consequences of a warming climate."

Virginia Beach is just 25 miles from North Carolina, where legislators in June banned state agencies from making any coastal plans or laws based on established scientific sea-level rise measurement until the state's own study is completed in three or four years.

2005 assets at risk: $2.7 billion
2070 est. assets at risk: $601.6 billion
2005 population at risk: 88,000
2070 est. population at risk: 1.9 million

Qingdao could have the highest proportional increase in population exposure to extreme climate events among the cities the OECD studied.

Rain from June through September brings about 75 percent of Qingdao's annual total, with two or three major storms. Flooding in 1990 and 2001 led the city to develop monitoring, prevention and warning systems.

2005 assets at risk: $109.2 billion
2070 Est. assets at risk: $623.4 billion
2005 population at risk: 696,000
2070 est. population at risk: 1.3 million

Since 1959, when a typhoon killed 3,300 people in Aichi Prefecture, where Nagoya is located, city planners have conducted disaster planning to that benchmark.

Nagoya designated parts of its waterfront as a disaster prevention zone. It also sets regulations on floor level for buildings to protect them from tidal waves and other storm disasters.

2005 assets at risk: $26.9 billion
2070 est. assets at risk: $652.8 billion
2005 population at risk: 1.9 million
2070 est. population at risk: 9.2 million

Ho Chi Minh City barely rises above sea level and faces serious flooding risk from tropical storms and typhoons. Growth patterns may be exacerbating the situation, according to a 2010 study by the Asian Development Bank. The bank is funding a $2.5 million project to assist a national program on climate change. Ho Chi Minh City itself has an urban flood-control program and has been attempting to upgrade the drainage systems of its major canal basins.

National and provincial governments have programs to address climate change, but the city still does not have the capacity to analyze and control development, according to Nguyen Quang, Hanoi (Vietnam)-based program manager for the United Nations Human Settlements Program. "They have been lucky so far," said Quang. "They have had some small floods, but not like what happened in Bangkok" last year.

2005 assets at risk: $114.9 billion
2070 est. assets at risk: $825.7 billion
2005 population at risk: 732,000
2070 est. population at risk: 1.4 million

The Netherlands has sea-level sensitivity built into its name, which means "lower lands." This advanced, densely populated nation is among the world's leading innovators in flood protection because it is so vulnerable historically.

Rotterdam, 40 miles from the country's North Sea coast, faces increased flood risk even before climate change is factored in. In the last 50 years, development has increased risk by a factor of seven, according to the Rotterdam Climate Initiative.

The boldly named Rotterdam Climate Proof program expects that by 2025, reinforced flood protections, alternative architecture and city planning and upgraded water and sanitation infrastructure will hedge the city's climate-change risks.

2005 assets at risk: $128.3 billion
2070 est. assets at risk: $843.7 billion
2005 population at risk: 839,000
2070 est. population at risk: 1.4 million

A fierce North Sea storm hit the Netherlands in early 1953, killing 1,836 people and causing 100,000 to be evacuated. The Dutch saw waters top about 150 dykes, their primary defense against rising waters.

Amsterdam's history of flood control is actually hundreds of years older than that. This accumulated knowledge is the foundation for its climate-change adaptation planning, according to a Carbon Disclosure Project report (PDF)on European cities released last month. Richer cities, such as Amsterdam, Rotterdam, Tokyo and London are protected to the level of a 1-in-1,000 year flood, the OECD reports.

2005 assets at risk: $215.6 billion
2070 est. assets at risk: $969.0 billion
2005 population at risk: 1.4 million
2070 est. population at risk: 2.0 million

Osaka has a coastline stretching 230 kilometers (143 miles) along Osaka Bay, where its population and businesses are concentrated.

A 1934 typhoon killed more than 3,000 people, its 18-foot storm surge destroying 43,000 buildings in and around Osaka. More than 200 people died in a 1961 typhoon, which wrecked 15,000 houses.

In the two decades after the 1961 Muroto II typhoon, municipal engineers built embankments, steel barriers, 80 pumping stations and six spillways.

Osaka's storm surge and risk of sea-level rise is exacerbated by land subsidence caused in part by groundwater pumping.

2005 assets at risk: $233.7 billion
2070 est. assets at risk: $1.0 trillion
2005 population at risk: 1.1 million
2070 est. population at risk: 1.4 million

Threats to New Orleans are legend. Subsidence lowers an elevation that is already at or close to sea level. The U.S. Army Corps of Engineers has levied the Mississippi river since the 1930s, pushing its silt into the Gulf of Mexico, where it can't accrete into hurricane-blocking marsh that the city needs. The existing Louisiana marsh was carved up and weakened by generations of industrial canals. Warming waters, rising seas and historical canal-building through marsh has brought a terrible net result: The Gulf swallows southern Louisiana land at a rate of approximately a football field every hour.

Louisiana has spent at least three decades developing plans to protect its southern flank against the Gulf of Mexico. The critical nature of these defenses was brought home by one of the most terrible American tragedies in modern history, Hurricane Katrina in August 2005. Despite advances since then, federal and state authorities still face years of work girding levees and deploying "multiple lines of defense" along the coast.

2005 assets at risk: $9.3 billion
2070 est. assets at risk: $1.1 trillion
2005 population at risk: 299,000
2070 est. population at risk: 3.3 million

A low-lying port in southeastern China, Ningbo could experience the largest proportional risk in assets at risk of all the cities ranked by the OECD. Ningbo, prone to flooding, issued new rules in 2000 and amended them in 2004. Ningbo is the first Chinese city to participate in the World Bank's Climate Resilient Cities program, which helps urban areas assess and address their vulnerabilities to disruptive events and long-term change.

Ningbo means "calm waves" in Chinese.

2005 assets at risk: $38.7 billion
2070 est. assets at risk: $1.1 trillion
2005 population at risk: 907,000
2070 est. population at risk: 5.1 million

This 14th-century-trading-post-turned-tourist-hotspot is often compared to Venice for the intricate canal system incorporated into the Chao Phraya River. Catastrophic monsoon flooding that began in July 2011 caused more than $45 billion in damage throughout the country, inundating the area's auto and technology manufacturing hubs. Water levels reached a depth of six feet in some flooded areas.

2005 assets at risk: $35.9 billion
2070 est. assets at risk: $1.2 trillion
2005 population at risk: 223,000
2070 est. population at risk: 687,000

Hong Kong has more than 450 miles of coastline, made up by the South China Sea on three sides and the Shenzhen River, which helps form its border with Mainland China, to the north. Within Hong Kong's borders are 19 square miles of water, almost five percent of the city's total surface area. Water level in Victoria Harbor rose an average of 28 millimeters per decade from 1954 to 2011.

2005 assets at risk: $174.3 billion
2070 est. assets at risk: $1.2 trillion
2005 population at risk: 1.1 million
2070 est. population at risk: 2.5 million

Tokyo's wealth has helped it establish protection against a once-in-a-millennium flooding event, outpacing measures taken by other top cities, including New York.

2005 assets at risk: $29.6 billion
2070 est. assets at risk: $1.2 trillion
2005 population at risk: 956,000
2070 est. population at risk: 3.8 million

Severe flooding could have a devastating impact on Tianjin's economy, including the fast-growing manufacturing sector that makes up more than half of the city's gross domestic product and includes an assembly plant for Airbus's new A320. The city also has large swaths of farmland and more than 1 billion tons of petroleum deposits.

Tianjin in May issued a flood- and drought-prevention plan that would raise drainage capacity in central areas. The city hasn't experienced severe flooding damage in the Haihe River basin since 1963.

2005 assets at risk: $46.2 billion
2070 est. assets at risk: $1.6 trillion
2005 population at risk: 2.8 million
2070 est. population at risk: 11.4 million

Mumbai, with an average elevation of just 46 feet above sea level, rose from a fishing village to become India's commercial and entertainment capital. Monsoon rains overwhelm its century-old drainage system every year. Almost all drains open out to the ocean and a lack of floodgates means seawater can flow in during high tide. Low-lying pockets of the city get waterlogged, paralyzing trains and traffic and shutting down schools and businesses. The city suffers losses of 15.5 billion rupees ($280 million) per year from flooding, according to a 2007 government estimate.

A 20-year effort to de-silt, widen and deepen waterways, build retaining walls and add pump stations and floodgates is about 50 percent done and may be completed within the next few years, according to a top city engineer.

2005 assets at risk: $72.9 billion
2070 est. assets at risk: $1.8 trillion
2005 population at risk: 2.4 million
2070 est. population at risk: 5.5 million

Shanghai experienced double-digit annual GDP growth from 1992 until the global recession began in 2008. Its position as a financial capital allowed the Yangtze River Delta city to establish flood protections similar to London's -- safeguards not typically seen in developing regions, the OECD said.

Shanghai has a rainy season in the early summer that raises water levels in the middle and lower reaches of the Changjiang River. The city suffered a heavy storm in August 1997 that caused more than 600 million yuan ($94 million) in economic losses and flooded more than 170 roads. Eight heavy storms two years later led Shanghai to build out drainage systems, raise storm drainage capacity to 56 millimeters in central business areas and clean out drainage pipes twice a year.

2005 assets at risk: $32.0 billion
2070 est. assets at risk: $2.0 trillion
2005 population at risk: 1.9 million
2070 est. population at risk: 14.0 million

Kolkata, which has the third-biggest gross domestic product among Indian cities, is situated near Sunderbans, the world's largest delta, and is susceptible to flooding every year during the June-September rainy season. The 140-year-old drainage system in the former capital of British India is among the oldest in the country and covers less than 50 percent of the city.

The Asian Development Bank is helping to finance a $400 million project to upgrade Kolkata's drains and sewers, clean out its canals and relocate squatters living on their banks. The five-year project, originally scheduled to be finished by 2007, is finally nearing completion.

In July 2007, Kolkata was inundated after getting 410 millimeters of rain, about a quarter of its annual total, over three days.

2005 assets at risk: $320.2 billion
2070 est. assets at risk: $2.1 trillion
2005 population at risk:: 1.5 million
2070 est. population at risk: 2.9 million

New York is the second wealthiest city on this list, but protections are only good enough to hold off a once-in-a-century deluge event. That's less than the security for London, Tokyo, Amsterdam and Shanghai, the OECD said.

In a 2006 op-ed piece suggesting reasons for inaction against climate change, Harvard psychology professor Daniel Gilbert once wrote: "No one seems to care about the upcoming attack on the World Trade Center site. Why? Because it won't involve villains with box cutters. Instead, it will involve melting ice sheets that swell the oceans and turn that particular block of lower Manhattan into an aquarium.

"The odds of this happening in the next few decades are better than the odds that a disgruntled Saudi will sneak onto an airplane and detonate a shoe bomb," Gilbert says. "And yet our government will spend billions of dollars this year to prevent global terrorism and ... well, essentially nothing to prevent global warming."

2005 assets at risk: $84.2 billion
2070 est. assets at risk: $3.4 trillion
2005 population at risk: 2.7 million
2070 est. population at risk: 10.3 million

Guangzhou is a top Chinese hub for manufacturing, transportation and trade. It's located on the Pearl River about 75 miles northwest of Hong Kong.

Extreme rains killed at least 86 people in Guangzhou and disrupted the lives of 8 million others in May 2010. The most damaging storm in 30 years cost Guangzhou 540 million yuan ($85 million). It challenged the city's flood-control drainage systems and impaired 256,800 acres of farmland. "This is meteorologically unusual," the city's vice minister for water resources said at the time.

Guangzhou in 2011 issued an emergency plan to effectively defend against floods and storms.

2005 assets at risk: $416.3 billion
2070 est. assets at risk: $3.51 trillion
2005 population at risk: 2.0 million
2070 est. population at risk: 4.8 million

"Unchained Goddess," a 1958 science program produced by Frank Capra, told television viewers that rising carbon dioxide emissions could melt polar ice caps, raise sea levels and inundate Miami under 150 feet of tropical water. That estimate was ludicrous but southeast Florida is nonetheless on the front line of climate change. Hurricane Andrew caused $25 billion in U.S. damage in 1992 from wind and storm surge, prompting a revision of building codes and storm water-management plans.

Miami-Dade County is working with four other counties in the southeast portion of the state to agree on likely impacts and potential responses to climate change.

The City of Miami, which includes the downtown financial district, isn't currently part of that process. Heavy storms already cause flooding along Brickell Avenue, a hot spot for condo development alongside Biscayne Bay that hosts such international banks as Banco Santander and JPMorgan Chase & Co. That area will be among the most vulnerable as sea levels rise.