World at riskGlobal hazard trends

Hazard trends (1)

Hazard trends, 1900–2005

Hazard trends (2)

• The graph on the last slide shows that the number of reported disasters has

risen significantly in recent years.• Part of this rise is likely to be due to more accurate recording and better

communications with isolated regions.• Note the rapid rise since around 1960, when satellite remote sensing and global

communications began.• Population growth has led to more people living in potentially hazardous

locations. This means there are greater numbers at risk.• Many of these people at risk live in the developing world, and are vulnerable

due to their low coping capacity.

Hazard trends (3)

Number of natural disasters by type, 1970–2005

Hazard trends (4)

• Some types of disaster show clearer trends than others.• The graph on the last slide compares trends in three disaster types.• The trend for earthquakes is fairly stable. There is no evidence that the

number of earthquake events is increasing. There are likely to have been more

people in earthquake-prone areas in 2000 than in 1980, and this would explain

the slight rise in disasters.• There is a clearer upward trend for floods and wind storms. This may indicate

an increase in the vulnerable population and a rise in the number of hazardous

events.• It could be the result of global climate change and/or other environmental

changes.

Hazard trends (5)

• Around 50–70 volcanoes erupt

every year.• There is no trend, upward or

downward, in eruption frequency.• Very large magnitude eruptions (e.g.

Mt Pinatubo in 1991) are rare.• There is a rising trend in the number

of people affected (see table).

Notice that 8 of the top 10

eruptions have occurred since 1990.• This reflects growing population

density in the developing world.

Country Year

Number of

people

affected

Philippines

(Mt Pinatubo) 1991 1,036,065

Nicaragua 1992 300,075

Ecuador 2006 300,013

Indonesia 1982 300,000

Indonesia 1969 250,000

Comoros 2005 245,000

Philippines 1993 165,009

Papua New Guinea 1994 152,002

Ecuador 2002 128,150

Dem. Rep. Congo 2002 110,400Top ten volcanic eruptions since 1900 by

number of people affected

Hurricane trends (1)

• Trends in hurricanes, especially in the Atlantic, are a controversial matter.• Some researchers have linked increased hurricane activity to global warming.• Others argue that there is a natural cycle in the Atlantic called the Atlantic

Multidecadal Oscillation (AMO) which explains the high number of major

hurricanes in the 1940s and 1950s, and more recently.• Despite variations in major hurricane frequency, there is a long-term trend in

the USA of falling hurricane-related deaths but rising economic costs.

Hurricane trends (2)

• One certain trend is the rise in the number of people living on the US coast. • In Florida and the Gulf Coast, some coastal areas have seen populations rise by

400% since 1980.• This means increasing numbers of people are at risk from hurricanes.• Although awareness of hurricanes, education, warning and evacuation systems

have all improved in the USA, the potential for economic loss continues to grow

as coastal populations rise.• The full impact of rising populations was felt in 2005, when the Florida and Gulf

Coasts were struck by five major hurricanes (Dennis, Emily, Wilma, Rita,

Katrina), causing an estimated US$120 billion in damage and the loss of 2,200

lives.

Global warming (1)

Global temperatures, 1850–2008

Global warming (2)

• Many scientists believe that increased global warming will lead to more

unpredictable weather and a rise in extreme weather events. • Global temperatures have risen since 1910, and at a consistently rapid rate

since the late 1970s.• The fact that there are only 30–35 years of reliable data about global

temperatures makes the scientists’ task of accurately predicting future changes

more difficult.• Some data, such as the 20 cm rise in global sea level since 1900 and the

decline in Arctic sea ice since the 1970s, are more reliable.• There is growing suspicion that rising trends in drought and flood events may

herald the effects of global warming to come.

Flood disaster trends (1)

Reported global flood disasters and death tolls, 1977–2007

Flood disaster trends (2)

• Trends in global flood disasters show significant rises since the early 1990s. • This could be an early signal of climate change. • It may also be related to rising populations, rapid urbanisation, deforestation

and other land-use changes.• Separating the climate change signal from the human factors that increase

flood risk is a real challenge.

El Niño/La Niña

• As well as global warming, the El Niño/La Niña cycle is known to have climatic

consequences on a global scale. • Changes in Pacific Ocean circulation have knock-on weather effects in other

parts of the world through teleconnections.• Hazards associated with El Niño are well known, such as drought in Indonesia

and flooding in Peru.• El Niño/La Niña cycles, which are unpredictable, add yet another layer of

complexity to the calculation of hazard risk.

Summer 2007 UK floods

• In summer 2007, many areas in the UK received over 100 mm of rainfall in 24 hours, causing widespread flooding.

• The media were quick to link the unprecedented flooding (50,000 homes and 7,000 businesses flooded, total cost £3 billion+) to global warming.

• The basic cause of the flooding was a southerly jet stream, meaning low pressure and rain over the UK at a time when high pressure was to be expected.

• Many meteorologists have linked this situation to La Niña conditions in the Pacific. Rainfall pattern, summer 2007

Human trends (1)

• Some trends among the human population add to increasing risk.• One of these is urbanisation. Over 50% of the world’s population now lives in

urban areas, compared to 29% in 1950.• These crowded spaces are especially vulnerable to major earthquakes, floods

and hurricanes.• World poverty continues to be a major issue, reducing the capacity to cope

with, and increasing the vulnerability to hazards. • Although the global proportion of people living on less than $1 per day is falling,

total numbers rose from 36 million to 50 million in Latin America, and 164 to

314 million in Africa between 1981 and 2001.

Human trends (2)

• Pressure on land from growing populations leads to deforestation and

conversion to farmland.• Deforestation can significantly increase hazard risk.• The risk of landslide is greater on slopes when trees are removed.• With no vegetation to intercept rain, flash-flood risk rises.• Without the evapotranspiration provided by trees, rainfall becomes more

variable and aridity increases.• Occasional flash floods can produce a cocktail of increased hazard risk and

falling food and water security.

Global trends

Disasters related to human development levels

Overall, global trends show that the numbers of reported disasters and people

affected are rising, but the number of people killed by disasters is falling.

Disaster management (1)

Disaster management cycle

Falling death tolls suggest

improvements in disaster

management.

Disaster management (2)

• Death tolls are reduced when populations are prepared for a possible hazard.• Some hazards can be predicted, e.g. floods, hurricanes, drought and volcanic

eruptions.• Prediction allows for warning, and, when possible, evacuation. This can save

lives, but is unlikely to reduce economic losses.• After a disaster, immediate rescue and relief is essential.• ‘Rapid response’ has improved considerably over the last few decades.

International relief efforts now occur quickly in response to disasters.• This saves lives but the numbers affected and the economic losses are still high.

The challenge is to ‘disaster proof’ communities using appropriate building

techniques, land-use zoning, education and developing prevention technology.

These responses are longer term, costly and beyond the reach of many in the

developing world.