Chapter 1; Global Hazards

Key terms:
Context hazard: A widespread (global) threat due to environmental factors such as climate change.
Hazard: A percieved natural event that has the potential to threaten both life and property.
Geophysical hazard: A hazard formed by tectonic/geological processes (earthquakes, tsunamis and volcanoes)
Hydro-Meteorological hazard: A hazard formed by hydrological (floods) or atmospheric (droughts) processes.
Vulnerability: A high risk combined with an inability of individuals and communities to cope.
Disaster: A hazard becoming reaility in an event that causes deaths and damage to goods/property and the environement.
Risk: The probability of a hazard event occuring and creating loss of lives and livelihoods.

Chronic Hazards
Chronic hazards such as global warming and the El-Nino and La-Nina cycle may increase threat from environmental hazards, for example a sea level rise increases the risk of coastal floods. 

Some key features of environmental hazards make them a huge threat.

• The warning time is normally short and the start of the hazard is quick.
• Humans are exposed to hazards because people live in hazardous areas.

The risk of disaster

What is risk?

Hazards to people

• Death and servere injury
• Disease

Hazards to goods

• Economic losses
• Infrastructure damage
• Property damage

Hazards to the environment

• Pollution
• Loss of flora and fauna
• Loss of amenity 

Exposure to a hazard is not always unavoidable. People may consciously place themselves at risk.

Changing risks
Natural hazards vary in space as well as time because of changing human activities and changing physical factors, such as tectonic plate movements. Deforestation of watersheds leads to less interception of rain and mor flashy hydrographs, increasinf the frequency and magnitude of flood events. 

Measuring risk
People living in areas of high physical exposure to hazards and with high levels of human vulnerability will be the most at risk and these people are largely found in the poorest countries of the world. 

The risk equation

Frequency or magnitude of hazard is inreasing
Use of fossil fuels is warming the planet. The resulting change in climate is increasing the frequency and severity of weather-related hazards.

Level of vulnerability is increasing
Unsustainable development involves poor land use (e.g. building on floodplains) and environmental degradation (e.g. bleaching of coral reefs). This is increasing the vulnerability of millions of people.

Capacity to cope is decreasing
Communities need skills, tools and money to cope with the effects of climate change. However, debt repayments, unfair trade arrangements , selective foreign investment, and rich countries directing aid funds towards politically strategic regions rathen than the most needy mean that the poorest and must vulnerable communities lack these resources.  

Key Terms:
Albedo: How much solar radiation a surface reflects
Climate change: Any long term trend or shift in climate detected by a sustained shift in the average value for ny climatic element.
Enhanced greenhouse effect: This occurs when the levels of greenhouse gases in the atmosphere increase owing to human activity.
Global warming: A recently measured rise in the average surface temperature of the planet
Tipping point: The point at which a system switches from one state to another 
Feedback mechanisim: Where the output of a system acts to amplify (positive) or reduce (negative) further output. (e.g. the melting of Arctic permafrost leads to the release of trapped methane which leads to further global warming). 

The greenhouse effect
The greenhouse effect is the process ny which the greenhouse gasses, water vapour (biggest contributor), carbon dioxide, methan, CFCs, nitrous oxide and ozone, absorb outgoing long-wave radiation from the Earth and send some of it back to the Earth's surface, which is warmed. This sustains the life on Earth by raising temeperatures to a global average of 15C. Without the greenhouse effect the Earth would be up to 30C cooler.
Human activities particulary the burning of fossil fuels, such as oil and coal. 

Why is global warming important?

• Changes in climate will affect ecology and wildlife, and could lead to the spread into new areas of diseases such as malaria.
• Rising ocean temperatues may cause an increasing frequency and magnitude of hurricanes.
• The Earth consists of a numver of interlocking systems which can impact on each other via postive and negative feedbacks. For example, as glacies and ice sheets melt, oceans become diluted by fresh water, which impacts on ocean circulation. Moreover, ice has a high albedo and as it melts more heat from the sun will be absorbed, which will raise the temperature further and make the remaining ice melt quicker.