- Created by: ayesha
- Created on: 29-03-11 18:21
Global Hazards- 1
Hydro-meteorological hazards - are formed by hydrological (floods) and atmospheric (storms and droughts) processes.
Geophysical hazards - are formed by tectonic/ geological events (earthquakes, volcanoes and tsunamis)
Risk (R) = frequency of magnitude or hazard(H) x level of vulnerability (v)
capacity of population to cope or adapt (c)
R = H x V
Global Hazards- 2 (Risk Equation Continued)
The risk is getting worse for many communities and countries because:
- the frequency and magnitue of hazards are increasing due to climate change
- vulnerability is increasing as a result of unsustainable development leading to poor land use and environmental degradation
- the capacity to cope is decreasing owing to povery and urbanisation
NOTE: The risk is much lower in economically developed countries. These countries have the resources and technology to provide protection from the worst impacts of disasters.
Natural Forcing Agents of Climate Change
The earth's climate has changed naturally throughout it's 5 million year history. There have been a series of very cold periods (glacials) and warmer periods (inter- glacials)
In the past these changes have resulted from natural forcing agents:
Volcanic Eruptions - the ash reduces the amount of sunlight reaching the earth which causes an increase in cloud cover
Metorite Collision - Vapourized material would be thrown into the atmosphere on impact, blocking radation from the sun --> causing an impact on winter - temperatures fall.
Changes in Solar Radiation - Sunspots (cooler areas on the surface of the sun caused by intense magnetic storms) change over time and this can impact upon climate i.e the higher the sunspot intensity the cooler the temperature
Variations in the Earth's Orbit - Milankovitch cycle theory suggests that the Earth's orbit changes over a cycle of 100,000 years and it's tilt alters over 41,000 years. These changes cause a change in the amount, distribution and seasonal timings or solar radiation.
The Greenhouse Effect
1. Solar radiation passes through the atmosphere
2. Some of the energy is reflected by the atmospher and the earth's surface
3. Solar energy warms the earth's surface
4. Infared energy is emmited by the earth
5. The heat is absorbed by greenhouse gases. they re-emit the heat, warming the earth. Some heat also escapes the atmosphere.
The acceleration of the Greenhouse effect (Global Warming) started during the Industrial Evolution in the 19th Century.
Evidence of Climate Change
Long Term Evidence
Ice Core Evidence – Air bubbles in ice provide a record of greenhouse gases which are used to reconstruct past climate
Sea Level Change – When ice caps melt, sea levels rise. During inter-glacial periods sea levels rise (thermal expansion) – glacial periods they fall
Pollen Evidence – Analysis of old pollen can be used to reconstruct past climates because they provide a record of vegetation at a particular time Different-shaped pollen grains signify different trees, some of which lived in Arctic conditions.
Glacial Evidence – Glacial landscapes represent past ice – ages – V Shaped Valleys, cirques, drumlins and glacial moraines
Ocean Sediment Evidence – ocean sediments are made from organic & inorganic materials. The chemical elements in them give clues about past climate conditions
Evidence of Climate Change
Medium Term Evidence
Historical records - from ancient Greece, cave paintings etc evidence suggests there was a 'Little Ice Age' from arounf 1500 to 1800
Tree rings (dendrochronology) - each tree ring represents annual growth, in warm, wet periods the ring sequence in wider.
Global Temperature Change - You can record global temperature - planets getting warmer (0.5 degrees in 50 years)
Species Distribution Change - changes in migration patterns i.e. polar bears being forced into towns and cities and north.
Extreme Weather - more extreme weather events - tropical storms & heatwaves
ice caps melting - sea levels rise ( also caused by thermal expansion)
Impacts on Global Warming
Case Study - Arctic
Average Arctic temperatures have risen twice the rate of the rest of the world (3-4 degrees in the last 50 years in Alaska and northwest Canada). Over the next 100 years this could rise to 3-5 degrees over land and up to 7 degrees iver the oceans.
Impacts on natural systems
Vegetation Shifts - predicited to shift northwards meaning the existing food chain will destabilise. BUT - longer, warmer growing season may benefit Arctic agriculture.
Thawing Permafrost - up to 40% of existing peramfrost is expected to thaw esp. in Siberia. In some areas lakes + rivers will drain = impact on species like freshwater fish such as Arctic Char and lake trout.
Increasing Fires + Insects - Global Warming will increase forest fires and insect-caused tree death