challenges of natural hazards- climate change Flashcards
where were the major flunctuations in history?
quaternary period
what is the quaternary period?
the geological time period that started around 2.6million years ago and extends to the present. `
how are scientists calculating the temo before instruments were invented?
They use the indirect data stored as fossil record, these are found in deep ocean sediments and frozen ice cores. When layers of sediment or fresh falls of snow become buried, they trap and preserve evidence of the global temp at that time. Scientist can then study the oxygen in the ocean sediment of water molecules in ice to calculate the temp and can then be accurately date this information and plot graphs.
what are the present day evidence that tehre is climate change?
1) rising sea levels
the sea has risen 21-24 cm ince rge 1800s and most of this has c=occured in the last 25 years. (teh sea also expands as water gets hotter(thermal expansion))
2) sinking glaciers and melting ice:
majority of glaciers and sea ice are shrinking and thining. Sea ice has thinned upt o 65% since 1975 and some will completly disapear by 2035
3) seasonal changes
seasonal patterns of wildlife are changing and this is because climates influence seasons
what is the greenhouse effect?
naturall process where greenhouse gases mainly CO2, methane and nortous oxides trap energy form the sun in the atmosphere which heats up the earth.
what are the natural factors which cause climate change?
Orbital changes, volcanic activity and solar output
how does the natural factoes affect climate change?
1) orbital changes:
Milankovitch discovered three distinct cycles that he believed affected the worlds climate. The orbital changes affect where the sun hits the earth and how intense the sun is, this affects the seasons and climate.
Scientist believe that orbital changes caused the temp fluctuations such as the glacial and interglacial periods.
2) volcanic activity:
The ashes and gases erupted into the atmosphere can cause a cooling effect on the earths climate such as a volcanic winter. The erupted substances affect us in 2 ways:
- the large amounts of volcanic ash can stay in the atmosphere and block out the sun and this results in short term impact of cooling
- the volcanic eruptions can also erupt sulfuourous gases which react to form aerosols which reflect solar radiations and this causes a long term impact/effect.
3) solar activity:
The suns output is not constant and scientist have detected cycles which link the solar output to the presence of sunspots. When sunspot cycle is minimum, there is reduced solar output which results in lower temps on earth. When sunspot cycle is maximum, there is an enhanced solar output which could cause large explosions to occur on the surface of the sun, resulting in solar flares.
what is orbital forcing
The influence of earth orbit on the climate
what is volcanic winter
The cooling of the lower atmosphere and the reduction of surface temp
what are sunspots?
A sunspot is a dark spot on the sun and the number of sunspot increases from a minimum to a maximum and then back to a minimum over a period of about 11years.
what are the human factors that affect climate change?
1) burning of fossil fuels which release greenhouse gases: \
Fossil fuels are coal, oil and natural gases and they are fuels because they release heat energy when they are burned.
How is it being used?
Fossil fuels are used to fuel cars, aeroplanes and in general: transportations. It is also used in toothpaste. Many objects like shoes, balls and Tv s are all products of oil and gases. As the population grows and people get richer, we require and can afford more of those objects which means more fossil fuels are burned.
How is it affecting us?
When fossil fuels are burned by carbon emissions (such as cars and power stations), unwanted gases such as methane, nitrous oxides and in particular carbon dioxide, enters our atmosphere. Although they have always been present, human activity is increasing the concentration of CO2 rapidly and this adds to the greenhouse effect as the atmosphere can now trap even more of the suns energy which leads to the planet getting warmer.
Facts:
CO2 accounts for an estimation of 60% of the enhanced greenhouse effect and the global concentration of carbon dioxide has increased by 30% since 1850.
2) Agriculture:
How are humans causing climate change through agriculture?
The demand for food is growing and this results in more land needing to be cleared for the agriculture sector = there are less trees to take in CO2.
At the same time the machines used on the land is a big emmitter of greenhouse gases.
Other ways:
-Methane is released from rice cultivation
-Methane is released from the enteric fementation in cattle
-nitrous oxides are released from fertilizer applications.
Together, agricultural processes comprise 54%of the methane emissions and around 80% of the nitrous oxide emissions,
3) Defirrestation:
About 18 million acres of land is estimated to be lost every year.
Why do we deforrest?
There are few main reasons:
- as population is growing, we need more land to build housing and facilities so we need to make more land available for urbanisation and housing
- to harvest timber in order to create commercial items such as paper, furniture and homes.
-to create ingredients that are highly prized consumers such as palm oil
- To create room for cattle ranching which the cattle is then used for food.
why are coal, oil and natural gases known as fossil fuels?
They are known as fossil fuels because they form from the remains of living organisms over millions of years sof years.
what is agriculture?
Agriculture is the cultivation of animals, plants, fungi and other life for food, medicine and other products used to sustain and enhance human life.
what is defforestation?
Deforestation is the permanent destruction of forests in order to make land available for other uses.
how is deforrestation affecting the climate (carbon cycle)
Trees can store lots of carbon and deforrestatimg trees not only decreases the amount of carbon stored but it also releases carbon dioxide into the air, this is because when trees die, they release the carbon that hey have been storing. At the same time, the deforested wood is often burnt for fuel and the burning of wood releases CO2 which was originally stored in the trees.
