Weather Hazards and Climate Change
Hadley Cells: Stretches from 30N to 30S. Warm trade winds blow towards the hadley cells. At the equatr, the trade winds from each hemisphrere meet. The warm air rises rapidly carrying thunderstorms. An area of low pressure where air from the two cells meet over the equator. The air at the tropospher move towards 30N and 30S where it becomes cooler and starts to sink back into the Earths surface. High pressure areas. Once returning to the grund some of the air returns to the equatorial areas as trade winds, it is a complete circle.
Global climate was different and continues to change
Climate change refers to how the average climatic conditions of the planet vary over time. At some point's in the history of the earth, the climate has been comparatively warmer and at some points it has been much colder. The history of the earth is divided into periods. The Quaternary period is the last 1.8 million years of the world's history. During this period, there has been many times where the temperature of the world has dropped. During these drops in temperature large continental ice sheets covered much of the Northern Hemisphere. When this happens, it is known as a glacial period or ice age. When the ice sheet melts due to warmer temperatures, this is known as an inter-glacial period. The last glacial period was between approximately 120,000 and 11500 years ago. Since this point, the earth has been in an interglacial period which is known as the holocene. There is still some glacial cover in parts of the world e.g. Greenland and Antarctica.
Milainkovitch Cycle
Eccentricity
Axial Tilt
Precession
The earths axis wobbles like a spinning top a wobble cycle takes around 26,000 years it is caused by the gravitational action of the sun and the moon. the wobble can depend on a season
Axial tilt, also known as obliquity, is when the earth is spinning on its own axis, but the axis is not upright. The angle of the axis changed from between 22.1 and 24.5 degrees. It takes 41,000 years for the Earth's axis to change from 22.1 to 24.5 and back again. When the Earth's axis is at a greater tilt, there will be more xetreme seasons on a global scale. Generally, this will mean that the world has higher average temperature so interglacial periods are more common when this occurs
the path of the earths orbit around the sun isnt always a perfect circle its an ellipse the shape of the earths orbit changes from a circle to elipse every 100,000 years
Solar Variation
Volcanic Eruptions
the amount of enery that the earth receives from the sun isnt constant. sometimes the earth receives more energy and sometimes less. these changes are very small and hard to dectect but are connected to the idea of sunspots. a sunspot is a dark patch on the surface of the sun the number of sunspots increases from a minimum to a maximum, then back down again over a period of about 11 years. this 11-year period is called a sunspot cycle when sunspot activity is at a maximum the sun gives off more heat. when sunspot activty is at a minimum the solar output is reduced, which can lead to lower temperatures on earth
Large volcanic eruptions release ash and sulphur dioxide into the atmosphere. The ash particles return quickly to the earth, but the sulphur dioxide can have a cooling effect. The eruption needs to be violent in nature to have an impact on the climate since the particles need to blast up through the stratosphere. The sulphur dioxide mixes with water in the atmosphere to form sulfuric acid droplets known as aerosols. There are microscopic droplets that absorb radiation from the sun. This means that these particles get hotter and heat the surrounding air. This process prevents the heat from the sun from reaching the earth. During the 1900's, there were 3 large eruptions that may have cooled the planet by as much as 1 °C each. Over time, these particles eventually get washed out with rainfall
The causes of climate change can be both natural and man made. Natural causes have been responsible for most climate change during the majority of Earth's history, with human causes having a greater impact over the last 250 years.
Jet streams
Polar front jet stream: this is formed when cold polar air meets warm tropical air high above the Atlantic Ocean. This normally occurs between latitdudes 40 and 60N and 40 and 60S. However, the exact location does vary. What is key is that this occurs at the division between the Polar and Ferrel Cells.
Subtropical jet stream - this is generally in a westerly direction. It can be found at approximately 25N and 35S
Reconstructing Past Climates
Tree Ring Information
Ice Cores
Pollen Records
Historical Documents
Daries and religious records detail more recent records but these are least useful as they can only go back a few hundred years and there was technology to measure it accurately back then
ice cores provide a longer record of information. Ice is extracted from the poles these can contain volcanic ash, pollen and even bubbles of air this is probably the most useful source of info about past climates
Pollen produced by all flowering plants. Pollen have distinct shapes and structures It allows us to work out which plant pollen is from. Certain plants can only grow in certain conditions. Therefore we can gather information about what climate must've been like when pollen was formed.
as trees grow theyre growth rings are wider when the temperature is warmer and thinner when cooler, however it only tells us about the climate the tree has lived in
Enhanced Greenhouse Effect
This phenomena is commonly refered to as climate change or global warming its the increased amount of carbon dioxide and other greenhouse gases that humans released since the industrial revolution
Methane
methane is a greenhouse gas this means that it can trap heat within the earths atmosphere it makes up 20% of the greenhouse gases in the atmosphere and 30 times worse than carbon dioxide
Human Effect on climate change
Industry
Tropical storms
Form over tropical and subtropical oceans between the tropic of Cancer and tropic of Capricorn
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Need water temps over 27 to form
Usully form towards end of summer and in the autumn