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Climate - Solar radiation, Hadley cells, biome distribution.
Transcript of Climate - Solar radiation, Hadley cells, biome distribution.
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The differences in temperature
between areas of more sunlight
and less sunlight causes
The Hadley cells cause the areas at 30 degrees N and 30 degrees S to be relatively DRY and COOL compared to adjacent regions.
Therefore, as you can see in the biome diagram, 30 degrees N and S are dominated by grasslands, savannahs and desert:
In other words - rainfall and average yearly temperature determine the biome.
See next 2 diagrams:
first shows biome distribution
second shows how average annual temperature and rainfall determine the biome.
sunlight, radiant energy, strikes at 90 degrees near the equator, therefore has greatest chance of penetration to heat the tropics
radiant energy heats earth and water near equator
hot air and evaporated water RISE!
as air + water rise, it cools in upper atmosphere
water vapour [water in gas form], condenses forming precipitation - RAIN
therefore tropical regions are hotter, and wetter than most areas on Earth.
when the air at the equator rises, it leaves a low pressure air mass behind.
air at the surface rushes in to fill the low pressure zone.
the rising air, and surface air, form a circular air flow as seen in the diagram.
at the equator hot, wet air rises; at 30 North and 30 South, dry, cooler [relatively speaking] air falls.
99%+ of Earth's energy budget is due to radiant sun striking the Earth.
When the Northern hemisphere faces the sun radiant energy strikes at a more direct angle, this increases the chances radiant energy strikes, and is absorbed, by Earth.
This dictates the summer season of Northern hemispheres and winter of the Southern hemi.
When the Earth's tilt places the Northern hemisphere away from the sun, radiant energy strikes at a less direct angle, increasing the chance of reflection off Earth atmosphere.
Less energy is absorbed by the Northern hemisphere and dictates the Winter season.
evidence for anthropogenic [human caused] climate change
Carbon dioxide and other greenhouse gases are transparent to some types of radiant energy, and opaque to others. They allow visible and UV light through to strike the Earth, but do not allow infrared radiation [the type released from the Earth] back out.
Therefore the Earth has a net gain of energy.
The following figure demonstrates the measured changes in CO2, methane and NO over the last 10000 years. Notice the sharp rise in all three over the past 100-150 years.
A very important question you should ask is:
"How do they know what the levels in these gases were 10000 yers ago."
Primarily ice core data. By drilling plugs of ice in the greenland and Antarctic ice sheets we can analyze approximately 500000 [yes 5 HUNDRED thousand] years into the past.
The figure above demonstrates measured changes in temperature over the past 34 years. As the dominant orange and red colours highlight, average temps have increased primarily between 1 and 3 degrees over much of the global surface area.
The figure is from the IPCC report.
The figure above demonstrate computer climate model predicted changes for the different scenarios programmed.
The images of the Earth on the right illustrate expected temperature changes for the periods 2020 and 2090. Temp change scale below the images. The greater the red/purple colour, the larger the increase in temperature change.
The sets of illustrations for three of the 6 models generated.
predicted / Expected ecosystem, economic, huam impact of climate change
Evidence - facts
There are a number of cources of evidence to inform us about how Earth's climate WAS like.
ice core sample -- go back almost 1 million years
tree ring information goes back thousands of years
radioactive element concentrations
direct measurements - some temperature recording go back hundreds of years.
The year to year changes in CO2 levels can be measured and seen in the figure to the left.
Q. Why the yearly fluctuations?
The Earth's Energy Budget:
Yellow indicates radiant energy input to the Earth's open system.
Pink indicates radiant energy output.
Objects of HIGH albedo cause a high degree of relfection:
In the diagram, clouds have a HIGH albedo, ground a LOW albedo.
Polar ice caps and snow cover have a HIGH albedo and reflect a large amount of radiant energy away from EARTH.
CO2 is transparent to most of the radiant energy INPUT from the sun. Hence CO2 allows radiant energy to strike the Earth to be absorbed.
Also, CO2 is opaque to most of the radiant energy emitted as infrared radiation. Hence CO2 traps Earth's emitted energy, trapping it within the Earth's climactic system.
The first law of thermodynamics tells us the energy striking Earth, and trapped by atmospheric gases, is not destroyed. Hence the Earth absorbes, and keeps more energy than it releases.
This is called - global warming.
CO2 is a carbon containing gas.
By understanding the carbon cycle, we can understand the sources and sinks for carbon dioxide. [A sink HOLDS something. Therefore a carbon sink stores carbon]
The largest sink for CO2 is found in the lithoshere - rocks. 65 million, billion tonnes.
The second largest sink is the hydrosphere - oceans. 39000 billion tonnes.
Soils hold 1580 billion tonnes of carbon. Mostly decaying organic matter.
Flow is also measured in billions of tonnes.
Photosynthesis extracts 111 billion tonnes of CO2 into organic molesulces [sugar] per year. 6CO2 + 6H2O --> C6H12O6 + 6O2
Respiration releases 110 billion tonnes per year.
C6H12O6 + 6O2 --> 6CO2 + 6H20
The unnatural sources of CO2 are released from fossil fuels and soil use [erosion]
6.3 billion tonnes and 1.6 billion tonnes respectfully are releasewd due to human activity per year. Hence the rise of CO2 levels from the historical peak of ~290 ppm to today's ~380+ ppm.
You should be familiar with the concept of food webs. Food webs illustrate the feeding relationships between organisms within an ecosystem.
Below is a sample food web. Important terms you should becomes familiar with are:
primary producer [organisms that use sunlight to produce their food.
primary consumer [generally herbivores, they are the first layer of organisms that eat the primary producers]
secondary and tertiary consumers [additional levels or organisms that generally eat the herbivores - may be classified as carnivores]
trophic levels - different deeing layers within an ecosystem....
As we learned in biology, the 1st law of thermodynamics states that energy is not created or destroyed - it is moved around or rearranged:
The food web demonstrates how 'energy' and mass, in the form of food moves in an ecosystem.
A second manner to demonstrate this are trophic pyramids. These diagrams often show a pictorial of mass, numbers or energy flow in an ecosystem as in the diagram below:
A loose guidline used suggest only 10% of the lower level energy is available to be passed to the next trophic level above it. 90% is used by the organisms of that level to survive.
Another trophic pyrimid below illustrates the flow of energy producer to apex carnivore.
Remember that 90% of the enegy [on average] does not transfer to the higher trophic level, it is used by the level for survival and growth.
you can watch this animation:
The graph can be used to predict the type of biome a region will have based on the average annual rainfall and temperature.