Frist Half Flashcards
what is the difference between climate and weather?
Weather = state of the atmosphere at a given time
climate = avg weather over a long period of time (typically 30yrs)
- it is a statistical measure and does not typically vary much
- climate systems also includes the oceans, cryosphere, vegetation and lithosphere as well as the atmosphere
two methods of weather observation
global surface weather stations
upper air radiosonde (balloon) stations in north america
surface weather stations “stevenson screen”
white box about 1 m off the ground
measures humidity, temp, pressure and wind
white to minimize overheating
vents to allow air flow
anemometer is 1m above ground to measure wind
weather balloons
measure the lowest 30km of the atmosphere twice a day around the world
measures temp, moisture, wind and these are used to create weather maps at diff altitudes
when the balloon reaches 30km the balloon bursts and the measuring package is dropped
4 different observations that show climate change is actually happening
- global annual mean surface air temp
- global mean sea level
- arctic summer sea ice extent
- atmospheric carbon dioxide concentration and ocean acidification
evidence 1: global mean surface temp
in the last 50yrs the global surface temp has increased by 1 degree celcius
warming hiatus from 2002 to2012
last 5 years have the warmest since 1880
evidence 2: global mean sea level
increasing at about 3.4mm/yr = 34 cm/ 100yrs
it is going to increase no matter what but it can be kept to a minimum
better indicator of climate change because it better indegrates on a global scale the effects of increased radiative forcing
two reasons why the sea levels are rising
- Melting land ice (not sea ice in the north pole) in greenland, antarctica and glaciers
- thermal expansion - as ocean waters heat up the water molecules move more and therefore take up more space, increasing volume without increasing mass
evidence 3: arctic sea ice extent
loosing 0.83 million square km per decade
lg amount of inter-annual variability
in the linear decline observed in the las 40yrs continues, the arctic will be ice free in 50 years
evidence 4: increasing atmospheric CO2 and its effect on ocean acidification
increasing CO2 in environment warms climate and acidifies the oceans
what happens to atmospheric pressure and air density with height?
both decrease exponentially
the decreasing air pressure with height creates an upward pressure that balances the downward force of gravity - this is called hydrostatic pressure
the atmospheric layers and their boundaries
troposphere: closest to the earth, active weather is here, clouds and precipitation, weather impacted by earths surface
equatorial tropopause= boundary
stratosphere: also the ozone layer, clear, very dry and stable
- the ozone layer protects us from harmful UV radiation by absorbing it ( this is why temp actually increases with height in this layer)
stratopause = boundary
mesosphere: temp decreases with height bc of ozone heating
mesopause
thermosphere - extends to space where the thermopause in theory exists
chemical composition of air
constant gasses: Nigtrogen Oxygen argon neon helium hydrogen
variable gasses: water vapour carbon dioxide nitrous oxide carbon monoxide chlorofluorocarbons
ozone
this gas is a minor player in climate change
most of it is found in the stratosphere where is absorbs harmful UV radiation from the sun - doesn’t reach earths surface
ozone in the troposphere is considered to be air pollution and is formed photochemically from nitrous oxides ( as a result of fossil fuel burning)
- ground level ozone is harmful to humans and plants
residence time
average lifetime of a molecule in the atmosphere
total mass in reservoir/ mass outflow rate
issue with residence time for carbon dioxide
according to the formual it is only 5 years
however the CO2 were adding is nowpart of the total climate system and goes intoplants and oceans fora few years and then comes back into atm so were not permanently removing it
reality is it takes hundreds of years to actually remove it
only way to get rid of it completely is to deposit it at the bottom of the ocean on the sea floor
hydrological cycle
this is the water cycle
evaporation/condensation transfer large amount of heat from the surface to air
then you get land percipitation
also have soem evaporation and transpiration
percoaltion = water flows into groud then ground water flows back into ocean
important facts about the ocean
71% of earths surface = ocean
ocean = 97% of earths water
avg depth is 3.7km deep
- deepest point is 11km
important for climate change because of their ability to store and transport huge amounts of energy and to delay temperature response because of its huge heat capacity
what is the temperature at the bottom fo the ocean and why?
bottom of ocean is very cold
the thermocline is the layer where the ocean temp decreases rapidly with depth
the deep ocean is cold bc the water source is the polar sea surface
- the densest water will be cold and salty and therefore sinks to the bottom of the ocean
properties of electromagnetic spectrum
amplitude
wavelength
frequency
waves are described based on specifying wavelengths or frequency
thermal radiation
radiation emitted by substances based on its temperature
the hotter the material the more radiation is emitted
- material gets hotter, radiaiotn being emitted shifts to shorter wavelengths
all matter emits electromagnetic radiation in accordance to its temperature
most solid surfaces and liquids are able to absorb and emit radiation at all wavelengths efficiently
black bodies
the material is able to absorb and emit radiation at 100% efficiency
gasses do not act as black bodies because they absorb and emit at very specific wavelengths
infrared radiation (IR)
invisible radiation with wavelengths that are longer than the visible red wavelengths
2 types for climate studies: solar infrared, terrestrial
solar infrared
near-infrared or shortwave infrared radiation
emitted by the sun
makes up approx. half of solar radiation
terrestrial infrared
longwave infrared radiation
emitted by the earths surface and atmosphere
strongly absorbed and emitted by greenhouse gasses and clouds in the atm
which electromagnetic waves can transmit through the earths cloudless atm?
some UV
most visible
some infrared
some microwaves
some radio
energy conservation for the climate
when energy in = energy out the earth will have a constant energy content and constant global avg temperature
albedo
fraction of incoming radiaiton that is reflectid by an object
an albedo of 1 = all incoming radiaiotn is reflected
an albedo of 0 = no radiaiotn is relfected, it is all absorbed
average planetary albedo is 0.3 (30%)
three factors that determine the globally averaged surface temperature
- amount of incoming solar radiation - sun’s surface temperature + distance from earth
- albedo of the earth - determined by brightness of clouds/surface
- greenhouse factor - determined by amount of greenhouse gasses and clouds
predicted planetary temp is -18 but the actual observed surface temp is 15
energy imbalance
this will occur when some of the outgoing terrestrial infrared radiation is reduced or blocked
out going terrestrial radiaiton gets progressively more blocked as teh greenhouse gas concnetration increases
- this is because greenhouse gasses absorb and emit at certain terrestrial infrared wavelengths
what happens if the atm becomes more opaque at certain wavelengths?
the radiation at those wavelengths wil not be able to penetrate as afr in teh atm
addition of more greenhouse gasses is making the atm more opaque at many of the terrrestiral wavelenghts
how adding greenhouse gasses warms the earth
as the greenhouse gas concentrations increase it makes the atm more opaque to certain wavelengths of terrestrial radiation
the penetration depth of the infrared radiaiton is reduced (i.e. the infrared radiaiton cannot travel as far in the atm)
as a result, more of the outgoing radiaiton escaping to space originates from higher in the atm where it is colder
but a colder srouce meits less thermal radiation
the result is that the earth is emitting less terrestrial infrared radiaiton back to spcae bc of the extra greenhouse gases
net incoming solar is the same - earth is accumulating energy which will drive up the global avg temp
energy imbalance at the top of the atm
earth has less terrestrail radiaiton outgoing to space bc the atm is more opaque to terrestrial infrared
net incoming solar energy is larger than outgoing - total energy content of the earth is increasing (temp increasing)
global warming is happening bc the extra greenhouse gases are making the atm less transpartnt in the infrared
acuumalted energy goes toward oceans (94%), melting ice sheets (3%), heating the land (3%)
achieving a new energy balance: stabilize greenhouse gases
as the heat content fo the earth increases: air, ocean and land temps will all increase, gradually increasing the amount of terrestrial infrared radiation escaping to space
results in eventually the outgoing terrestrial infrared energy becoming equal with incoming solar energy
energy balance is re-established however teh new steady state is at a hgiher surface temp
how is heat related to warming?
heat capacity
if we add the same amount of heat to two systems with different masses, the larger system will have a smaller temperature increase and the change will occur slowly
rate of temperature increase depends on heat capacity
how is the current energy surplus the earth is experiencing being used up?
heating the oceans (94%)
melting ice sheets and glaciers (3%)
heating the land and sub-surface (3%)
how does the ocean cause a time delay in climate system and a reduction in the temperature response?
oceans have a large heat capacity - able to absorb a lot of heat without increasing the temperature much
also explains the difference between a maritime climate and continental climate
