lecture 1 - 15 Flashcards
(218 cards)
1
Q
Difference between climate and weather
A
Climate is the average weather - extended period of time
Weather is the state of the atmosphere at a given time
2
Q
Example of annectodal climate change
A
Hurricane dorian is ghe worst hurricane ever recorded in the bahamas
3
Q
What does the surface weather station stevenson screen measure?
A
Temperature, humidity, pressure. Wind
4
Q
What are weather balloons used for?
A
Profile lowest 30 km of the atmos twice a day around the world
5
Q
Climate change evidence #1 is the global mean surface temp - how is this evidence of climate change
A
Global average is increasing, hottest period since 1980
6
Q
What are the four strong evidence for climate change
A
Mean surface temp increasing
Global mean sea level rising
Arctic sea ice extent - declining
Increasing atmospheric carbon dioxide + ocean acidification
7
Q
Explain hydrostatic balance in the atmosphere
A
Atmo pressure and air density decrease exponentially with height
Decreasing air pressure w height makes an upward pressure force the balance the downward force of gravity
8
Q
Where do clouds and precipitation occur in the atmosphere?
A
Troposphere
9
Q
What are the greenhouse gases
A
Water vapour CO2 Methane Nitrous oxide Ozone CFCs
10
Q
99.9% of the dry atmosphere consists of what gases?
A
Nitrogen
Oxygen
Argon
11
Q
Where is the ozone layer found in the atmosphere
A
Stratosphere
12
Q
What is tropospheric ozone?
A
Air pollution
Made from nitrous oxide emitted from fossil fuel burning
13
Q
What is residence time
A
Average lifetime of a molecule in armosphere
14
Q
What is a steady state
A
Inflow rate (sources) equal the outflow rate (sinks)
15
Q
Explain the bathtub analogy for residence time
A
Resevior is like a bathtub
If the atmos gas concentration stay the same, then the source and sinks must equal each other
Water flow into tub must equal water flow out of tub
16
Q
Which gases have the longer residence time in the atmosphere?
A
Nitrogen and oxygen
17
Q
Why are the oceans a key factor in determining climate and climate change
A
Ability to store and transoprt huge amounts of energy and delay the temperature response because of its heat capacity
18
Q
What is the thermocline?
A
Layer where the ocean temp decreases rapidly with depth
19
Q
Why is the deep ocean cold?
A
Because the water comes from the polar sea surface
Densest surfa e waters are near the poles —> denser water sinks —> this supplies cold eater in the deep ocean
20
Q
What is the eath’s energy balance
A
Incoming solar energy absorbed = terrestrial infrared radiation emitted to space
21
Q
What are the properties of an electromagnetic wave
A
Wavelength, frequency, amplitude
22
Q
The analysis of radiation by wavelength or frequency is called
A
Spectroscopy
23
Q
What is thermal radiation
A
Radiation emitted by substance because of its temp
24
Q
As a substance gets hotter, the emitted thermal radiation wavelength gets longer or shorter
A
Shorter
25
A materials ability to emit radiation is the same as it’s ability to...
Absorb radiation
26
What is black body radiaiton
Efficiency is 100% to absorb and emit radiation
27
What is infrared radiation
Invisible radiaiton
| Wavelengths that are longer thsn the visible red wavelengths
28
What are the two types of radiation important for climate change
1. Solar infrared radiation - shortwave, emitted by sun, makes up 1/2 solar radiation
2. Terrestrial infrared radiation- longwave, emitted by earth and atmosphere, STRONGLY ABSORBED AND EMITTED BY GREENHOUSE GASES AND CLOUDS
29
Which electromagnetic waves can transmit through the earth’s cloudless atmosphere
Some UV, most visible light, some infrared, some microwave and some radio
30
What causes the greenhouse gas effect
Complete of partial blocking of some of the infrared wavelengths
31
The fraction of incoming radiation that id reflected by an object is called the ... of the object
Albedo
32
What does an albedo of 1 mean? How about 0?
```
1 = 100% reflected
0 = 0% reflected, all is absorbed
```
33
The average planetary albedo is 0.3, what does this mean?
30% of incoming radiation is reflected, 70% is absorbed
34
What reflects most of the sunlight and what absorbs most of it?
Relfects = clouds, ice, desertd
Absorbs = trees/forest, oceans
35
What is the effective planetary temperature
Temp earth appears to emit from space
Teff must be big enough to make enough outgoing thermal radiation to balance the net incoming solar radiation
Increases if more solar radiation
Decreases if earth gets higher albedo
36
Why is the effective planetary temperature lower/colder than the actual observed average surface temp?
Teff does not take into account the greenhouse gas effect which raises the surface temp
37
What 3 factors determine the globally averaged surface temperature
Amount of incoming solar
Albedo of earth
Greenhouse gas effect
38
The terrestrial infrared radiation gets progressively more blocked as the greenhouse gas concentration increases. Why?
Greenhouse gases absorb and emit at certain terrestrial infrared wavelengths
Increasing amount of g gases reduce the penetration depth of the terrestrial infrared radiation at the specific wavelengths that interact with the g gases
39
What happens if the atmosphere becomes more opaque at cetain wavelengths?
The radiation at those wavelengths can’t penetrate as far
40
Radiation that escapes to space starts from colder, higher up regions of the atmosphere where radiation reaching the ground starts from lower down. How does the increasing opaqueness of the atmosphere effect the greenhouse gas effect?
More opaque, radiation can’t penetrate as far into the atmosphere
More radiation reaches the ground + g gas effect is larger
41
How does adding g gases warm the earth
G gas concentrations increase - atmos more opaque
Penetration depth of infrared radiation is reduced - can’t travel as far
outgoing terrestrial radiation escaling to space comes from higher up in the atmos where it is colder
Colder atmos release less thermal radiation
Results - earth releasing less terrestrial bc of g gases but the net incoming solar is staying the same
42
Why is global warming happening (essentially)
The extra g gases are making the atmosphere less transparent in the infrared
Net incoming solar radiation energy is larger than the outgoing terrestrial
43
Where does the accumulated energy from the imbalance of solar snd terrestrial radiation go?
94% to ocean warming and 3% to melting ice sheets, 3% to heating land
44
Will the energy imbalance between solar and terrestrial persist forever?
No - it will eventually reach a new steady state
Ocean, land and air temp sill increase gradually and gradually increase the amount of terrestrial infrared escaping to space
But new steady state will have higher surface temp
45
How is the current energy surplus that the earth is experiencing being used up?
Heating ocean
Melting ice sheets and glaciers
Heating land and sub-surface
46
Explain the difference between a maritime climate and a continental climate
The heat capacity of the oceans imposes a time delay In the climate system
Takes longer to heat oceans
47
What are some consequences of the high heat capacity of the oceans
Warmest summer temp occur month of two after max solar energy on june 21
Annual temp extremes are smaller nearest ocean
Full impact of global warming is delayed while oceans warm up
Tropical oceans are heat sources to drive tropical cyclones
48
Why are the poles cold?
Earths angle, solar radiation near pole is spread out over a larger area, so less energy per unit area
49
Why do we experience seasons?
Earth’s tilt
50
What are the two types of local radiative energy imblanaces
1. Net radiative surplus (positive) over the tropics and net radiative deficit over the poles
2. Locally earth;s surface has a surplus whereas local atmos above has a deficit
51
What motion does the energy imbalance of the poles and equator drive?
What about the local imbalance of the surface and the atmos?
Pole-equator - drives the meridional dynamics / motion of the atmosphere and the oceans
Locally - drives the vertical dynamics the lower atmos (troposphere)
52
The latitudinal imbalance in radiative energy get balanced in total by what..
The internal dynamical motions of the at atmos and oceans
Transfers sensible and latent heat from thd tropics to the poles
53
What internal dynamical processes transfer sensible and latent heat from the tropics to the poles?
Had;ey cells, tropical cyclones, extratropical cyclones snd ocean circulstion
54
Explain the net radiative imbalance between the atmosphere and the surface?
Surface has net radiative heating
Atmos has net radiative cooling
*turbulence, convection, thunderstorms - transfers surface heating to atmosphere so that total energy balance occurs everywhere
55
What is the earth’s general circulation?
Transfers sensible and latent heat from regions of net radiative heating to regions of net radiative cooling
Dynamical motions set in place to achieve local energy balance everywhere
56
What are the two main climate regimes?
1. Tropical and sub-tropical
(30 deg n and s)
2. Extra-tropical
(Poleward of 30 deg latitude)
57
Explain the tropical and subtropics climate regime
```
30 deg n and s
Horizontally uniform temp
Active weather (thunderstorms, tropical cyclones
Weak seasonality
Monsoons, hadley cells
Easterly trade winds
```
58
Monsoons are a heat capacity effect. Explain
Air over land is warmer than ocean air in the summer —> oceans have large heat capacity, don’t warm up as fast
Sets up a circulation of air - warm rises over land and cool sinks down over ocean
This cycle reverses in the winter - seasonal varying rainfall is called monsoon
59
What drives the thermohaline ocean circulation
Local net radiation imbalance
60
What is the thermohaline ocean circulation
Deep circulation
Transfers heat, water and salt
Caused by ocean water density differences
Densities determined by temp and salinitydifferences
61
Where does the oceans deep water come from?
Greenland and the antarctic seas
62
Consider an atmosphere with no greenhouse gases and no clouds. How would this effect the energy of the earth?
It would be in a steady state / balanced
Atmos transparent to long-wave terrestrial and not emit any longwave
Surface temp would be the effective planetsry temp (-18 deg)
63
No consider an atmos with greenhouse gases and clouds creating a “blanket” in the atmos. Explain the blanket analogy
G gases emit more terrestrial infrared back to the ground than to space because its warmer in the atmos closer to the ground
Top of blanket is colder - less emitted
Bottom of blanket warmer - more emitted
Amount of infrared emitted depends in temp
64
Why does the planet need the greenhouse gas effect
Without it, surface temp would be teff (-18 deg) and freeze all water and life as we know it - greenhouse gas effect helps keep the planet warm and liveable
65
What is radiative forcing
Chg in net total radiation at the top of the atmos which occurs bc of a chg in climstr system (i.e increasing co2, changing solar input, adding volcanic aerosols)
66
The net total radition is the difference between what
Between downward and upward solar shortwave and terrestrial infrared radiation
67
What happens to the terrestrial infrared radiation if we instantly double the amount of carbon dioxide
The surface temp is still at 15 deg
The blanket is thicker
Penetration depth of long-wave ir is reduced
Stronger absorption of long-wave ir
Top of the blanket is now colder because the long-wave being emitted to space is at a higher altitude
68
What happens to the terrestrial infrared radiation if we double the amount of carbon dioxide and a new steady state is established
The warming of the atmos and surface continues until teff emitting level of terrestrial IR to space is back at -18
The surface temp will warm by 3 deg to 18 deg
This change takes time because of the oceans time delay
69
What causes the greenhouse gas effect
Emission of terrestrial infrared radiation by g gases and clouds downward to the earth’s surface
70
Is venus’ surface warmer because it’s closer to the sun?
No
It has a stronger greenhouse gas effect
71
What is a greenhouse gas
Molecule that can absorb terrestrial infrared radiation with wavelengths in the 4-100 um
72
How many atoms does a greenhouse gas have
3 atoms or more
73
Greenhouse gases are... or... atomic molecules
Tri or polyatomic
74
Greenhouse gases are tri or polyatmoic molecules giving them different vibrational modes. How does this effect their ability to absorb and emit in the infrared?
If vibrational mode matches the infrared radiation wave frequency, the molecule can emit or absorb
75
What are the 5 greenhouse gases
```
Methane
CO2
Water vapour
Nitrous oxide
Ozone
Halocarbons
```
76
What are the two vibrational modes of carbon dioxide? Explain them
Bond stretching and bond bending
The two frequencies correspond to specific wavelengths in the terrestrial infrared where they can emit and absorb
77
What contributed to the natural greenhouse effect
Water vapour
Clouds
Other gases (mostly CO2)
78
What is the natural greenhouse gas effect?
Warms the earth surface from the teff of -18 deg to the actual surface temp of 15 deg
79
What accounts for 70% of the natural greenhouse gas effect
Water vapour and clouds
80
Why does the concentration of CO2 oscillate annually?
Global photosynthesis and respiration
81
When do the co2 concentrations show a minimum globally? What about an increase?
Minimum during nothern hemispheric autumn after summer’s new biomass growth removes co2 through photosynthesis
82
How do we know the pre-industrial co2 concentrations of about 280ppm?
Air bubbles trapped in ice cores drilled from the Greenland and antarctic ice sheets
83
What are the main anthropogenic sources of methane
```
Rice paddies
Cattle
Biomass burning
Fossil fuels
Landfills
```
84
What are some natural sources of methane?
Wetlands
| Lakes, termites, oceans, permsfrost
85
What is a natural sink of methane
Chemical reactions in atmos
| Sink in soils
86
What is most of the increase in nitrous oxide emissions from?
Agricultural sctivites
Fertilizer
Animal production
87
What is the global warming potential
By definition the gwp of co2 is always..
Radiative forcing of a gas averaged over the given time period compared to same mass of co2
Gwp is always 1
88
The extent to which a greenhouse gas directly contributes to climate change depends on what 3 things
Quantity of gas
Time before its removed from atmos
Infrared energy absorption propreties
89
The global warming potential is usually averaged over what length of a time period
100 year time period
90
Methane is 23 times more potent as a greenhouse gas than co2 but co2 still exerts more radiative forcing than methane in the atmosphere... why?
Because there’s more co2 in the atmos
91
The gwp potential of nitrous oxide is much larger than methane because...
Nitrous oxide has a longer lifetime than methane
92
Why does water vapour not have a global warming potential
Because it’s a natural greenhouse gas nad only has a lifetime of 1 week
93
What is equivalent co2
Concentration of co2 that would result the same level of radiative forcing for a given type and concentration of another greenhouse gas
94
Is equivalent co2 larger of smaller than actual co2 ppm
Larger
Usually by 25-30%
95
If we eliminated all anthropogenic aerosols, how would it affect to co2 concentrations?
It would increase them almost instsntly
Believed that snthroopgenic aerosol cooling effect is offset by non-co2 g gases
96
Why do they recommend reducing blsck soot?
Its the only aerosol that significantly warms the climate by directly absorbing solar energh
Removing soot reduces radiative forcing directly
97
What are the two bad properties of halocsrbons (hfcs)
Destroys atmospheric ozone by releasing chlorine
Strong greenhuose gas - 5000 times stronger than co2, long lifetime,
98
Ground level ozone pollution is formed by what
Oxygen + volatile organic compounds + nitrous oxide (traffic exhaust + indutries) = react with sunlight = makes smog
Harmful to humans and plants
99
Where does the carbon being released via fossil fuels go
Oceans and land + most into the atmosphere
100
What are three forms of carbon storage?
```
Inorganic carbon (co2 in oceans, atmos, valcanic vents)
Organic carbon (photosynthesis)
Carbon in rocks
```
101
What is co2 residence time in the atmosphere/
4 years
102
CO2 is nesrly uniformly mixed in the atmos since global atmos mixing occurs on a time scale of less than year... however the anthropogenic carbon pulse lifetime in the total climate system is much longer... why?
Because its determined by the final burial rste of carbon into the ocean bottom, which is very small
103
What is the difference between emissions and concentrations
Emissions is what were adding
Concdntrations is how much there is total
104
What are two anthropogenic carbon dioxide sinks
Land biomass and oceans
105
What are the sources and sinks of anthropogenic co2
Sources
Fossil fuels and land use (deforestation)
Sinks
Oceans, land biomass, stays in atmosphere
106
What is gross primary productivity?
Photosynthesis removign atmospheric co2 — creating new biomass
107
What does deforestation do to the csrbon budget?
Appears as a source because it reduces the removal of co2 from the atmos
108
Explain the ocean biological carbon pump
Photosynthesis in surface waters - stores carbon as organic matter, reduces partisl pressure of surface ocean co2
Helps draw down carbon dioxide from atmosphere
109
What is happening to the ph of the oceans as more co2 is drawn in
Becoming more acidic, affecting ecosystems
110
Fresh water makes up 3% of all water on earth. 70% of thst fresh water is icecaps and glaciers and 30 % is ground water... what makes up that last 0.3% of fresh water?
Lakes and swamps and rivers
111
What is runoff?
Precipitation - evapotranspiration
112
In the global annual average the total amount of evaporation of water and ice from the earth’s surfacd must equal the total what?
Precipitation
113
What makes the oceans locally saltier? What makes them locally fresher?
Saltier - evaporation greater than precipitation - drought can occur and ocean becomes saltier
Fresher - evaporation less than precipitation - excess water runoff returns to oceans
114
What is the residency time of water vapour in the atmos? How does the effect tropospheric aerosols and pollution?
One week
Pollution and tropospheric aerosols wash out with rain - so their residency time is also about a week
115
Why does you skin feel cold after coming out from swimming in a lake? How would a windy day affect this?
Cold water on skin evaporates
This requires energy/latent heat
Latent heat is extracted from your body/skin
Wind = low humidity = evaporation rate is faster and cooling is faster
116
In the phases of water, what processes require latent heat input? What processes release latent heat?
Require - evaporation and sublimation of ice (from ice to vapour)
Release - condensation and deposition (vapour to ice)
117
What drives the hydrological cycle?
The atmosphere has a net radiation deficit and the surface has a net radiation surplus
118
When does the latent heat get released back into the atmosphere as sensible hest in the hydrological cycle?
When it rains, the latent heat gets released as sensible heat
119
In the atmosphere how is the latent hest being transferred?
Going from evaporation to condensation sites
Energy from surface up to the higher latitude in the atmosphere
120
What is the saturation water vapour
Max amount of water vapour at equilibrium
It increases with temperature
121
What is the relative humidity?
Ratio of actual amount of water vapour to the saturation amount of water vapour
122
What happens when the relative humidity is 100%
The air parcel is being cooled when its being lifted into the atmosphere and forms a cloud
123
What happens to the relative humidity as the air parcel cools? (Hint; air that goes up is make]ing rainy clouds, sir thst going down is cloud-free and sunny)
When it coolsmas it moves upward, the amount of water vapour stays the same
As temp decreases the saturated amount lg water vapour decreases
As a result, the relative humidity increases, and once it reaches 100% the water vapour condenses and makes a CLOUD
124
What causes rain?
Air parcel rises, expands to match air pressure which gets smaller w height
Volume increases and parcel does work against surrounding sir which uses internal energy - parcel starts to cool
Relative humidity increases as parcel cools - at 100% makes a cloud because parcel is saturated with water vapour
Eventually gets cold enough, ice crystals forms and grow and fall out of the cloud, melt and rain to the ground!!!
125
What 2 things is the rainfall rate proportional to?
Amount of water vapour being lifted
Strength of the upward motion in the cloud
126
Most desert are located under what
The descending branch of the hadley cells
Warms air and evaporates the clouds
127
High precipitation occurs where
Near equator with the ascending branch of the hadley cell
Warm moist air being lifted upwards
128
What are some climate vegetation interactions
Vegetation and albedo
- dense forest = dark = absorb sun
- pasture = light = reflects
Transpiration increases water vapour in atmos
129
What are aerosols
Tiny particles
0.01-10 um
130
What are primary aerosols? What are secondary aerosols?
Primary = crested st earth’s surface and lofted by wind
Secondary = made by gas to particle chemical reactions in atmosphere
131
What is the lifetime of aerosols?
Only about a week in troposphere
132
By burning fossil fuels, how are aerosols created?
Incomplete combustion
133
Why are aerosols important?
Reflect sunlight back to space(cooling)
Act as nuclei centre for cloud droplets and ice crystals
Health concern + air quality
Acid rain
Volcanic eruptions - aerosols in strato
Reduce visibility (planes can’t see shit)
134
What is the direct aerosol effect?
Aerosols reflect sunlight to space
Exception - soot absorbs sunlight
135
More aerosols mean more cloud droplets because they can act at nuclei for them. How does this affect the cloud properties and the climate?
Clouds are brighter and reflect more sun
136
What is the indirect aerosol effect (cooling effect)
Aerosols make clouds brighter so they reflect more sun back to space
They have smaller droplets making it harder for the cloud to rain and therefore they last longer in the atmosphere
137
How long can volcanic aerosols that reach the stratosphere reside there? Why?
1-2 years
Lacks clouds and rainfall to remove them
138
What is a positive feedback?
Amplifies the original change, can be negative or positive amplification / increase or decrease
139
What is a negative feedback
Reduces the magnitude lf the original change, regardless of whether the change was an increase or a decrease
140
Why is the water vapour feedback large and positive?
Global air temp increases bc co2 concentrations increase, water vapour increases in atmos, increased greenhouse gas warming from water vapour
Amplified
141
Why do the nighttime temps in a desert get very cold even though it was very hot during the day
Amount of atmos water vapour in desert is low
The blanket is thinner, penetration depth is longer, more terrestrial radiation from the ground going upward and cooling at the ground
142
Do high clouds warm or cool the earth?
Warm the earth
Transmit most solar but block warm infrared from the surface and emits cold infrared to space
143
Do low clouds warm or cool the earth?
Cool the earth
Reflect most solar back to space and emit warm thermal infrared radiation
144
What type of cirrus clouds show a positive feedback? What type show a negative feedback?
more thin cirrus clouds - warming (thin wispy clouds)
Less thin cirrus clouds - negative feedback
145
Cumulus clouds - positive and negative feedback
More cumulus clouds - cooling - negative feedback
Less cumulus clouds - warming
Positive feedback
146
What is an uncertainty with clouds and climate change?
Whether it will be a positive or negative feedback
If its cirrus clouds (more infrared blocked) or less total clouds (more solar reaching surface) then it will be positive feedback — more warming
If its low clouds (increase solar albedo) and less thin cirrus clouds - negative feedback, cooling
147
The ice albedo and temperature feedback - positive or negative? Explain
Positive
Warming - increased open water in summer, thinner ice, less snowmcover - more shortwave solar absorbed into system - more warming
148
Large areas in arctic ocean are currently dark... this means
Absorbing solar radiation - positive feedback
149
Vegetation has some positive and negative feedbacks. Give examples or each
Positive
Albedo; higher temp - more veg - darker surfsce - more absorption- higher temp
Moisture supply; more veg - more evapotranspiration - more water vapour - more rain - more veg
Negative
Carbon budget; more co2 - more veg - more photosynthesis - removal of co2
150
About 1/3 of all land has been converted to what... how does the effect climate
Cropland or pasture
Surface albedo, soil moisture and carbon fluxes
151
What are some possible feedback in the biosphere that we need to know to predict future co2?
```
Plankton multiplier
Soil microbial activity
Biosphere dieback
Release of stored methane
(All positive)
```
Carbon dioxide fertilization (negative)
152
Methane temperature feedback - positive or negative? Explain
Positive
| Temperature goes up - permafrost thaws - co2 and methane release into atmosphere - temp warms
153
The climate consists of 5 interacting components... what are they
```
Atmosphere
Hydrosphere
Cryosphere
Land surface
Biosphere
```
154
What is the main difference between weather and climate forecasting?
Weather forecast = predict future atmosphere state at a particular time and location, minimizing difference between predicted and actual weather at that place and time
Climate = we don’t care about weather at a particular time, but care about the average predictions and the extended time period
155
How is weather forecasting done?
Computers numerically solve atmospheric equations or motion
156
What are the 3 equations that have to be solved to predict weather? What equation predicts what?
Momentum - predict winds
Energy - predict temp
Continuity - density of air and water
157
Why aren’t the weather forecasts perfect?
Gaps and errors in measurement
Limited spatial resolution of computer model
- need faster computers to improve models
Approximations in the equations
-
Non linearity of system - limits range of weather predictions to weeks, not an issue for climate models though
158
How do we model complex sub-grid processes like clouds?
Approximate the small scale effects, measure on a small scale
159
What are the steps in running a global climate model (global circulation model - GMC)
1. Specify input - choose boundary based on known changes of solar, co2, ice sheets, mountains, continent position
2. Run model simulation of ocean and atmos - physical laws or radiation + circulation
3. Analyze climate output
4. Compare - data from earth’s history
160
What are some main difference in climate vs weather models in terms of resolution, simulation time, vegetation, oceans
```
Climate
Resolution = 100km
Oceans = full air-sea interaction. Ocean dynamics
Time - >30 years
Veg = highly interactive
```
```
Weather
Resolution = 10km
Oceans = fixed sea surface temp
Time = 2-14 days
Vegetation = fixed or ignored
```
161
Climate models are now so sophisticated that they are now called...
Earth systems models
162
Testing the climate models ability to predict 20th century temps is part of the validation procedure. Models tend to do a good job of predicting 20th century climate but it can be right for the wrong reasons... what are some future improvements for climate models
```
Faster computers
higher spatial resolution
Improve parameters around some processes
More observational data
More inter-model comparisons from groups around the world
```
163
How were climate models used to understand current climate change
Cooling of sea surface temp in North Atlantic may be caused by anthropogenic aerosols from europe, helped weaken African monsoon
Also weakened monsoon circulation and shifted inter-tropical convergencezone
164
What equilibrium climate sensitivity?
Equilibrium / final steady state change in the global mean surface temp following doubling of pre-industrial co2
165
What is the transient climate response
20 year global mean surface temp chg after 70 years of carbon dioxide increasing at 1% per year compounded
- results in a doubling of co2 in 70 years
166
What are some positive feedbacks in the earth’s climate system
Water vapour
Ice albedo
Clouds
167
the equilibrium climate sensitivity would only be about 1.2 deg if we just consider the effects of a doubling co2 concentration. Why is actually 3 deg?
Because of the positive feedbacks
168
What does a low sensitivity mean/ what about a high sensitivity?
Low = low change, climate change will be much easier to deal with
High = climate change will be detrimental and cost to adapt is high
169
Whatis the precautionary principle
Principle in environmental law
Dictates that we should plan for a higher value, don’t ignore the high value rven though you have an average
Insurance policy
170
Why do we still have some uncertainty in the model derived equilibrium climate sensitivity?
Because the feedbacks have significant uncertsinties
Especially clouds and oceans
171
What is the transient climate response
Amount of warming expected in 70 years for a doubling of co2
172
What is the range for the transient climate reponse
1-2.5 deg in the next 70 years
173
Climate sensitivity is designed to look at graudal average trends in climate induced by gradual change in radiative forcing. It does not account for...
Rapid changes
| Unstable tipping points
174
Who makes assessment reports roughly every 6-8 years to update climate forecasts, using w0 global climate models from various centres around the world and creates model predictions to project climate change in the next 100 years...
Ipcc
Intergovernmental panel on climate change
175
What are representative concentration pathways
Four future radiative forcing pathways developed for the climate odeling cmomunity as a basis for modelling experiments
I.e models for climate scientists to follow so that the reports are comparable
176
How are rcp’s set up?
Final radiative forcing values of 2.6-8.5 With co2 concentrations and the effects/pathway of each value
177
What is our current radiative forcing value (2011)? What is the value is co2 doubles?
2. 3 W / m2
| 3. 8 W / m2
178
Which rcp pathway are we currently following?
Rcp 8.5 - this is the worst one :)
179
The last 542 million years was the..
Phanerozoic
180
What was the main controller of temperature in the phanerozoic?
Co2
181
The earth’s crust is divided into...
Plates that move in response to convection in the mantle
182
Explaine the relationship between volcanism and rock weathering
If rock weathering sink of co2 exceeds volcanism’s supply/source of co2
Atmos co2 decreases, climate cools, vice versa
183
What 3 things do tectonics control
Volcanism
Continental drift
Orogenesis (mountain making, continental plates collide)
184
Is weathering a negative or positive feedback on tectonic forcing
Negative feedback
Prevents extreme temps by stabilizing amount of co2
System adjust to reduce initial change
185
What ended after an asteroid hit 65 million years ago near the yucatan peninsula
Cretaceous period
186
What are the 6 major extinction events that happened during the Phanerozoic in order
Often-sit down, perhaps their-joints creak, agonizingly
Ordovician - silurian (glaciation)
Late Devonian (dust, volcanoes)
Permian (largest mass extinction)
Triassic/jurassic (floods)
Cretaceous/ palocene (k-t event - asteroid)
Anthropocene - current day, caused by humans
187
Earth has been gradually cooling over the last 50 million years, how do we know this?
Temps derived from oxygen isotope analysis of marine organisms buried in the sea floor
188
Why did the global climate cool over the last 50 million years? (3 things)
Sea floor spreading rate decreased, slowing the rate of co2 input
Weathering caused faster removal of co2, formation of Himalayas
Poleward ocean heat transport reduced and deep water formation shifts to high latitudes
189
What formed the Himalayas? Effect on climate?
Collision of indian subcontinent with asia
Exposed rock for chemical weathering
Removed co2 and cooled climate
190
What allowed Antarctica to cool and start growing ice sheets?
Opening of drake’s passage helped isolate Antarctica from meridional (north-south) heat transport
191
We are in a long glaciation epoch although currently we are in an interglacial period called the..
Holocene
192
How do we deduce recent psst climates?
Tree rings
Ice core drilling
Lake sediment
193
Atmospheric co2 lowered from the pre-industrial holocene concentration of 280 ppm to 190ppm during the glacial maximum about 20,000 years ago...mwhere did this 90 ppm of co2 go?
Deep ocean
194
Glaciation is initiated by the earth’s orbit which is controlled by attractions between the earth, moon, sun and other planets (mostly Jupiter). What are the three orbital variations
1. Earth’s tilt varies over 41,000 year - solar input varies in high latitude
2. Orbit around sun varies every 100,000 years - seasons
3. Position of solstices
195
What are milankovitch cycles? (3 variations do to with earth’s orbit)
Earth’s orbit around the sun
Tilt of earth
Soltices
196
How can glaciation start
Summer solar energy needs to be weak enough to not melt all the previous winter’s snow
Ice sheets need to form on land
SUMMER SOLAR ENERGY AT 65 DEG NORTH LATITUDE
197
What is the key variable to predict the growing ice sheets
SUMMER SOLAR ENERGY AT 65 DEG NORTH LATITUDE
198
What was the period of deglaciation cooling that happened over 12,000-10,700 years ago
Younger dryas
199
What is some evidence for the younger dryas cold period
Southward re-advancement of polar water in the north atlantic to 45 deg north
Scotland reverted to arctic vegetation
Insect fossil in Britain indicated cooler temps
200
What caused the younger dryas
Change in melt-water flow in north america during deglaciation
Drainage direction of north American ice sheet changed from southward to gulf of Mexico to northward into the hudson bay + arctic ocean
Brought pulse of fresh water, cutting off deep water formation and cooling the region
201
Why were the monsoons much stronger 10,000 years ago?
Because sun was much closer to earth
202
When did the transition for hunsting-gathering to farming start? Why?
About 10,000 yesrs ago
Monsoons much stronger because Northern hem summers much warmer and wetter
203
About 5000 years ago, many civilizations started to collapse (china, indus, nile, peru, maya, and some others)... why?
Drought
204
During a little ice age, about 1400-190p in europe, what sun spots occured?
Maunder sunspot minimum
Sporer sunspot minimum
205
What are some possible explanations for the little ice age that happened in europe and destroyed many villages and farmhouses in the alps
Change in ocean circulation- thermohaline circulation may have slowed down
Strong volcanoes putting aerosols in stratosphere, reducing solar radiation reaching surface
206
What interglacial period happened about 120,000 yesrs ago, had sea levels about 4-6 m higher than today’s and a smaller greenland ice sheet? Its also a potential indicator for what our future may look like in the next hundreds of years
Eemian
207
The eemian is believed to have been only 1 deg warmer than today and sea level was 4 m higher at its maximum. Why?
May be because the collapse if west Antarctica ice sheet caused rapid sea level rise without an accompanying warming
208
What period is an analog for our future in next 1000 years
Mid-pliocene warm period, 3.3 million years ago
209
What period had temps 2-3 deg highter, sea level 25 m higher, Greenland ice sheets much smaller
Mid pliocene
210
The global cooling that occurred towards the end of the pliocene may be responsible for what shift in vegetation
Forests to grasslands and savannas
211
Why is the pliocene s]a useful period to use as an analog
Continental positions were basically the same
Ocean circulation and biota were similar
Give us an idea what to expect with a warmer equilibrium established on earth with co2 over 400 ppm
212
What were the pliocene biomes like
Northward shift to temperate and boreal vegetation zones, expansion of tropical savannahs
High arctic covered in boreal forests, glaciation in canada not happening yet
213
The mid pliocene was around 400 ppm, 2-3 deg warmer, sea level was 25 m higher suggesting reductions in contniental ice sheets and warmer ocean temps... why is this important to us now
Its a window into out future, what to expect in the long-term
214
What period is an analog for rapid warming?
Paleocene-eocene thermal maximum (PETM)
215
In which period did global temp rise by 6-8 deg over a 20,000 year period , where many benthic forminifera a d terrestrial mammals wen’t extinct, but numerous modern mammalian order emerged?
Petm
216
What were the 2 observations that indicated a massive release of carbon at the petm?
Large global negative carbon isotope excursion
Dissolution of deep ocean carbonates
217
What was it likely that the negative shift in carbon isotope was likely organic carbon
Organisms discriminate againt carbon 13 during photosynthesis
218
What limits the petm analog?
Ice sheets and ocean circulation quite different as well as continental positions
