Embed Size (px)
Citation preview
In nature there are neither rewards nor punishments – there are consequences Robert G. Ingersoll
CO2 balance and composition - the atmospheric energy balance -
In nature there are neither rewards nor punishments – there are consequences Robert G. Ingersoll
The CO2 cycles and flow The slow cycle is based on inorganic chemistry processes that are called weathering and are based on the slow conversion of limestone and other mineral materials to calcium and acids.
Will be discussed in a later lecture on paleoclimate
The fast cycle is based on organic chemistry in plants, photosynthesis converting CO2 to O2 with chlorophyll as catalyzer and light as energy source. The amounts are in Gtons/y.
CO2 exchange with ocean water varies
CO2 storage
Estimated size of major stores of carbon on the Earth.
Sink Amount in Billions of Metric Tons
Atmosphere 578 (as of 1700) - 766 (as of 1999)
Soil Organic Matter 1500 to 1600
Ocean 38,000 to 40,000
Marine Sediments and Sedimentary Rocks
66,000,000 to 100,000,000
Terrestrial Plants 540 to 610
Fossil Fuel Deposits 4000
Organic Carbon Cycle The pre-industrial (1800) amount of CO2 in the atmosphere was 600Gt, balanced by equilibrium between absorption by photosynthesis and sequestration and emission through respiration and release.
nrespiratiosoiloceanatm
ems
photosynthsoiloceanatm
abs
emsabs
y
Gt
y
Gt
y
Gt
dt
COd
y
Gt
y
Gt
y
Gt
dt
COd
dt
COd
dt
COd
50506.74)2(
1006.074)2(
0)2()2(
.
Each process has its own time scale depending on the conversion rate which in turn depend on environmental conditions such as light, water, temperature. The conversion rate is proportional to the product of CO2 abundance in the reservoir, the conversion cross section <(LHT)> and the leaf area A.
ATHLNR COconv ,,2
OHCOOOHC
OOHCsunlightlchlorophylOHCO
222612
261222
6666
6666
and respiration
Photosynthesis
Chemical reaction takes place on a pico-second timescale which translates into a high reaction probability or cross-section. The absorption yield depends on the cross section integrated over the spectrum of the incoming light and the luminosity the actual light absorption and conversion cross section depends on the wavelength, the leaf structure, the pigment composition and the cell conversion mechanism.
The timescale for CO2 absorption is fast, making photosynthesis an extremely efficient absorption process if sufficient leaf surface area is available!
Change of balance Increase of CO2 emission and increase of deforestation since the 19th century!
Drastic increase of the anthropogenic CO2 production due to fossil fuel consumption by growing industrialization
Impact on CO2 equilibrium conditions, which maintain the present status quo in climate !
Observational evidence, CO2
The dashed red line with diamond symbols represents the monthly mean values, centered on the middle of each month. The black line with the square symbols represents the same, after correction for the average seasonal cycle. The curve shows a continuous increase of the CO2 level in Earth’s atmosphere .
YEAR
Impact of CO2 abundance on black-body radiation emission pattern
http://climatemodels.uchicago.edu/modtran/
CO2 Global Distribution
Strong seasonal variations due to climate variances between the northern and the southern hemisphere and feed back correlations over the year.
CO2 observations from Mauna Loa reflect medium location in northern hemisphere, but the observations reflect consistently the seasonal variations in CO2 emission
Other Greenhouse Gases N2O nitrous oxide level was stable for the last 3000 years according to ice core analysis. The present annual increase in emission by 0.2% to 0.3% is due to widespread and rapidly increasing applications of nitrogen based fertilizers, tropical deforestation, and conversion of forest to pasture and farmland.
CH4 methane increases at an annual rate of 0.8% to 1%. This tracks well with population growth. Naturally occurring from wetlands such as bog and swamp emissions the increase is associated with rice cultivation, landfills, biomass burning, mining, natural gas venting, and pipeline leaks. Release of CH4 from Alaskan and Siberian permafrost regions could result in an sudden increase by 500Gt within next century.
CFC chlorofluorocarbons have been developed in the 1920ies for cleaning solvents, refrigerants, and propellants spray cans. Industrial mass production after 1950 caused an unprecedented increase. Inert to chemical processes expected to occur in the troposphere, CFCs accumulate in the stratosphere, where photodissociation breaks up molecules, releasing halogen gases.
Anthropogenic sources of CO2
Alternative World Views
"... the world need[s] to differentiate between the survival emissions of the poor and luxury emissions of [the] rich." Sunita Narain, 2002
Territory size shows the proportion of carbon dioxide emissions in 1980, 2000, 2006.
http://www.worldmapper.org/display.php?selected=295
CO2 emission 1980
CO2 emission 2006
CO2 emission 2000
CO2 emission 2006 per capita
~3t/p >17t/p ~8t/p
~6t/p >2t/p
>2t/p
Population growth
1960 2050 projected
The world population in 1960 was 3 039 million. Today its is with about 7 280 million twice as much. As is the case today, the populations of China and India are (independently) more than twice as big as that of the next largest territory. Every half second a new child is born, every second somebody dies. This causes an increasingly rapid increase in population with increasing needs at decreasing resources
By 2050 it is estimated that the earth's human population will be 9.07 billion. 62% of the people will live in Africa, Southern Asia and Eastern Asia - numerically this is the same as if all the world's current population lived just in these regions. In addition another 3000 000 000 will be spread across the rest of the world.
http://www.worldometers.info/world-population/
Greenhouse gases Greenhouse gases trap the emitted infrared radiation from earth surface in the lower troposphere by atomic or molecular absorption processes, causing a gradual heating of the lower atmosphere layer.
H2O is the most natural occurring greenhouse gas (humidity, clouds). CO2 is primarily an anthropogenic greenhouse gas (industry, traffic). Additional anthropogenic greenhouse gases are industry produced Chlorofluorcarbons (CFCs) and Hydrofluorcarbons (HCFCs).
Single layer Greenhouse model Infrared radiation from the earth surface of emission temperature Te is completely absorbed in atmosphere and radiates into space and back to earth surface increasing surface temperature Ts.
Incoming net solar flux: 4
)1( 0FFavg
Flux A↑ radiated to space depends on atmospheric temperature Ta :
ATA a
4
Flux S↑ radiated from surface with terrestrial surface temperature Ts
4
sTF
0
AFF in
F↑
F0
F0
ees
ees
TTT
TTF
T
19.12
24
)1(
4
4404
4 0
4
)1(
FTeEmission temperature:
Emission temperature Te=255K=-18oC Surface temperature: Ts=303K=30oC
Considering a change in albedo and an atmospheric absorption
4
04
40
2
12
4
1
FTT
FT
es
e
Earth’s surface temperature depends on the albedo . Increasing the albedo (reflection of incoming radiation) reduces the emission temperature Te and therefore also the temperature Ts of the earth surface. Enhanced cloud coverage would cause a temperature reduction.
sea
es
TTT
TT
44
4
2
1
2
1
2
2
A leaky greenhouse where only a fraction of the emitted radiation is absorbed by the atmosphere (full absorption =1) reduces the greenhouse effect and lowers the surface temperature Ts (This corresponds to a reduction of greenhouse gases) and also the atmospheric temperature Ta .
No absorption: 0 ≤ ≤ 1 full absorption
Examples
seaes TTTTT
444
2
1
2
1
2
2
200
220
240
260
280
300
320
0 0.2 0.4 0.6 0.8 1 1.2
Te
Ts
Ta
Tem
per
atu
re
[K]
4
0
4
1
FTe
Emission temperature depends on the amount of incoming solar radiation flux, the insolation Fo !
22
0
4
64
35.011
4
1
m
W
m
W
FTF ee
The globally averaged solar incident
(or emitted) flux Fe on the surface is only a fraction f≈0.16 (for =0.35) of the incoming total flux Fo.
Climate feed-backs Greenhouse models have to account for several potential positive or negative feedbacks that can occur, if the equilibrium of the climate system is perturbed by an additional energy input or energy loss dQ (in units W/m2). The impact can be expressed in terms of surface temperature change dTs .
Q
T
dQ
dT ss
is a measure for climate sensitivity
KTforWm
KT
Q
T
constT
Tsince
TTTTTQ
ee
BB
s
s
e
seeeeBB
25526.04
44
2
13
334
For every Q=1 Wm-2 increase in the forcing of energy balance at the earth’s surface, the surface temperature Ts will change by 0.25K ! Each such change requires altering total insolation by 6 Wm-2 due to albedo or geometrical shifts!
Climate feedback from water vapor in the atmosphere depends on the saturated vapor pressure SVP. If the temperature increases the amount of water at saturation increases, enhancing the greenhouse effect of water and raising the temperature (humid and hot weather conditions).
10067.0
11.6
C
mbarA
eASVP T
See lecture 7.1.
A change by 1oC leads to a 7% change in SVP
KTforWm
K
Q
Te
OHBB
s 2555.02
2
sdT
SVP
SVPd
Taking into account the water vapor for every Q=1 Wm-2 increase in the forcing of energy balance the surface temperature Ts will change by 0.5K ! This is a positive feedback of water vapor formation. However, water vapor will favor cloud formation which increases albedo, reduces insolation and therefore reduces temperature as negative feedback.
Observed annual global temperature trends compared with the simulated global mean surface temperatures, considering separately the natural and anthropogenic forcing contributions. The observed trend suggests an increasing dominance of anthropogenic based forcing contributions. This conclusion is still heavily contested!
Temperature increase predictions as a function of future CO2 emission
Predictions IPCC 2001 for the development of mean temperatures in Europe until 2080 Reality in summer 2010
Comparison with 2003 Science 332 (2011)
Conclusions by the intergovernmental Panel on Climate Change (IPCC)
Possible consequences predicted by theoretical model studies of the IPCC and other research institutions or research groups. Detailed analyses and study are summarized in a number of different reports by the National Academies and are available on-line:
www.nap.edu/topics.php?topic=367
