Stability
affects
pollution
patterns
Pollution
dispersion most
effective under
unstable
conditions
Inversions due
to advection
Climate Change
Milankovitch Theory of Climate Change
The Earth changes its:
a) orbit (eccentricity), from ellipse
to circle at 100,000 year cycles,
b) wobble (precession), affects
timing of seasons with respect to
perihelion, at 23,000 year cycles
c) tilt (obliquity), from 22° to 24.5°
at 41,000 year cycles.
THESE FACTORS AFFECT GLOBAL CLIMATE BECAUSE OF
GREATER LAND AREA IN THE NORTHERN HEMISPHERE
Climate Change is Nothing New
TODAY
*
The rate of climate warming projected by the IPCC is
believed to be very rapid compared to past climate changes
*NB: The temporal scale used to examine climate change
is very important, as different patterns are revealed, depending
on the timescale used.
The last glacial maximum
[insert
fig 164c]
Temperature variation during
the past two millenia
[insert
fig 166]
Climate Since the
Most Recent Ice Age
Recent Climate Change:
The Infamous “Hockey Stick” Figure
The Jurassic
A much warmer Earth with more CO2
Climate and CO2 Concentrations: 2 to 590 million years BP
Current Global
Mean Temperature
& [CO2]vap
Berner RA and Kothavala Z. 2001. GEOCARB III: A revised model of atmospheric CO2 over Phanerozoic time. American Journal of
Science. 301: 182-204
Does a large, composite volcano
affect climate on a global scale?
Effect of Mount Pinatubo Eruption
Note:
Volcanoes also
release CO2, and
warming occurs
in the long term
during tectonically
active periods
(eg. Triassic/Jurassic
boundary)
TEMPORARY
COOLING
Mt. Pinatubo aerosols
[insert
fig 1613]
Ice core data
Temperature,
CO2 and CH4
are all in
phase
Are the gas
concentrations
an effect or a
cause of
warming or
both?
Climate Change
•Carbon dioxide
absorbs outgoing
longwave radiation
emitted by the Earth
•This causes
temperature to rise
on a global scale
•CO2-induced global
warming first predicted
by Arrhenius (1896)
•Concentrations have
increased from 280ppm
(preindustrial) to
385 ppm (2007)
http://www.glumbert.com/media/globalwarming1958
K TO SPACE=31
L
L TO SPACE=69
100-31-69=0
100
GREENHOUSE
EFFECT HERE
ABSORPTION
46+19+4=69
Heat transfer
7+24=31
Compensates
for radiation
imbalance at
surface
L<K !!
46-15=31
Source: NOAA
The Global Carbon Cycle - 1990s
Units Gt C and Gt C y-1
Atmosphere
3.
…are leading to a
build up of CO2
in the atmosphere.
500
3.2
750
63
Plants
60
Soil
2000
6.3
About
16,000
1.6
1.
91.7
Fossil emissions
90
2. …and
land clearing
in the tropics...
The Kyoto Protocol sought
to reduce net carbon
emissions by about 0.3 Gt C
below 1990 levels in
‘developed’ nations
Fossil Deposits
Oceans
39,000
Climate Change
The Observed Record (IPCC)
The 20th century was unusually wet in much of North America.
Source: IPCC
Temporary,
regional
cooling
effect
Source: IPCC
1950
Climate
Modelling
2006
Future Scenarios
THE YEAR 2050 IN SOUTHERN ALBERTA
Temperature Increase
+2.5 to + 5.7C
above 1971-2000
climate normals
(McGinn and
Shepherd, 2003)
Growing Degree Days
Barrow and Yu (2005) In: Sauchyn (2007), with permission
Future Scenarios
THE YEAR 2050 IN SOUTHERN ALBERTA
Precipitation Increase
+3 to +36 %
above 1971-2000
climate normals
(McGinn and
Shepherd, 2003)
More rain and
less snow from
autumn to spring
(Lapp et al., 2005)
Annual Moisture Index: ET > P
Barrow and Yu (2005) In: Sauchyn (2007), with permission
OLDMAN RIVER FLOW
PROJECTIONS
Annual flow projected
to vary from -13 to +8%
(mean -4%).
•
Increased winter
rain:snow ratio and
above-freezing
temperatures will
increase winter runoff
•
Earlier spring melt and
increased
evapotranspiration will
decrease summer
runoff
SEASONAL FLOWS (2039-2070)
m3 s-1
•
CURRENT
ECH
HAD
NCAR
Pietroniro et al. (2006) In: Sauchyn (2007)
Carbon ‘Enrichment’
MORE EFFICIENT PLANTS?
Faster growth rates
Increased water-use efficiency
•lower stomatal conductance required
to maintain ci
Increased nitrogen-use efficiency?
Impact of global change on WUE
depends on net result of opposing
effects of increased Ta and VPD
vs. elevated [CO2]vap
Will the same species
be dominant in a 2xCO2
environment?
Future Scenarios
NET PRIMARY PRODUCTIVITY OF ALBERTA GRASSLANDS
Ecosys Model accounts for both climate change and
CO2 enrichment (Li, Grant and Flanagan, 2004)
Input
Canadian Regional Climate Model II climate change projections
(IS92a emissions scenario).
Results
•Lengthened growing season
•Transpiration increases from higher temperatures were offset by
increasing plant water-use efficiency caused by rising CO2
•Increased net primary productivity offset by increasing respiration, so that
carbon sequestration only increased very slightly (2 g C m2 y1) under
climate change
N.B.: Climate change may alter interspecies competition/dynamics and
cause migration. Rapid change may also reduce biodiversity.
Enhanced photosynthesis
Source: IPCC
Meanwhile, we are detecting
stratospheric cooling !
Why ?
Ozone depletion
Tropospheric [CO2] increases
1. Reduced biodiversity
Rapid change may exceed capacity of
plants and animals to adapt to changing
climate and new interspecies dynamics
2. Sea level rise and coastal flooding
Thermal expansion + melting ice
3. Expansion of tropical disease range
4. Soil moisture decreases and
desertification
Evapotranspiration increases may
exceed increases in precipitation
5. Increased frequency of heat illness
6. Increased frequency of severe events?
More energy for tropical cyclones
(supports this hypothesis), but reduced
latitudinal temperature gradients could
reduce middle-latitude storm intensity
7. Engineering problem of thermokarst
(transportation and housing)
8. Affect on outdoor winter recreation
and winter tourism
9. Decreased summer river flow due to
smaller glacier volume and a higher
rainfall:snowfall ratio in Alberta
(eg. Lapp et al. 2005)
Risky global experiment with
uncertain consequences
Alberta’s Fragile Fresh Water Supply
•Partially supported by glacial meltwater
•Glaciers are retreating
•Future ET >> P?
1. Increasing ecosystem productivity?
Higher photosynthesis rates and
water use efficiency due to higher
CO2 concentration*
2. Increased food production?
Higher photosynthesis rates, northward
expansion where soils adequate, longer
growing season
*Depends on soil moisture/depth/nutrients. Lower
production where soil moisture decreases.
PHOTOSYNTHESIS (A)
6CO2 + 6H2O + sunlight  C6H12O6 + 6O2
A LEAF IN CROSS-SECTION
cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
stoma
H20
CO2
Stomata open to maintain internal
CO2 concentrations (ci) during photosynthesis.
Transpiration (E): H20 is lost during this process.
Photosynthesis Measurement
STOMATAL CONDUCTANCE (gs)
• Plant Regulation of CO2 and H2O Exchange
CONDITIONS REQUIRED
FOR OPEN STOMATA
STOMATAL
CONDUCTANCE
1. Adequate sunlight (PPFD)
2. Available moisture
3. Reasonable temperature
4. Low vapour pressure deficit (not too dry)
5. Low internal [CO2]
10-50 m long, <10 m wide
50-500 stomata per mm2
LIGHT
(PPFD)
TLEAF
VPD
(dryness)
CO2
(ca)
LEAF H2O
POTENTIAL
3. Increased water-use efficiency
• Plants reduce stomatal conductance,
yet maintain sufficient internal CO2
• May mitigate desertification and soil
moisture deficit somewhat
4. Increased nitrogen-use efficiency?
Is less Rubisco required at higher
temperatures? (Drake et al. 1997)
5. High latitude warming
Both a negative effect (loss of key Arctic
species, ways of life) and positive effect
(crop growth & NPP - soil permitting)
Free Air Carbon Dioxide Enrichment (FACE)
FACE Results:
NPP increases
(eg. 40% in cotton; 25%
for Sweetgum for 550
ppm vs. 370 ppm)
Carbon sink potential limited for forests: Increase in
wood production is short-lived; C goes mainly to fine
roots and leaves (Korner 2006); affected by soil fertility
No effect on LAI
Stomatal conductance decreases (increased wateruse efficiency)
Lower leaf nitrogen concentration:
Do they need less? Have less? Due to C:N ratio?
Source: IPCC