Earth

1
Earths carbon balance
2
The Basic Principle
CO2 is a greenhouse gas it absorbs infra-red
radiation as heat
There are other greenhouse gasses, such as CH4
and NO2 but CO2 is the major one
3
How is CO2 measured?
Infra red gas analyzers
NOAA monitoring System on Mauna Loa
System for measuring leaf photosynthesis
CO2 absorbs infra red radiation
A test gas sample is compared with a reference gas
4
World network
5
NOAA Stations
Mauna Loa
US Somoa
South Pole
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Mauna Loa CO2
International Geophysical Year
Trend and annual cycle
7
Northern hemisphere effect
March-May maximum
South pole out of phase
8
Global growth rate in atmospheric CO2
Influence of economic downturns can be seen
9
Changes in mean annual global temperature
10
Sea level rise
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Potential effects of sea level rise
Estimates of sea level rise range between 20 and
110 cm by 2100
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Why climate change effects on oceans may pose a
serious threat
In what is being described as "a groundbreaking
move for local government", politicians in the
Florida Keys have recognised that climate change
is likely to threaten their reefs and beaches
with severe damage.
http//news.bbc.co.uk/hi/english/sci/tech/newsid_6
79000/679959.stm
Why climate change effects on sea level poses a
serious threat
Small increases in mean sea level may have large
effects during storm conditions, e.g., Florida,
Maldives, Bangladesh
Possible changes in ocean currents, e.g., the
Gulf Stream and its effects on Northern Europe
dramatic not incremental
Melting of the West Antarctic ice sheet not
included in calculating current estimates of sea
level increase (potential 5m rise).
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Two Biological Questions
1. Could the earths biological systems
accumulate sufficient CO2 to balance emissions?
2. What effects may global change have on the
earths biological systems?
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Summary of the earths current carbon balance
All figures are in billions of tonnes of carbon,
Gt C 1 tonne 1,000 kilo grams
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1. Could the earths biological systems
accumulate sufficient CO2 to balance emissions?
Anthropogenic release
6.3
Net uptake by terrestrial vegetation
-0.7
Net uptake by the oceans
-2.3
Gain by the atmosphere
3.3
Net uptake by terrestrial vegetation would have
to be increased four-fold to off-set the current
rate of increase in atmospheric C
Could any impact be made as part of a
multiple solution approach?
16
A more detailed look at the global carbon cycle,
1990s
17
Net primary production is the difference between
the amount of carbon gained by growth of plants
minus that lost by respiration and decomposition
18
Global carbon amounts net primary production in
different biomes
First
tC/ha/yr
Second
19
Some definitions
Biome all organisms, as well as the physical
environment, in a particular area. Biomes
are usually characterized by their plant life.
E.g., Tundra, tropical rainforest.
Biomass the weight of living material.
SINKS places where a material, or energy,
accumulates
SOURCES places that produce or supply a material
or energy
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Tropical forests have the highest biome net
primary production and the second highest total
biomass. They are strong SINKS for carbon but
if disturbed so that their soil C is respired
they can be strong SOURCES
Although temperate forests have the second
highest net primary production they have a small
global area and so a low total biome C
Note that croplands have a low net primary
production. This is because crops usually do not
cover the ground for much of the year
21
Growth of young forests to absorb CO2
Kyoto Forests
To balance the net gain of 6 Gt of carbon by the
atmosphere through planting young forests,
and, assuming an increase in production of 5 t
ha-1 over the vegetation replaced, e.g.,
replacing a crop, requires over 109 hectares of
young forest, 14 times the size of Washington
State. Balancing the CO2 input from the US
alone would require an area 3 times Washington
State ( 1.2 times the size of California)
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2. What effects may global change have on the
earths biological systems?
A. Direct effect of elevated CO2
B. Multiple effects of elevated CO2 , elevated
temperature, and changed nutrient inputs
C. Possible changes on the distribution range of
biomes and crops
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Direct effect of elevated CO2
Net primary productivity is likely to rise but
Enhancement declines as the period of CO2
enrichment is extended
CO2 enrichment experiments
Acclimation a change in physiology that enables
a plant to maintain a particular pattern or rate
of growth, e.g., reduction in stomatal density
Naturally CO2 enriched sites
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FACE Free Air Carbon Dioxide Enrichment
CO2 is released into the air to achieve an
elevated concentration
Panama
Brookhaven National Lab
Experiments are being conducted with a range of
crop and vegetation types
Catherine Potvin
25
B. Multiple effects of elevated CO2 , elevated
temperature, and changed nutrient inputs
Gain in uptake of carbon may be offset by an
enhanced respiration, especially microbial
respiration associated with decomposition in the
soil and organic litter
Anthropogenic nitrogen from automobile exhausts
and agriculture may cause an increase in
productivity
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C. Possible changes on the distribution range of
biomes and crops
Use of global climate change models to predict
climate change, along with known present day
environmental conditions of different biomes,
leads to prediction of major areas of change in
vegetation types and that the geographic range of
crops will change
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Simulated changes in species distributions
Sitka spruce expansion as coastal region becomes
wetter
Sitka spruce
Douglas fir
Douglas fir some contraction and expansion
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Simulated changes in species distributions
Incense cedar
Sitka spruce
Western red cedar
Western hemlock
Engleman spruce
Douglas fir
Lodgepole pine
Ponderosa pine
29
Information about potential tree species change
in the western US can be found at http//greenwoo
d.cr.usgs.gov/pub/circulars/c1153/c1153_4.htm
1. Substantial changes in tree species
distribution are predicted.
2. The changes are individualistic not the
same for all species.
3. Similar types and sizes of change have taken
place since the end of the last glaciation
4. Predictions of expansion DO NOT TAKE ACCOUNT
of trees dispersal requirements
5. Changes in tree distribution since the last
glaciation occurred over 10 thousand years.
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Conclusions
A business as usual approach to CO2 emissions
will lead to a major increase in atmospheric
concentrations, doubling by the end of the next
century is quite possible
Such a change is bound to have major effects on
the earths biological and geophysical systems
31
Sections you need to have read
7.13 35.10 38.4
http//www.umac.org/climate/Papers/pg56-64.html
Courses that deal with this topic
There are many courses and seminars that cover
particular aspects of climate change. Two to
consider are
ESC 202 Global Changes and Forest Biology
ATM S 211 Climate and Climate Change