Lecture 24 - Global Systems

Global Carbon Cycle

UN Climate Change Conference - write your own message to leaders of the world

Review of C cycle - a good synthesis topic…..probably good final exam material

Biotic and abiotic influences
geologic influences
fluvial systems may interact with biologic systems, drving aerobic respiration to
anaerobic respiration, transports organic matter
bedrock - chemical processes form rocks, rocks get weathered, C returned to
system
rocks are a major C sink, greatly drew down CO2 in the atmosphere in the past
today we are extracting pools of C (oil), burning it, and putting it back in to the
atmosphere
biological influences-photosynthesis, vegetation type, land use/land cover

Global Carbon cycle
not really in balance in past history or today

C is cycled on the scale of gigatons
There are large pools of C and large fluxes
pools-vegetation, ocean
fluxes-burning fossil fuels

sinks take CO2 out of the atmosphere but there is a limit to how much vegetation and the ocean can increase their uptake-> CO2 in the atmosphere is building up

Where is the C coming from?
Fossil Fuels
Land use/landcover change

"Missing sink" we cannot balance C budget of land, ocean and atmosphere
* everything doesn't add up—we think we have a good idea of where C is coming from that is atmosphere and ocean

* pretty confident the sink is in terrestrial systems, in the northern latitudes but don't know where it is

Experiments that alter CO2 concentration
*Prairie grasses response to increased CO2
Found that all the increased growth was in one species
calls in to question how will communities change?
will a small number of species begin to dominate

*FACE (Free Air CO2 Enrichment)experiments
fast growing species on nutrient poor soils—need to look at
labeled N with isotopes to track soil nutrients during these exp
plants are finding sources of N but don't know where it's coming from
occult N???

Summary: Duke Forest FACE site conducted an experiment, providing more CO2 to a population of commercially grown, fast-growing Pines in nutrient poor soil. The expected result was an instant spike in productivity with a quick drop off due to limited nutrients, such as nitrogen. Actual results were that these Pines were finding sources of nutrients, either from deeper in the soil or from a gas form, and after 10 years, the plants are still able to maintain the increased growth from the extra CO2. Hence, the legend of the "occult nitrogen" continues. Conclusion is, in some cases, increased CO2 does result in increased vegetative production, despite other limiting factors.

Modeling C budgets - take data from other studies and combine them so we can look at larger spatial scales and longer time periods

Process Based Models - develop a mechanistic model of cause and effect which include fine scale processes and the tested and verified - FACE

individual based models
modeling individual organisms and their spatial environment
take our existing knowledge of competition, resource use->then create
population and community response models
GAP models - a very successful example of forest dynamics and biomass and
the interaction of individuals on each other

Lumped-parameter model big leaf model
older and more widely used
used in global change
simulate ecophysiology of plants but lumped over a large area
ecological mechanisms between individuals is less well represented

Needs for the future in terms of models
*dynamic coupling of interactions - active area of research
*finer resolution
*socioeconomic feedback
*address fragmentation and heterogeneity

Dynamic Global Vegetation Models DGVM
one type of vegetation can replace another
grassland replacing coniferous system via global climate change
grasses move in and if they compete well, they will overtake
link in a physical way to the atmosphere
exchange water, albedo etc
hydrology is key link - able to see how a shift in biomes will change fluxes
model can be tested against flux tower data

Finer Resolution
10km resolution currently, want to push it to 1km
takes tons of computational power

Socioeconomic Drivers and Feedbacks
village in India - villagers depend on forest for livelihood and subsequently impact
forest
model developed to link livelihood, C, and forest health
found that late successional forest was able to support livelihoods but early
successional forests were not

Fragmentation and Heterogeneity
lots of towers are in wild land systems and ignore edges and fragmentation
human effects are important to include

Carbon Mitigation slowing the rate of the rise of CO2 in the atmosphere
the loner we wait to cut emissions the more it will take to reduce CO2

IPCC carbon cycle perspective: Atmosphere has 760 Billion tons of Carbon with an accumulation of about 3.3 gigatons / year. As a result, the IPCC predicts global mean temperature increase. It also has made predictions based on different levels of possible mitigation, including no change. Their charts and graphs illustrate where the levels of carbon in the atmosphere need to peak, where the level needs to go, and what reduction is required to prevent any temperature increase.

Stabilization Wedges
it is possible to slow the rise of CO2
if we set a goal of having 2000 level emissions 50 years from now
the difference between the 'business as usual' and the flat rate is the 'wedge'
wedge is divided in to different components
increasing efficiency of automobiles
energy technologies
biofuels
*can calculate the degree each technology needs to be scaled up to achieve 2000 levels 50 years from now - some are feasible and some are not

Bathtub Analogy
The current pool of carbon in the 'tub' is 800 billion tons. 8 billion is added each year by fossil fuel burning, and 4 is taken in by land and ocean sinks. That leaves a net of 4 added to the pool. See the following link for a great illustration and article about the "Bathtub Analogy": http://ngm.nationalgeographic.com/big-idea/05/carbon-bath

Copenhagen and Conference on Climate Change
Main thing that is needed in another agreement to extend beyond 2012
Will developed countries help developing countries limit the growth of their
emissions?

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