Download Soils and Global Warming: A Positive or Negative Feedback?

Soils and Global Warming: A Positive or Negative
Feedback?
•Global soils have a large C pool
•Rates of cycling of this pool indicate that they can affect/respond to
atmospheric processes on annual to decadal time scales
•One of the immediate effects of human induced global change is
warming - will that change soil C?
Soil C and Temperature
dC/dt = I - kC
•Climate change may change inputs
•Will climate change loss rates? (k)
–Virtually all studies show it will (at least on short term)\
–Microbes increase rates, decompose the most readily accessable C
materials (and therefore increase CO2 losses)
•Some recent discussions have confused soil respiration vs. MAT with the
need to know rate (K vs. MAT).
–Led to highly publicized view that soils will exacerbate global CO2
buildup during warming….
The contrast between rate and total respiration
- respiration must be normalized to the amount of
reactant available
Soil Carbon
Resulting soil respiration rates
temperature
(k)
Decomposition
rates
Sierra Nevada Soils as Guide to Climate Response
A Simple Analysis of How Soils May Respond to
Global Warming Based on Changes in k
a one time 0.5C increase in temperature:results based on
Sierran soils
Simple Analysis Assuming Constant Warming
(0.03C/yr)
C(t)  ((
I
I
k t
 Ct1 )e f ) 
kf
kf
where : t  specificyear
and
k f isadjustedforeachtimestep
Soils in the UN Climate Change Negotiations (Kyoto
Protocol)
•UN “assessment report” of CO2 increases and its climatic and ecological
ramifications presents a chilling view of next century
•Ratifying Kyoto Protocol would obligate
–Industrial (Annex 1) countried to reduce their CO2 emissions during
the period 2008 to 2012 to levels below their production in 1990
–This ‘reduction’ merely slows the rate of CO2 buildup in atmosphere,
and doesn’t stop it.
•Ways countries can reduce net CO2 emissions:
–Reduce fossil fuel consumption
–Increase C storage (forests, soils, etc)
–Pay Annex 2 countries (tropics) to stop deforestation
Present Status of UN Climate Change Agreement
• Visit web site
•Should have enough countries to ratify agreement and
implement it
•US has not signed-will face financial sanctions
•Individual countries taking more aggressive stance:
e.g. Britian wants to go to ~ 40% renewable energy in
50 years….