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How Scientists Study Climate Change A Rangeland
Perspective
Photo Sam Cox
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How Scientists Study Climate Change

• Reviewing our present state of knowledge
• What we know (accepted by scientists)
• Predictions implications uncertainty
• How we study the problem (techniques that
  scientist use, their strengths and limitations)
• Observation
• Manipulative experimentation
• Modeling

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WHAT WE KNOW Atmospheric CO2 concentrations
measured accurately for many decades they are
steadily increasing.
Annual cycle due to photosynthesis and
respiration of soils.
Long term trend due to emission of fossil fuels
Charles David Keeling 1928-2005 2002 Natl Medal
of Science
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WHAT WE KNOW Ice core sampling other
techniques indicate rising CO2 in
Earths atmosphere is a relatively new phenomenon.
IPCC Working Group I Report, Chapter 2, 2007
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WHAT WE KNOW A direct effect of rising CO2
Stimulation of plant growth.
CO2
Food, Glorious Food!
Nutrients, H2O
Any change in light, water, nutrients or carbon
dioxide will alter plant growth.
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WHAT WE KNOW Global average surface temperature
has increased 0.74 C (1.2 F) in the last hundred
years. Rate of warming has doubled in the past
50 years.
Predictions indicate future accelerated
extreme warming.

IPCC 2007 WG1-AR4
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IMPLICATIONS OF WHAT WE KNOW Warmer temperatures
mean Longer growing season Desiccation due to
warming Altered hydrologic cycle atmosphere
holds more water vapor intense rainfall
events timing (altered seasonal precipitation
earlier loss of snow pack) some regions
will experience more drought
Photo Sam Cox
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Areas of Uncertainty weather, climate
rangeland responses
How will climate change be expressed at local and
regional scales?
How will climate change be expressed at regional
and local levels?
How will rangelands respond to increased occurrenc
es of extreme events?
How will rising CO2, warmer temperature and
altered pre- cipitation affect rangelands? How
will rangelands rangeland managers adapt to a
more variable environment?
Photos Cox, Derner SGS LTER
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OBSERVATIONAL INFORMATION Historical records
correspondences of early explorers settlers.
Caption from Barker et al., 1934 speaks of
Coronado and his Band wandering across burning
sands, but the expeditions journal of 1541
recorded not deserts but grasslands. (Hart and
Hart. 1997. Rangelands 194-11)
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OBSERVATIONAL INFORMATION Photographs can
provide additional qualitative information
Mesquite encroachment in SW over past two
centuries (photograph courtesy of ARS Jornada
Experimental Range photo gallery).
Honey locust tree islands in Kansas Tallgrass
Prairie. Present-day encroachment? Fire removal,
climate change, CO2? (photograph courtesy of Alan
K. Knapp).
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OBSERVATIONAL INFORMATION Quantitative
monitoring for management purposes may be
especially useful for climate change
Aerial photography imaging software for
quantifying range condition. High resolution
infor- mation for assessing rangeland ecological
services.
Booth, Cox Simonds
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Observation Combined with Experimental
Treatments Over Time Can Be Powerful
Derner Schuman. 2007. Jour. Soil Water
Cons. 6277-85
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Plants leave geochemical fingerprints in soils !
C4 Vegetation
Warmer/dry C4 grasses
0-10 ka Bignell Loess
10-13 ka Brady Soil
13-23 ka Peoria Loess
Cooler/wet C3 shrubs grasses
Kelly and Busacca, in Prep
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Observational Information

• Information on ecosystem attributes, obtained in
  realistic environments, oftentimes of
  considerable time lengths
• Information is often complicated by other
  factors, like management, which have changed over
  time
• Interpretations often speculative
• Limited information on future environments,
  including multiple changes

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Manipulative Research for Assessing Ecosystem
Responses to CC
IR Warming on Tibetan Plateau
Free Air CO2 Enrichment in Mojave
Mostly single factor experiments Run for two to
several years Photos Nowak, Wang Knapp
Precipitation manipulation in Kansas tallgrass
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Open Top Chamber CO2 Enrichment Work on the
Colorado Shortgrass Steppe 1996-2001 USDA-ARS
Shortgrass Steppe LTER

• Doubling Ambient CO2
• Increased NPP 44
• Increased plant WUE
• Favored some plant
• spp. over others
• Forage N and forage
• quality declined

• CO2-production responses
• cool-season, C3 grasses
• fringed sage, 40-fold

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Prairie Heating and CO2 Enrichment
(PHACE) Cheyenne, Wyoming, USA (summer, 2008)
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PHACE EXPERIMENTAL TREATMENTS
ACN
AHN
ECN
EHN
ACIs
ACId
Ambient CO2 Ambient temp No irrigation
Ambient CO2 High temp No irrigation
High CO2 Ambient temp No irrigation
High CO2 High Temp No irrigation
Ambient CO2 Ambient temp Shallow irrigation
Ambient CO2 Ambient temp Deep irrigation
2 IRRIG Trts (5 reps each)
2 CO2 by 2 TEMP factorial (5 reps each)
CO2 A (present ambient, 380 ppm), E
(elevated, 600 ppm) TEMP C (present
temp), H ( 1.5/3.0 C day/night) IRRIG
Is (several seasonal water additions), N
(non-irrigated) IRRIG Id (one or two
annual water additions)
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PHACE EXPERIMENTAL TREATMENTS
ACN
AHN
ECN
EHN
ACIs
ACId
Ambient CO2 Ambient temp Shallow irrigation
High CO2 Ambient temp No irrigation
Does water replacement give the same response as
elevated CO2?
CO2 A (present ambient, 380 ppm), E
(elevated, 600 ppm) TEMP C (present
temp), H ( 1.5/3.0 C day/night) IRRIG
Is (several seasonal water additions), N
(non-irrigated) IRRIG Id (one or two
annual water additions)
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Prairie Heating and CO2 Enrichment (PHACE)
Experiment (Cheyenne, WY, USA)
CO2 ring
Direct Responses to GC Factors
Indirect Effects of Water
Sentek SWC
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Trace gas exchange
Root dynamics
Canopy photosynthesis
Plant species abundances
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Manipulative Experiments

• Can expose plants and plant communities to
  altered environmental conditions
• Can provide mechanistic information (NOT
  considered simulations of the future)
• Manipulations artificial, often with known and
  unknown artifacts
• Costly
• Few multiple GC experiments

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Modeling

• Mathematical representations of reality
• empirical (based on observation practical)
• theoretical (based on mechanisms)
• Useful for understanding how systems function
• Can fill in knowledge gaps
• Predictive tools

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Plant Community Modeling

• Modeled Future Relative Abundances in Temperate
  Grasslands of North South America.
• Based on
• GCMs
• Relative Abundance Equations

Based on observations measurements obtained in
the real world. Empirical relationships may not
capture CO2 response
Epstein, Gill, Paruelo, Lauenroth, Jia and Burke.
2002. J. of Biogeography 29875-888
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Summary

• Observation, manipulation, modeling useful
  tools for studying climate change and impacts on
  rangelands
• The complexities and uncertainties of climate
  change argue strongly for
• utilizing all of these in our predictions
• accepting that policy and management decision
  will always rely on a certain amount of
  uncertainty

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Summary

• Science can help us understand deal with that
  uncertainty
• weather forecasting, monitoring and decision
  support systems can help us cope with an
  increasingly uncertain world
• learning from other regions/countries where today
  we may find examples of our future climates
  (e.g., Australia in terms of variable weather)

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THANKS FOR YOUR ATTENTION
2008 SUMMER BIOMASS FIELD CREW
2008 SUMMER HARVEST FIELD CREW