Climate Change and Possible Impacts on Soil and Water

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Climate Change and Possible Impacts on Soil and
Water

• Eugene S. Takle
• Professor of Agricultural Meteorology, Department
  of Agronomy
• Professor of Atmospheric Science, Department of
  Geological and Atmospheric Sciences
• Iowa State University
• gstakle_at_iastate.edu

ISU Soil and Water Conservation Club, 12
September 2005
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Climate Change

• What is changing?
• How much is it changing?
• Why is it changing?
• How might it affect soil and water?
• What should we do about it?

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Source IPCC, 2001 Climate Change 2001 The
Scientific Basis
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Source IPCC, 2001 Climate Change 2001 The
Scientific Basis
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JJA Daily Maximum Temperature Trends, 1976-2000
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Warming Hole
C
DTmax (JJA)
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Surface Energy Balance
Latent
Conv Cond
IR
IR
Solar
T
Soil
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Surface Energy Balance
Latent
Conv Cond
IR
IR
Solar
T
Soil
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El Chichon (1982)
Agung, 1963
Mt. Pinatubo (1991)
Hansen, Scientific American, March 2004
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Carbon Dioxide and Temperature
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Carbon Dioxide and Temperature
2004 (377 ppm)
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Carbon Dioxide and Temperature
Business as Usual (fossil intensive) 2100
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http//www.earth-policy.org/Indicators/CO2/2004.ht
m
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V
V
V
Source Jerry Meehl, National Center for
Atmospheric Research
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Tropical Atlantic Ocean
Hurricane Power Dissipation Index (PDI)
Sea-surface temperature
V
V

• V

Emanual, Kerry, 2005 Increasing destructiveness
of tropical cyclones over the past 30 years.
Nature, 436, 686-688.
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Sea-Surface Temperatures in August 2005
Weather Underground http//www.wunderground.com/
tropical/
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Source National Center for Atmospheric Research
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The planet is committed to a warming over the
next 50 years regardless of political decisions
Source National Center for Atmospheric Research
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40 Probability
5 Probability
Source Intergovernmental Panel on Climate
Change, 2001 Report
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For the Midwest

• Warming will be greater for winter than summer
  ()
• Warming will be greater at night than during the
  day ()
• A 3oF rise in summer daytime temperature triples
  the probability of a heat wave
• Growing Frost-free season will be longer (, 8-9
  days longer now than in 1950)
• More precipitation ()
• Likely more soil moisture in summer
• More rain will come in intense rainfall events
  ()
• Higher stream flow, more flooding
• already observed
• North American Regional Climate Change
  Assessment Program is underway but results for
  impacts wont be available for several months.

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Sub-Basins of the Upper Mississippi River Basin
119 sub-basins Outflow measured at Grafton, IL
Approximately one observing station per
sub-basin Approximately one model grid point per
sub-basin
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Hydrologic Budget Components Simulated by SWAT
under Different Climates
Hydrologic budget components Calibration (1989-1997) Validation (1980-1988) NNR (1980-1988) CTL (around 1990s) SNR (around 2040s) Change (SNR-CTL)
Precipitation 856 846 831 898 1082 21
Snowfall 169 103 237 249 294 18
Snowmelt 168 99 230 245 291 19
Surface runoff 151 128 151 178 268 51
GW recharge 154 160 134 179 255 43
Total water yield 273 257 253 321 481 50
Potential ET 947 977 799 787 778 -1
Actual ET 547 541 528 539 566 5
All units are mm Yield is sum of surface runoff,
lateral flow, and groundwater flow
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Climate Change Impacts on Soil and Water (my
speculations)

• Increase in CO2
• increase in water-use efficiency by plants and
  accelerated growth
• Increase in night-time temperatures
• Higher night-time respiration by plants
• Higher soil respiration and loss of soil carbon
• Less dewfall
• Increase in daytime maximum temperatures
• More heat waves

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Climate Change Impacts on Soil and Water (my
speculations)

• Higher absolute humidity
• More freeze-thaw cycles
• Decreased mean wind speed
• Altered large-scale weather patterns, storm
  tracks
• Changes in precipitation
• Increased amount -gt more soil erosion, more
  nitrate leaching
• Larger fraction of total rain will come in heavy
  rain events and may produce more floods and
  droughts
• Possible changed seasonality
• Possible changed diurnal patterns -gt changes in
  soil moisture

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Mitigation vs. AdaptationSince we are already
committed to a global warming of about 2-4o F
over the next 40 years we need to focus on

• Adaptation to climate change for soil and water
  conservation in the next half decade
• Mitigation of continued rise in greenhouse gases
  so our (great)n -grand children will have as many
  opportunities as we have had.
• More dialog between soil/water/conservation
  scientists and climate scientists to help
  prioritize climate research efforts.

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For More Information
For peer-reviewed evidence supporting these
slides (except some of my speculations), see my
online Global Change course http//www.meteor.i
astate.edu/gccourse Contact me
directly gstakle_at_iastate.edu For a copy of this
presentation http//www.meteor.iastate.edu/facul
ty/takle/