Effects of Global Warming on Crops

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Effects of Global Warming on Crops

• Ted Sammis
• State Climatologist NMSU
• Hydrologist by training

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A Climatologist

• A person dealing with the science of climate and
  climatic phenomena
• Climate- the prevailing or average weather
  conditions of a place as determined by the
  temperature and meteorological changes over a
  period of years.

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70 million years ago

• In the late Cretaceous period climate in New
  Mexico created vegetation that formed a tropical
  savanna
• The information is based on fossil remains and
  some disagreement about the vegetation at that
  time occurs in the scientific community.

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60-20million years ago

• In the Paleocene through the Oligocene period the
  climate created tropical forest and short tree
  forest in New Mexico

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18-20million years ago

• During the Miocene period the drying trend
  continued and elements of modern woodland
  grassland, and deserts began to develop

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18-presentmillion years ago

• The drying process continued and from the late
  Miocene to the present the fossil plants are very
  similar to the current vegetation types.

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Short term climate change impacts

• The southern part of New Mexico has seen a shift
  in vegetation from a semidesert grassland to
  desert shrubland in the last 100 years.
• The southwest encountered a warming trend from
  1900 to 1940 and a resulting increase in winter
  precipitation tended to encourage the
  establishment of C3 shrub plants instead of C4
  grasses.

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• The summer droughts in the 1940s early 1950s
  also favored establishment of perennial desert
  shrubs.
• Overgrazing during this time period would have
  acted synergistically with climate change to
  enhance desertification

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New Mexico has 8 climate zone
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Climate has been measured since 1890 by
volunteers
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NWS Cooperator Site including Temperature and
Rainfall
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Automated Climate Station
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Plant growth

• Plant and insects develop according to climate
  conditions, mainly temperature
• Plant development can be defined over time or
  over growing degree days.
• GDD (max temp. min temp.)/2 base temperature
  
• For Corn the base temperature is 10 C and any
  temperature over 30 C gets set to 30 or below 10
  C get set to 10 degrees.

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Field Corn Hybrid Maturity Classification.

• Maturity Days GDD
• Early-season 85-100 days 1200-1300
• Mid-season 101-130 days 1300-1550
• Full-season 131-145 days 1550-1770
• As global warming occurs the GDD for an area
  increases.

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• The duration between frost dates also increases
  with global warming and you can grow longer
  season crops with higher yields if water is
  available.
• If Global warming increase average temperature by
  3 degrees C the GDD will increase for 100 day
  corn by 300 GDD or from early to mid season
  varieties.

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Hardiness zone where crops will survive and grow

• A hardiness zone is a geographically-defined zone
  in which a specific category of plant life is
  capable of growing, as defined by temperature
  hardiness, or ability to withstand the minimum
  temperatures of the zone

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Plant Hardiness Zones

• The Plant Hardiness Zones divide the United
  States and Canada into 11 areas based on a 10
  degree Fahrenheit difference in the average
  annual minimum temperature.
• The lowest average temperature in Zone 2 is -50
  to -40 degrees Fahrenheit, while the minimum
  average temperature in zone 10 is 30 to 40
  degrees Fahrenheit

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Warming trend changed hardiness zone locations
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• Hardiness Zones have moved north due to global
  warming.
• Perennial plants that would not survive the
  winter at a given location may now survive.

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Example- Oleander plants need a hardness zone 8
or higher and will now grow in the Carlsbad NM
area
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Predicted climate change from 2002 to 2100

• Predicted from two major global climate models
  in 2000

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"Prediction is very difficult, especially if it's
about the future." --Nils Bohr, Nobel laureate
in Physics
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• temperatures in New Mexico are projected to
  increase. of 5-11 F or 3 to 6 C.
• Both models predict an increase in rainfall

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Future Temperature and Precipitation change
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Vegetation change

• Vegetation models run under the Hadley and
  Canadian scenarios suggest an increase in plant
  growth, and a reduction in desert areas.
• The vegetation will shift toward more woodlands
  and forests from grassland

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Future vegetation change.
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Predicted climate change based on 18 Global
Climate Models

• Predicted in 2007 different than in 2002

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Temperature

• Temperature will rise 7 degrees F (3.8 degree C)
  in the next 100 years
• Heat island effects will increase this rise in
  temperature
• The number of extremely hot days is project to
  rise.

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Rainfall

• Prediction changed is that the southwest will get
  drier not wetter as predicted in 2000.
• The change in prediction was due to a better
  understand of the Hadley Cell circulation.

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Hadlely Cell

• Globally hot air rises from the tropics and
  descends in the subtropics. The high pressure of
  the descending air reduces cloud formation.
• The area of the Hadely cellss descending air is
  project to widen and the jet stream that
  transports rain and snow during the winter and
  spring is expected to move poleward resulting in
  less rain to New Mexico.

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• The southwest faces extensive drought in coming
  years and problems in the water supply due to
  global climate change.

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Why is global warming occurring.

• CO2 levels have varied over time but they have
  risen markedly in the past century, especially in
  the last half-century.

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• The atmosphere has gained about 200 Pg
  (petagrams trillion metric tones) of carbon
  since the Industrial Revolution.
• This is about 40 of the carbon we put into the
  air from using fuels and deforesting large areas,
  totalling about 500 Pg.

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• The ocean is absorbing about 40 of our addition,
  and extra growth of land plants at high CO2
  absorbs around another 20.
• The rest goes into the atmosphere and increases
  CO2.
• Each year addition adds to the total in the
  atmosphere.

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The impact of Climate change on the Energy Budget
and Et of crops

• FACE measurements of stomata resistance with
  increased CO2 showed an increase in stomata
  resistance and a decrease in water use.
• Snyder calculated at Davis California increasing
  only air temperature by 3 degree C, resulted in a
  18.7 percent increase in Eto based on
  Penman-Monteith equation.

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• Increasing the air and dew point temperatures by
  3 degrees C led to a 8.5 percent increase in ETo.
  
• Increasing the temperatures and the canopy
  resistance to 87 s/m led to a 3.2 percent
  increase in ETo over current conditions.

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Penman-Monteith equation calculation
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Economics of global warming

• In the United States some studies show a decrease
  in farm values where other show no change in the
  cereal crops (wheat, corn, barley) but do show a
  decrease special crop (vegetables).
• Some studies show a 5 increase in the United
  States
• Global farm output and value will decrease by 5
  or more, especially in the non industrial
  countries

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Conclusion

• In the future rainfall will decrease, temperature
  will increase and water resources will be less
  available in New Mexico
• Populations will increase
• Climate variability and drought durations will
  increase