Transcript II. Changes in climate

Summary: Functioning of ecosystems varies predictably with climate
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Combination of temperature and precipitation
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II. Changes in climate
A. Yearly (interannual)
B. Millennial scales
C. Human impacts
- Is global warming for real?
- How do we know that it isn’t just a natural fluctuation in temperature?
- What are some of the forces that lead to natural climate variability?
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II.A. Interannual Variation – El Niño Southern Oscillation
- The Pacific Ocean strongly influences the global climate system because it is the
largest ocean basin
- Normal ocean current and wind direction in central Pacific is easterly
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ENSO events result from weakening
of tropical Pacific atmospheric and
oceanic circulation
Climatic connections carry these
climate effects throughout
the globe
(e.g., El Niño creates warm
winters in Arkansas and lots of rain
in California)
ENSO occurs every 3-6 years
with severe events every 8-15
years.
http://www.youtube.com/watch?v=Ivm
eUStFvz8
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II. B. Millennial scale variation
Changes in orbit cause long-term variations in solar input to Earth
Shape of orbit
(100,000 years)
Wobble of tilt
(23,000 years)
Angle of tilt
(41,000 years)
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Eccentricity: The Earth's orbit around the sun is an ellipse. The
shape of the elliptical orbit, which is measured by its eccentricity, varies
through time.
The eccentricity affects the difference in the amounts of radiation the Earth's
surface receives at aphelion and at perihelion.
When the orbit is highly elliptical, one hemisphere will have hot summers and
cold winters; the other hemisphere will have warm summers and cool winters.
When the orbit is nearly circular (now), both
hemispheres will have similar seasonal
contrasts in temperature.
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Rotation axis executes a slow precession with a period of 23,000 years (see
following figure)
Pole Stars are Transient
Wobble in
the tilt
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Precession: Present and past orbital locations of the Earth during the N
Hemisphere winter
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Milankovitch cycles
• The interactive effects of Earth’s orbital variation on timing
and distribution of total solar input.
• Strong effect on glacial/interglacial cycles
http://en.wikipedia.org/wiki/Image:Vostok_420ky_4curves_insolation.jpg
http://www.youtube.com/watch?feature=player_embedded&v=L2m9SNzxJJA
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D. Human effects
Earth’s climate is now warmer than at any time in the last 1000 years
• Global warming
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How can the
atmosphere warm?
1. Increased solar input
2. Less reflected shortwave, less
sulfate aerosols, darker surface of
Earth (land-cover change)
3. More absorbed longwave
more “greenhouse gases”
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Most major greenhouse gases are increasing
in atmospheric concentrations
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Earth’s climate is now warmer than at any time in the last 1000 years
1. increased solar input (small warming effect)
2. Increased sulfate aerosols reflects radiation (small cooling effect)
3. Increased greenhouse gas concentrations (large warming effect)
4. Land-cover change creates a darker surface (large warming effect)
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Climate is warming most rapidly at high latitudes
This warming is most pronounced in Siberia and western North America
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Case Study: Agriculture
• Question: Why do we care about Global
Climate Change in Champaign, IL?
• What is central Illinois good at?
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SoyFACE
• Dr. Carl J. Bernacchi at the
University of Illinois studies how
increased atmospheric CO2 and
temperature affects how corn
and soy grow
• Higher temperatures have a
negative effect on growth and
physiology of soybean. The
effect of temperature, however,
was offset when CO2 was
increased simultaneously with
temperature. The benefit of
combined increases in CO2
and temperature were less than
predicted.
http://www.igb.illinois.edu/soyface/sites/igb.illinois.edu.soyface/files/uploads/UrsulaRuiz2010.pdf
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Changing Climate Conditions
 Temperature increases: longer growing seasons, less frost, warmer nights
 Precipitation changes: deficits, excesses, timing shifts, changing mix of rain/snow
 Increased intensity of precipitation events: more flooding and more droughts
 Increasing carbon dioxide concentrations
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Effects and Sensitivity Vary by Commodity
• Corn: high nighttime temperatures, high temperatures
during pollination, water stress
• Soybean: water stress, high temperatures
• Wheat and small grains: extreme events, frost
during flowering, water stress
• Rice: temperature extremes during pollination, water
management
• Cotton: high temperatures during boll fill
• Pasture and rangeland: water stress
• Fruit trees: chilling requirements not met, high
temperatures during fruit development
• Specialty crops: water stress, high temperatures
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Agriculture is the source of 30% of total
global human impact emissions of GHGs
• Particulate matter & GHGs from land
clearance by fire & burning of residues
laobumpkin.blogspot.com
• > ½ total global anthropogenic emissions
of CH4 and N2O
– CH4: from rice & livestock production
– N2O from fertilizers & manure
www.dowagro.com
(FAO 2003, Gomiero et al. 2008)
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www.ncagr.gov
• Particulate matter & GHGs from land
clearance by fire & burning of residues
laobumpkin.blogspot.com
• > ½ total global anthropogenic emissions
of CH4 and N2O
– CH4: from rice & livestock production
– N2O from fertilizers & manure
www.dowagro.com
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www.ncagr.gov
Other sources:
CO2 emissions from
• Field work, machinery
• Production of fertilizers & pesticides
“Food miles” thought to be relatively minor source
• shifting <1 day/wk’s consumption of red meat to other protein
sources or vegetable-based diet = same impact as buying local
 GHG emissions dominated by production phase = 83% of
average US household’s 8.1 tons CO2/yr footprint for food
consumption
(Gomiero et al. 2008, Niles et al. 2002, Weber & Matthews 2008)
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Extreme Events*
Change in Dry Periods and Hot Nights by 2100 (high emissions, “SRES A2”)
Year
Event
Location
Economic Impact
2011
Missouri River Flooding
Upper Midwest
(MT, ND, SD, IA, KS, MO)
$2.0 Billion
2011
Mississippi River Flooding
Lower Mississippi River (AR, TN, LA,
MS, MO)
$1.9 Billion
2011
Heat/Drought
Southern Plains, Southwest
$10 Billion
2009
Drought
Southwest/Great Plains (CA, TX, GA,
TN, NC, SC)
$5.3 Billion
2008
Flooding
Upper Midwest (IA, IL, IN, MO, MN,
NE, WI)
$15.8 Billion
NCDC 2011
Currently, NCDC estimates that the cost of the 2012 drought that affected much of the U.S. had an economic impact
of $12B. This estimate was not reviewed or available prior to publication of this report, however, and may change.
* Extreme events have been shown to be more probable than 40–50 years ago. However,
one cannot attribute any single event to climate change alone.
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Other solutions and adaptations
Changing Demand

Switch from beef & dairy
to other proteins, veggies
(Weber & Matthews 2008, FAO 2003)
Travel-eat-sleep.com
news.bbc.co.uk
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Agriculture and Climate Change
• Agriculture has been and will continue to be
significantly affected by changes in climate conditions
• Existing adaption strategies can help offset many – but
not all –effects over the next 20-30 years; effects are
very likely to worsen significantly beyond then,
especially if GHG emissions remain high
• Improving the resilience of agricultural systems to
climate change requires protection of the natural
resource base (water & soil) and development of new
strategies, tools, and practices for adaptation
For more information, please visit
http://www.usda.gov/oce/climate_change/effects.htm
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Some Discussion Questions:



Do developed nations have an obligation to reduce their
consumption of beef?
Biofuels are one of the recommended mitigation strategies in
the FAO report… but how does this interact with concerns
over food supply?
Do you see improved land management practices being
implemented in reality? Why/why not?
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Acknowledgements & References
Thanks to Alex Ruane for helpful suggestions
Agriculture & the environment: Changing pressures, solutions, and trade-offs. In: World Agriculture:
Towards 2015/2030 – An FAO Perspective. Ed. Bruinsma, J
Climate change and agriculture: physical and human dimensions. 2003. In: World Agriculture: Towards
2015/2030 – An FAO Perspective. Ed. Bruinsma, J
Easterling, W.E., et al. 2007: Food, fibre and forest products. Climate Change 2007: Impacts, Adaptation
and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der
Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 273-313
Gomiero, T., et al. 2008. Energy and Environmental Issues in Organic and Conventional Agriculture,
Critical Reviews in Plant Sciences,27(4),239-254
Niles, J.O., et al. 2002. Potential carbon mitigation and income in developing countries from changes in
use and management of agricultural and forest lands. Phil. Trans. R. Soc. Lond. A, 360:1621-1639.
Patterson, D.T., et al. 1999. Weeds, insects, and diseases. Climatic Change, 43: 711-727.
Weber, C., & Matthew, H.S. 2008. Food-miles and the relative climate impacts of food choices in the
United States. Environmental Science & Technology, 42: 3508-3513.
Charlie Walthall [email protected] Jerry Hatfield [email protected]
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