Zong-Liang%20Yang

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Short-Term Climate Variability and Climate Change

• Zong-Liang Yang
• liang_at_mail.utexas.edu
• www.geo.utexas.edu/climate
• Department of Geological Sciences

GEO 392M Modern Geological Sciences 20 November
2008
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OUTLINES
1. Introduction 1.1 Weather versus Climate 1.2
Climatic Controls 1.3 Climate Classifications 1.
4 Climate System Components 2. Climate
Variability 2.1 Diurnal Cycle 2.2 Seasonal
Cycle 2.3 Interannual Variations (ENSO, NAO,
) 2.4 Decadal Variability (PDO, ) 3. Climate
Change 3.1 Global Warming 3.2 Greenhouse
Effects 3.3 Causes of Change (Internal Versus
External Factors) 4. Climate Modeling 4.1
Coupled Ocean-Atmosphere-Land-Ice Model 4.2 Role
of Forcing Factors Natural volcanoes sun
Variability versus Human GHG sulfate
Effects 4.3 The Future of Climate Modeling
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1.1 Weather versus Climate
Weather
The condition of atmosphere at a given time and
place

• Short-term (and large) fluctuations that arise
  from internal instabilities
• of the atmosphere

• Occurs as a wide variety of phenomena that we
  often experience

• Effects are immediately felt

• Social and economic impacts are great but are
  usually localized

• Many such phenomena occur as part of
  larger-scale organized systems

• Governed by non-linear chaotic dynamics not
  predictable
• deterministically beyond a week or two

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Surface Weather Map
Meteorologists may study larger weather patterns
with space borne instruments, while ground-based
tools often measure a) air temperature b) air
pressure c) humidity d) clouds e) precipitation
f) visibility g) wind at a single point.
Meteorologists generate diagrams of observed
weather from ground-based instruments. This
surface map overlaps in time with the above
satellite image.
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Three-Cell Model (Palmen-Newton Model)
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Extratropical Storms

Extratropical or middle latitude
storms are embedded in the
tropospheric
westerlies Winds converging into the
low, pull cold air from the poles toward
the equator, and warm air from the equator
to the poles.
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Close look at a cyclonic system
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Low Pressure High Pressure
Anti-Cyclonic Turning divergence leads to
downward vertical motions.
Cyclonic Turning Convergence leads to upward
vertical motions.
Cold Air
Warm Air
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Northern Hemisphere Circulation SystemPlanetary
Scale Waves
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1.1 Weather versus Climate
Climate

• Defined as the average state of the atmosphere
  over a finite time
• period and over a geographic region (space).

• Can be thought of as the prevailing weather,
  which includes the
• mean but also the range of variations

• The wide range of natural variability associated
  with daily weather
• means small climate changes are difficult to
  detect

• Intimate link between weather and climate
  provides a basis for
• understanding how weather events might change
  under a
• changing climate

• Climate is what you expect and weather is what
  you get.

• Climate tells what clothes to buy, but weather
  tells you what clothes to wear.

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Climate change and its manifestation in terms of
weather (climate extremes)
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Climate change and its manifestation in terms of
weather (climate extremes)
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Climate change and its manifestation in terms of
weather (climate extremes)
Global warming increases the frequency and
intensity of extreme weather events
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Climate Change in Texas from WCRP CMIP3
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A aggressive
1 Global
2 Regional
B Balanced
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Climate Change in Texas from WCRP CMIP3
More heavy rainfalls and more floods
More dry periods and intense droughts
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Global warming
? Heating ? ? Temperature ? Evaporation ?
? water holding
capacity ?
? atmospheric moisture ? ?
? greenhouse effect ? rain intensity ?
? Floods Droughts
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1.1 Climate versus Weather
Climate

• Defined as the average state of the atmosphere
  over a finite time
• period and over a geographic region (space).

• Can be thought of as the prevailing weather,
  which includes the
• mean but also the range of variations

• The wide range of natural variability associated
  with daily weather
• means small climate changes are difficult to
  detect

• Intimate link between weather and climate
  provides a basis for
• understanding how weather events might change
  under a
• changing climate

• Involves atmospheric interactions with other
  parts of the climate
• system and external forcing

• Climate prediction is complicated by considering
  the complex
• interactions between, as well as changes
  within, all components

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1.2 Climatic Controls

• The world's many climates are controlled by the
  same factors affecting weather,
• intensity of sunshine and its variation with
  latitude,
• distribution of land and water,
• ocean temperature and currents,
• mountain barriers,
• land cover,
• atmospheric composition.

This map shows sea-level temperatures (F).
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1.3 Climate Classification
Ancient Greeks classified 3 climate regions as
tropical, polar, and temperate zones. The Koppen
classification system is now widely used, based
on temperature and precipitation, and
distinguishes 5 major climatic types as tropical
moist, dry, moist mid-latitude with mild winters,
moist mid-latitude with severe winters, and polar
climates. Thornthwaite's classification system
considers precipitation to evaporation ratios.
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Koppen's Worldwide Distribution of Climatic
Regions, I
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Koppen's Worldwide Distribution of Climatic
Regions, II
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1.4 The Climate System Components
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1.4 Climate System Components

• Atmosphere
• Fastest changing and most responsive component
• Previously considered the only changing
  component

• Ocean
• The other fluid component covering 70 of the
  surface
• Plays a central role through its motions and
  heat capacity
• Interacts with the atmosphere on days to
  thousands of years

• Cryosphere
• Includes land snow, sea ice, ice sheets, and
  mountain glaciers
• Largest reservoir of fresh water
• High reflectivity and low thermal conductivity

• Land and its biomass
• Slowly changing extent and position of
  continents
• Faster changing characteristics of lakes,
  streams, soil moisture
• and vegetation

• Human interaction
• agriculture, urbanization, industry, pollution,
  etc.

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2. Climate Variability
2.2
2.1
Climate variability Diurnal cycle Seasonal
cycle Interannual variability
2.3
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2.3a What is El Niño?

• Warming of sea surface waters in the central and
  eastern tropical Pacific Ocean
• El Niño the ocean part warm phase of ENSO (El
  Niño Southern Oscillation)
• Southern Oscillation the atmospheric part a
  seasaw pattern of reversing surface air pressure
  at opposite ends of the tropical Pacific Ocean
• La Niña the cold phase of ENSO Cool sea surface
  temperatures in the central and eastern tropical
  Pacific Ocean
• EN events occur about every 3-7 years

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ENSO
A natural mode of the coupled ocean-atmosphere
system ENSO EN and SO together Refers to
whole cycle of warming and cooling. ENSO events
have been going on for centuries (records in
corals, and in ice layers in glaciers in South
America) ENSO arises from air-sea interactions in
the tropical Pacific Ocean
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Non-El Niño Conditions
In the southern Pacific Ocean, high pressure in
the east pushes surface winds, and waters, toward
the low in the west. The trade winds are part of
a east-west circulation the Walker Circulation.
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El Niño Conditions
The change in air pressure causes the trades to
weaken or reverse direction. Warm water moves
back eastward across the Pacific, like water
shifting in a giant bathtub. The warm water and
shifting winds suppress the upwelling of cool,
nutrient-rich water.
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El Nino Kelvin Wave
Satellite imagery shows the eastward movement of
higher ocean levels, or Kelvin wave, in white and
red colors, caused by the reversal of the Walker
Circulation and El Nino event.
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Sea Surface Temperature Departures from Normal as
Measured by Satellite
Warmer SST During the El Nino conditions
Cooler SST during the La Nina conditions
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ENSO Index
El Nino Southern Oscillation (ENSO) intensity has
been tracked using 6 parameters, including air
and sea temperature, sea level pressure, wind
speed and direction, and cloudiness. A graph of
the ENSO index shows eastern Pacific warm El Nino
and cool La Nina years. Two largest ENSO
events 1982-83 and 1997-98.
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2.3b The North Atlantic Oscillation
A Dominant Orchestrator of NH Weather and Climate
Positive Phase
Negative Phase

• Changes in mean wind speed and direction
• Changes in number, intensity, paths of storms
• Changes in moisture transport

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The Spatial Structure of Climate and Climate
Variability

• When averaged over time, planetary waves are
  geographically
• anchored as a result of land/ocean contrasts
  and mountains
• The result is high and low pressure systems that
  appear to persist
• throughout the year so-called semipermanent
  lows and highs

• Variations in the strength of these
  semipermanent features
• produce changes in weather and climate over
  large regions

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Strong Westerly Flow onto Europe
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A substantial portion of the Northern Hemisphere
warming in recent decades is associated with the
upward trend in the NAO
The Earths climate record includes both natural
variability as as well as human-induced effects
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NAO Influence on Winter Precipitation

• This pattern, together with the upward trend in
  the NAO, is consistent
• with observed changes in precipitation over the
  Atlantic basin
• Advance of Scandinavian glaciers
• Retreat of Alpine glaciers
• Severe drought over parts of the Iberian
  peninsula

• Together with surface warming, there are
  significant impacts, e.g.
• Agriculture (longer growing season)
• Energy supply/demand and water management
• Marine and terrestrial ecosystems

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2.4 Pacific Decadal Oscillation
Scientists recently discovered a 20 to 30 year
sea surface temperature (SST) reversal in a more
northern section of the Pacific. During the
warm, positive, phase, SSTs are warmer off the
Pacific Northwest coast, which strengthens the
Aleutian low and generates warmer
winters. During a cool phase, Pacific Northwest
coastal SSTs are cooler, causing colder winters.
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3. Climate Change Is a Household Name
http//www.geo.utexas.edu/courses/302c/NEWS/index.
htm
http//www.geo.utexas.edu/climate/NEWS/index.htm
www.google.com as of April 16, 2007 (April 13,
2006)
Climate change 85 (247) million Global warming 70
(94) million Greenhouse effects 2 (20) million
Tax cut 47 (102) million
Child care 122 (448) million Family value 198
(336) million
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Climate Change Since the Last Glacial Maximum
About 1000 y.a., the N.H. was cooler than now
(e.g., 1961-1990 average). Certain regions were
warmer than others.
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Instrumental Records
gt 200 years of temperature records in Europe and
North America
Temperature stations increased significantly
during the 20th century
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Temperature Trends from 1850 to 2006
http//www.ucsusa.org/global_warming/science/recor
dtemp2005.html
Data over the globe (land and sea). Warming
periods 1900-1945 (by 0.5C), the mid-1970s to
present. The warmest decade the 1990s. The
warmest year 1998. Top 20 includes every single
year since 1992. Over last 25 years warming
0.5C. Over past century warming 0.75C Cooling
periods 1945-1975.
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Yearly Temperature Change Since 1850
1998
Data from thermometers
http//commons.wikimedia.org/wiki/ImageInstrument
al_Temperature_Record.png
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Surface Air Temperature Trends Over the Past
Century
Warming greatest at night over northern
mid-to-high latitude land Stronger warming
during winter and spring Greater than the global
average in some areas Cooled in some areas
(southern Mississippi Valley in USA) IPCC 2007
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Annual Surface Temperature Trends in C/decade
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Land precipitation is changing significantly over
broad areas
Smoothed annual anomalies for precipitation ()
over land from 1901 to 2005 other regions are
dominated by variability.
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The Earths Climate History

1. Over the last century, the earths surface
   temperature has increased by about 0.75C (about
   1.35F).
2. Little Ice Age Cooling during 1,400 A.D.
   1,900 A.D. (N.H. temperature was lower by 0.5C,
   alpine glaciers increased few sunspots, low
   solar output)
3. Medieval Climate Optimum (Warm Period) Warming
   during 1,000 A.D. 1,300 A.D. in Europe and the
   high-latitudes of North Atlantic (N.H. warm and
   dry, Nordic people or Vikings colonized Iceland
   Greenland)
4. Holocene Maximum 5,000-6,000 ybp (1C warmer
   than now, warmest of the current interglacial
   period)
5. Younger-Dryas Event 12,000 ybp (sudden drop in
   temperature and portions of N.H. reverted back to
   glacial conditions)
6. Last Glacial Maximum 21,000 ybp (maximum North
   American continental glaciers, lower sea level
   exposed Bering land bridge allowing human
   migration from Asia to North America)
7. We are presently living in a long-term Icehouse
   climate period, which is comprised of
   shorter-term glacial (e.g., 21,000 ybp) and
   interglacial (e.g., today) periods. There were
   four periods of Icehouse prior to the current
   one.
8. For most of the earths history, the climate was
   much warmer than today.

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Glaciers and Sea Level
Kilimanjaro glaciers will disappear in 15 years.
Sea level rises 12 cm last century.
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Reason for Climate Concern
Oceans might rise by 65 m if all of earth's
glaciers, which cover 10 of the land surface,
were to melt. At present, 70 of the worlds
sandy beaches are retreating. Smaller predicted
sea level change of 1 m might still devastate
many areas.
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Sea Level Rise in the Next 100 Years
Many importantplaces on the Texas Coast will
disappear
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An increasing body of observations gives a
collective picture of a warming world and other
changes in the climate system

• Global mean surface temperature increase
• (NH, SH, land, ocean)
• Melting of glaciers, sea ice retreat and
  thinning
• Rise of sea levels
• Decrease in snow cover
• Decrease in duration of lake and river ice
• Increased water vapor, precipitation and
• intensity of precipitation over the NH
• Less extreme low temperatures, more
• extreme high temperatures

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Recent Range Shifts due to Warming
Species Affected Location Observed Changes

Arctic shrubs Alaska Expansion into shrub-free areas
Alpine plants Alps Elevational shift of 1-4 m per decade
39 butterfly spp. NA, Europe Northward shift up to 200 km in 27 yrs.
Lowland birds Costa Rica Advancing to higher elevations
12 bird species Britain 19 km northward average range extension
Red Arctic Fox Canada Red fox replacing Arctic fox
Treeline Europe, NZ Advancing to higher altitude
Plants invertebrates Antarctica Distribution changes
Zooplankton, fish invertebrates California, N. Atlantic Increasing abundance of warm water spp.
Walther et al., Ecological responses to recent
climate change, Nature 416389 (2002)
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http//www.ucsusa.org/global_warming/science/recor
dtemp2005.html
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Natural or Anthropogenic?
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Its Not Trivial to Understand Climatic Cause and
Effects!
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3.2 Atmospheric CO2 Concentrations Are Increasing
as a Result of of Human Emissions
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Increases in atmospheric CO2 concentrations began
with the industrial revolution.
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Deforestation increases atmospheric CO2
concentrations, because trees remove CO2 from the
atmosphere.
Source OSTP
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USA at Night
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Global average temperatures are increasing with
increases in CO2.
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1998 was the warmest year on record.
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Global temperature over the last 1000 years.
Global temperature over the past 1000 years.
The past 140 years
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3.3 Mechanisms of Climate Variability and Change
External versus Internal Forcing
External

• Changes in the Sun and its output, the Earths
  rotation rate,
• Sun-Earth geometry, and the slowly changing
  orbit

• Changes in the physical make up of the Earth
  system, including
• the distribution of land and ocean,
  geographic features of the land,
• ocean bottom topography, and ocean basin
  configurations

• Changes in the basic composition of the
  atmosphere and ocean
• from natural (e.g., volcanoes) or human
  activities

Internal

• High frequency forcing of the slow components by
  the more rapidly
• varying atmosphere

• Slow variations internal to the components

• Coupled variations Interactions between the
  components

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4. Climate Modeling
4.1 Coupled Ocean-Atmosphere-Land-Ice Model
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Fundamental Physical Quantities Equations

• At every grid cell GCMs calculate
• Temperature (T)
• Pressure (P)
• Winds (U, V)
• Humidity (Q)

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Worlds Fastest Supercomputer in 2002 35.6
trillion math operations per second 640 nodes,
5104 processors Occupies 4 tennis court Earth
Simulator Project 4/19/2002
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Texas Advanced Computer Center
Ranger is the largest computing system in the
world for open science research.
System Name Ranger Operating
System Linux Number of Nodes 3,936 Number of
Processing Cores 62,976 Total Memory 123TB Pea
k Performance 579.4TFlops Total Disk 1.73PB
(shared) 31.4TB (local)
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Validation of Climate Model Predictions
FAR 1990 SAR 1996 TAR 2001
IPCC 2007
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Evolution of Climate Models Over the Last Few
Decades Increased Complexity
IPCC 2007
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Evolution of Climate Models Over the Last Few
Decades Increased Spatial Resolution
IPCC 2007
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4.2 Role of Forcing Factors(the degree by which
change in a factor can raise the global mean
surface air temperature)
IPCC 2001
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Growing Cooperation BetweenModelers and
Field-Scientists
Your tools are terribly antiquated and imprecise
You produce junk and waste a lot of money
Climate Modeler
Field-Geologist
Solution interdisciplinary collaborations! Requir
ement understanding each others language
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Global warming
? Heating ? ? Temperature ? Evaporation ?
? water holding
capacity ?
? atmospheric moisture ? ?
? greenhouse effect ? rain intensity ?
? Floods Droughts
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A aggressive
1 Global
2 Regional
B Balanced
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Our Generation
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4.3 The Future of Climate Modeling

• Higher resolution, greater regional fidelity
• Increased sophistication e.g., ecosystem
  dynamics and biogeochemical cycles
• Future projections need more sophisticated
  socio-economic scenarios
• Assessment science
• vulnerability,
• mitigation,
• adaptation,
• equity,
• regulatory environments, etc.
• Confluence of the natural and the social science

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Components Of Terrestrial Biogeoscience
Chemistry CO2, CH4, N2O ozone, aerosols
Climate Temperature, Precipitation, Radiation,
Humidity, Wind
CO2 CH4 N2O VOCs Dust
Heat Moisture Momentum
Minutes-To-Hours
Biogeophysics
Biogeochemistry
Carbon Assimilation
Aero- dynamics
Decomposition
Energy
Water
Mineralization
Microclimate Canopy Physiology
Hydrology
Phenology
Inter- cepted Water
Bud Break
Soil Water
Snow
Days-To-Weeks
Leaf Senescence
Species Composition Ecosystem Structure Nutrient
Availability Water
Gross Primary Production Plant
Respiration Microbial Respiration Nutrient
Availability
Evaporation Transpiration Snow Melt Infiltration R
unoff
Years-To-Centuries
Ecosystems Species Composition Ecosystem Structure
WatershedsSurface Water Subsurface
Water Geomorphology
Disturbance Fires Hurricanes Ice Storms Windthrows
Hydrologic Cycle
Vegetation Dynamics
Gordon Bonan
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Complexity of Models Broader and Deeper
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Models of Everything
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Modules of Models
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An Integrated Framework for Modeling and
Assessment
Remote Sensing
Global Climate Change and Variability
Water Resources Applications
Coupled Ocean-Atmosphere Models
Air Quality Models
Mesoscale Models
Soil-Vegetation-Atmosphere Transfer
Policy
Hydrologic/Routing Models
In Situ Data
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• Acknowledgements
• Caspar Amman, NCAR
• Jim Hurrel, NCAR
• Tim Killeen, NCAR
• Peter Harley, NCAR
• www.gcrio.org/ipcc/qa
• http//ipcc-wg1.ucar.edu/wg1/wg1-report.html
• Physical Climatology http//www.geo.utexas.edu/cou
  rses/387h

Thank You!
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Atmospheric Layers
4 layers are defined by constant trends in
average air temperature (which changes with
pressure and radiation), where the outer
exosphere is not shown.
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The Global Energy Budget Driver of Atmospheric
Motion
A balance exists between the incoming solar
and outgoing longwave energy averaged over the
globe and the year
However, the tilt of the Earth means this
balance is not maintained for each latitude
DEFICIT
SURPLUS
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• To compensate for this energy
• imbalance, winds in the
• atmosphere and currents in the
• oceans transport cold air and
• water toward the equator
• About 1/3 of this transport
• occurs from the evaporation of
• tropical waters and subsequent
• transport into high latitudes,
• where it condenses and
• releases latent heat
• About 1/3 occurs from the
• poleward transport of warm
• waters by ocean currents
• The remaining 1/3 occurs from
• middle latitude cyclones and

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Annual Global Mean Surface Temperature and
Carbon Dioxide Concentrations
Global Temperature (C)
CO2 Concentration (ppmv)
T
CO2
Year