Transcript Chapter 14

Earth’s Atmosphere & Climate
Change
Fig. 2, p. 312
Chapter Objectives
• Weather, climate & climate basics
• Climate change through geologic time
• Ice ages
• Present day climate change
Table 9.1
I. Weather & Climate
Is there a difference?
Absolutely!
A. Weather 
Fluctuations in temperature, precipitation,
atmospheric pressure, and winds on time
scales of less than a year.
I. Weather & Climate
B. Climate 
“long term” changes or patterns in
temperature, precipitation, wind,
atmospheric pressure, etc…
• generally accepted intervals of 30 years or
more
I. Weather & Climate
“Climate is what you expect,
weather is what you get!”
II. Climate Basics
A. Earth’s heat budget
• Balance between incoming solar heat &
heat loss to space
• What controls the budget?
• Atmospheric gasses vs. solar radiation
II. Climate Basics
B. Today’s Atmosphere
• gaseous envelope around solid Earth
• 3 main elements  99% of atmosphere
• N-O-Ar
II. Climate Basics
C. Temperature & Greenhouse Effect
• Trapping of solar heat by atmosphere
• H2O, CO2, CH4, N2O, CFC’s
• role of O3  filters UV radiation
*natural & absolutely critical process!
Greenhouse Effect
• The greenhouse effect is a naturally occurring process
that aids in heating the Earth's surface and atmosphere.
It results from the fact that certain atmospheric gases,
such as carbon dioxide, water vapor, and methane,
are able to change the energy balance of the planet by
absorbing longwave radiation emitted from the Earth's
surface.
• Without the greenhouse effect life on this planet would
probably not exist as the average temperature of the
Earth would be a chilly -18° Celsius, rather than the
present 15° Celsius.
(taken from The Greenhouse Effect, Chapter 7, Physical Geography.net)
II. Climate Basics
D. Other contributing factors
1. Solar fluctuations
• long term; change in solar output
• short-term; solar flare (sunspots) cycles
2. Earth’s rotational changes
3. Volcanic eruptions
III. Climate Through Earth
History
Take Home Message based on geologic
record
Although there have been relatively long intervals
of “stable” climate, overall…..
Climate has been in constant long-term change
throughout Earth’s history
• numerous episodes of warmer & colder periods
III. Climate Through Earth
History
A. Reading Earth’s Climate History
• how do scientists study and interpret
ancient climate?
• many tools or “proxies” for interpreting
past conditions
Studying Earth’s Climate History
1. Tree Rings
•
Thicker-thinner, lighter-darker rings 
•
Seasonal to annual variations in
•
Moisture, temperature, fires
Studying Earth’s Climate History
2. Sediment layers - lake beds & ocean floor
• Layer thickness  seasonal variations
• Wetter vs. drier years
• Sediment chemistry  atmospheric conditions
Studying Earth’s Climate History
3. Specific rock types  sedimentary rocks
•
Limestones = warm water
•
Salts = warm (desert salt flats)
•
Coal = warm (swamp deposits)
•
Tillites = cold (glacial deposits)
Studying Earth’s Climate History
4. Fossils in rocks
•
Tropical fossils  corals and marine
fauna = warm vs. cold conditions
•
Land animals  dinosaurs, etc. = warm
•
Plant fossils  deciduous vs. coniferous
vs. grassland/tundra
Studying Earth’s Climate History
5. Ice layers
• Annual layers of ice in glaciers
• Trapped gasses and dust  CO2, etc.
• Atmospheric conditions, volcanic activity
• Dated layers tell about specific conditions
Ancient ice layers; summer (lighter)
vs. winter (darker)
Studying Earth’s Climate History
6. Chemical Isotopes
• abundances of oxygen isotopes give ages
and atmospheric compositions
• recorded in rocks, fossils, sea floor
sediment, glacial ice
Studying Earth’s Climate History
Take Home Message 
Geologists and climate scientists have many
tools, proxies for determining past climate
conditions.
III. Climate Through Earth
History
B. Early Earth = a hot house Earth
• much higher CO2, CH4, etc., very low oxygen
• “intense” greenhouse effect
• more “modern Earth  much less CO2, O-rich
• where did the CO2 go & why did Earth become
more oxygen rich over time?
III. Climate Through Earth History
C. Ice Ages vs. Warm Periods
• numerous “colder than normal” vs.
“warmer than normal” episodes
Ice Age  extended period of geologic time
when Earth’s temperature is below the
average
• at least 5 ice ages throughout time
Earth’s Global Ice
Ages (orange)
Numerous “ice ages” (at least 5)
recorded in the geologic record,
when Earth’s temperatures
where cooler than today.
Also, numerous episodes when
Earth’s temp. was warmer than
today.
III. Climate Through Earth History
D. Cenozoic Climate Change
• warming peak at ~55 MY ago
• last 55 MY, slow, gradual cooling
• Continental sized glaciers in N. America
 ~2.0 MY
• Pleistocene ice age
Plot of southern ocean temperatures (based on oxygen isotopes in
sediments), showing max. ocean temps. ~55-50 MY ago, presumably
the warmest conditions in last 100 MY.
III. Climate Through Earth History
E. Pleistocene Ice Age
•
most recent ice age
•
~2.0 MY – 16,000 BP
•
North America  northern U.S., Canada,
Greenland
•
Northern Europe + Siberia
Pleistocene North America: note distribution of major continental ice sheets,
also the relative sea level differences compared to today.
Pleistocene North America:
note the distribution of
climate controlled
vegetative zones
compared to today’s
vegetative zones.
III. Climate Through Earth History
F. Advances vs. Retreats
• numerous warming – cooling trends during the
Pleistocene
• Glacials vs. interglacials
• Glacials  cold = glaciers grow & advance
southward
• Interglacials  warm = glaciers melt & retreat
northward
Take Home  even during ice age, climate fluctuated
Climate fluctuations (warm-cold) over the last 3 MY, based on oxygen
isotope data
III. Climate Through Earth History
G. Closer Look: most modern times
• Ice core data: Greenland & Antarctica
• CO2 & CH4 concentrations in ice
• Dust concentrations
• Ice layers dated oxygen isotopes
• CO2 & CH4  correlate to temperature
EPICA Ice cores from Dome Concordia archive
composition of atmosphere for 650,000 years
(Science/November 25, 2005)
Antarctic Ice Core Data (Dome Concordia)
Note ~100,000 cycle peaks of CO2 & CH4
IV. Present Day Climate Change
& Global Warming
So, What Do We Know About
The Present Climate Change
Pattern?
Senator James Inhofe,
R-Oklahoma
Senate Committee on the
Environment and Public Works
"much of the debate over global warming is predicated on
fear, rather than science." I called the threat of
catastrophic global warming the "greatest hoax ever
perpetrated on the American people,"
“most media-hyped environmental issue of all time”
“the American people have been served up an
unprecedented parade of environmental alarmism by
the media and entertainment industry”
“We have a very brief window of opportunity”
Dr. James Hansen, Director, NASA Goddard Institute for Space Studies
“We have a very brief
window of opportunity to
deal with climate change . . .
no longer than a decade at
the most.“
If the world continues with
"business as usual,"
temperatures will rise by 2
to 3o Celsius (3.6 to 7.2o F)
and "we will be producing a
different planet"
Eleven Warmest Years Worldwide
(since the 1880)
2005, 2010*(tied)
#2 1998
#3 2003
#4 2002
#5 2009
#6 2006
#7 2007
#8 2004
#9 2001
#10 2008
13 of the 14 warmest years have occurred since 1995!
22 of 23 warmest years have occurred since 1980!!
#1
(National Climatic Data Center, 2010)
2010 Temperature Data
• Ocean surface temperatures = 3rd
warmest on record
• Land surface temperatures = warmest
on record for northern hemisphere
• Land & ocean temperatures  warmest
on record
2000-2009 warmest decade on record!
(National Climatic Data Center)
For 1990-1999:
• Avg. global surface temperature 0.65o above 20th
Century avg.
For 2000-2009:
• avg. global surface temperature 0.86o above 20th
Century avg.
Take home  rate of warming is increasing
IV. Present Climate Trend
A. Global Warming  overall “gradual”
warming of Earth’s surface, atmosphere
& ocean temperatures
B. Cause?
•
Natural causes
•
Anthropogenic (human influences)
•
GHG’s must be considered!
IV. Present Global Warming
Anthropogenic contributions
• Increased GHG’s to atmosphere 
burning of fossil fuels since start of the
Industrial Revolution
• Significant increases in CO2, CH4, N2O,
CFC’s
Anthropogenic CO2
• ~29 gigatons CO2 per year (presently)
• 1 gigaton = 1 billion tons
• 500 gigatons since the Industrial Revolution
Atmospheric CO2
Atmospheric CO2
• ~280 ppm CO2 = pre-Industrial Revolution
age levels
• 391 ppm CO2 = March 1, 2011
• The rate of CO2 & CH4 increase over the
last 150 years is higher than at any time in
the last 850,000 years
Atmospheric CO2
• CO2 levels 30% higher than anytime since
the last glacial maxima
• Estimated present rate of CO2 increase is
200x faster than anytime in last 850,000
years!
• CH4 levels 130% higher
CO2 rises exceed worst-case scenarios
(Proceedings of the National Academy of Sciences/May 22, 2007)
• The world's recent carbon
dioxide emissions are
growing more rapidly than
even the worst-case climate
scenario used by the
Intergovernmental Panel on
Climate Change (IPCC)
• C02 emissions from fossil
fuels increasing at 3 times
the rate of the 1990’s
CDIAC & EIA data compared to IPCC
Global avg. temps, 1856-2005
Global mean surface temperature anomalies
& simulations with natural forcings only
(IPCC AR4, 2007/ The Physical Science Basis/p. 684, Fig. 9.5)
Global mean surface temperature observations in black
(anomalies relative to period 1901-1950)
AOGCM simulation range in blue/mean in dark blue
(58 simulations/14 models)  model simulations without anthropogenic
GHG’s
Global mean surface temperature anomalies
& simulations with anthropogenic forcings
(IPCC AR4, 2007/ The Physical Science Basis/p. 684, Fig. 9.5)
Global mean surface temperature observations in black
(anomalies relative to period 1901-1950)
AOGCM simulation range in yellow/mean in red
(58 simulations/14 models)
Projected Temps. @ present rates
GW: “Possible” vs. Observed Effects
• Temperature rise  2 to 5oC by 2100
• Precipitation changes  less vs. more H20
• Severe storms  higher intensity
• Melting glaciers & sea level rise
• Biological “shifts” and extinctions
• Sea water acidification
• Melting permafrost
• Social effects  massive human migrations
Significant majority of
mountain glaciers worldwide
are retreating (melting) due
to increased temps.
Kilimanjaro ice cap gone by 2030
Greenland melt zone 1979-2002
(Arctic Climate Impact Assessment, 2004)
Fig. 11-33, p. 336
NASA GRACE satellite detects
significant Antarctic ice mass loss
(University of Colorado/March 2, 2006)
(photo courtesy British Antarctic Survey)
University of Colorado (Boulder) scientists demonstrated for the
first time that Antarctica's ice sheet lost a significant amount of
mass since the launch of GRACE [Gravity Recovery and Climate
Experiment] in 2002.
RELEASE: 06-085
Projected Sea Level Rise
• Greenland ice sheet  ~23’ rise in SL
• West Antarctic ice sheet  ~16’ rise
• East Antarctic ice sheet  ~190’ rise
Sea Levels: Past, Present, & Future?
September Arctic sea ice at record low
(NASA/Earth Observatory/September 16, 2007)
Arctic sea ice
reached a
record low in
September
2007, below
the previous
record set in
2005 and
substantially
below the
long-term
average
Melting sea ice stresses polar bears
(Integrative and Comparative Biology/April, 2004)
• Polar bears cannot survive
without sea ice and, in all
likelihood, summer sea ice
will be gone from the north
polar basin within the next
few decades (Center for
Biological Diversity 6/15/06)
(photo by Dan Crosbie)
• Given the rapid pace of
ecological change in the
Arctic, the long generation
time and highly specialized
nature of polar bears, it is
unlikely that polar bears will
survive as a species if the sea
ice disappears
Global warming impacts on permafrost & tundra
Western Siberia thawing for the first time in 11,000 years
(New Scientist/August 11, 2005)
•
An area stretching for a million
square kilometers across the
permafrost of western Siberia is
turning into a mass of shallow lakes
as the ground melts.
•
The sudden melting of a bog the size
of France and Germany could
unleash billions of tons of methane,
a potent greenhouse gas.
•
Sergei Kirpotin of Tomsk State
University describes an "ecological
landslide that is probably
irreversible and is undoubtedly
connected to climatic warming.“
•
Western Siberia has warmed some 3
°C in the last 40 years.
(photo courtesy of BBC News)
Ocean acidity studies: ocean pH
levels are changing
• pH stable from 1000 to 1800
• drop of 0.1 of a pH unit from 8.16 to 8.05
(since the industrial revolution)
• Predicted 0.3-0.4 drop by 2100
 Reduced carbonate uptake by CaCO3
secreting organisms  plankton, coral,
etc.
Fig. 11-34, p. 338
What if the scientists
are wrong about global
warming?
We can afford to be wrong, we just can’t
afford to be right and do nothing about it.
I left Earth three times, and found no
other place to go. Please take care
of Spaceship Earth.
Wally Schirra, NASA
IT IS TIME TO ACT!
(AP photo courtesy of Dan Crosbie/Canadian Ice Service)