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Get Fuzzy by Darby Conley
An Inconvenient Truth
Discussion
Lis Cohen
Department of Meteorology
University of Utah
Lis.cohen@utah.edu
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Summary and
Comments
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Overall Impression
• Very Very well done
– Climate change is a complicated topic
– The science is often hard to explain
• Gore did a very good job explaining the fundamentals of the science
• Gore did a very good job explaining the urgency of the situation
• Most of my criticisms are very nitpicky
– These critiques should not substantially weaken the credibility of
this movie.
– The science and importance of global warming is well portrayed.
– RealClimate.org (complete discussion)
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Global Climate Change
• There is no longer any
scientific doubt that the
Earth’s average surface
temperature is increasing
– 1.3°F in last century
– Recent decades warmer than
any comparable period in last
400 years (possibly much longer)
• Ocean temperature, ice and snow cover, and sea level
changes consistent with this global warming
– Sea level up 7 inches in 20th century
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Causes of Recent Climate Change
• There is very high confidence that humangenerated increases in greenhouse gas
concentrations are responsible for most of
the global warming observed during the
past 50 years
• It is very unlikely that natural climate
variations alone, such as changes in the
brightness of the sun, have produced this
recent warming
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Invasive species, disease and
global warming
• Invasive species due to
land use change and
importation
• Not sure how invasive
plants and insects will
respond
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Lack of cloud modeling
uncertainties in the movie
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Ice Core and CO2
• Long ice core records of CO2
•
•
and temperature in Antarctic
ice cores
View 1: other climate forcings
besides CO2 contribute to the
change in Antarctic
temperature between glacial
and interglacial climate.
View 2: Gore is careful not to
state what the
temperature/CO2 scaling is.
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Aerosol Concentrations in ice cores
• Gore claims that you can see
•
the aerosol concentrations in
Antarctic ice cores change "in
just two years", due to the
U.S. Clean Air Act.
You can't see dust and
aerosols at all in Antarctic
cores — not with the naked
eye
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CO2 and Temperature connections
in the ice core record
• Observed long-term relationship
•
•
between CO2 and temperature in
Antarctica supports our understanding
of the warming impact of increased
CO2 concentrations
Moreover, our knowledge of why CO2
is changing now (fossil fuel burning)
is solid.
Carbon cycle
– CO2 is a greenhouse gas
– Carbon cycle feedback is positive
(increasing temps lead to increasing CO2
and CH4)
– Future changes in CO2 will be larger than
we might anticipate.
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Climate impacts on the ocean
conveyor
• Timing is uncertain.
• Younger Dryas 11,000 y.a.
– A large discharge of fresh water
into the North Atlantic disrupted
currents, causing significant
regional cooling.
• IPCC predicts a slowdown in
the circulation ~ 30% by 2100
– Circulation modeling and future
inputs of melted ice -not well
understood.
– Few scientists are willing to
completely rule out the possibility
of a more substantial change in
the future.
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Ice-sheet driven sea level rise
• Gore correctly asserted that melting of
Greenland or the West Antarctic ice sheet
would raise sea levels 20ft (6 meters).
– No time frame, very uncertain
– 20 ft
• about how much higher sea level was around
125,000 years ago during the last inter-glacial
period.
– Then, global temperatures were only a degree or two
warmer than today
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Impact of sea ice retreat on
Polar bears
• Summer Arctic sea ice shattered all
records this year for the minimum
extent.
• Polar bears
– depend on the sea ice
• hunt for seals in the spring and
summer
– disappearance ice
• likely to impact them severely
– Studying the regional populations of
polar bears is not easy and assessing
their prospects is tough.
• Arctic ecosystems are changing on
many different levels.
– It may be the smaller and less
photogenic elements that have the
biggest impact. –RealClimate.org
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Pacific island nations needing
to evacuate
• Much of Tuvalu
– is only a few feet above sea level
– With more sea level rise
• increasing brine in groundwater
• increasing damage and coastal
erosion from tides and storm surges
• Government of Tuvalu asked
•
New Zealand to be ready to
evacuate islanders
In the movie: "That's why the
citizens of these pacific nations
have all had to evacuate to
New Zealand“.
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Kilimanjaro
• Ongoing discussion in the
Feb 1993
literature:
– Is retreat of ice on Kilimanjaro
related to the direct effects of
climate change?
• warming atmospheric temperatures
– Or indirect effects of climate
change
• altered patterns of humidity, cloud
cover, and precipitation influencing
Kilimanjaro's ice mass
Feb 2000
• Take home message
– (a) ice field that we know has
existed for at least the past 12,000
years is shrinking
– (b) most of the other glaciers are
disappearing as well.
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http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/kilimanjaro_etm_93_00.jpg
Drying up of Lake Chad
• Extremes
– Droughts
– Flooding
• Lake Chad Change
http://www.dailymail.co.uk/pages/live/articles/news/worldnews.html?in_article_id=479576&in_page_id=1811
– reduction of rainfall across entire Sahel from 1950s to
1980s
– rainfall today still substantially below high point 50 years
ago
– Other factors
• Irrigation and upstream water use.
• Substantial evidence that at least a portion of this drying out is
human-caused.
• Indian Ocean changes in sea surface temperature
• Increase in atmospheric aerosols in the Northern hemisphere.
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Hurricane Katrina and global
warming
• Katrina is used
– Destructive power of hurricanes
– Cope with natural disaster
– Ex. of what could get worse in a warmer
world.
• Nowhere does Gore state that Katrina
was caused by global warming.
– Individual hurricanes cannot be attributed
to global warming, but the statistics of
hurricanes, in particular the maximum
intensities attained by storms, may be.
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http://geology.com/news/images/hurricane-katrina-satellite-image.jpg
Impact of ocean warming on
coral reefs
• Stress Factors
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Overfishing
deliberate destruction
water pollution
sea level rise
ocean acidification
http://web.syr.edu/~tjconena/coral_reefs.htm
warming oceans.
That rising temperatures and other factors cause coral bleaching
is true.
• Bleaching episodes happen when the coral is under
stress, and many examples have been linked to
anomalously warm ocean temperatures
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Priority Actions for American
Consumers
• Vote!
• Transportation
– Choose a place to live that reduces the
need to drive.
– Think twice before purchasing another
car.
– Choose a fuel efficient, low polluting
car.
– Set concrete goals for reducing your
travel.
– Whenever practical walk, bicycle or
take public transportation
– Brower, 1999
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Priority Actions for American Consumers
• Food
– Eat less meat.
– Buy certified organic produce.
• Household Operations
– Choose your home carefully.
– Reduce the environmental costs of
heating and hot water.
– Install efficient lighting and appliances
– Choose an electricity supplier offering renewable
energy.
• Policy
– Vote, write letters, attend rallies, call your
representatives and express your views.
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– Brower, 1999
Summary
• Climate Change will
•
•
•
•
impact Utah in a variety
of ways.
An Inconvenient Truth did
a great job explaining
climate change.
Most of my comments are
very nitpicky
You can help slow down
climate change!
Take Action Today!
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Thank you!
Lis.cohen@utah.edu
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Background Slides
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Old ideas about cooling earth
• The reason scientists thought the earth was cooling was
•
•
because they had just discovered the milankovic cycles
and saw sea core bed data that indicated we might be
due for another ice age. The didn't know about the fact
that many of the components of the milancovic cycle all
needed to fall in phase for the ice age to begin.
Temps decreased for about 30 years and scientists were
just starting to look at climate data.
Few scientists thought this was happening with a lot of
press.
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Reference: CO2 changes during the
ice ages
• A full understanding of why CO2 changes in
precisely the pattern that it does during ice ages
is elusive, but among the most plausible
explanations is that increased received solar
radiation in the southern hemisphere due to
changes in Earth's orbital geometry warms the
southern ocean, releasing CO2 into the
atmosphere, which then leads to further
warming through an enhanced greenhouse
effect.
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British Judge
• The judge appears to have put words in Gore's
•
mouth that would indeed have been wrong had
they been said (but they weren't).
The judge was really ruling on how "Guidance
Notes" for teachers should be provided to allow
for more in depth discussion of these points in
the classroom.
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Drying up of Lake Chad
• Gore uses this example to illustrate that there are droughts in
•
•
some regions even while other areas are flooding.
Unfortunately this is what models suggest.
The dominant cause
– reduction of rainfall across entire Sahel from 1950s to 1980s
– rainfall today still substantially below high point 50 years ago
– Other factors
• Irrigation and upstream water use.
• Substantial evidence that at least a portion of this drying out is humancaused.
– Recent papers (Held et al, PNAS; Chung and Ramanathan and Biasutti
and Giannini) have addressed causes ranging
• Indian Ocean changes in sea surface temperature
• Increase in atmospheric aerosols in the Northern hemisphere.
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Impact of sea ice retreat on
Polar bears
• Summer Arctic sea ice shattered all records this year for the minimum
extent.
– This was partially related to wind patterns favorable to ice export in the spring,
but the long term trends are almost certainly related to the ongoing and
dramatic warming in the Arctic.
• Polar bears do indeed depend on the sea ice to hunt for seals in the spring
•
•
and summer, and so a disappearance of this ice is likely to impact them
severely.
The specific anecdote referred to in the movie came from observations of
anomalous drownings of bears in 2004 and so was accurate.
However, studying the regional populations of polar bears is not easy and
assessing their prospects is tough.
– In the best observed populations such as in western Hudson Bay (Stirling and
Parkinson, 2006), female polar bear weight is going down as the sea ice retreats
over the last 25 years, and the FWS is considering an endangered species listing.
– However, it should be stated that in most of the discussions about polar bears,
they are used as a representative species.
• Take home message: Arctic ecosystems are changing on
many different levels. In the end, it may be the smaller
and less photogenic elements that have the biggest
impact.
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Drying up of Lake Chad
• Gore uses this example to illustrate that there are
•
•
droughts in some regions even while other areas are
flooding.
Unfortunately this is what models suggest.
The dominant cause
– reduction of rainfall across entire Sahel from 1950s to
1980s
– rainfall today still substantially below high point 50 years
ago
– Other factors
• Irrigation and upstream water use.
• Substantial evidence that at least a portion of this drying out is
human-caused.
• Indian Ocean changes in sea surface temperature
www.WeatherOutreach.org
• Increase in atmospheric
aerosols in the Northern hemisphere.
Impact of ocean warming on
coral reefs
• Stress Factors
–
–
–
–
–
–
–
–
Overfishing
deliberate destruction
water pollution
sea level rise
ocean acidification
warming oceans.
That rising temperatures and other factors cause coral bleaching is true.
Bleaching episodes happen when the coral is under stress, and many
examples have been linked to anomalously warm ocean temperatures
(Australia in 1998 and 2002, all over the Indian Ocean in recent years).
Corals are a sobering example of how climate change exacerbates
existing vulnerabilities in eco-systems, potentially playing the role of the
straw that breaks the camel's back in many instances.
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Figure 1. Model Simulation of Trend in Hurricanes (from Knutson et al, 2004)
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wer dissipated annually by tropical cyclones
in the North Atlantic (the power dissipation inde
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Can giant hurricanes exist all around the
world like in the Day After Tomorrow?
• Clusters of thunderstorms cannot merge
together to form a continent-scale blizzard
with a calm eye over land.
• Huge storms with calm eyes happen over
the oceans not over land.
– Hurricanes or Tropical Storms
• Require that the core of the storm be over warm
ocean water
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Photo: earthobservatory.nasa.gov/NaturalHazards/Arch...
What process could most likely change the climate?
More moisture in
the air
Warmer climate
Circulation slows down
and changes
More evaporation at the equator
More moisture can
be held in the air
Water does not sink in the northern latitudes
Melting Glaciers
Ocean is not as
salty and dense
More freshwater
in the ocean
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More rain
at higher
latitudes
Three Glaciers Retreating
Denver Glacier in Recession,
Alaska, British Columbia
• Source:
1938 C.L. Andrews. 1912, 1938. Denver Glacier: From
1912
the Glacier Photograph Collection . Boulder, CO: National
Snow and Ice Data Center. Digital Media; Marion T.
Millett. 1958. Denver Glacier: From the Glacier
Photograph Collection . Boulder, CO: National Snow and
Ice Data Center. Digital Media.
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Temperature and Ice Accumulation
vs. Time
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Data Sources
• The 2007 IPCC (Intergovernmental Panel on Climate
Change) report
– Includes
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•
•
•
•
•
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2,500 + scientific expert reviewers
800+ contributing authors
450+ lead authors from
130+ different countries
6 years of work
4 volumes
1 report
• Scientific Literature
• Presentations from experts at the University of Utah –
Dr. Dave Chapman, Dr. Tim Garrett, Dr. Gerald Mace, Dr.
Thomas Reichler
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Temperature Analysis
• “Warming of the climate system is
unequivocal, as is now evident from
observations of increases in global
average air and ocean temperatures,
widespread melting of snow and ice,
and rising global average sea level”
(IPCC report 2007).
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Contributions to Sea Level Rise
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Long-term Changes in Climate
• Long-term changes are observed at:
– Continental Scales
– Regional Scales
– Ocean basin Scales
• These changes include:
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Changes in Arctic temperatures and ice
Widespread changes in precipitation amounts
Ocean salinity
Wind patterns
Aspects of extreme weather
• Droughts
• Heavy precipitation
• Heat waves
• Intensity of tropical cyclones
- 2007 IPCC report
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What can change our climate?
• Changes in these factors alter the energy
balance of the climate system:
– Solar radiation
– Land surface properties
– The atmospheric abundance of greenhouse
gases and aerosols
-2007 IPCC Report
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The Greenhouse Effect
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How are greenhouse gas impacts
measured?
• These impacts are expressed in terms of
radiative forcing, which is used to compare
how a range of human and natural factors
drive warming or cooling influences on
global climate.
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LOSU = level of understanding
RF = Radiative Forcing
Error bars
Additional forcing factors not included here are considered to have a very low
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level of scientific understand.
How is the sun affecting climate
change?
The effect of the sun’s variations
accounts for +.12 W/m2.
There is very high confidence that
the globally averaged net effect of
human activities since 1750 has
been one of warming, with a
radiative forcing of +1.6
[+0.6 to +2.4] W/m2.
Natural Climate Variability because
of the sun has been not very
significant.
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How do we know that this is
not a normal cycle?
We use past climate data and
compare influencing factors.
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How do we know about past
climates?
• Tree Rings – Growth is controlled by temperature,
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•
•
•
precipitation and sunlight
Pollens – give a good indication of what was living at the
time indicating a temperature range
Ice and sea bed cores – Gasses in bubbles, dust,
isotopes, accumulation rate
The fossil record
Coral beds
Note: Uncertainties generally increase with time into the
past due to increasingly limited spatial coverage.
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Paleoclimate Information
“Paleoclimate information supports the
interpretation that the warmth of the last
half century is unusual in at least the
previous 1300 years.”
“The last time the polar regions were significantly
warmer than present for an extended period
(about 125,000 years ago), reductions in polar ice
volume led to 4 to 6 meters (13-20 feet) of sea
level rise.”
-2007 IPCC Report
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What has Changed and what
has Not Changed?
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Aspects of climate that have NOT changed
• Day night temperature differences have remained
constant. Both the maximum and minimum
temperatures have increased at the same rate. The
trends are highly variable from one region to another.
• Antarctic sea ice extent continues to show inter-annual
variability and localized changes but no statistically
significant average trends, consistent with the lack of
warming reflected in atmospheric temperatures averaged
across the region.
• There is insufficient evidence to determine whether
trends exist in
– Meridional overturning circulation of the global ocean
– Small scale phenomena
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Tornadoes
Hail
Lightning
Dust-storms
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Consequences of
Climate Change
Ward Hunt Ice Shelf, 2002
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Muir Inlet, Alaska
Larsen B ice shelf,
Antarctica
1941
Larsen B ice shelf, Antarctica
ca. 100 x 80 miles
Feb. 17, 2002
2004
National Snow and Ice data center
http://nsidc.org/cgi-bin/gpd_run_pairs.pl
Glacier Bay National Park and
Preserve
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Mar. 5, 2002
Arctic Polar Ice Cap
1979
2003
• Since 1979, the size of the summerhttp://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html
polar ice cap has shrunk more
than 20 percent.
• On Sept. 21, 2005, sea ice extent dropped to 2.05 million sq. miles,
the lowest extent yet recorded in the satellite record.
• This loss is twice the size of Texas.
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NASA
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References
• Climate Change 2007: The Physical
Science Basis. Intergovernmental Panel
on Climate Change.
• Garrett, T. “Rapid Arctic Climate Change
Forcing the Feedbacks.” 2007.
• Chapman, D. “Global Warming – Just Hot
Air?” 2006.
•
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Thank you!
Questions?
Presentation can be found at:
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Lis Cohen: liscohen@met.utah.edu
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Alaska
Tundra
Travel Days
Decreased
by Half
Since 1970
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Changes in Greenhouse Gases from
Ice-Core and Modern Data
The global increases in
carbon dioxide
concentration are due
primarily to fossil fuel
use and land-use
change.
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Changes in Greenhouse Gases
The increases of methane
and nitrous oxide are
primarily due to agriculture.
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