Transcript ESYS 10 Introduction to Environmental Systems February 26

ESYS 10
Introduction to Environmental Systems
March 7, 2006
Reading: Chapter 16 Global Warming and Technical Summary
for the IPCC
Chapter 16 problems: review questions 2, 3, 10, due Tuesday
March 14
Problems from chapter 8 due today
Case Study 3 due next Tuesday March 14
Term papers due Thursday March 16
Discussion time: Complete Case Study 3, handout for C.S. 4
http://realclimate.org site contributed to by climate scientists
http://www.marshall.org/ somewhat objective site, but funded by Exxon, some good links
Global Change
• “Change” a synonym for anthropogenic climate
change, as opposed to “variability” which is a
synonym for natural climate variation.
• Evidence of global change
– CO2 rise - documentation and evidence that it is
anthropogenic
– Temperature change
– Sea level change
– Permanent ice cover changes in Arctic and Antarctic
• Climate modeling using expected CO2 rise,
predictions for climate change
• Temperature rise - documentation and evidence
that it is anthropogenic
Natural climate “modes” (patterns)
• What are the dominant natural modes of climate
that impact us on decadal to millenial scales (short
of glaciations)?
• El Nino Southern Oscillation
• Pacific Decadal Oscillation
• North Atlantic Oscillation (or Northern Annular
Mode)
• Southern Annular Mode
• Atlantic thermohaline circulation changes
• Go to separate powerpoint for these patterns
CO2, CH4 and T changes through history
Present
Age (kyr B.P.)
PAST
Various greenhouse
gas histories
CO2 rise
“Keeling” CO2 curve at Mauna Loa
Fossil fuel reserves
Fossil Fuels
Fossil fuel reserves
•
•
•
•
•
Reservoir
Coal
Oil
Natural gas
Total
Size Gton
3500
670
500
4570
Burning rate Gton/yr
2.4
2.7
1.3
6.4
Deforestation also produces about 1.5 per year
Thus 670 years reserve if all fossil fuels in all forms were
used up.
Who is doing the burning?
Where does the total of 7.5 to 8 Gton/yr of carbon go?
Fossil fuel consumption (Gtons C/yr)
(1 Gton = 1 billion metric tons
1 metric ton = 1000 kg)
•
•
•
•
•
•
•
N.America
Central and S. America
Western Europe
Eastern Europe
Middle East
Africa
Far East
• Total
1.832
0.269
1.000
0.844
0.288
0.240
1.970
6.443 GtC/yr
ESYS 10
Introduction to Environmental Systems
March 9, 2006
Reading: Chapter 16 Global Warming and Technical Summary
for the IPCC
Chapter 16 problems: review questions 2, 3, 10, due Tuesday
March 14
Case Study 3 due next Tuesday March 14
Term papers and presentation due Thursday March 16
Discussion time: Term paper presentations and handout for C.S.
4
http://realclimate.org site contributed to by climate scientists
http://www.marshall.org/ somewhat objective site, but funded by Exxon, some good links
Is Earth’s climate changing?
The problem of attribution
Attribution and consistency
Detecting that some climate change has taken place does
not immediately imply that we know the cause of the
detected change. The practical approach to attribution that
has been taken by climatologists includes a demand for
consistency between the signal amplitudes projected by
climate models and estimated from observations
(Hasselmann, 1997). (IPCC, 2001)
Detection and attribution of climate change is a statistical “signal-in-noise”
problem, it requires an accurate knowledge of the properties of the “noise”.
Ideally, internal climate variability would be estimated from instrumental
observations, but a number of problems make this difficult.
Lots of great websites
Particularly:
U.S. EPA on global warming
http://yosemite.epa.gov/OAR/globalwarming.nsf/UniqueKeyLookup/SHSU5BUN59/$File/gw_faq.pdf
“Keeling” CO2 curve at Mauna Loa
What is the evidence that the CO2 rise is anthropogenic?
1000 million metric tons = 1GTon
Is the increase in atmospheric CO2 and other
greenhouse gases anthropogenic in origin?
Yes:
(1) The observed increase is consistent with fossil fuel burning
(2) The isotopic composition (type of carbon) in the air today is
very different from air from 100 to 1000 years ago, based on
analyses of air from ice and firn (snow layer) cores. The
present-day composition indicates fossil fuel burning is
responsible for the CO2 increase. (the “Suess effect”,
another UCSD/SIO carbon great)
“Keeling” curve and
same in southern
hemisphere.
Oxygen in
atmosphere
(Manning and
Keeling, 2005)
13C/12C isotopic
ratio in CO2 at
Mauna Loa,
showing increase
that matches with
global emissions of
carbon
CO2 rise in the atmosphere: about 3 GtonC/yr of the 6-7
GtonC/yr. This is the portion that fuels greenhouse gasinduced climate change.
Textbook version - preindustrial revolution
numbers for atmosphereocean CO2 exchange
60 62
3 Gton/yr stays in
atmosphere
2 Gton/yr into ocean
0.5 Gton/yr into
vegetation
Remainder: 2 Gton/yr mystery???
Sink of anthropogenic CO2?
90 92
Fossil fuel burning
and changing land
use create about 6-7
GtC/yr excess. Of
this, about 1/2 stays
in the atmosphere,
1/3 goes into the
ocean, and 1/6 goes
into new terrestrial
vegetation.
OK - CO2 rise is anthropogenic, but are
observed changes in temperature, ice cover,
sea level, etc. caused by the rise in greenhouse
gases?
Look at temperature observations, and then at large
computer simulations of climate.
Earth’sgreenhouse effect
Earth’s global mean energy balance
Kiehl and Trenberth, 1997
Earth’s surface
temperature
variations
Last 120 years
Last 2000 years
Moberg et al
(2005)
reconstruction
Earth’s surface temperature variations:trend from
1901 to 2004
Smith and Reynolds, 2005
Arctic warming and ice retreat
http://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html
1990
1999
Impacts of ice melt: (1) sea level rise, (2) low salinity cap on
North Atlantic that would impeded deep water formation and
change circulation/climate of North Atlantic region/world.
The year 2002 showed lowest level of sea ice on record (NASA)
Arctic warming and ice retreat
http://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html
1999
2002
At the rate of melting in last 15 years, could disappear entirely
by the end of the century. Melt period begins earlier than 10
years ago. Strong feedback with climate (ice-albedo)
Greenland ice cap
http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4035
Time magazine Feb. 27, 2006
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Has the Meltdown
Begun?The discovery that
Greenland's glaciers are
melting faster than anyone
expected has experts worried
anew about how high the
seas will rise
By MICHAEL D. LEMONICK
Greenland ice cap
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://cires.colorado.edu/science/groups/steffen/greenland/melt2005
/
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Greenland ice velocities, Rignot
and Kangaratnam, Science Feb.
17, 2006
Antarctic ice shelf melting
Mechanism for breakup: warmer weather
creates melt water ponds on the surface that
seep down and weaken the ice
Larsen ice shelf on the Antarctic peninsula:
piece larger than Rhode Island broke off
Jan. 31, 2002
http://nsidc.org/iceshelves/larsenb2002/index.html
March 5, 2002
Antarctic ice shelf melting
Big concerns (media scares) seem to center on breakup of the
West Antarctic Ice Shelf. Very large - if it were to go, then sea
level would rise 10 meters.
Very unlikely to happen for several centuries but …
March 3, 2006, 1:30AM
Antarctica's ice melts faster than snowfall can
replace it Satellite survey indicates that the
continent is steadily shrinking
By ROBERT LEE HOTZ Los Angeles Times
(based on paper appearing in Science, March 3,
2006)
Observed temperature changes: are they due
to anthropogenic forcing?
Temperature increases can be due to:
(1) Solar radiation changes (cools or warms) - 11year cycle
0.6 to 0.7 W/m2. All reconstructions indicate that the direct effect of variations in solar
forcing over the 20th century was about 20 to 25% of the change in forcing due to
increases in the well-mixed greenhouse gases (IPCC, 2001)
(2) Volcanic eruptions (more particles, sulphates, cools the
planet) -3 W/m2
(3) Anthropogenic greenhouse gases (warms climate)
(4) Anthropogenic aerosols (mostly cools climate)
How to tell the difference between (1) and (3)?
Natural versus anthropogenic Temperature
change? Reason 1
(1) Observed warming is stronger at high latitudes than low
latitudes ---> anthropogenic cause because:
(a) If due to solar radiation forcing, then water vapor would
increase, and most warming would be in the wet lower
latitudes.
(b) If anthropogenic CO2 increase is the cause, warming
would be at higher latitudes since CO2 is more uniformly
spread through all latitudes, and CO2 is a much higher
relative part of greenhouse gases in the dry high latitudes
Earth’s surface temperature variations:trend from
1901 to 2004
Smith and Reynolds, 2005
Earth’s surface temperature variations:trend from
1979 to 2004
Smith and Reynolds, 2005
Natural versus anthropogenic Temperature
change? (high latitudes warm more)
The spatial pattern of the simulated surface temperature response
to a steady increase in greenhouse gases is well documented
(e.g., Kattenberg et al., 1996; Chapter 10). The warming is greater
over land than over ocean and generally small during the 20th
century over the Southern Ocean and northern North Atlantic
where mixing extends to considerable depth. The warming is
amplified in high latitudes in winter by the recession of sea ice and
snow, and is close to zero over sea ice in summer.
Natural versus anthropogenic Temperature
change? Reason 2
(2) Warming is more evident in nighttime temperatures
(difference between day and night temperatures is decreasing)
---> anthropogenic change because:
greenhouse gases trap heat at night as well as during the day,
so there would be relatively more warming at night
Earth’s surface
temperature
variations:
maximum and
minimum
temperatures and
diurnal range
Difference - shows night is
warming more
Maximum = day
temperatures
Minimum = night
temperatures
Vose et al., 2005
Natural versus anthropogenic Temperature
change? Reason 3: Stratospheric cooling
“The vertical response to solar forcing (Figure 12.5) includes
warming throughout most of the troposphere. The response
in the stratosphere is small and possibly locally negative, but
less so than with greenhouse gas forcing, which gives
tropospheric warming and strong stratospheric cooling. The
dependence of solar forcing on wavelength and the effect of
solar fluctuations on ozone were generally omitted in these
simulations. Hence, the conclusion that changes in solar
forcing have little effect on large-scale stratospheric
temperatures remains tentative.” (IPCC, 2001)
Natural versus anthropogenic Temperature
change? Reason 3
(3) Stratospheric cooling: a
signature of anthropogenic
warming
Figure 12.5: (a) solar forcing.
(b) greenhouse gas-induced temperature change
Natural versus anthropogenic Temperature change?
(observations of stratospheric cooling)
Results of warming
Change in precipitation patterns
Rise in sea level - melting of land ice, increased
temperature of oceans causing them to expand,
(rebound of land from last ice age)
Change in extreme weather (greater variability bigger extremes)
Observed
trends in
precipitable
water (warmer
world has
more water
vapor)
Trenberth et al. 2005
Sea level - what causes it to change?
1. Add more water to the oceans: melt glaciers and landfast ice
(Antarctic ice cap and Greenland ice cap are the biggest).
2. Warm the ocean: thermal expansion of water will cause sea
level to rise. This has been the main effect in observed sea
level rise
3. (NOTE: melting sea ice does not cause sea level to rise)
How fast is sea level rising? 2 to 3 mm/year, about 2/3 due to
thermal expansion, 1/3 due to land ice melt.
Observed global mean sea level rise (Barnett, 1988)
14 cm
(2 mm/year)
(other
estimates
are up to 20
cm)
Sea level rise: world sea level has risen up to 20 cm in the
past century (60 years of data required to discern trends)
Sea level rise - vulnerable areas
National Academy of Sciences 2001
Sea level rise
From NAS workshop, 2001
Major impacts are on deltas with
low sediment input
Chesapeake Bay already impacted
(crabbing industry)
Delaware Bay, Outer Banks, other
regions of east coast
Expected accelerating impacts on
Mississippi Delta (New Orleans
and barrier islands - about 1/3 lost
since 1880), Venice
Sea level impacts in eastern U.S. (U.S. EPA
global warming - publication)
Predicting the future: from Intergovernmental
Panel for Climate Change (2001) Technical
summary
Climate
models for
global
change
Climate models
IPCC (2001) uses results from 20 Atmosphere-Ocean Global
Climate Models (AOGCMs). These come from world modeling
centers. In the U.S., some of the centers that participate are the
National Centers for Environmental Prediction (NOAA), the
NOAA Geophysical Fluid Dynamics Laboratory in Princeton, the
National Center for Atmospheric Research in Boulder, Los
Alamos (DOE).
Each modeling center is given the forcings for the IPCC
scenarios and then runs its climate model with these forcings.
The IPCC committees then compare the results, evaluate the
models, and average the results to yield a prediction and error bar.
The models differ from each other - sometimes significantly
Modeling CO2 rise in
atmosphere and
associated climate
change
IPCC 2001 Scenarios
A: strong steps to curb
emissions
B: medium steps to curb
emissions
C: rapid growth, multiple
energy sources
D: “business as usual” continue
as we are going today, most
energy from fossil fuels
Modeling CO2 rise and global change
Old scenarios for IPCC (prior to 2001 report, which was the
“Third”):
Doubling CO2 in the atmosphere creates about 2.5°C change
So each doubling causes change: “business as usual” scenario
prediction is 5°C change over next 100 years.
Conclusion of the previous 2 reports that (1) greenhouse gases
were increasing, and (2) that observed temperature changes
might or might not be attributable to greenhouse gas increases.
-----------------------------------------------------------------------IPCC 2001 (“Third Assessment Report”): definitive conclusion
that observed temperature changes result from anthropogenic
forcing.
Expressing greenhouse gases as “radiative forcing”
4.4 W/m2 <---> double CO2 levels <---> 2.5°C change
Predicting temperature change by 2300
Prediction is 5-fold
increase in CO2 --->
about 10°C change by
year 2300 before decrease
Decrease in atmospheric
CO2 is due to the
processes we have
discussed: ocean uptake,
sea-floor sedimentation
and dissolution,
weathering
Temperature change in climate models with anthropogenic
CO2 forcing
Patterns of
predicted
temperature
change:
Model results
from IPCC.
Scenario
D
(business
as usual)
Scenario
B (modest
growth,
some
measures
to curb
emissions)
Global sea level projections
Modeled changes in
biomass for doubled
CO2
Is the Earth’s climate changing?
“The answer is unequivocally “Yes”.”
IPCC 2001 Technical Summary
“Arctic-dwelling Inuit have a word for their crazy weather - Uggianaqtuq.
Pronounce it "oog-gi-a-nak-took." It means "to behave unexpectedly”. The
Arctic, (scientists) say, is undergoing profound ecological change. It's
become the poster child for global warming. Not only are average air
temperatures rising, ice sheets thinning, and permafrost melting, the
whole complex interconnected network of arctic life and its environment
are changing in ways not reflected in the geological record or Inuit lore.
This no longer is a forecast of what might happen in future decades. It is
happening right now.”
Robert C. Cowen, Christian Science Monitor, Jan. 6, 2005
Term paper presentations
The purpose is to inform the class about the topic - useful
takeaway information, resources, etc.
6-7 groups total
1 hr 20 minutes -> about 10 minutes per topic
Each group - coordinate your information and decide how to
present. You can delegate to 1 or 2 people to present everyone’s
information, or have a tightly choreographed presentation with
everyone getting up and doing 1 slide/overhead.
Organization suggestions:
Science first - what happens, how does it happen