Will Ferrell http:www.transbuddha.commediaHolder.phpid1147

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• Will Ferrell http//www.transbuddha.com/mediaHold
  er.php?id1147

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• Role of Working Group 1
• Describe progress to understand
• human and natural drivers of climate change
• observed climate change, climate processes and
  attribution,
• projected future climate change

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FAQ 1.2, Figure 1
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• Time line of IPCC Assessment Reports
• 1990 First Report (FAR)
• 1995 Second Report (SAR)
• 2001 Third Report (TAR)
• 2007 Fourth Report (AR4)

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Figure 1.1
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Greenhouse gas trends
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Figure 2.3

• CO2 concentrations (monthly averages) and
  atmospheric oxygen (O2) The O2 concentration is
  measured as per meg deviations in the O2/N2
  ratio
• (b) Annual global CO2 emissions from fossil fuel
  burning and cement manufacture in GtC yr1
  (black) and annual averages of the 13C/12C ratio
  measured in atmospheric CO2 at Mauna Loa

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Figure 2.4
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Figure 2.5
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Whats in the Full Report?

• Policy Summary (18 pp)
• Technical Summary (74 pp)
• Chapters 1-11 (1000 pp)
• 1- Historical Overview
• 2- Changes in Atmospheric Constituents and in
  Radiative Forcing
• 3- Observations Surface and Atmospheric Climate
• 4- Observations Changes in Snow, Ice and Frozen
• 5- Observations Oceanic Climate Change and Sea
• 6- Paleoclimate
• 7- Couplings Between Changes in the Climate
  System     and Biogeochemistry
• 8- Climate Models and their Evaluation
• 9- Understanding and Attributing Climate Change
• 10- Global Climate Projections
• 11- Regional Climate Projections

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Box TS.5
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Human and natural drivers of climate change
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Human vs. natural factors

• Human
• Greenhouse gases
• Aerosols
• Land surface properties

• Natural
• Solar activity
• Volcanic activity (usually not considered since
  episodic).
• Internal natural variability

These factors - change the energy balance of
climate system - are measured in terms of their
radiative forcing - change climate, given a
certain climate sensitivity
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FAQ 1.1, Figure 1
Earths energy balance
Green-house effect
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Radiative forcing RF and climate sensitivity ?

• Radiative forcing Wm-2 expresses how a factor
  changes in- or outgoing energy of the system.
• Positive forcing tends to warm, negative tends to
  cool
• IPCC 2005 values relative to 1750.

• Climate sensitivity is often expressed in terms
  of the temperature increase due to a doubling of
  CO2 (2xCO2) concentrations above the
  preindustrial levels, e.g., 2 - 4.5K.

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Figure TS.25
Climate sensitivity due to 2xCO2
Cumulative distributions of climate sensitivity
derived from observed 20th-century warming (red),
model climatology (blue), proxy evidence (cyan)
and from climate sensitivities of AOGCMs (green).
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Climate feedbacks

• Without feedbacks

• With feedbacks
• If temperatures change in response to forcing,
  other quantities may also change, e.g. water
  vapor, clouds. This in turn can significantly
  change magnitude, timing, and spatial structure
  of the overall sensitivity.
• The difficulty to determine the size of feedbacks
  (in particular from clouds) remains the largest
  source of uncertainty.

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Figure SPM.2
Radiative forcings
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Radiative forcings Summary

• AR4 There is very high confidence that the
  effect of human activity since 1750 has been one
  of warming, with a radiative forcing of 1.6 (0.6
  to 2.4) Wm-2.
• Main GHG CO2, CH4, N2O, etc.
• Unprecedented rate of increase.
• Aerosols Cooling effect.
• Direct and indirect effect.
• Dominant source of uncertainty.
• Other O3, CFCs, land cover change, soot, etc.
• Solar Small warming effect 0.12 Wm-2

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Direct Observations of Recent Climate Change
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Components of the cryosphere and their time
scales.
Fig. 4.1 of WG1
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Northern Hemisphere March-April average
snow-covered area
Figure 4.2 of WG1
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Figure 4.5
1875
1975
Ice-freeze and Ice-breakup dates

Red River D 1 month
Fig. 4.5 of WG1
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Figure 4.15
Ice mass balance (a) and contribution to
sea-level rise (b). Fig. 4.15 of WG1.
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Permafrost in Russiaa. Sitesb. Thickness
anomoly of active layerc. maximum soil freeze
depth anomoly.Figure 4.20 of WG1
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The ocean as a reservoir of atmospheric change
(heat, CO2, etc)
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Ocean heat content for 0-700 m layer
Figure 5.1 of WG1
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Figure 5.9
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Dissociation of CO2 in water
CaCO3 CO2 H2O Ca2 2 HCO3- H2O CO2
H2CO30 H2CO30 H HCO3- HCO3- H
CO3-2 H2O H OH-
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Dissolved CO2 in water
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Anthropogenic CO2 inventory is dominated by
downwelling in the North Atlantic
Fig. 5.10 of WG1
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Figure 5.11
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Global mean sea level rise
Fig. 5.13 of WG1
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Sea level rise measured from satellites
Fig. 5.14 from WG1
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Sea level rise attributed to thermal expansion
Fig. 5.19 of WG1
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FAQ 5.1, Figure 1
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Paleoclimate
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Antarctic ice core record (Vostok) compared to
stacked ocean isotope record (fig. 6.3 of WG1)
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Figure 6.4
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Michael Manns hockey stick Figure TS.20 of WG1
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FAQ 6.1, Figure 1
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Attribution of Climate Change
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Figure SPM.4
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Figure 3.2
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Figure TS.8
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Figure 3.13
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Figure 3.14
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Figure TS.11

• There has been little or no long-term trend in
  the average number of tropical cyclones that
  occur across the entire globe each year.
• It is likely that intense hurricane activity has
  increased over the Atlantic Ocean since 1970.
• Although global warming may affect the frequency
  of intense hurricanes, direct attribution for the
  creation of individual hurricanes to global
  warming is not possible.

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Projections of future climate
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Advances in climate modeling

• More realistic models
• More models
• More simulations
• Various (SRES) scenarios
• AR4 A major advance is the large number of
  simulations available from a broader range of
  models.

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Figure 1.2
Increased model complexity
The complexity of climate models has increased
over the last few decades. The additional
physics incorporated in the models are shown.
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Figure 1.4
Increased model resolution
Geographic resolution characteristic of the
generations of climate models
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SRES emission scenarios

• Alternative estimates for how the emissions
  during the 21st century may evolve.
• Depend on demographic, political, socioeconomic,
  and technological factors.

A1FI business as usual A2 pessimistic, ca.
3xCO2 B1 optimistic, ca. 2xCO2 A1B
intermediate, most often used COMMIT 20th
century stabilization, hypothetical
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Figure TS.32
Global mean surface warming
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Next two decades

• 0.2 K global warming per decade.
• Largely independent of SRES scenario.
• Comparison
• 0.2 K warming is twice as large as natural
  climate variability.
• Current warming is 0.15 - 0.3 K
• COMMIT predicts 0.1 K per decade.

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Figure TS.28
Global mean surface warming
Projected surface temperature changes for the
early and late 21st century relative to the
period 1980 to 1999.
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Figure SPM.7
Changes in precipitation (A1B)
Relative changes in precipitation (in percent)
for the period 20902099, relative to 19801999.
Values are multi-model averages based on the SRES
A1B scenario for December to February (left) and
June to August (right). White areas are where
less than 66 of the models agree in the sign of
the change and stippled areas are where more than
90 of the models agree in the sign of the change.
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21st century
Continued greenhouse gas emissions at or above
current levels would cause further warming and
induce many changes that would very likely be
larger than those observed during the 20th
century.
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Beyond 2100

• Both past and future anthropogenic carbon
  dioxide emissions will continue to contribute to
  warming and sea level rise for more than a
  millennium, due to the time scales required for
  removal of this gas from the atmosphere.

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