A World Of Change: Climate Yesterday, Today, and Tomorrow

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A World Of Change Climate Yesterday, Today, and
Tomorrow Susan Solomon Senior Scientist,
NOAA, Boulder and ex-co chair IPCC WG1
IPCC, post-IPCC, irreversibility, and other key
aspects of what we know about climate change
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The World Has Warmed
2008 10th warmest Widespread warming has
occurred. Globally averaged, the planet is about
0.75C warmer than it was in 1860, based upon
dozens of high-quality long records using
thermometers worldwide, including land and ocean.
IPCC WG1 (2007)
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Global Average Climate Change
Ups and downs from year to year? Yes, true.
Relevant? No.
See Easterling et al., GRL, 2009
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Our lives are heavily influenced by local
weather. Its important to distinguish between
weather and climate.
Fronts move air from one region to another (e.g.,
winter cold fronts) and cause large local
variability. Averaging over space and/or time is
critical to deducing meaningful climate changes.
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Local And Global Changes (from NCDC data)
http//www.ncdc.noaa.gov/gcag/index.jsp
Fewer cold extremes
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Many Changes Signal A Warming World
Rising atmospheric temperature

• And
• Atmospheric water vapor increasing
• Glaciers retreating
• Arctic sea ice extent decreasing
• Extreme temperatures increasing
• .

Warming is Unequivocal
Rising sea level
Reduction in NH snow cover
IPCC WG1 (2007)
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Human Drivers of Climate Change Unprecedented

• CARBON DIOXIDE
• A critical greenhouse gas
• Dramatic increase in industrial era, forcing
  climate change
• Higher concentration than for more than 600,000
  years

IPCC WG1 (2007)
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Carbon Dioxide at Mauna Loa
The biosphere breathes every year in its
growing cycle, but the human trend is clear.
Big natural fluxes? Yes. Relevant? No
http//www.esrl.noaa.gov/gmd/ccgg/trends/
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Forcing of Climate Change 1750 to Present-day
Carbon dioxide is causing the bulk of the
forcing, and it lives a long time in our
atmosphere (some of it lives for more than 1000
years). Every year of emission means a
commitment to climate change for more than 30
generations.
Global-average Radiative Forcing (RF) (W m-2)
IPCC WG1 (2007)
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Are Humans Responsible?
IPCC (1995) Balance of evidence suggests
discernible human influence IPCC (2001)
Most of global warming of past 50 years likely
(odds 2 out of 3) due to human activities IPCC
(2007) Most of global warming of past 50 years
very likely (odds 9 out of 10) due to human
increases in greenhouse gases
Observations
Volcanoes proof of principle that forcing
changes climate. GHG increases dominate forcing
and climate changes of past 50 years.
IPCC WG1 (2007) ch 9 and summary
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Are Humans Responsible?
Why can we say its very likely (90 odds) that
most of the warming is due to increased
greenhouse gases? High statistical confidence
based on multiple fingerprints in time and space.
IPCC WG1 (2007) ch 9 summary
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The Pine Beetle Perfect Storm
Reduced moisture, trees stressed esp. lodgepole
pine
Longer beetle breeding season (two cycles, not
one)
Fewer extreme cold snaps to kill beetle in winter
(below -20F)
Photo http//www.for.gov.bc.ca
Photo by Ken Papaleo / The Rocky Mountain News
See, recent papers by Kurz et al in Nature and
Mantgen et al in Science.
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A different climate on each continent by 2050
A changing world for everyone, including science
and scientists. What about smaller scales?
IPCC WG1 (2007) ch 11
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A World of Change More Rain for Some, Less for
Others
Regional changes (/-) of up to 20 in average
rainfall. At mid to low latitudes, dry get drier,
wet get wetter. Dust bowl and other major
droughts of the past 5-15 less rain over 10-20
yrs.
(2090s medium emissions scenario highest
confidence in stippled areas)
DJF seasonal precipitation
IPCC WG1 (2007) SPM
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A World of Change Less Rain for Some, More for
Others
Dry regions in the subtropics, wet regions at
higher latitudes basic pattern is linked to
fundamental physics
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UNFCCC and Science
This part of the talk irreversible changes that
can be expected with high scientific confidence.
observed changes are already occurring, and
there is evidence for anthropogenic contributions
to these changes the phenomenon is based upon
physical principles thought to be
well-understood projections are broadly robust
across available models Geoengineering to
remove carbon or artificially cool
not considered here.
High confidence, well quantified information
Very useful.
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Beyond the 21st Century
EMICs New Tool to Probe the Very Long Term
UNFCCC Article 2 Stabilization of GHG at a
level that avoids dangerous interference. Articl
e 3 emphasizes serious or irreversible damage
IPCC, WG1 (2007), chapter 10
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Stop Emissions Completely Can The World Return
to A Natural State?
One test ramp towards 750 stabilization, then
stop. 450 ppmv left in 3000 Warming remains
constant 0.5C for more than a thousand years.
IPCC, WG1 (2007), chapter 10
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Carbon Cycle It Really Is A Cycle
Some man-made CO2 goes (in the short-term) from
the atmosphere to vegetation, surface ocean.
Long term sink is deep ocean. Its very slow.
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Carbon Dioxide Is A Unique Gas Multiple
Timescales
CO2 dissolves in seawater to acidify the ocean
(1). Dissolution is limited by buffering. Added
carbonate (eg rock weathering) can very slowly
dissolve more (2).
(1) CO2 H2O lt-gt H HCO3- (2) CO2 H2O CO3
-2 lt-gt 2HCO3-
Initial step
100,000 years
Archer (many papers) review in Solomon et al.,
PNAS, 2009
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Carbon Cycle Back to Basics (Revelle and Suess,
1957)
Isotopes ocean sink and speed Long-term
20 of human Gts input retained (Revelle factor)
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Carbon Cycle Gts And ppmv
Half of human CO2 emissions (Gts) retained in
atmosphere each year (airborne fraction or
instantaneous Revelle factor). Long-term
human CO2 Gts retained will be 20, due to well
understood processes in the ocean (Revelle
factor).
Long-term concentration retained will be
0.2/0.5, or about 0.4 of the peak concentration
enhancement above pre-industrial value of 278
ppmv.
Solomon et al., PNAS, 2009
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Carbon Sink and Heat Transport Links to Deep
Ocean
Linked physics and relationship to timescales for
carbon and climate system inertia (also SLR due
to thermal expansion).
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Carbon Sink, Heat Transport, Climate Change, and
Sea Level Rise Due to Thermal Expansion
Broad range of test cases Every year of
climate change that occurs (warming, precip, snow
cover, sea ice retreat, ocean acidification,
etc) due to carbon dioxide increases is
irreversible for at least 1000 years. Sea level
rise is slower, but is irreversibly linked to the
peak CO2 we reach.
Solomon et al., PNAS, 2009
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Irreversible Precipitation Changes
5 to 10 per degree of warming in e.g.,
Southern Europe, North Africa, Western Australia,
SW North America, South Africa in the respective
dry seasons. Forever. Compare to dust bowl
or other major droughts, typically 5-15 over
10-20 years.
White fewer than 2/3 of the models agree colors
and gray gt2/3
Solomon et al., PNAS, 2009
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Precipitation Change How Far Will We Go?
Best estimate of 21st century choices. The longer
we wait to act, the more rainfall change we will
be locked into.
Solomon et al, PNAS, 2009
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Irreversible Sea Level Rise How Far Will We Go?
Thermal expansion only 0.2-0.6 m/C Locked in
during 21st century
add glaciers (0.2-0.7m) add ice sheets?
Solomon et al., PNAS, 2009
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Add Ice Sheets? How Quickly Do They Melt?
Charbit et al., GRL, 2008
Can ice sheets outlast the carbon for some levels
of perturbation? How much?
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Sea level rise of 0.5-1.0 meter would have
large impacts in many parts of the world.
From IPCC WG2 (2001).
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Carbon Dioxide Emission From Fossil Fuel Burning
Who?
Source Energy Information Agency, DOE
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Why Going, Doing, Making, Being Comfortable..
In short, just about everything.
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Carbon Dioxide Emission From Fossil Fuel Burning
5.5 B people now in the developing world emit
about 5x less fossil CO2 per person than the 1B
in the developed world
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Changes in Total and Per Capita Emissions of
Carbon Dioxide From Fossil Fuel Burning in China
and the USA
Last decade China is getting richer, and
emitting more CO2 Kyoto Protocol?
Source Energy Information Agency, DOE
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Climate And Bathtubs A Poorly-Understood
Principle
Stabilization of CO2 would require 50
emissions reductions (for a few decades) and then
80 Geoengineering? Cool the planet? Real and
artificial trees?
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How Far Will We Go?
The longer we wait to act, the more climate
change we will be locked into.
Image Socolow and Pacala
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Some Possible Future Choices Just Illustrations
50x wind or 700x current solar
60 mpg cars
Successful tests completed
Reduce deforestation
Double current capacity
There are no silver bullets but there is much
silver buckshot. Technology matters.
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• Some Things I Hope Youll Remember About Climate
  Change
• -Caused mainly by different long-lived gases
  produced by people via a well understood physical
  mechanism. CO2 from fossil fuel burning is (by
  far) the main climate change agent.
• -Abundant data for at least a century, carefully
  calibrated, show the changes in the industrial
  era.
• -Temperatures are rising globally. There is
  local variability.
• -Young people today will live in a world some
  5-10F warmer by the time they are old men and
  women, if emissions continue ramping.
• Rainfall changes with climate change would affect
  many people and ecosystems. Droughts like the
  dust bowl would be widespread.
• Climate changes from CO2 emissions should be
  expected to last more than 1000 years (unless we
  find a miracle cure to remove CO2)
• -Climate change challenges us to think beyond our
  own backyards.

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• Thanks for your attention

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Additional Slides (not for presentation)
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Rainfall Changes with Warming
22 AR4 models Regional averages over the
respective dry seasons (not JJA, DJF, etc.),
relative to 1900-1950 baseline Future changes
dominated by GHG in these runs
Solomon et al., PNAS, 2009
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Context 5-15 less rain is a lot
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Uncertainty, Risk, and Confidence
Climate change A mix of things we now know
quite well, and other things that represent
high-impact but highly uncertain risks. Do more
to identify what is well known..separate from
the much more uncertain risks to aid clarity and
consensus.
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How Accurate Are Model Simulations of Rainfall?
Observed annual average precipitation (cm/year),
1980-1999 CMAP climatology
Multi-model average
IPCC WG1 (2007), chapter 8
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The World Is Still Warm (post-IPCC 2007)
Short-term variations (e.g., volcanoes, El
Nino/La Nina in some years) dont change the
global big picture.
From www.realclimate.org
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Some Key Underpinnings Held and Soden Seidel
et al
Change in obs bigger than models. expansion of
tropics mean rainfall trends heavy rain
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Carbon Sink, Heat Transport, Climate Change, and
Sea Level Rise Due to Thermal Expansion
Broad range of test cases Every year of
climate change that occurs (warming, precip, snow
cover, sea ice retreat, ocean acidification,
etc) due to carbon dioxide increases is
irreversible for at least 1000 years. Sea level
rise is slower, but is also irreversibly linked
to the peak CO2 we reach.
Solomon et al., PNAS, 2009
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Realized Warming
During the period of CO2 rise, the realized
warming fraction is about 50-60 of the climate
sensitivity. After emissions stop, warming
remains 5010 of that for equilibrium relative
to CO2 peak value.
Actual and equilibrium temperatures, relative to
CO2 change.
Solomon et al., PNAS, 2009
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