Turning Up the Heat on the Future: Global Warming and Its Consequences

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Turning Up the Heat on the Future Global Warming
and Its Consequences

• Dr. John Heinrichs
• Department of Geosciences

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Presentation outline

• Basics about global warming and the greenhouse
  effect
• The most recent findings about changes in the
  polar regions
• Have we passed the tipping point?
• What to do for the future?

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What is the greenhouse effect?

• Certain gases are transparent to visible light
  but absorb infrared
• Called greenhouse gases
• Include water vapor (H2O), carbon dioxide (CO2),
  methane (CH4)
• Greenhouse gases allow sunlight to pass through
  and warm the surface
• When the Earth emits infrared, it is absorbed and
  reemitted (trapped) by the greenhouse gases
• Without the greenhouse effect, Earths surface
  would be 30 colder than it is
• Venus has a much thicker CO2 atmosphere, and a
  much stronger greenhouse effect (surface
  temperature 490 C)

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Schematic diagram of the greenhouse effect
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Greenhouse gases over the past millenium

• Exponential increase over the past 1000 years in
  CO2, CH4, and N2O is clear
• CO2 concentrations have increased by about 35
  since pre-industrial times
• Methane concentrations have more than doubled

Source 2001 IPCC report
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The global instrumental temperature record

• Quality instrument measurements begin about 1850
• Global record shows approximately 1 C increase
  over past 150 years
• Note Dust Bowl peak around 1940
• Warming is greater in Northern Hemisphere than
  Southern

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Seasonal temperature trends

• Temperature increase has been greater in winter
  than any other season key smoking gun

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• Key findings
• Cold nights and days are decreasing, warm nights
  and days increasing
• Decreases in cold nights, increases in warm
  nights are much greater than corresponding
  changes during daytime
• Consistent with warming caused by enhanced
  greenhouse effect

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The long-term temperature record

• The past 100 years have been the warmest in the
  past 1000

Source IPCC, 2001
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Sea ice trends
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Temperature change by 2100 with CO2 stabilization
at 450 ppm
Source IPCC, 2001
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Temperature change by 2100 with continued CO2
increases
Source IPCC, 2001
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Global mean surface temperature under different
scenarios
Source IPCC, 2001
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Predicted precipitation changes

• Overall increase in precipitation
• Some areas (Arctic, Sahara, Antarctic) become
  wetter
• Other areas become drier

Annual mean precipitation change 2071 to 2100
Relative to 1990 Source IPCC, 2001
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Sea ice will continue to decline dramatically
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Sea level rise

• Global sea level will rise between 0.3 and 0.9
  meters, depending on scenario
• Causes melting polar ice, thermal expansion of
  water

Source IPCC, 2001
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Some recent results (mostly from the polar
regions)
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Why are the polar regions so important?

• Ice and snow are white losses in cover result
  in darkening of the Earth and an acceleration
  (positive feedback) of warming
• Predicted by models to show earliest impacts of
  warming
• Continental ice sheets contain large quantities
  of water, sufficient to raise sea level
  substantially
• Ice sheets have large thermal inertia take a
  long time to melt and a long time for melting to
  stop

http//www.msc.ec.gc.ca/crysys/education/snow/snow
_cover_loop.gif
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The Greenland Ice Sheet
Thickness 3300 m max Sea level equivalent 7 m
http//www.climatechange.umaine.edu/Research/proje
cts/Greenland/home.htm
Source Box et al., 2005
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The Antarctic ice sheet
Thickness 4700 m max, 2200 m average Sea level
equivalent 70 m
http//science.nasa.gov/headlines/y2002/images/ice
/icecontinent.gif
http//students.washington.edu/srh13/SPole/Geograp
hy.html
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• Key findings
• Greenland mass balance is negative and decreasing
• Results consistent with other recent studies

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• Key findings
• Greenland mass balance has become more negative
  in most recent period

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• Key finding
• Greenland ice sheet is thickening in center,
  losing mass along W coast

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Box, J.E., D.H. Bromwich, B.A. Veenhuis, Le-S.
Bai, J.C. Stroeve, J.C. Rogers, K. Steffen, T.
Haran, S.-H.. Wang, Greenland ice sheet surface
mass balance variability (1988-2004) from
calibrated Polar MM5 output, J.Clim., 2005.

• Key findings
• Net mass loss for entire ice sheet of 78 km3/yr
• Thickening in center, thinning along coasts (both
  trends increasing)
• Contribution to sea level 2.2 mm from 1991 to
  2000

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• Key findings
• Greenland showing slight mass increase
• Thickening in center
• Thinning along coasts
• Antarctica showing mass loss
• East Antarctic ice sheet thickening
• West Antarctic ice sheet thinning
• All results consistent with greenhouse effect
  predictions
• Overall contribution to sea level of all ice
  sheets 0.05 0.03 mm/yr

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From Stroeve et al., 2005
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Are we at a tipping point?

• Evidence suggests sea ice may be past the tipping
  point

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Current polar climate processes
Polar climate processes after loss of permanent
ice

• Key findings
• Arctic sea ice cover is decreasing, eventually
  permanent sea ice will be gone or greatly reduced
  in next century
• Once permanent pack ice is gone, no feedback
  process will exist to reverse trend

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Are we at a tipping point?

• Ice sheet evidence generally suggests we are past
  the tipping point
• Most studies show Greenland with a negative mass
  balance, all show increasing thinning along ice
  sheet margins
• All recent studies show Antarctica with negative
  mass balance

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What to do about the future?
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Possible futures CO2 concentrations
Source IPCC, 2001
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Projected levels of atmospheric CO2 during the
next 100 years would be higher than at anytime in
the last 440,000 yrs
Source IPCC, 2001
CO2 Concentration (ppmv)
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Possible futures - temperature
Source IPCC, 2001
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Long-term predictions

• Some effects continue long after CO2 emissions
  reduced
• Note ice melt may continue for several thousand
  years (ice-albedo feedback)

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Major greenhouse gas emitters

• Most greenhouse emissions come from developed
  countries
• US and Australia are leaders
• The US, with 6 of the worlds population,
  contributes 25 of the total emissions

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Sources of emissions

• Industry (primarily electric power generation and
  cement production) is the leader
• Transportation is second

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Where will future emissions come from?

• The US and Western Europe are the current leaders
• Developing countries (particularly India, China,
  and Eastern Europe) will contribute a much larger
  share in the future

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Stabilization of atmospheric concentrations of
CO2 will require emissions reductions globally
Source IPCC, 2001
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Who will have to reduce?

• Industrialized countries are greatest users of
  energy and carbon emitters - must reduce first
• Developing countries increasing energy
  consumption faster must reduce as well

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How to reduce emissions

• Few technological solutions, if any
• No way to remove carbon fast enough (planting
  crops, trees too slow, requires lots of water)
• Nuclear power can help, but long lead time to
  build plants
• Scrubbers can be built to remove CO2, but are
  very expensive
• Only realistic guaranteed solution is dramatic,
  rapid lifestyle change
• Lower, more efficient electric power usage
• Reduced use of fossil fuels for transportation
  (goodbye to SUVs and large personal cars)
• Higher-density housing
• Lifestyle changes are very unpopular, but if not
  done reductions will be involuntary eventually