The Greenhouse Effect and Global Warming

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The Greenhouse Effect and Global Warming Powered By Docstoc
					Chapter 21: Global Climate
  The issue of global climate change may be
  one of the most important issues facing
  humanity in its history
  This issue has the potential to affect the
  economies, safety and health of the entire
  world’s population
  Hopefully you’ll understand after this review
  why the science of this topic is so difficult to
  understand and why it generates so much
  political controversy
                                         The Earth Systems Science Approach recognizes four
The Earth’s climate system consists of   natural subsystems: atmosphere, hydrosphere, geosphere
complex interactions between many        and biosphere. Most researchers now recognize a fifth,
components!                              non-natural subsystem: the anthroposhere.
Global Climate Change
   We’ll focus on some basics of the climate
   system such as atmospheric chemistry and
   the greenhouse effect
   While examining the probable way human
   actions may be modifying climate and
   contributing to global warming, we’ll also
   recognize that there are natural mechanisms
   of climate change (Remember our discussion
   of glacial-interglacial mechanisms?)
Climate Basics – Greenhouse Effect
   Greenhouse Effect - the gradual warming of
   the Earth’s atmosphere and surface resulting
   when heat radiated from the Earth’s surface
   is absorbed by certain atmospheric gases
   (e.g., water vapor, carbon dioxide, CO2, and
   methane, CH4)
   The gases that absorb and reradiate the heat
   are called greenhouse gases; these gases are
   present in trace concentrations (see figure) in
   our atmosphere
        About 30% of incoming                  Greenhouse Effect – gradual
        solar energy reflected back to space   warming of the Earth’s lower
                                               atmosphere and surface when
  Sun                                          certain gases (e.g., H2O, CO2 and
                                               CH4 ) absorb heat radiated from the
                                               Earth’s surface

                                           Greenhouse gases absorb radiated heat and
                                           reradiate some of it to the lower atmosphere

Earth materials and atmosphere absorb about 70% of
incoming light energy; some portion of this energy is
emitted to the atmosphere as radiated heat
Greenhouse Effect
Earth’s Atmospheric
Composition (Dry Air)
Greenhouse Effect
   Don’t use the terms “greenhouse effect”,
   “greenhouse warming” and “global warming”
   synonymously - they are related, but different
   Would the average person view the
   greenhouse effect as beneficial or
   Most people erroneously think that the
   greenhouse effect is detrimental; the
   greenhouse effect is a natural phenomenon
   that helps modify the Earth’s climate and
   produce livable biological niches
Greenhouse Effect
   Atmospheric scientists suggest the
   Earth’s average surface temperature
   would be about 60 - 70 degrees F
   colder without a greenhouse effect;
   under these conditions most of the
   Earth’s surface would host Arctic
   conditions - the flora and fauna of Earth
   would be drastically reduced in number
   and diversity
Greenhouse Effect
   So: the greenhouse effect is a natural
   phenomenon; “global warming”
   indicates that average global
   temperatures are rising but implies no
   particular cause(s); “greenhouse
   warming” indicates that average
   temperatures are rising due to
   increased concentrations of atmospheric
   greenhouse gases
Global Warming
  There is firm evidence that the greenhouse effect is
  being enhanced and that we are entering a global
  warming period
  This evidence includes:
  26 of the highest world average annual temperatures
  ever recorded (since ~ 1880) recorded from 1976-
  2010; every year since 1998 has made the Top 10
  list of hottest years with 2010 being the hottest (prior
  to 2010, the hottest year on record was 2005);
  about a 50% reduction in European Alps glacier ice in
  the last 100 years;
                            Global Warming

an average rise in world
sea levels of about 1
foot during the last
a decline of about 42%
in Arctic sea ice volume
in the last 30 years; and
the quick melting of
portions of Antarctic ice
shelves (1995, 2002 and
2008 – in March 2002 a
portion of the Larsen ice
shelf the size of Rhode
Island (1250 mi2 )
collapsed into the
Antarctic Ocean) (see
Global Warming
  The accumulating evidence suggests
  global warming is occurring but whether
  natural or human forces (or both) were
  causing climate change was vigorously
  However, the debate in the scientific
  community has mostly ceased
  Why? See slides
Global Climate Research
   The IPCC (Intergovernmental Panel on Climate
   Change – consisting of more than 1500 scientists
   from about 60 nations) released a paper in February
   2001 contending the evidence was significant to
   support that human actions are modifying the climate
   Furthermore: a November, 2004 report published by
   250 scientists from eight nations indicates that the
   Arctic is warming twice as fast as the rest of the
   globe – in their opinion likely the consequence of
   increased atmospheric levels of greenhouse gases
   due to increased fossil fuel combustion by humans
Global Climate Research
   Finally: in February, 2007 the IPCC issued
   their latest report. They contend that the rise
   of global temperatures since the mid-1900s is
   very likely (90% certainty) the product of the
   release of fossil fuel combustion gases
   However, note the partial scan of the
   following recent newspaper article that
   suggests a similar warming trend occurred
   naturally during the last millennium
During 2009, the IPCC
was criticized when
“hacked” e-mails
suggested some
researchers sought to
suppress radical
opposing views and for
a few content errors in
their latest reports
Consequently, the IPCC
has called for an
external review of the
report science
'Climategate' inquiry largely clears scientists
British lawmakers say science sound, but want transparency news services
updated 6:52 p.m. ET, Tues., March. 30, 2010
LONDON - The first of several British investigations into the e-
mails leaked from one of the world's leading climate research
centers has largely vindicated the scientists involved.
The House of Commons' Science and Technology Committee
said they had seen no evidence to support charges that the
University of East Anglia's Climatic Research Unit or its
director, Phil Jones, had tampered with data or perverted the
peer review process to exaggerate the threat of global warming
— two of the most serious criticisms levied against the
climatologist and his colleagues.
Global Climate Research
   What can we say with 100% certainty?

   Atmospheric concentrations of
   greenhouse gases (especially carbon
   dioxide) are increasing; the increase of
   atmospheric CO2 parallels the increased
   consumption of fossil fuels worldwide
   (CO2 is a byproduct of the combustion
   of any C-bearing fuel) (see figures)
Average 2008 levels: 385 ppm
Data from 1958 – present,
measurements of atmosphere;
prior to 1958, analysis of ice
core air bubbles
Global Climate Research
   In simple models, the more greenhouse
   gases in the atmosphere the more
   radiated heat from the surface gets
   trapped and the higher the atmospheric
   and surface temperatures
   What are some natural sources of
   greenhouse gases?
Greenhouse Gas Sources
   What are some other
   natural sources of
   greenhouse gases? Are
   these sources easy to
   accurately quantify on a
   worldwide basis?
   Is this a simple or
   complex research topic?
Global Climate Research
   How can we discern with 100%
   certainty whether humans are the
   primary cause of any global warming
   that’s occurring? Don’t forget - the
   Earth has been experiencing a global
   warming since the end of the last ice
   age approximately 12,000 years ago!
Climate Reconstruction Research
  Ice sheet core samples (see
  figure) and other materials
  are being ingeniously
  investigated for their ability
  to retain indications of prior
  atmospheric chemistry and
  Scientists are attempting to
  detail ancient atmosphere
  greenhouse gas levels to see
  if they’ve ever fluctuated as
  much naturally as they’ve
  done in the last 52 years
Climate Reconstruction Research
   Particularly, scientists are interested in
   establishing how pre- and post-
   Industrial Revolution atmospheric
   greenhouse gases have fluctuated
   Why is this research important? Why
   should you care?
Global Climate Research
   Although evidence supports that circa
   1840 air CO2 levels were about 270
   ppm (parts per million) and that
   measured air CO2 levels from 1958 to
   present have risen from about 310 ppm
   to about 385 ppm, we still can’t discern
   what percentage factor human activities
   are to atmospheric chemistry and
   climate changes
Global Climate Research
   Why the uncertainty? Although reconstruction
   of ancient atmospheric chemistries and
   climates suggest that air CO2 levels haven’t
   been higher than currently in the last 420,000
   (maybe 650,000) years, the same data
   suggest CO2 levels have naturally fluctuated
   much more than within the last 160 years
   (millions of years ago). (see figure)
Global Climate Research
   These same studies do support that
   higher atmospheric CO2 levels are
   associated with warmer climates
   In addition, we are still learning about
   the natural sources of greenhouse
   gases and can’t be sure that we’ve
   quantified their releases accurately (see
Possible Global Climate Change
   If atmospheric greenhouse gas
   concentrations continue to rise and enhance
   the greenhouse effect, what are some of the
   proposed consequences of global warming?
   Remember: although the topic discussed is
   often called “global warming” the entire globe
   won’t be affected similarly, subsequently
   many researchers and politicians now employ
   the phrase, “global climate change”
Possible Global Climate Change
   Consequences could
   include: 1)
   significant rises in
   sea levels as
   increased glacial ice
   melting occurs; the
   rising waters could
   displace millions of
   people (see figures);   National Geographic: August, 2007
Possible Global Climate Change
Possible Global Climate Change
  Note the adjacent
  example of the
  threat of rising seas

  2) Reduction of
  tillable land as sea
  levels rise;
Possible Global Climate Change
 3) Changes in world
 weather patterns
 and a higher
 frequency of severe
 weather events
 (e.g., hurricanes,
 thunderstorms,        North Atlantic Tropical Storm Frequency
 blizzards, extended
 heat waves);
                          National Geographic: August, 2007
Possible Global Climate Change
 4) A greater
 percentage of land
 becomes arid and
 less productive; the
 glacial source of
 some major rivers
 (e.g., the Ganges)
 may be reduced or
 ultimately eliminated
Possible Global Climate Change
 5) The biodiversity of
 coastal ecosystems
 declines due to an
 inability to adapt quickly
 to rising, warming and
 acidifying seas (e.g.,

Possible Global Climate Change
   6) Infectious diseases spread by flies and
   mosquitoes become more prevalent as the
   warmer climates allow these insects to extend
   their biological niches to new areas (think
   about the rapid spread of West Nile Virus
   across the U.S.)
   7) The deep-water return flow of the Gulf
   Stream current is reduced/eliminated leading
   to much colder conditions in the North
   Atlantic (see figure)
Gulf Stream

                   Warm, less salty surface current

              Cold, salty deep current
Possible Global Climate Change
   Most climate scientists think there is enough
   evidence of these effects occurring to
   strongly support that global climate change is
   occurring at a rate that requires worldwide
   Complicating factors: How would climate
   change influence the weather patterns
   generated during El Nino and La Nina events?
Possible Global Climate Change
   Please remember that the seven categories of
   global climate change outcomes we discussed
   are projections, not a guaranteed reality - the
   projections are based on incomplete data and
   an incomplete mathematical understanding of
   the Earth’s dynamic processes
   The first global warming computer models
   treated the Earth as a rocky ball devoid of life
   - simpler to model mathematically!
Global Climate Change Alternatives
   There are alternatives that have been
   proposed to the global warming model.
   1) A few scientists have proposed that
   as air CO2 levels rise, plant productivity
   will rise since CO2 is necessary for
   photosynthesis; the more CO2 absorbed
   by plants the less likely a global
   warming event
Global Climate Change Alternatives
   Experiments with plants in CO2-enriched lab
   atmospheres and outside forest plots have
   produced variable results - hardwood trees
   respond positively and absorb more CO2 for a
   few years; most grasses and ferns show
   declines in productivity
   Therefore could the distribution, and type, of
   plant species (and animals) across the globe
   be altered? (see figure)
Source: National
Geographic, June, 2008
Global Climate Change Alternatives
   A nutrient (iron) seeding project in a portion
   of the southern Pacific ocean in 1993
   successfully increased the population of CO2-
   absorbing phytoplankton, however the
   positive results were short-lived
   Do you advocate “geoengineering” on a large
   scale? (see slide)
   A Californian company, Climos, wants to
   commercialize iron fertilization and an
   India/Germany iron fertilization experiment
   was completed in 2009
 Note the
 India/Germany iron
 experiment was not
 very successful

                      Earth Magazine, June 2009
Source: Earth Magazine; December 2008
Global Climate Change Alternatives
   In addition, fairly recent (2004) data from the
   TERRA satellite suggests plant productivity
   has increased 5-10% on average worldwide
   during the last twenty years
   How would this hypothesis be affected by
   continued deforestation and land
Global Climate Change Alternatives
   2) Some scientists have proposed the
   world’s oceans could absorb enough air
   CO2 to offset a significant global
   warming event; investigations are being
   conducted to test this hypothesis
Global Climate Change Alternatives
  Preliminary results (2003)
  suggest the oceans absorb
  more carbon than they emit
  – about 2 billion tons
  Potential problems:
  a) warm waters absorb less
  carbon dioxide; if the oceans
  continue to warm this
  carbon dioxide “sink” will
  decrease (see article);
  b) increased carbon dioxide
  absorption by the ocean will
  decrease the pH (make more
  acidic) of the ocean’s waters
  and threaten to dissolve the
  exoskeletons of reef corals
  and certain shellfish (see; 5/18/2007

          Implications for
          world oceans?
Global Climate Change Alternatives
   3) Multiple hypotheses exist involving clouds;
   one scientist contends that slight warming
   will result in more atmospheric water vapor
   and more high-elevation clouds; he believes a
   4% increase in high-elevation clouds will
   cause enough sunlight to be reflected (off
   cloud ice crystals) back to space to offset a
   significant global warming event (see figure)
                                  reflected sunlight


high-altitude clouds
Global Climate Change Alternatives
   4) Other modelers suggest that if any
   additional clouds form at low altitudes (these
   lack many ice crystals) that they would spur a
   significant global warming event since water
   vapor is an effective greenhouse gas (see
   These are only a few of the future climate
   models - this field of study is very complex!
                      no ice
low-altitude clouds

Another Complicating Factor
   Atmospheric particle and aerosol
   pollution reduces sunlight penetration
   to the Earth’s surface (a cooling effect);
   what happens if the world continues to
   reduce this type of air pollution but
   doesn’t reduce greenhouse gas
  If you’re interested in the worldwide
  political and economic implications of
  this topic, conduct a Web search using
  the key words “Kyoto Protocol”, IPCC
  (Intergovernmental Panel on Climate
  Change) or 2009 Copenhagen climate
  change conference

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