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					                     Climate change: human-induced effects and natural fluctuations



                            Climate Change
                       Human-induced effects and/or
                          natural fluctuations?
         Alberto Montanari - University of Bologna - alberto.montanari@unibo.it




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



                    Why to study climate change is important??
    • Water resources management – Water Framework Directive
       - Evaluation of future water resources availability
       - Design of measures for contrasting water scarcity (water
         management policies, artificial reservoirs).
       - Implementation of economical policies.

    • Design of water distribution networks
       - Evaluation of future water demands.

    • Assessment of hydrological risk
        - Assessment of future flood flows.
        - Design of river engineering works.
        - Design of civil protection measures.
Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                     Climate change is a controversial issue…..
    Despite of what the media tell us, detection of climate change is
    subject to a relevant uncertainty.

    Climate is surely changing, but….

     Scientific questions (often not mentioned by
     the media):
     - Is the climate change irreversible or is it
         just a temporary fluctuation?
     - If it is a temporary fluctuation, how long is
         it?
     - Climate change is a human-induced effect
         or a natural variation?
     These scientific questions have relevant
     economic and social implications – Much
     more relevant than what we can imagine!

     Remember: climate is changing for sure!

Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



                                    A practical example - 1

    Water resources management – Water Framework Directive
     - In order to meet the demands of the Water Framework Directive, regional
       administrations in Italy have to prepare a master plan for water management.
     - In the Emilia-Romagna region, the master plan has to propose efficient
       solutions for mitigating the impacts due to the release of the environmental
       flow.
     - Water resources managers are undergoing a political pressure in order to
       substantiate the necessity of a huge dam on a Appennine River, that should
       accumulate water during the winter to assure water for irrigation and
       environmental flow during the summer.
     - Politicians say that the dam is needed because we cannot withdraw water
       from the Po River anymore, because climate change is reducing the Po river
       flows. However….



Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                         Climate change: human-induced effects and natural fluctuations


                                              A practical example - 2
                                               Portate idriche medie annuali
                                              Po@Pontelagoscuro 1918-2003

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Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                           Climate change: human-induced effects and natural fluctuations


                                                A practical example - 3
                                                Portate idriche minime annuali
                                                Po@Pontelagoscuro 1918-2003

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Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                          Climate change: human-induced effects and natural fluctuations


                                            A practical example - 4
                                            Portate idriche minime annuali
                                            Po@Pontelagoscuro 1943-2003

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        0
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Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations

A first scientific example – Global warming due to greenhouse effects
                            The “Official” Warming Estimates
                    (U.N. Intergovernmental Panel on Climate Change)
          Computerized climate models have led to future warming
       estimates by 2100 of from 1.1 to 2.9 deg. C (low emissions) to
                      2.4 to 6.4 deg. C (high emissions)..
            Direct surface warming from 2xCO2 is only 0.6 deg C
                                 (about 1 deg. F)
          Thus, climate models have net POSITIVE feedbacks (they
       respond to a warming tendency with changes that amplify the 1
                          deg. F CO2-only warming).
           There is a WIDE range of warming estimates, illustrating
        substantial uncertainty (mainly from cloud feedback differences
                                 between models)

Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



             Why warming estimates could be overly pessimistic.

     The Earth’s greenhouse effect is mostly due to water vapor
      and clouds, which are under the control of weather processes
      (mostly precipitation systems).
     A few percent increase in low clouds, or a small increase in
      precipitation efficiency, could entirely offset the warming
      tendency from carbon dioxide (neither of these processes are
      well understood).
     Big Question: Do precipitation systems stabilize the Earth’s
      temperature at a preferred temperature?




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                          Most of our atmosphere is being continuously
                     Climate change: human-induced effects and natural fluctuations
                          recycled by precipitation systems, which then
                          determine the strength of the Greenhouse Effect


                                                          Cooling (loss of IR radiation)
                                                          by dry air to space




    Heat
    released through                               Air sinks in
    condensation                        response to precipitation systems:
    causes air to rise,                    Sinking air is relatively dry
    rain falls to surface




                                                                                 Sunlight absorbed
                                     Boundary layer                                  at surface

                               warm, humid air                             cool, dry air
                                                          evaporation
                                                                             Ocean or Land
                                                          removes
Alberto Montanari, University of Bologna, alberto.montanari@unibo.itheat
                     Climate change: human-induced effects and natural fluctuations




                           Climate Models do not yet
                 contain the processes that stabilize the climate
                      system against significant warming.

         MOST of these stabilizing processes can probably be traced to
               “thermostatic” effects of precipitation systems, which
        adjust global water vapor and cloud amounts to maintain a natural
                 Greenhouse Effect and temperatures that depend
                       upon how much sunlight is available.

            Bottom Line: How much you believe climate model predictions
            of future warming depends upon how much faith you have that
            the models contain all of the important atmospheric processes
             (feedbacks) that determine how the atmosphere responds to
                               greenhouse gas forcing.


Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


       A second scientific example - The Hockey stick controversy
                             http://en.wikipedia.org/wiki/Hockey_stick_controversy


                                                              Mann et al. 1998.
                                                              McIntyre and McKitrick, 2005;
                                                              See http://www.realclimate.org
                                                              and http://www.climateaudit.org.




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


       A second scientific example - The Hockey stick controversy
                  Manipulation operated by the Media
                                   (Uncertain results given as certain…..)




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


       A second scientific example - The Hockey stick controversy
                  Manipulation operated by the Media
                                     (Presentation of partial results…..)




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                        The famous Mann et al. “Hockey Stick” had errors in
                                   statistical analysis methods.
                          (A National Academies Review Panel [July 2006]
                             changed the Hockey Stick conclusion from
                        “warmest in 1,000 years” to “warmest in 400 years”)


                                                   McIntyre-McKitrick, 2003




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                      Climate change: human-induced effects and natural fluctuations


                                                                 We are probably not
                                                                 as warm as during
                                                                Medieval Warm Period




The GRIP (Greenland) borehole record is one of the best records because it is not a proxy, it is a DIRECT measure
of temperature. Shown are the last 2000 years. (Dahl-Jensen et al. 1998, Science, 282, 268-271 "Past Temperatures
Directly the Greenland Ice Sheet"). A similar reconstruction occurs for the Ural Mountain borehole temperatures
 Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
(i.e. warmer 1000 years ago, Bemeshko, D., V.A. Schapov, Global and Planetary Change, 2001.
                     Climate change: human-induced effects and natural fluctuations


                                  Climate change
                         Manipulation operated by the Media
                                          (Catastrophic views…..)




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                                  Climate change
                         Manipulation operated by the Media
                                          (Catastrophic views…..)




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                                     Climate change
                      Is it possible to gain an impartial view???




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



   A fundamental starting point: the IPCC fourth assessment report



    The Intergovernmental Panel on Climate Change (IPCC) has been established by World
    Meteorological Organisation (WMO) and UNEP (United Nations Environment
    Programme) to assess scientific, technical and socio- economic information relevant for
    the understanding of climate change, its potential impacts and options for adaptation and
    mitigation. It is currently finalizing its Fourth Assessment Report "Climate Change
    2007", also referred to as AR4. The reports by the three Working Groups provide a
    comprehensive and up-to-date assessment of the current state of knowledge on climate
    change.




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations




                                                                       IPCC fourth assessment report
                                                                       http://www.ipcc.ch/SPM13apr07.pdf




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                         The IPCC fourth assessment report
                      Independent Summary for Policy Makers




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                         The IPCC fourth assessment report
                      Independent Summary for Policy Makers




        The growth rate of CO2 emissions (in carbon equivalent) is equal to or slightly below
        the growth rate of world population (see Figure ISPM-2). Global per capita carbon
        emissions peaked at 1.23 tonnes per person in 1979 and the per-person average has
        declined slightly since then.
        As of 2003 the global average is 1.14 tonnes per capita, an average that has not
        changed since the early 1980s. If this trend continues, global emissions growth in the
        future will be constrained by total population growth.
Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                      The IPCC fourth assessment report
                 Independent Summary for Policy Makers - Sun




     If the sun does have a strong effect on climate, this adds importance to
   recent projections that solar output is likely to decline over the next several
                        decades (e.g., Zhen-Shan, 2007)

Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                   The IPCC fourth assessment report
          Independent Summary for Policy Makers - Temperature

                   Problems with the surface temperature record
      Research on the nature of the surface thermometer network has cast
        some doubt on the claim of the IPCC that the surface temperature
     record is free of biases related to non-climatic effects, such as land-use
     change, urbanization and changes in the number of stations worldwide.
       For example, studies have shown that the spatial pattern of warming
        trends over land correlate strongly with the distribution of industrial
         activity, even though such a correlation is not predicted by climate
                   models (e.g., de Laat and Maurellis 2004, 2006).


                                     Urban heat island effect



Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations




       The IPCC fourth
      assessment report
    Independent Summary
      for Policy Makers
        Temperature




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                   The IPCC fourth assessment report
          Independent Summary for Policy Makers - Precipitation
        • There is no globally-consistent pattern in long-term precipitation
          trends.
        • At the global level, slight decline was observed in total precipitation
          from 1950 to the early 1990s, which has since reversed.
        • Precipitation in North and South America has risen slightly over the
          past century in many places, though in some regions it has fallen.
        • The drying trend noted in the 1980s in the Sahel (the coastal
          region in Africa bordering the Sahara desert) has since reversed
          considerably.
        • Rainfall in India increased from 1901 to 1979 then declined through
          to the present and there is no overall trend. Australian precipitation
          trends vary by region and are closely linked to the El Niño cycle.
        • Perceptions of increased extreme weather events are potentially
          due to increased reporting. There is too little data to reliably
          confirm these perceptions.
Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                    The IPCC fourth assessment report
             Independent Summary for Policy Makers – Sea level

     • Regional trends in sea level are quite varied and some regions are
       experiencing declining sea levels. Changes in air pressure and wind account
       for some observed sea level increase.
     • While global sea level rose by approximately 120 metres during the several
       millennia that followed the end of the last glacial maximum, the level stabilized
       between 3000 and 2000 years ago. Since then, paleo sea level indicators
       suggest that global sea level did not change significantly: the average rate of
       change from 2000 years ago to about 100 years ago is near zero.
     • Although regional variability in coastal sea level change had been reported
       from tide gauge analyses, the global coverage of satellite altimetry provides
       unambiguous evidence of non-uniform sea level change in open oceans.
     • For the past decade, the western Pacific Ocean and eastern Indian Oceans
       show the highest magnitude of sea level rise, however, sea level has been
       dropping in the eastern Pacific and western Indian Oceans.



Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                    The IPCC fourth assessment report
             Independent Summary for Policy Makers – Sea level
 • Except for the Gulf Stream region, most of the Atlantic Ocean shows sea level rise
   during the past decade.
 • Sea level increases over the past decade are not uniform, and it is presently
   unclear whether they are attributable to natural variability.
 • The instrumentally-based estimates of modern sea level change provide evidence
   for an onset of acceleration at the end of the 19th century. Recent estimates for
   the last half of the 20th century (1950.2000) give approximately 2 mm/year global
   mean sea level rise.
 • New satellite observations show that since 1993 sea level has been rising at a rate
   of 3.1 mm/year.
 • Satellite data also confirm that sea level is not rising uniformly over the world.
 • It is presently unclear whether the higher rate of sea level rise in the 1990.s
   indicates an acceleration due to global warming, or a result of natural climate
   variability, or a combination of both effects.



Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                 The IPCC fourth assessment report
       Independent Summary for Policy Makers Snow and Glacier
• Most archives from the Northern Hemisphere and the tropics show small or absent
  glaciers between 9,000 and 6,000 years ago.

• Glaciers began growing thereafter, up to the 1800s. This tendency is primarily related
  to changes in the Earth’s orbit. However shorter, decadal-scale, regionally diverse
  glacier responses must have been driven by other factors which are complex and
  poorly understood.

• General retreat of glacier termini started after 1800, with considerable mean retreat
  rates in all regions after 1850 lasting throughout the 20th century. A slowdown of
  retreats between about 1970 and 1990 is evident in the raw data. Retreats were again
  generally rapid in the 1990s; though advances of glaciers have been observed in
  western Scandinavia and New Zealand.

• There are few records of directly measured glacier mass balances, and they stretch
  back only to the mid 20th century. When areal weighting and spatial interpolation are
  used to estimate large-scale patterns from the available data, the 1990s trend towards
  glacier retreat appears to have leveled off or reversed after 1998.

Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                   The IPCC fourth assessment report
          Independent Summary for Policy Makers - Paleoclimate
   The earth was ice-free during most of its history.

   The Pliocene (about 3 million years ago) was the most recent time in Earth’s
   history when mean global temperatures were substantially warmer (about 2°C
   to 3°C warmer).

   On the other hand, temperatures during most of the most recent 1 million years
   (the Pleistocene) have been colder than at present. Long glacial periods have
   alternated with short (10 to 30,000 year long) interglacials.

   Globally, there was less glacial ice and higher sea level on Earth during the
   Last Interglacial than now. This suggests significant meltback of the Greenland
   and possibly Antarctica ice sheets occurred. The climate of the LIG has been
   inferred to be warmer than present, although the evidence is regional and not
   neccessarily synchronous globally.

   The causes of large-scale climate variations on the century and longer time
   scales are not well-understood.
Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations


                 The IPCC fourth assessment report
       Independent Summary for Policy Makers – Climate models



   The output and the projections of climate models are highly uncertain.

   Climate models are calibrated.

   Some observational data do not concur with the output of climate models.

   Different models provide different outcomes with a wide spread.




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



              The IPCC fourth assessment report
Independent Summary for Policy Makers – The attribution problem



  The climate is subject to natural variability over a wide range of time scales

  Internal variability and irreversible change are difficult to distinguish (if not
  impossible, given the present state of the knowledge).

  The current level of uncertainty in climate studies prevents to reach statistically
  significant conclusions.




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations



                   The IPCC fourth assessment report
          Independent Summary for Policy Makers – Conclusions

    The climate in most places has undergone minor changes over the past
     200 years, and the land-based surface temperature record of the past
       100 years exhibits warming trends in many places. Measurement
     problems, including uneven sampling, missing data and local land-use
    changes, make interpretation of these trends difficult. Other, more stable
     data sets, such as satellite, radiosonde and ocean temperatures yield
   smaller warming trends. The actual climate change in many locations has
     been relatively small and within the range of known natural variability.

        There is no compelling evidence that dangerous or unprecedented
                             changes are underway.




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it
                     Climate change: human-induced effects and natural fluctuations




Alberto Montanari, University of Bologna, alberto.montanari@unibo.it

				
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