July 12, 2013

Climate Briefing 1

John Houghton


Tropical forests … contain perhaps half of all Earth's biological species.
[Only] about half of the mature tropical forests that existed a few hundred years ago still stand.
At the present rate of destruction, all will be gone by the end of the twenty-first century.
(p 198)

[The] amount of fossil fuel that we now burn worldwide every year [injects about a million years worth of fossil carbon into the atmosphere.]
(p 199)

The world's forests and deforestation

The total area covered by forest is almost one-third of the the world's land area, of which 95% is natural forest and 5% planted forest.
  • About 47% … are tropical,
  • 9% subtropical,
  • 11% temperate and
  • 33% boreal.
[The] net loss of forest area during the 1990s was an estimated 940,000 km^2 (2.4% of total forest area.) …
Deforestation of tropical forests averaged about 1% per year.

(p 250)

The Unity of the Earth

James Lovelock:
[Gaia] is no doting mother tolerant of misdemeanors, nor is she some fragile and delicate damsel in danger from brutal mankind.
She is stern and tough, always keeping the world warm and comfortable for those who obey the rules, but ruthless in her destruction of those who transgress.
Her unconscious goal is a planet fit for life.
If humans stand in the way of this, we shall be eliminated with as little pity as would be shown by the micro-brain of an intercontinental ballistic nuclear missile in full flight to its target.
(The Ages of Gaia, 1995, p 212)
The Gaia scientific hypothesis [helps us] to recognise two things: …
  • the inherent value of all parts of nature, and …
  • our dependence on the Earth and on our environment …
(p 204)

Environmental Values

In the methodology and the practice of science are many assumptions of value. …
  • that there is an objective world of value out there to discover,
  • that there is value in the qualities of elegance and economy in scientific theory [and]
  • that complete honesty and cooperation between scientists [is central] to the scientific enterprise.
(p 206)

Stewardship — Dominion

[The story of the Garden of Eden leaves us] with a picture of the first humans as 'gardeners' of the Earth …
[Seeing the world as a garden suggests] four things:

  • A garden provides food and water and other materials to sustain life and human industry. …
    The Earth provides resources of many kinds for humans to use as they are needed.

  • A garden is to be maintained as a place beauty. …
    Humans are to live in in harmony with the rest of creation and to appreciate the value of all parts of creation.
    [A] garden is a place where care is taken to preserve the multiplicity of species, in particular those that are most vulnerable. …
    Gardens are meant to be enjoyed.

  • A garden is a place where humans [can express their creativity.] …
    [Scientific] and technical knowledge coupled with the enormous variety of the Earth's resources … create new possibilities for life and its enjoyment [as well as great] potential for evil …
    [Good] gardeners intervene in natural process [only] with a good deal of [cautious] restraint.

  • A garden is [a place] to be kept so as to be of benefit to future generations.

(pp 208-209)

The Will to Act

We are not short of statements of ideals.
[What is lacking is] the capability and resolve to carry them out. …

[Action] addressing environmental problems depends not only on knowledge … but on the values we place on the environment and our attitudes towards it. …
[What we must recognise is] that, just as
  • the totality of damage to the environment is the sum of the damage done by a large number of individuals,
  • the totality of action to address environmental problems is the sum of a large number of individual actions to which we can all contribute.
Edmund Burke (1729-1979):
[No one makes] a greater mistake than [he who does] nothing because he could only do so little.
(p 211)

The Precautionary Principle

[Significant] anthropogenic climate change is not an unlikely possibility but a near certainty …
[It] is no change of climate that is unlikely.
The uncertainties that … have to weighed lie in the magnitude of the change and details of its regional distribution. …

An argument … sometimes advanced for doing nothing now is that by the time action [cannot be avoided, better] technical options will [have become] available. …
But [this] argument works [both ways.]
The thinking and … activity generated by considering appropriate actions now … will itself be likely to stimulate the … technical innovation that will be required [later.]
(p 229)

Climate Insurance

[There is a greater than 66% probability that unmitigated] climate change [will,] in the long term … exceed the capacity of natural, managed and human systems to adapt.
(AR4, IPPC, 2007, p 65)
With typical levels of [global] economic growth being between 2-4% per annum, [six economic models have estimated] the cost of [stabilising carbon dioxide levels] at 450 ppm [at] less than one year's economic growth over fifty years [ie < 2% per year].
(p 235)

(Global Warming: The Complete Briefing, 2004)


The Greenhouse Gases
The Impacts of Climate Change
Why should we be concerned?

Weighing the Uncertainty


Former Chairman, Scientific Assessment Working Group, IPCC.
Former Professor of Atmospheric Physics, Oxford University.

  • Global Warming: The Complete Briefing, 3rd Ed, Cambridge University Press, 2004.


    Carbon Dioxide and the Carbon Cycle

    The biological pump in the oceans

    Plankton are small plants (phytoplankton) and animals (zooplankton) that live in the surface waters of the ocean …
    Plant and animal debris from these living systems sinks in the ocean.
    While sinking, some decomposes and returns to the water as nutrients, some (perhaps 1%) reaches the deep ocean or ocean floor, where it is lost to the carbon cycle for hundreds [to] millions of years.
    The net effect … is to [remove] carbon from the surface waters to the lower levels in the ocean.
    As the amount of carbon in the surface is reduced, more carbon dioxide from the atmosphere can be drawn down [into the ocean] to restore the surface equilibrium. …

    When there is less atmospheric carbon dioxide, the cooling by radition from the surface of ocean increases.
    Since convection in the upper layers … is driven by cooling at the surface, the increased cooling results in a a greater depth of the [mixing] layer near the top of the ocean where all the biological activity occurs.
    [A] a greater depth of the [mixing] layer means more plankton growth.
    [This is called] the 'plankton multiplier'.

    [Under global warming conditions, higher ocean surface temperatures reduce convection and slow the biological pump.
    This decreases ocean uptake of atmospheric carbon dioxide and, therefore, acts as a positive feedback to global warming.]

    (p 35)

    [Increased] carbon dioxide in the atmosphere leads to increased growth in some plants …
    (p 36)

    [This] carbon dioxide fertilisation effect is … a negative feedback because, as carbon dioxide increases, it tends to increase the take-up of carbon dioxide by plants and therefore reduces the amount in the atmosphere, decreasing the rate of global warming.
    [However,] there are more potentially positive processes than negative ones.
    (p 39)
    Feedbacks in the biosphere

    Three other positive feedbacks are potentially important, although our knowledge is currently insufficient to quantify them precisely.

    • [The] effect of higher temperatures on respiration, especially through microbes in soils, leading to increased carbon dioxide emissions. …
      [Studies of El Nino events that a short term change of] 5°C in average temperature leads to a 40% [increase] in global average respiration rate …
      [Whether] this relation holds [over longer — decadal or century timescales — has yet to be resolved.]

    • [The] reduction of growth or the dieback … in forests because of the [temperature and water] stress cause by climate change, which may be particularly severe in Amazonia. …
      A number of carbon cycle models show that … during the second half of the twenty-first century the residual terrestrial [carbon sink could] become a substantial net source.

    • [The] release of methane as temperatures increase — from wetlands and from very large reservoirs of [methyl hydrates] — methane trapped in [ocean] sediments in a hydrate form [ie bound to water molecules under pressure —] mostly at high latitudes. …
      [Were] global warming to continue to increase … for more than a hundred years, releases from hydrates could … act as a large positive feedback on the climate.
    (p 40)

    Particles in the Atmosphere

    [Natural sources of atmospheric particulates include those:]
    • blown of land surfaces, especially in desert areas …
    • forest fires …
    • sea spray [and]
    • volcanoes …
    (p 48)

    [Anthropogenic sources include:
    • sulphates (negative)
    • fossil fuel burning — black carbon (positive) and organic carbon (negative), and
    • biomass burning (negative).
    These aerosols result in direct radiative forcing effect.]

    Two mechanisms of indirect forcing have been proposed.

    • [The] influence of the number [and size] of particles … on cloud radiative properties.
      [If large numbers of particles are present during cloud formation,] the resulting cloud [has a larger] number of smaller drops than would otherwise be the case …
      Such a cloud will be more highly reflecting [ie have higher albedo] than one consisting of larger particles …

    • [Changes in droplet size and number affect] precipitation efficiency, lifetime of clouds and hence the geographic extent of cloudiness.

    There is observational evidence for both of these mechanisms but the processes involved are difficult to model and … vary a great deal with the particular situation.
    [Consequently, estimates] of their magnitude [are] very uncertain.
    (pp 49-50)


    The impacts of sea level rise

    Bangladesh is a densely populated country of about 120 million people located in the complex delta region of the Ganges, Brahmaputra and Megna Rivers.
    About 10% of the country's habitable land (with about six million population) would be lost with half a metre of sea level rise and about 20% (with about 15 million population) … with a 1-m rise.
    Estimates of the sea level rise are of about 1m by 2050 (compounded of 70cm due to subsidence because of land movements and removal of groundwater and 30cm from … global warming) and nearly 2m by 2100 (1.2m due to subsidence and 70cm from global warming) — although there is large uncertainty in these estimates. …

    [Substantial] amounts of good agricultural land will be lost.
    [Half] the country's economy comes from agriculture and 85% of the … population [depend on it for their] livelihood.
    (p 150)

    Many … are at the very edge of subsistence. …

    Bangladesh is extremely prone to … storm surges.
    Every year, on average, at least one major cyclone attacks Bangladesh. …
    The storm surge in November 1970 … is estimated to have claimed lives of over a quarter of million people.
    Well over a 100 000 are thought to have [died] in a similar storm in April 1991.
    Even small rises in sea level add to the vulnerability … to such storms.
    (p 151)

    At the present time … in some parts of Bangladesh, saltwater extends seasonally inland [for] over 150 km.
    With a 1-m rise in sea level, the area affected by saline intrusion could increase substantially … [Although this may be offset to some degree by increased monsoonal] rainfall. …

    No significant areas of agricultural land are available elsewhere in Bangladesh to replace that lost to the sea …
    [Nor] is there anywhere else in Bangladesh where the [displaced population could be easily relocated. …]
    [How the] sediment brought down by the rivers into the delta region … is used [could] have a large effect on the level of the land affected by seal level rise.
    Careful management if therefore required upstream as well as in the delta itself …
    [Groundwater] and sea defences must also be managed carefully if some alleviation of the effects of sea level rise is to be achieved. …

    [In] the Nile delta … as for Bangladesh [sea levels are expected to rise by] approximately 1m by 2050 and 2m by 2100.
    About 12% of the country's arable land with a population of over seven million people would be affected by a 1-m rise of sea level.
    Some protection [is afforded by] extensive sand dunes but only up to half a metre or so …
    (p 152, emphasis added)

    The impacts of climate change on fresh water resources

    [Precipitation] is expected to increase in northern high latitudes in winter and the monsoon regions of south-east Asia in summer, while other regions (eg southern Europe, Central America, southern Africa and Australia) can expect significantly drier summers.
    [Higher temperatures will result in increased evaporation.]
    In regions with increased precipitation some or all of the loss due to evaporation may be made up.
    However, in regions with unchanged or less precipitation, there will be substantially less water available at the surface.

    The [combination] of less rainfall and more evaporation means
    • less soil moisture [will be] available for crop growth and
    • less runoff [for domestic and industrial use. …]
    [Runoff] is highly sensitive to changes in climate …
    [In] the Sacramento Basin in California … a 4°C regional temperature rise [with a 20% decrease in rainfall would result in falls in summertime runoff of] between twenty … and 50% …
    (p 158)


    Drylands … cover about 40% of the total land area of the world and support over one-fifth of the world's population. …

    Desertification … is the degradation of land brought about by climate variation or human activities that have led to
    • decreased vegetation,
    • reduction of available water,
    • reduction of crop yields and
    • erosion of soil.

    [It is estimated] that over 70% of [the world's drylands ie 25% of the world's land area] are degraded …
    [Degradation] can be exacerbated by
    • excessive land use …
    • increased population …
    • political or economic pressures [such as] the need to grow cash crops to raise foreign currency [and]
    • is often triggered or intensified by … drought.

    [More] frequent and more intense droughts are likely to result from climate change during the twenty-first century.
    (p 163)

    Impact on agriculture and food supply

    Modelling the impact of climate change on world food supply

    [Based on a business-as-usual emissions trajectory, crop] yields in the mid to high latitudes are expected to increase, and at low latitudes (especially the arid and sub-humid tropics) to decrease.
    This pattern becomes more pronounced as time progresses.
    The African continent is … likely to experience
    • marked reduction in yield,
    • decreases in production and
    • an estimated sixty million or more additional people at risk of hunger …
    [This is without considering the impact of changes in:]
    • climate extremes,
    • availability of water supplies for irrigation, or
    • the effects of future technological change on agricultural productivity. …
    [These results give] a general indication of the changes that could occur [but] should not be treated as a detailed prediction.
    (p 168)

    The impact on ecosystems

    For the likely changes in climate in the twenty-first century, a substantial proportion of existing trees will be subject to unsuitable climate conditions.
    [In] the boreal forests of the Northern Hemisphere [the trees will become less healthy, and increasingly] prone to pests, die-back and forest fires.
    [Up] to 65%t of current boreal forested area could be affected.
    (p 172)

    Forests, deforestation and climate change

    [Under business-as-usual conditions] substantial reductions in precipitation are projected for areas of Amazonia [leading] to die-back of the Amazonian forest and significant releases of carbon [into] the atmosphere …
    As the forest dies back … rainfall is further reduced [due to changes in the] land surface …
    [By] the end of the twenty-first century … much of the forest cover [could be replaced] by semi-arid conditions.
    [While such projections are] subject to considerable uncertainties … they illustrate the type of impacts that might occur and … the importance of understanding the interactions between climate and vegetation.
    (p 173)

    80% of above-ground and 40% of below-ground terrestrial carbon is in forests.
    [Tropical] deforestation due to human activities is probably releasing between 1 and 2Gt of carbon [per] year. …
    [If] substantial stress and die-back occurs in boreal and tropical forests a [substantial] release of carbon will occur [— perhaps as much] as 240Gt over the twenty-first century …
    (p 175)

    The impact on human health

    In large cities where heat waves commonly occur, death rates can be doubled or tripled during days of unusually high temperatures. …
    [Studies] are equivocal regarding whether the reduction in winter mortality will be greater or less than the increase in summer mortality.
    (p 178)

    Costing the total impacts

    For those impacts against which some value of damage can be placed, estimates [range from] fifty-five to seventy-five [billion US] dollars per annum or between 1.0% and 1.5% of … GDP in [developed countries. …]
    For the developing world, estimates of annual cost were typically around 5% of GDP [—] with a range of … 2-9% …
    Aggregated over the world the estimates are between 1-2% of [global world product. …]

    [In] the agricultural sector [for] a doubling of atmospheric carbon dioxide concentration, studies of global aggregate economic impact vary from the slightly negative to the moderately positive …
    Beneficial effects are expected predominantly in the developed world [while] strongly negative effects are expected for populations that are poorly connected to regional and global trading systems.
    (p 184)

    Regions that will get drier or are already quite hot for agriculture … will suffer, as will countries that are less well [equipped] to adapt …
    Overall, climate change is likely to tip [agricultural] production in favour of the well-to-do and well-fed regions at the expense of less well-to-do and less well-fed regions.
    [The] influence of climate extremes and … factors such as water availability [have largely ignored due to] the lack of detailed information …

    '[Singular] events' or irreversible events of large or unknown impact [ie tipping points, have] a potential damage cost … of 1% of GWP for a warming of 2.5°C and about 7% of GWP for a warming of 6°C.
    Such calculations are necessarily based on highly speculative assumptions …
    [Nevertheless, they could end up representing] the largest single contributor to the total overall cost. …

    If some allowance is made for [extreme events, the cost of damage] induced by a doubling of the pre-industrial carbon dioxide [is] around
    • 1-2% of GDP for developing countries and …
    • 5% or more [for] developing countries.
    (p 185)

    [These] projections extend to] about the middle of the [21st century.]
    [Longer] term impacts [under business-as-usual conditions] are likely to be much greater.

    [Non-monetary impacts include:]
    • loss of life,
    • human amenity,
    • natural amenity [and]
    • [biodiversity. …]

    [The] total number of persons displaced by … global warming could [be in] the order of 150 million by the year 2050 (or about three million per year on average) —
    • about 100 million due to sea level rise and coastal flooding and
    • about fifty million due to the [disruption] of agricultural production [— mainly] drought.
    The cost of resettling three million displaced persons per year (assuming [this] is possible) has been estimated at [around ten billion] US dollars …
    [The potential for social and political instability could be very large.]
    (p 187)


    The IPCC Assessments

    [In order] to achieve the best assessment of present knowledge and to express it as clearly as possible … the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) [set up the IPCC in 1988.]
    (p 218)

    [Three] working groups [were established:]
    • one to deal with the science of climate change [WGI],
    • one with impacts [WGII] and
    • a third to deal with policy responses [WGIII].
    (p 219)

    … I was chairman [of the Science Assessment Working Group] from 1988 until 1992 and [then co-chairman] until 2002 …

    For the first report [in 1990,] 170 scientists from 25 countries contributed and a further 200 … were involved in its peer review.
    [By] the third assessment report in 2001 [there were:]
    • 123 lead authors and 516 contributing authors involved in the various chapters,
    • together with 21 review editors and 420 expert reviewers involved in the review process. …

    [It is] clear that the responsibility of scientists to convey the best possible information [cannot] be discharged without making estimates of the most likely magnitude of the change coupled with clear statements of [the] assumptions and the level of uncertainty [implicit in those] estimates.
    Weather forecasters … may feel uncertain about tomorrow's weather [but] they cannot refuse to make a forecast.
    If they do refuse, they withhold from the public [the most] useful information they possess.
    [And despite the inherent] uncertainty in a weather forecast, it [still] provides useful guidance to a wide range of people.
    [Similarly, on a longer time-scale,] climate models, although [also] subject to uncertainty, provide useful guidance for policy.
    (p 220)

    [Because the IPCC] is an intergovernmental body [its] assessments are in a real sense owned by governments as well as scientists — an important factor when it comes to policy negotiations. …
    In the run up to the United Nations Conference on Environment and Development (UNCED) at Rio de Janeiro in June 1992 [the "Earth Summit"], the fact that [the politicians and policymakers] accepted the reality of the problem led to the formulation of the [[UN Framework Convention on Climate Change (UNFCCC).]
    [Without] the clear message that came from the world's scientists … the world's leaders would never have agreed to sign the Climate Convention.

    Since the publication of the reports … a few scientists have criticised the reports [for understating] the uncertainties …
    [On the other hand, others were disappointed that the reports did not spell] out the potential dangers to the world more forcefully.
    (p 221)

    Narrowing the uncertainty

    For the science of change, the main tools of progress are observations and models. …

    • Observations are required to detect climate change [and] to validate [the] models.
      [Regular,] accurate and consistent monitoring is required with good coverage in both space and time. …
      [The] Global Climate Observing System (GCOS) has been set up to orchestrate and oversee the provision of observations on a global basis.

    • Models are needed to integrate all the scientific processes that are involved [and] provide a method of projecting climate change into the future.

    (p 222)

    Space observations of the climate system

    [Weather] observations provide a basic input to climate models.
    But for climate prediction and research, comprehensive observations from … the oceans, ice and land surface are [also required.]

    ENVISAT [was] launched by the European Space Agency in 2002 …
    [Its] instruments are directed at the measurement of
    • atmospheric temperature and composition (MIPAS, SCIAMACHY and GOMOS),
    • sea surface temperature and topography, the latter for ocean current information (AATSR and RA-2) …
    • ocean biology and land surface vegetation (MERIS) and
    • sea-ice coverage and ice-sheet topography (ASAR and RA-2).
    (p 223)

    Principles for international action

    [Four principles] form the basis of international action.
    They are all [enshrined] in the [1992] Rio Declaration on Environment and Development

    • The Precautionary Principle …

      Principle 15:
      In order to protect the environment, the precautionary approach shall be widely applied by Sates according to their capabilities.
      Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

    • The Principle of Sustainable Development …

      Principle 1:
      Human beings are at the centre of concerns for sustainable development.
      They are entitled to a healthy and productive life in harmony with nature.

      Principle 7:
      States shall cooperate in a spirit of global partnership to conserve, protect and restore the health and integrity of the Earth's ecosystem.
      In view of the different contributions to global environmental degradation, States have common but differentiated responsibilities.
      The developed countries acknowledge the responsibility that they bear in the international pursuit of sustainable development in view of the pressures their societies place on the global environment and of the technologies and financial resources they command.

    • The Polluter-Pays Principle …

      Principle 16:
      National authorities should endeavour to promote the internalization of environmental costs and the use of economic instruments, taking into account the approach that the polluter should, in principle, bear the cost of pollution, with due regard to the public interest and without distorting international trade and investment.

    • The Principle of Equity — International and Intergenerational …

      Principle 3
      The right to development must be fulfilled so as to equitably meet developmental and environmental needs of present and future generations.

      Principle 5
      All States and all people shall cooperate in the essential task of eradicating poverty as an indispensable requirement for sustainable development, in order to decrease the disparities in standards of living and better meet the needs of the majority of the people of the world.

    (pp 230-231)

    Some Global Economics

    Consider the situation when [atmospheric] carbon dioxide … has doubled from its pre-industrial value [raising global average temperature by about 3°C.]
    [This] will occur when [about 800 Gt] has been emitted …
    [About half of this] carbon dioxide will remain in the atmosphere … for about one hundred years.
    Assuming [the the cost of damage due to global warming at twice pre-industrial carbon dioxide levels is around] 2% of global world product — or $US 600 billion per annum [or $60 trillion over 100 years —] the cost per tonne of carbon [works] out to be [roughly] $US 70.
    [($60,000 x 10^9) / 800 x 10^9 t = $75/t]

    [However, it is] the incremental damage cost [— ie] the cost … of each additional] tonne of carbon emitted [—] that is really really required and also … a discount rate [to account] for the fact that [the damage is occurring in the future.]
    Estimates [range from] $US 5-125 per tonne of carbon [depending on] the discount rate that is [used …]
    [These estimates are highly] sensitive to the discount rate that is assumed …
    (p 233)

    [For example, over] one hundred years [a 2% discount rate devalues costs by] a factor of seven [while a 5% discounts them by a factor of] 170.

    [There is, needless to say, no agreement among economists] about how to apply discount accounting to long term problems of this sort or about what rate is most appropriate.
    [Partha Dasgupta has suggested] that the effects of carbon emission could make substantial negative perturbations on future economics thus threatening the basis on which discount rates for future investment are set.
    [And, that some likely damages cannot be easily quantified in monetary terms:] such as large-scale loss of land … due to seal level rise or large scale loss of habitats or species.
    [If this is true,] smaller … rather than a larger [discount rates for damage estimates] should be employed [eg equivalent to $US 50-100] per tonne of carbon emitted as carbon dioxide.
    (p 234)

    In summary, the items in the overall global warming balance sheet … are:

    • [The cost of] those items which can be quantified in terms of money …
      [These] are typically
      • 1-2% of GDP in developed countries and …
      • 5% or more in developing countries.

    • [The] cost of adaptation …
      Even if the maximum possible mitigation takes place … the requirement for adaptation will continue for many centuries into the future [eg due to sea level rise …]

    • [Impacts] that are difficult [or] impossible to value in money terms …
      • those with social consequences,
      • those that affect human amenity and 'natural' capital [and]
      • those that have implications for national security.

    • [The cost of mitigation …
      [These] are typically less than one year's economic growth by 2050.
    (p 238)

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