Climate change
“The United Nations Framework Convention on Climate Change (UNFCCC) definition is: 'a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods'. [2]

The IPCC definition of climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). It may be due to natural internal processes or external forces, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.” [1]

References

“IPCC 3 rd Assessment Report: “Climate Change 2001: The Scientific Basis ” Appendix I: Glossary
» Available: http://www.grida.no/climate/ipcc_tar/wg1/518.htm[accessed 2007, Feb. 24]

As greenhouse gases warm, they re-emit infrared radiation in all directions reheating the earth or radiating some into space. And a new equilibrium is established at a warmer temperature. Different gases have different potential to warm their environment! Their Global Warming Potential is described by the IPCC as follows: -

“The GWP has been defined as the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas (IPCC, l990):

where TH is the time horizon over which the calculation is considered, ax is the radiative efficiency due to a unit increase in atmospheric abundance of the substance in question (i.e., Wm-2 kg-1), [x(t)] is the time-dependent decay in abundance of the instantaneous release of the substance, and the corresponding quantities for the reference gas are in the denominator. The GWP of any substance therefore expresses the integrated forcing of a pulse (of given small mass) of that substance relative to the integrated forcing of a pulse (of the same mass) of the reference gas over some time horizon. The numerator of Equation 6.2 is the absolute (rather than relative) GWP of a given substance, referred to as the AGWP. The GWPs of various greenhouse gases can then be easily compared to determine which will cause the greatest integrated radiative forcing over the time horizon of interest. The direct relative radiative forcings per ppbv are derived from infrared radiative transfer models based on laboratory measurements of the molecular properties of each substance and considering the molecular weights”.

References

“IPCC 3 rd Assessment Report: “Climate Change 2001: The Scientific Basis: 6.12 Global Warming Potentials”
» Available: http://www.grida.no/climate/ipcc_tar/wg1/247.htm [accessed 2007, Feb. 24]

Greenhouse gases - from an Australian Greenhouse Office article [1]

What are greenhouse gases?
Greenhouse gases are a natural part of the atmosphere. It is the increase in the amounts of these gases through human activity that causes global warming. Human activity such as land clearing and burning fossil fuels have increased the concentration of these gases. Humans have had most impact on the enhanced greenhouse effect through increases in the amounts of carbon dioxide, methane and nitrous oxide.

Water vapour
Water vapour is the most important greenhouse gas, but human activity has little direct impact on the amount in the atmosphere

Carbon dioxide (CO 2)
The amount of carbon dioxide in the atmosphere is about 30% higher now than 200 years ago. The main causes of this increase are:

Methane (CH 4)
The amount of methane in the atmosphere is about 145% higher now than 200 years ago. The main causes of this increase are:

This gas is the second biggest contributor to the enhanced greenhouse effect (about 20%)

Nitrous oxide (N 2O)
The amount of nitrous oxide in the atmosphere is about 15% higher now than 200 years ago.The main causes of this increase are:

Halocarbons
These greenhouse gases have been reduced since the Montreal Protocol initiated phasing out of chlorofluorocarbons (CFCs) to protect the ozone layer. However, other halocarbons effecting the atmosphere include perfluorocarbons (PFCs) emitted during aluminium production. > [1]

Global Warming Potentials - from a USDOE EIA article [2]
“Global warming potentials (GWPs) are used to compare the abilities of different greenhouse gases to trap heat in the atmosphere. GWPs are based on the radiative efficiency (heat-absorbing ability) of each gas relative to that of carbon dioxide (CO2), as well as the decay rate of each gas (the amount removed from the atmosphere over a given number of years) relative to that of CO2. The GWP provides a construct for converting emissions of various gases into a common measure, which allows climate analysts to aggregate the radiative impacts of various greenhouse gases into a uniform measure denominated in carbon or carbon dioxide equivalents. (Ref IPCC)” [2]

References

Notes on Ice Core Measurements

The ratio of oxygen isotopes 18O to 16O in water from ice core samples can give a measure of climate temperatures, as water formed from 18O evaporates less readily than water formed from 16O and this difference in evaporation depends also on temperature. Similar evidence can be obtained from the measurement of oxygen isotopes in calcite from sediment cores in the ocean floor.

Near the surface core material resolutions of 1 year can be obtained (the last few hundred years. The time resolution for deeper core samples becomes progressively harder to resolve.

References

Data from Tree Rings

“Tree rings provide a record of local climate during the life of the tree. Many trees are hundreds of years old, and a few live thousands of years. Thus the rings provide information that is not available from scientific records.

In a tree the cambium, the cells that will become wood or bark, grows in a light layer during late spring/early summer changing to a dark layer in later summer/early fall. This is the pattern in Alaska. The light layer is early wood, formed when the tree is growing rapidly. The dark layer is late wood and is grown more slowly. The growth occurs at the outside of the trunk, just under the bark, so that a light and dark ring pair represents one year.

Cores are used to read living trees. An instrument called an increment borer is drilled into the tree. This extracts a piece of wood about the size of a drinking straw that shows the growth rings. Using this method, the rings can be read without killing the tree. The growth of a tree's annual rings is related to the weather in the area. If it has been a dry summer a tree does not grow very much during that and the following year or two. If it was a wet summer than there is more growth. The figure above is an X-ray of the core from a white spruce. Notice the thin rings just following 1950, and again in the dry years of the late '50's.

To study past weather, a scientist studies trees that are very sensitive to weather changes. In Alaska, they also have to look at trees which grow rapidly. Some species of trees, such as Alaska's interior black spruce, are so slow growing that the rings are too compact to read. In Alaska, scientists usually look at white spruce” [1]

References

Uncertainties & The Hockey Stick Graph

Reference: AGO http://www.greenhouse.gov.au/science/hottopics/pubs/topic3.pdf

“Mann et al. (1998) found that the 1990s were likely to have been the warmest decade, and 1998 the warmest year, of the past millennium in the northern hemisphere. Jones et al. (1998) reached a similar conclusion from largely independent data and an independent methodology. Crowley and Lowery (2000) found that medieval temperatures (between the mid-12th and early 14th centuries) were no warmer than mid-20 th century temperatures. These results, and those of two other reconstructions (Briffa et al., 2001), are shown above. Independent borehole temperature reconstructions (Pollack and Smerdon, 2004) also indicate that the recent warming is unusual in the context of the last 500 years. More recent research has shown that the late 20th century warmth in the northern hemisphere is unprecedented for at least the past 1,800 years (Mann and Jones, 2003). A claim that the pre-1900 variability may be underestimated by a factor of two (von Storch, 2004) has been challenged (Wahl et al, 2006) Northern Hemisphere temperatures similar to those in the 20th century before 1990 may have occurred around 1000-1100 AD (Moberg et al, 2005). The robustness of multi-proxy reconstructions of temperature over the last millennium needs further investigation (Bürger and Cubasch 2005).”

“Some of these results have been questioned. A study by Soon and Baliunas (2003) challenged the unusual nature of the 20th century warming, but this study was found to be scientifically flawed (Mann et al., 2003a; Mann and Jones, 2003). Another study by McIntyre and McKitrick (2003) claimed that temperatures estimated by Mann et al. (1998) from 1400 to 1980 contained errors, and that corrections to the data showed that the early 15th century was warmer than any period in the 20th century. However, these claims were countered by Mann et al. (2003b) who found that McIntyre and McKitrick (2003) made errors in their analysis and omitted or truncated key proxy indicators from 1400-1600. Mann et al. (2004) acknowledge that their 1998 paper contained several errors that, when appropriately corrected, had no effect on previously published results. McIntyre and McKitrick (2005) claimed that the method of Mann et al. (1998) is biased toward producing a ‘hockey stick’ shaped curve and underestimates uncertainty in the 15th century. This assertion was tested by von Storch and Zorita (2005) and Huybers (2005) who found that the normalization used by Mann et al (1998) tends to bias results toward having a “hockey stick” shape, but the scope of this bias is exaggerated by the choice of normalization used by McIntyre and McKitrick (2005) and by an error in their estimation of significance levels. The IPCC (2001) concludes that global warming over the past 50 years was mainly caused by human activities that have increased atmospheric concentrations of greenhouse gases.” [1]

References

“How unusual is the late 20th century warming. Australian Greenhouse Office”
» Available: http://www.greenhouse.gov.au/science/hottopics/pubs/topic3.pdf [accessed 2007, Feb. 24]

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The Surface & Troposphere Temperature Records

“The density of observing stations always has been and still is extremely inhomogeneous, with many stations in densely populated areas and virtually none in huge oceanic areas. In recent times special earth-observation satellites have been launched, providing a wide range of observations of various components of the climate system all over the globe. The correct interpretation of such data still requires high quality in situ and surface data. The longer observational records suffer from changes in instrumentation, measurement techniques, exposure and gaps due to political circumstances or wars. Satellite data also require compensation for orbital and atmospheric transmission effects and for instrumental biases and instabilities. Earlier the problems related to urbanisation were mentioned. To be useful for the detection of climate change, observational records have to be adjusted carefully for all these effects.”

References

Climate Change 2001:Working Group I: The Scientific Basis 1.3.2 Modeling and Projection of Anthropogenic Climate Change.
» Available: http://www.grida.no/climate/ipcc_tar/wg1/045.htm#133

“Satellite-based measurements of decadal-scale temperature change in the lower troposphere have indicated cooling relative to Earth's surface in the tropics. Such measurements need a diurnal correction to prevent drifts in the satellites' measurement time from causing spurious trends. We have derived a diurnal correction that, in the tropics, is of the opposite sign from that previously applied. When we use this correction in the calculation of lower tropospheric temperature from satellite microwave measurements, we find tropical warming consistent with that found at the surface and in our satellite-derived version of middle/upper tropospheric temperature.”

The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature Mears, CA and Wentz FJ Science
» Available: http://www.sciencemag.org/cgi/content/short/309/5740/1548

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Volcanoes and Global warming

“Volcanoes emit water vapour and carbon dioxide, but contribute little to global changes in atmospheric greenhouse gas concentrations. Large volcanic eruptions, however, can blast huge amounts of sulfur dioxide into the upper atmosphere (the stratosphere). There, the sulfur dioxide transforms into tiny particles of sulfate aerosol. These particles reflect energy from the sun back into space, preventing some of the sun’s rays from heating the Earth. Conversion of sulfur dioxide to sulfuric acid aerosol in the stratosphere takes some months, so maximum cooling occurs up to a year after the eruption. It may take as long as seven years before the cooling influence of the volcanic aerosol disappears completely.

When Mt Pinatubo in the Philippines erupted in 1991 it blasted up to 26 million tonnes of sulfur dioxide into the stratosphere. This led to a global surface cooling of 0.5°C one year after the eruption. This cooling offset the warming effects of both El Niño and human induced greenhouse gases from 1991 to 1993. As well as cooling the lower atmosphere (troposphere), volcanic aerosol can absorb both thermal radiation from the ground and solar radiation, leading to a warming of the stratosphere.” [1]

References

“Climate Change Science” Australian Greenhouse Office.
» Available: http://www.greenhouse.gov.au/science/qa/pubs/science-qa.pdf [accessed 2007, Feb. 24]

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Impacts & Responses

Climate change scenario’s & models
Climate change scientists use models and scenario’s to try and predict how the climate is going to change and how the change will affect us. Models are ways of using mathematics and physics to describe how the climate operates normally. Scenarios are inputs to these models; they describe how humans may behave to affect the climate. By combining scenarios with models climate change scientists can predict how CO 2 and temperature may change and some of the impacts resulting from these changes

“Studies of projections of future climate change use a hierarchy of coupled ocean/atmosphere/sea-ice/land-surface models to provide indicators of global response as well as possible regional patterns of climate change. One type of configuration in this climate model hierarchy is an Atmospheric General Circulation Model (AGCM), with equations describing the time evolution of temperature, winds, precipitation, water vapour and pressure, coupled to a simple non-dynamic “slab” upper ocean, a layer of water usually around 50 m thick that calculates only temperature (sometimes referred to as a “mixed-layer model”). Such air-sea coupling allows those models to include a seasonal cycle of solar radiation. The sea surface temperatures (SSTs) respond to increases in carbon dioxide (CO2), but there is no ocean dynamical response to the changing climate. Since the full depth of the ocean is not included, computing requirements are relatively modest so these models can be run to equilibrium with a doubling of atmospheric CO2. This model design was prevalent through the 1980s, and results from such equilibrium simulations were an early basis of societal concern about the consequences of increasing CO2.” [1]

“In 1996, the IPCC began the development of a new set of emissions scenarios….Four different narrative storylines were developed to describe consistently the relationships between emission driving forces and their evolution …….. The resulting set of forty scenarios (thirty-five of which contain data on the full range of gases required for climate modelling) cover a wide range of the main demographic, economic and technological driving forces of future greenhouse gas and sulphur emissions. “ [2]

Example B2 . “ The B2 storyline and scenario family describe a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.” [2]

Historical temperature change and future changes for the six scenarios using a simple climate model tuned to seven Atmosphere-Ocean General Circulation Models (AOGCM)…. The bars show the range of simple model results for 2100 [3][4][5]

References

“9.1.1 Background and Recap of Previous Reports” IPCC - Climate Change 2001: The Scientific Basis
» Available: http://www.grida.no/climate/ipcc_tar/wg1/341.htm [accessed 2007, Feb. 24]

“9.1.2 New Types of Model Experiments since 1995” IPCC - Climate Change 2001: The Scientific Basis
» Available: http://www.grida.no/climate/ipcc_tar/wg1/343.htm [accessed 2007, Feb. 24]

“F.2 Projections of Future Changes in Greenhouse Gases and Aerosols” IPCC - Climate Change 2001: The Scientific Basis
» Available: http://www.grida.no/climate/ipcc_tar/wg1/030.htm [accessed 2007, Feb. 24]

“Summary for Policymakers” Climate Change 2001: Synthesis Report.
» Available: http://www.grida.no/climate/ipcc_tar/vol4/english/pdf/spm.pdf [accessed 2007, Feb. 24]

“Human influences will continue to change atmospheric composition throughout the 21st century” IPCC Climate Change 2001: The Scientific Basis
» Available: http://www.grida.no/climate/ipcc_tar/wg1/008.htm [accessed 2007, Feb. 24]

Energy Units

Energy Units [1]

1 J (joule) = 1 Ws = 0.2388 cal

1 GJ (gigajoule) = 10 9 J

1 TJ (terajoule) = 10 12 J

1 PJ (petajoule) = 10 15 J

1 EJ (exajoule) = 10 21 J

1 kWh (kilowatt hour) = 3,600,000 Joule

1 toe (tonne oil equivalent)

= 7.4 barrels of crude oil in primary energy

= 1270 m 3 of natural gas

= 2.3 metric tonnes of coal

= 41.868 GJ (41.868x10 9J)

Note 1 Mtoe (million tonne oil equivalent) = 41.868 PJ (41.868x10 15)

References

“Wind Energy Reference Manual Part 2: Energy and Power Definitions” Danish Wind Industry Association.
» Available: http://www.windpower.org/en/stat/unitsene.htm [accessed 2007, Feb. 24]

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Biomass

Abstract for Energy from the Biological Conversion of Solar Energy
by N.K.Boardman, M.W.Thring, D.R.Johnston, D.T.Swift-Hook

Philosophical Transactions of the Royal Society of London.
Series A, Mathematical and Physical Sciences, Volume 295, Issue 1414, pp. 477-487

“Trees and other forms of vegetation are well designed for the collection and storage of solar energy. Moreover, photosynthetic organisms show enormous diversity and are well adapted for a wide range of environments. Biomass is convertible to liquid and gaseous fuels by a number of established processes, and this paper examines the possible contribution of biomass to world energy demands. The maximum efficiency of solar energy conversion in plant production is 5-6% (1), but plants grown under usual field conditions do not achieve this degree of conversion. The highest yielding crops convert solar energy into plant material with an efficiency of 1-2%, but the average yields of the major crops and forests indicate considerably lower efficiencies. The average efficiency of solar energy conversion on a global scale is estimated as about 0.15%. The energy content of the annual biomass residues in Australia and U.S.A. is equal to about one-quarter of the primary energy use in those countries, but only about one-third of the residues are considered to be readily recoverable. A number of high yielding crops are examined as potential fuel crops. Energy inputs for growing non-irrigated crops in Australia are estimated to amount to 7-17% of the solar energy stored in the total crop biomass. Irrigation adds considerably to the energy cost of producing crops. The overall energy efficiency of fuel production from biomass varies from 20 to 58%, depending on the nature of the biomass and the process used to produce liquid or gaseous fuel. A recent estimate by an Australian committee of the potential contribution of biomass to liquid fuel production in Australia is presented. It is concluded that biomass will not be able to provide a substantial fraction of the world's energy demand, although it can make a useful contribution.” [1]

N. K. Boardman, M. W. Thring, D. R. Johnston, D. T. Swift-Hook “Energy from the Biological Conversion of Solar Energy” Phil Trans R. Soc. Lon.. Series A, Math & Phys Sci, Vol. 295, No. 1414 (Feb. 7, 1980)

Some cautions on considering biomass

May compete with food production.
May lead to soil infertility.
Land clearing and poor farm practice may lead to pollution
Large scale agro-farming may lead to social disruption

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Notes on Nuclear Energy:-

Fast breeder reactors
Natural uranium contains 99.3% 238U isotope and 0.7% 235U. It is the 235U isotope which is capable of undergoing nuclear fission and the 238U goes to waste or to make coatings for armour piercing missiles. Fast Breeder reactors generate energy while converting 238U into 235U so that they can increase the energy available from uranium by a factor of x140. Most breeder reactors are illegal for commercial power generators in the USA because of the weapons proliferation risk. The fast breeder principle is being used as part of the design of a new generation of reactors known as Generation IV. These reactors are attempting to achieve the advantages of better fuel utilisation and lower levels of waste while reducing the risk of weapons proliferation.

Thorium
Thorium is not fissile but can be used as a fuel in fission reactors that have a neutron source such as fuel rods of plutonium or 235U or connection to a particle accelerator set up to generate neutrons. Thorium is three times as abundant and has about 40x the fissionable energy density of natural uranium. India and Australia have the world’s largest reserves of thorium..

Application

Thorium is three times more abundant in the earths crust than uranium

Thorium can be used as a nuclear fuel through breeding to uranium-233

Thorium fuel cycle produces much less plutonium and other transuranic elements compared with uranium fuel cycles.

100% of thorium is useable in a reactor, compared with the 0.7% of natural uranium, (This does not take into account the use of fast breeder reactors and other technologies which are capable of extracting far more energy from uranium and consequently of reducing the waste products)

Fuel reprocessing can be carried out chemically rather than isotopically and has led to the design of reactors with self contained fuel cycles.

Thorium with a seed quantity of plutonium is compatible with existing reactors. Currently Russia is using this approach to dispose of its weapons grade plutonium

Research to date
Research on thorium as a nuclear fuel has been carried out for the last 30 to 40 years in Germany, India, Japan, Russia, the UK and the USA. Problems with the use of thorium include the high cost of fuel fabrication and unresolved problems with reprocessing due to traces of high radioactivity isotopes of uranium and thorium. The presence of U233 also presents some weapons proliferation risk. Nevertheless a thorium based reactor has been included in one of the six reactor technologies proposed for deployment between 2010 and 2030 by the ten country members of the Generation IV International Forum. A number of test reactors including at least one commercial reactor have been set up using thorium-based fuel.

Fast Breeder Technologies and Thorium Usage in Nuclear Reactors
fast Breeder technology and thorium fuelled reactors can provide fuel for nuclear fission power for many thousands of years. They also have the potential for reducing the critical waste storage time from tens of thousands of years to between fifty to several hundred years. The technologies are not likely to be available for commercial use for another twenty years. The costs, levels of waste and immunity to weapons proliferation have yet to be determined.

WIND

Abstract for Evaluation of Global Wind Power
by Cristina L. Archer and Mark Z. Jacobson

Journal of Geophysical Research
» Available: http://www.stanford.edu/group/efmh/winds/Archer2004jd005462.doc