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Carbon sink

A carbon sink is a reservoir that can absorb or 'sequester' carbon dioxide from the

atmosphere and include forests, soils, peat, permafrost, ocean water and carbonatedeposits in the deep ocean. Most of these carbon sinks are very large and very slow

moving; human influence on these sinks is generally deemed fairly minimal, with thepossible exception of soils and agriculture. Oil, coal and natural gas represent the final

evolution of pre-historic carbon sinks that are now "fossilized" into mineral form.

The most commonly referenced form of carbon sink is that of forests. Plants and trees

absorb carbon dioxide from the atmosphere via photosynthesis, retain the carbon

component as the building block of plant fiber and release oxygen back into the

atmosphere. Therefore, long lived, high biomass plants, such as trees and forestsrepresent effective carbon sinks as long as they are maintained.

Refer to the Forestry Issues paper released by Gareth Phillips et al. of SGS for additional

forests as sinks information.

The degree to which the positive impacts of 'sinks', forestry and otherwise, can becaptured and utilized in an emissions trading context is still a matter of contentious

debate at the Intergovernmental Panel on Climate Change (IPCC) and other forums.

Refer to the Presentations from our event in Bonn at COP 6 Part 2 entitled Forestry

Issues Arising From COP 6" for additional information.

Certain gases, such as chlorofluorocarbons, contribute two-fold to climate change by

simultaneously trapping reflected heat and thinning the protective ozone layer. This

ozone depletion reduces the atmosphere's ability to absorb and reflect solar radiation. Asa result more solar radiation is able to reach the earth's surface and potentially acceleratethe process of climate change.

What is the science behind climate change?

The earth's atmosphere acts as a filter for solar rays; approximately half of the visible

light and ultraviolet radiation given off by the sun is either absorbed by the various layersor reflected back into space. Most of the 50% that does get through heats the earth's

surface and is eventually reflected back into space as infrared radiation. The 'greenhouse

effect' is the atmospheric trapping of that infrared radiation; a natural phenomenon

without which the Earth would be uninhabitably cold for humans.

During the combustion of carbon-based fossil fuels, greenhouse gases such as carbon

dioxide, methane and nitrous oxide are emitted. These gases add to that atmospheric layer

that is permeable to ultraviolet, but not infrared radiation. As more fossil fuels areburned, the layer of greenhouse gases thickens; solar radiation continues to pass through

unimpeded, while heat reflected from the earth finds it harder and harder to escape into

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space. In the medium to long term, this results in the gradual increase in the Earth's

temperature known classically as 'global warming'.

Global climate dynamics, however, are unpredictable. Climatic models show that theshort to medium impacts of an increase in the atmosphere's concentration of greenhouse

gases will likely lead to increased warming in some areas with deep cooling in others. Forexample, consider the impact of the disruption of the gulf stream, the oceanic system that

keeps the British Isles a comfortable temperature at the same latitude as Moscow. Theunpredictability of the global climate system's response to an increase in carbon dioxide

has recast the term "global warming" into its now accepted "global climate change".

Certain gases, such as chlorofluorocarbons, contribute two-fold to climate change by

simultaneously trapping reflected heat and thinning the protective ozone layer. Thisozone depletion reduces the atmosphere's ability to absorb and reflect solar radiation. As

a result more solar radiation is able to reach the earth's surface and potentially accelerate

the process of climate change.

The six greenhouse gases specified in the Kyoto Protocol are:

1. Carbon dioxide (CO2)

2. Methane (CH4)

3. Nitrous oxide (N20)4. Hydrofluorocarbons (HFCs)

5. Perfluorocarbons (PFCs)

6. Sulphur hexafluoride (SF6)

Approximately 25 other gases, such as chloroform and carbon monoxide, qualify asclimate-changing greenhouse gases, but only the above mentioned six are released in

sufficient quantities to justify regulation under Kyoto. Water vapour is a very important

greenhouse gas, but is not controllable by human intervention.

Carbon dioxide (CO2) - Carbon dioxide comes from the decay of materials, respirationof plant and animal life, volcanic and thermal venting, and the natural and human-

induced combustion of materials and fuels. It is removed from the atmosphere through

photosynthesis and ocean absorption.

Methane (CH4) - Methane is a more effective heat-trapping gas. It comes from theanaerobic (without oxygen) decay of matter. Primary sources include wetlands, rice

paddies, animal digestive processes, fossil fuel extraction, pulp and paper processing and

decaying garbage.

Nitrous oxide (N2O) - Soils and oceans are the primary natural source of nitrous oxide.

Humans contribute through soil cultivation and use of nitrogen fertilizers, nylon

production, and the burning of organic material and fossil fuels.

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Halocarbons (HFC and PFC) - Halocarbons are human-produced chemical compounds

containing members of the halogen family (bromine, chlorine, and fluorine) and carbon.

They are some of the most effective heat trapping greenhouse gases of all; however, mostof them are already regulated under the Montreal Protocol (a treaty for the protection of

the ozone layer). These newer gases are regulated by the Kyoto Protocol because

although they are ozone friendly, they are greenhouse unfriendly.

Sulphur hexafluoride (SF6) - Sulphur hexafluoride is emitted by the electric powerindustry in circuit breakers, gas-insulated substations and switchgear. That industry uses

a significant percentage of the 6,500 to 7,500 metric tonnes produced worldwide each

year.

What are carbon dioxide equivalents (CO2 eq)?

Carbon dioxide equivalents (CO2 eq) provide a universal standard of measurement

against which the impacts of releasing (or avoiding the release of) different greenhouse

gases can be evaluated. Every greenhouse gas has a Global Warming Potential (GWP), ameasurement of the impact that particular gas has on 'radiative forcing'; that is, the

additional heat/energy which is retained in the Earth's ecosystem through the addition of

this gas to the atmosphere.

The GWP of a given gas describes its effect on climate change relative to a similaramount of carbon dioxide and is divided into a three-part "time horizon" of twenty, one

hundred, and five hundred years. As the base unit, carbon dioxide numeric is 1.0 across

each time horizon. This allows the greenhouse gases regulated under the Kyoto Protocol

to be converted to the common unit of CO2 eq.

Global Warming potentials for the greenhouse gases regulated under the Kyoto Protocolunder a 100 year timeframe are as follows

(Source - US EPA):

Carbon dioxide has a GWP of 1

Methane has a GWP of 21

Nitrous oxide has a GWP of 310

Halocarbons (HFC) has a GWP of 140 to 11,700

Sulphur Hexafluoride has a GWP of 23,90

This means that in 100 years, one tonne of methane will have an effect on global

warming that is 21 times greater than one tonne of carbon dioxide, and so forth. No singlenumber can accurately represent the GWP of a given gas, as certain gases remain in theatmosphere much longer than others. The uncertainty ranges for the fluorocarbon

derivative indicates the continued uncertainty regarding their long term decomposition in

the atmosphere as these are fairly newly 'designed' gases. Short-lived gases are lessharmful in the long-term than they are in the short-term, which means that the carbon

dioxide equivalency of a given gas can vary dramatically over time.