the sensitivity of an option’s delta to changes in the price of the underlying futures contract.

   general autoregressive conditional heteroscedasticity. A statistically advanced method for measuring time-varying volatility.

   1) Natural gas covers a range of gases that occur naturally and are composed mainly of methane (CH4) and ethane. In the UK gas supply industry, it refers to the gas supplied through the mains system (mainly CH4). North Sea gas usually has a declared heating value of 1,035 British thermal units per cubic foot. 2) North American abbreviation for gasoline.

   a US industry forum that aims to develop and promote standards that will lead to a seamless market for natural gas.

   in the US, nomination deadlines are where each pipeline has a scheduled deadline before which shippers must book gas for the following month.

   in the UK, the gas year begins at 0600 on October 1. This is also known as the contract year, as it is when purchase contracts begin.

   a middle distillate and form of heating oil used primarily in heating and air-conditioning systems. One of the most actively traded oil products, gasoil is the underlying in a key International Petroleum Exchange futures contract. In refining terms, gasoil comes between fuel oil and the lighter products such as naphtha and gasoline. In its broader definition, it covers the oil products used for diesel automotive fuel and jet fuel.

   a light-end hydrocarbon distillate used for internal combustion engines, actively traded as futures and options contracts on Nymex. Also known as petrol.

   (UK) Gas Consumers Council, known as Energywatch. (Middle East) Gulf Co-operation Council.

   gross calorific value. see also calorific value

   the gearing of a derivative is the price of the underlying divided by the price of the derivative. This can be used for crude assessments of leverage and option pricing. A more sophisticated measure is effective gearing (or lambda), which is the traditional gearing multiplied by the derivative’s delta. see also leverage

   the generating availability database (Gads) collects, records and retrieves operating information about the performance of electricity-generating equipment. More than 180 generating facility operators in the US and Canada voluntarily participate in Gads.

   the process of producing electrical energy by transforming other forms of energy. The amount of energy produced is expressed in watt hours.

    see stochastic process

   log return.

   energy derived from the heat of the earth’s core. Geothermal energy sources include steam, hot water or hot rocks lying close to the earth’s surface.

   an electricity price index for the whole of Germany, launched by Dow Jones in January 2001. Created through the merger of the Central European Price Index and the Electricity Index South.

   the Italian electricity market operator that was set up by the independent transmission system operator (GRTN) and operates the Italian wholesale electricity market. GME is responsible for issuing the electricity market rules, subject to input from the electricity and gas regulator (AEEG) and approval by the Minister of Industry. GME is also responsible for managing the Italian electricity market to promote competition between producers, to ensure an adequate availability of power reserves, enforcing merit-order economic dispatch and managing the Italian power exchange. It became operational in 2004 and it is owned by the Italian Ministry of Finance and the economy.

    see Polish Power Exchange

   1 billion joules, approximately equal to 948,000 British thermal units.

   1 billion watts

   1 billion watt hours

   global warming is the progressive gradual rise of the earth’s surface temperature, thought by many scientists to be caused by the greenhouse effect and responsible for changes in global climate patterns.

    H See Gestore del Mercato Electrico

   an order given to a futures broker that stays live until fulfilled, or until the close of the market, whichever is sooner.

   in the US, a clause in a contract that allows a prior law to take precedence over newly introduced legislation.

   a measure of the sensitivity of an option’s value to changes in the parameters used to value it. Greek measures include delta, gamma, rho, theta and vega.

   previously undeveloped site considered suitable for commercial development or industrial projects, but currently in its natural state or used for agriculture.

   an increase in global temperature caused when the earth’s atmosphere traps solar radiation. It occurs due to the presence in the atmosphere of gases such as carbon dioxide, water vapour and methane, which allow incoming sunlight to pass through, but trap heat radiated back from the earth’s surface. The burning of fossil fuels is thought by many scientists to be a major contributory cause of the greenhouse effect.

   an electricity transmission system.

    see system operator

    see good till the close