Telecommuting refers to a work arrangement where an employee communicates with work colleagues or other personnel via telecommunications technologies such as the internet or phone, instead of travelling to a central workplace.  An employee that telecommutes may work from home or choose to work from other locations such as a library or coffee shop.

Terrestrial sequestration refers to using land such as agricultural areas and forests, as areas for carbon storage.  This process takes place during photosynthesis, as carbon from atmospheric carbon dioxide is converted into components necessary for plants to live and grow.  Plants may retain the sequestered carbon for a long period of time, however once the plant dies, the plant material decomposes and the carbon is released.  Terrestrial sequestration benefits the environment by mitigating greenhouse gases and improving water, soil and habitat.

The Earth Charter is a global declaration of fundamental ethical principals promoting sustainable living, sustainable human development, ecological respect, social justice, and a culture of peace and democracy in the 21st century.  The charter began as a United Nations initiative, but it was carried forward and completed as a people’s charter in 2000 by an independent international entity known as the Earth Charter Commission.

The Stern Review on the Economics of Climate Change was released by economist Nicholas Stern for the British government in 2006.  This report is a comprehensive, well-known study into the effects of global warming and its impacts on the world economy.  The key findings of the report conclude that the benefits of strong, early action on climate change far outweigh the environmental and economic costs of prolonging action. 

Thermal mass refers to a building’s ability to absorb and store heat energy, and then to release it slowly at a later time.  The addition of thermal mass materials to a structure helps to improve comfort for building occupants by reducing the need for artificial heating and cooling.  Concrete and bricks are commonly used as thermal mass materials in a structure.  The use of insulation and passive solar techniques also help to maintain a steady comfortable temperature inside whilst incurring as little energy costs as possible. 

Thermal Performance refers to how well a building responds to external high and low temperatures during daily and seasonal cycles.  This level of performance will dictate how comfortable the building interior will be to the buildings occupants.

Thermal pollution refers to urban water runoff that has an elevated water temperature, and may potentially harm aquatic organisms in surface water.  This may include discharged heated water from industrial process, or stormwater runoff from roads and parking lots.

Thermal resource refers to a facility that generates electricity by using a heat engine to power an electric generator.  The heat may be provided by the combustion of coal, oil, natural gas, biomass, or other fuels, such as solar or geothermal resources.

Thermal storage refers to technology that collects excess energy for later use.  For example, the heat obtained in summer from a solar collector can be stored for winter heating or hot water.  Alternatively, cold air obtained in winter can be used for summer air conditioning.  Thermal storage mediums include heat storage in tanks or rock caverns, hot rocks, concrete and native earth; electric thermal storage heaters; ice-based technology; cryogenic energy storage; and molten salt technology.

Third generation biofuels are produced from non-food feed stocks such as microalgae, which is a fast-growing algae.  Biofuel is considered to be one of the most sustainable alternative sources to petroleum as it does not compete with food or feed crops, and can be grown cheaply in oceans or on non-arable land.  Several technological and economic challenges exist to create a market for third-generation biofuels. 

The term threatened species refers to wild species of flora and fauna that are vulnerable, and are expected to become endangered within the future because of a decline in numbers.

Tidal power is a form of hydropower and refers to electricity generated by capturing the tides movement.  While tidal power is more predictable than solar or wind energy, it is not well utilised at it is expensive to produce and has a limited availability of sites with sufficiently high tidal ranges or flow velocities.

Titanium dioxide (TiO2) occurs in nature as well-known minerals rutile, anatase and brookite.  It is utilised in a range of applications including paint, sunscreen, cement, windows, tiles, food colouring, or other products requiring sterilising or deodorising properties.  Titanium dioxide causes major ecological impacts as it is sourced primarily from sand mining, which damages sensitive coastal dune systems. 

Toluene is a clear, sweet smelling liquid mostly derived from crude oil.  It is commonly used as component of petrol, and is also found in solvent, paint thinner, industrial feedstock, lacquers, adhesives, rubber and cleansing agents.  Toluene has been identified as carcinogenic by the International Agency for Research on Cancer (IARC).  It is highly flammable, irritating to skin, damaging to lungs if consumed, and may cause drowsiness, dizziness, or severe neurological harm if inhaled.  It is also associated with the possible risk of harming an unborn baby and may cause serious damage to human health by prolonged exposure. 

Tonnage is a measurement used to determine waste generation rates.  It can be applied to the amount of waste, recycling or organic materials collected within a locality, or it can refer to the amount of waste that a landfill accepts in accordance with its permit.  Tonnages are commonly expressed in tonnes per month. 

Toxic refers to a substance that is harmful to environment or living organisms via ingestion or absorption, and may cause sickness, death, disease, or birth defects.

A toxic cloud is an airborne plume of gases, vapours, fumes, dust, mist or aerosols that contain toxic materials.

Toxic sites refer to land areas that are contaminated with toxic pollution as a result of industrial processes or waste disposal.  These sites are generally unsuitable for human habitation or for growing food.

Toxicity refers to the degree to which a chemical substance or mixture of substances can adversely affect living organisms.  Acute toxicity produces harmful effects through a single or short-term exposure, while chronic toxicity causes harmful effects over an extended period, usually upon repeated or continuous exposure. Subchronic toxicity refers to a substances ability to produce harmful effects for a period of more than one year, but for less time than the exposed organism’s lifetime.

Trace elements naturally occur in small amounts in the earth’s crust.  In living organisms, trace elements are essential for normal metabolism, growth and development. 

A trace gas refers to one of the minor gases present in the Earth's atmosphere, and includes all gases except for nitrogen and oxygen. 

Tragedy of the commons is an economic term referring to individuals that try to acquire the greatest benefit from a resource for their own self-interest.  As resource demand overwhelms the supply, the resource becomes harder to access and may be no longer available for additional users of the resource.  An example of this is the use of fossil fuels in western countries, and the increased use of fossil fuels by developing nations to improve living standards, which may eventually reduce the living standards for all global citizens.

Transboundary pollution refers to pollution that travels from its country of origin to another one, crossing local or international boundaries.  This type of pollution often relates to air and water pollution, and is damaging to the environment in both developed and remote areas.

A transfer station is a facility where solid waste, recyclables, organics and hazardous materials are collected and sorted before being transferred to a landfill, recycling facility or hazardous waste facility.

Transportation control measures (TCMs) refer to programs or activities implemented within a locality to reduce emissions from motor vehicles and trucks, to improve air quality.  Initiatives may include encouraging public transport use and carpooling, improving bus and bicycle lanes, and encouraging utilisation of emission control technology improvements in motor vehicles.

Tree free refers to papers that are produced from sources other than trees including flax, bamboo, hemp, bananas, cotton and agricultural residues such as sugarcane, husks and straw.

Triethanolamine is used as a pH adjuster, fragrance ingredient, buffering agent and surfactant in nearly all beauty, hair and skin care products. 

Studies have shown strong evidence that Triethanolamine is an allergen and potentially toxic. Regulations do exist in how much TEA can be included in personal care products. 

Triple bottom line is a concept that replaces the traditional business bottom line of financial profit with a system that considers social, financial and environmental outcomes.  The triple bottom line approach is commonly referred to as people, profit, and planet.

A trombe wall is a sun-facing wall separated from the outdoors by glass with an air space and solid, dark masonry wall behind to absorb and re-radiate heat.  The wall heats up slowly during the day, and then as it cools during the night, it gradually gives off its heat inside the building.

Turbidity refers to a reduced water clarity or cloudiness, caused by the presence of suspended material or organic matter in the water.  Turbidity is an indicator of poor water quality.