Environment
Climate, sustainability, ecology, conservation, and environmental science
The Montreal Protocol: How the World Agreed to Save the Ozone Layer
The Montreal Protocol (1987) is the international treaty that phased out ozone-depleting substances — the only UN treaty ratified by all 198 member states.
CFCs: The Miracle Chemicals That Tore a Hole in the Ozone Layer
CFCs were widely used refrigerants and propellants until the discovery that they destroy stratospheric ozone — their ban under the Montreal Protocol is history's most successful environmental treaty.
Scope 1, 2, and 3 Emissions: The GHG Protocol Accounting Boundaries
The Greenhouse Gas Protocol divides corporate emissions into Scope 1 (direct, on-site fuel and process emissions), Scope 2 (purchased electricity and heat), and Scope 3 (everything else in the value chain). Scope 3 typically dwarfs the other two for technology and consumer brands.
The Coal Question
The Coal Question (1865) is William Stanley Jevons's book on Britain's coal dependence. It argued that exponential coal demand against a finite geological stock would undermine British industrial leadership, and — in its most lasting contribution — introduced what is now called the Jevons paradox: that efficiency gains in fuel use tend to increase, not decrease, total consumption.
Jevons Paradox
The Jevons paradox is the 1865 observation by William Stanley Jevons that improvements in the efficiency of resource use tend to increase total consumption of that resource, because lower effective prices expand the range of profitable applications faster than per-unit savings can contract them.
William Stanley Jevons
William Stanley Jevons (1835-1882) was an English economist and logician, a central figure in the 1870s marginal revolution and the founder of energy economics. He is best remembered for the marginal utility theory of value, the 1865 book The Coal Question, and the Jevons paradox on efficiency and consumption.
The Kigali Amendment: Phasing Down the Greenhouse Gases That Replaced Ozone-Killers
The 2016 Kigali Amendment to the Montreal Protocol requires an 80-85% global phase-down of HFC refrigerants — potent greenhouse gases — estimated to prevent 0.5°C of warming.
HFC Refrigerants: Ozone-Safe but Climate-Damaging, Now Facing Global Phase-Down
HFCs replaced ozone-depleting refrigerants but turned out to be potent greenhouse gases, now subject to an 80-85% global phase-down under the 2016 Kigali Amendment.
HCFC Refrigerants: The Transitional Chemicals That Still Depleted the Ozone Layer
HCFCs were transitional refrigerants that replaced ozone-destroying CFCs in the 1980s but still caused ozone depletion, now being phased out globally by 2030.
Life Cycle Assessment (LCA): Quantifying Environmental Impact from Cradle to Grave
Life Cycle Assessment is a standardized method (ISO 14040/14044) for quantifying the environmental impact of a product across all stages of its life: raw materials, manufacturing, distribution, use, and end-of-life. It underpins embodied-carbon claims and eco-labels.
Embodied Energy: Cradle-to-Gate Energy in Materials and Products
Embodied energy is the total primary energy consumed across raw-material extraction, processing, manufacturing, and transport before a product leaves the factory gate. It is the backbone metric for lifecycle assessments comparing materials, buildings, and electronics.
Cooling Tower
A cooling tower rejects waste heat to the atmosphere by evaporating a small fraction of recirculated water. They are widely used in power plants, large HVAC systems, and data centers because evaporation moves heat far more efficiently than dry air exchange, but they consume water and require chemical treatment.
Rebound Effect (Energy Economics)
The rebound effect is the difference between projected and realized energy savings from an efficiency improvement, caused by lower effective prices increasing demand. It has direct, indirect, and economy-wide components; when economy-wide rebound exceeds 100% the situation reduces to the Jevons paradox.
The Green Grid
The Green Grid is a non-profit industry consortium, founded in 2007, that develops data center efficiency metrics including PUE, WUE, and Carbon Usage Effectiveness. Its definitions have since been adopted as ISO/IEC 30134 standards.
Embodied Carbon in Computing Hardware
Embodied carbon is the greenhouse-gas emissions released to manufacture, transport, and eventually dispose of a piece of hardware — distinct from {{operational carbon}} burned while the device runs. For modern {{GPU}}s and AI accelerators, embodied carbon can be a large fraction of lifetime emissions.