Climate and environment glossary – N–P

A–B | C–D | E | F–G | I–M | N–P | R–S | T–Z


neoliberalism: a policy approach or philosophy that is commonly defined as characterised by a belief in sustained economic growth as the means to achieve human progress, confidence in free markets as the most efficient way of allocating resources, an emphasis on minimal state intervention in economic and social affairs, and commitment to the freedom of trade and capital.

net zero emissions: referring to the world as a whole, the IPCC defines net zero emissions as follows: ‘When anthropogenic emissions of greenhouse gases (GHGs) to the atmosphere are balanced by anthropogenic removals over a specified period.’

There are different ways to measure ‘net zero’ depending on which GHGs are involved (eg global warming potential, global temperature change potential) or factors such as time horizon. Achieving net zero emissions involves reducing the GHGs of an organisation, business, product or individual as far as possible, then using offsetting techniques – such as tree planting, selling surplus renewable energy to the electricity grid or buying carbon credits – so that a net zero (balance of emissions and removals of GHGs) is achieved. See also carbon neutral.

Note: ‘net zero’ may be used by some as a form of greenwashing, if the claim is not substantiated by quantifiable removal over a specified period.


ocean warming: higher ocean water temperatures, resulting from increasing atmospheric temperatures and thus increased amounts of heat being absorbed by oceans. Warmer water leads to lower levels of oxygen in oceans, affecting marine plants and animals. The phenomenon of coral bleaching is attributed to ocean warming.

ozone and the ozone layer: a form of oxygen created by ultraviolet light from the sun which converts oxygen molecules (O2) into ozone molecules (O3). This conversion generally happens in the Earth’s stratosphere, where the gas forms the ozone layer (‘ozone shield’), which protects the Earth from the full force of the sun’s ultraviolet radiation. Ozone is also present in the lower atmosphere (troposphere), where it is created from the interaction of pollutants such as nitrogen oxides and volatile organic compounds (VOCs), resulting in smog and poor air quality that can contribute to human health problems (eg asthma).


Paris Agreement: a legally binding international treaty on climate change. It was adopted by 196 Parties (states that have signed up to the agreement) at COP 21 in Paris on 12 December 2015 and came into force on 4 November 2016. Its goal is to limit global warming to well below 2°C, and preferably to 1.5°C (see 1.5 degrees), compared to pre-industrial levels. To achieve this long-term temperature goal, countries aim to reach global peaking of greenhouse gas emissions as soon as possible to achieve a climate-neutral world by mid-century.