What is Net Zero?

This was set out in the UNFCC Paris Agreement on Climate change as an objective (Article 4) In order to achieve the long-term temperature goal (set out in Article 2) as 1.5-2 degrees, Parties aim to reach global peaking of greenhouse gas emissions as soon as possible, … and to undertake rapid reductions thereafter… so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases.


The Paris Agreement requires net-zero GHG emissions globally in the second half of the century. The UK interpretation is that all greenhouse gases (GHGs) contribute to climate change and must be reduced substantially to meet the Paris temperature goal. To stabilise global temperatures, emissions of long-lived gases like CO₂ must be reduced to net-zero. Emissions of short-lived gases like methane must be stabilised, but need not reach net-zero.

The UK target is for all greenhouse gases. Morever, the aim should be to meet the target through UK domestic effort, without relying on international carbon units (or ‘credits’)

Carbon Credits

The concept of netzero recognises the balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases. Various forms of carbon removal in carbon sinks can be used in various forms can be used to generate carbon credits to offset residual carbon emissions. When applied to an isolated system like a building or campus development then the netzero position, then requires carbon accounting of the of carbon emissions and the validity of any carbon credits. There are well developed protocols for carbon accounting at the organisational and building operational levels. For reference Greenhouse Gas Protocol

The GHG Protocol Corporate Standard classifies a company’s GHG emissions into three ‘scopes’. Scope 1 emissions are direct emissions from owned or controlled sources. Scope 2 emissions are indirect emissions from the generation of purchased energy. Scope 3 emissions are all indirect emissions (not included in scope 2) that occur in the value chain of the reporting company, including both upstream and downstream emissions. A similar approach can be taken with the built environment.

Scope 1 would be sources which are direct emissions from owned or controlled sources, usually energy supplies like gas and diesel supplies brought on on site, but would also include emissions from company vehicles and fugitive emissions such as leakage of refrigerant gases and any industrial process emissions.

Scope 2 refers to the carbon intensity associated with purchased energy, that have indirect emissions associated with them such as grid electricity but would also include heat, chilled water and steam if delivered from a third party.

Scope 3 then includes Purchased goods and services, Business travel, Employee commuting Waste disposal, Third party transportation and distribution.

In Netzero3 where we explicitly look at the emissions associated with heat power and transport then emissions can move between scopes. For example, electrifying heat will move heat from scope 1 to scope 2, while provision of electricity for transport may move emissions from scope 1 or scope 3 to scope 2 depending on what vehicles are involved.

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