What does Net Zero mean?

What does Net Zero mean?

Net Zero (also referred to as 'carbon neutrality') refers to balancing city-wide carbon emissions with carbon reduction and removal activities.

What do we mean by ‘balance’?

Net Zero means achieving an equilibrium (a balance) between the greenhouse gases that are caused by human activity/put into the atmosphere and those taken out.

Long lived and short lived greenhouse gases

Greenhouse gases are gases in the Earth’s atmosphere that trap heat.

Global Net Zero emissions of long-lived greenhouse gases and stable or falling emissions of short-lived greenhouse gases are needed to stop global temperatures increasing.

Long-lived greenhouse gases accumulate in the atmosphere, so continued emissions of these gases leads to continually increasing warming.

Warming created by long-lived gases is not naturally reversible even with a timescale of decades to centuries.

Short-lived greenhouse gases such as methane affect the climate in different ways to carbon dioxide, with constant rates of emission leading to an approximately constant level of raised global average temperature but not continually increasing warming

What greenhouse gases are included in the Net Zero target?

Sometimes Net Zero refers to carbon dioxide (CO2) only and sometimes it refers to all greenhouse gas (GHG) emissions.

There are seven main GHGs that contribute to climate change:

  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Nitrous oxide (N2O)
  • Hydrofluorocarbons (HFCs)
  • Perfluorocarbons (PFCs)
  • Sulphur hexafluoride (SF6)
  • Nitrogen trifluoride (NF3)

Each GHG has differing warming impacts depending on how long they remain in the atmosphere and how effective they are at retaining energy – this is their global warming potential (GWP).

With the exception of water vapour, CO2 is one of the largest global GHG (accounting for up to 81% of global emissions) and remains in the climate system for a very long time, causing increases in concentrations that will last for thousands of years.

CO2 is commonly used as a reference greenhouse gas for determining Net Zero targets and in accordance with international norms, Newcastle will adopt the same approach.

In order to capture the impact of other GHGs, in many places throughout the Net Zero Newcastle: 2030 Action Plan, carbon dioxide equivalent or CO2(e) is used which is a universal unit of measurement to indicate the GWP of GHGs, expressed in terms of the GWP of one unit of carbon dioxide.

In all cases, we will use the UK Government’s GHG conversion factors which are published every year to determine the applicable CO2(e) figure.

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