• Graham Harris

When is zero not zero? Or, why you need to understand 'net zero'.

While working on a municipal GHG inventory recently, I got into an illuminating discussion with my client about the meaning of the term 'net zero'. My client municipality has committed to achieving net zero GHG emissions by 2050 - good on them! - but what does this really mean? Having calculated their total GHG emissions footprint, completed a Business As Usual forecast and projected the impact of their existing targets, it was clear that despite their progressive intentions, they still have a way to go to reduce their GHG emissions to zero.

And that's where we started to get into the meaning of net zero. Because net zero is not the same as absolute zero.

Indeed, through this discussion, it occurred to me that this is a term that is often used when we talk about the need to reduce our carbon footprint, but that the subtle distinctions of its meaning are often not appreciated, even by professionals in this area.

I believe this is a particularly important term to understand and to communicate, especially given the 'its either the environment or jobs' narrative that is frequently employed by those who resist actions to reduce carbon emissions.

For example, for someone who works in the fossil fuel industry and understands that the climate change goal is absolute zero emissions, resistance to action is not surprising. After all, it sounds like a goal that guarantees their unemployment. If the goal was indeed absolute zero, then no GHG emissions could be emitted. At all. Ever. So absolutely no combustion of fossil fuels. Absolutely no methane releases from decomposing waste in landfill. Absolutely no leakage of SF6 from high voltage switchgear. And so on.

On the other hand, net zero, while still a challenging target, is achievable and permits a level of flexibility in how we reach our ultimate goal. Why? Because with a net zero target, any GHG emissions released need simply to be matched by GHG removals. The intention is not to eliminate all GHG emissions completely, but to ensure that the stock of GHGs in the atmosphere does not increase. In other words, 'net zero' implicitly recognizes the role that carbon sequestration plays - and will need to play - in successfully reaching our climate change goals.

Understanding this distinction is particularly critical for industries and communities that currently see no viable pathway to reducing their carbon footprint to zero. With an absolute zero target, it is indeed hard to see any long term future for the fossil fuel industry. But under a net zero target, the industry has a path forward - reduce emissions as far as possible, then remove emissions from the atmosphere to balance those remaining.

I invite you to inject this into the discussion the next time you hear someone saying that achieving zero emissions is impossible, or that the only way to achieve zero is the complete shutdown of an industry! Because from a climate science perspective, the only zero that matters is net zero.

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