Un-netting Net Zero: part 2

Part 1 of this three-part series defined the various concepts that we often hear in climate-related discussions. Using a branch of Systems Thinking - System Dynamics, we translated those concepts into "states" which could be thought of as the greenhouse gas (GHG) reality of an entity at a point in time. As you read through the various definitions you probably registered that the four main states differ only in the degree of reduction and/or removal rates. As promised, in part 2 we will use basic System Dynamics theory to take a deeper dive into each state, understand why net zero is the generally agreed upon goal, and the fundamental importance of the "bathtub effect" which I first read about in Bill Gates' book, "How to Avoid a Climate Disaster". My wish is that after reading this article, you come out confident to discuss these and other concepts related to climate change.

Four main states

Absolute zero

Absolute zero means no greenhouse gas emissions are attributable to an actor’s activities. In other words an entity doesn’t produce any emissions, negating the need for any removal efforts. It's a GHG-free state. However, just because an entity claims absolute zero status doesn't mean it hasn't emitted any historic emissions. When thinking about these concepts and applying them in practice, you must acknowledge an entity's historic emissions inventory. Its emissions inventory is the cumulative amount of emissions that have already been released into the atmosphere over an entity's existence, contributing to what some might call the "bathtub effect".

The bathtub effect

The bathtub effect characterizes the nature of our climate. Once GHGs are released into the atmosphere they accumulate and stay there for a long time. What's a long time? Science tells us that the mixture of all these gases emitted today remain in the atmosphere well beyond any of our lifetimes.

CO2

Atmospheric CO2 is part of the global carbon cycle, and therefore its fate is a complex function of geochemical and biological processes. Some of the excess carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for anywhere between 300 to 1000 years.

Methane

Methane traps very large quantities of heat in the first decade (usually 12 years) after it is released into the atmosphere, but quickly breaks down. After a decade, most emitted methane has reacted with ozone to form carbon dioxide and water. This carbon dioxide continues to heat the climate for hundreds or even thousands of years.

Nitrous Oxide

Nitrous oxide molecules stay in the atmosphere for an average of 114 years before being removed by a sink or destroyed through chemical reactions. The impact of 1 pound of N2O on warming the atmosphere is almost 300 times that of 1 pound of carbon dioxide.

Fluorinated gases

Fluorinated gases have no natural sources and only come from human-related activities, but are the most potent and longest lasting type of greenhouse gases emitted by human activities. Although they exist in low atmospheric concentrations relative to other GHGs they remain in the atmosphere anywhere from 250 to 50 000 years.

Why is this important? Because the astronomical amount of GHGs constantly being released into the atmosphere (about 50 billion tons per year) resemble a giant bathtub that's slowly filling up with water. The problem is that this bathtub's outlet plug can't drain the water fast enough.

You might argue that the climate does in fact have a great "outlet plug" in the form of natural carbon sinks. You are absolutely correct. Prior to 1870, which saw the start of the second industrial revolution, the earth's natural carbon sinks kept the climate in a careful balance - and it took eons to get to that state. But post 1870, increased economic activity coupled with fossil fuel combustion caused more GHGs to be released and accumulate in the atmosphere than could be sunk naturally, causing the earth to warm at an unnaturally fast rate. The result? Global warming.

Let's return to basic System Dynamics theory and relate it to the earth's atmosphere. Let the bathtub represent the state of GHG emissions in the atmosphere. Water flowing from the tap represents the rate at which we produce emissions, and let the rate at which water can be drained from the outlet plug represent the earth's natural sinks. As I have explained, the rate at which the water is flowing out of the tap far exceeds the rate at which the outlet plug can drain the water. The plug simply wasn't designed for this. And it certainly doesn't help that the outlet plug is getting substantially smaller each year due to environmental degradation. No scenario depicts us reaching absolute zero. Fossil fuels are far too entrenched in the way we do things. So the point here is that even if we slow the rate of water flowing from the tap, the tub will continue to fill which means temperatures will continue to rise. Therefore, the disaster we have to prevent is the water spilling out onto the floor. In other words, to keep our rubber ducky in the bathtub.

The disaster we have to prevent is the water spilling out onto the floor.

Net zero

Being the internationally agreed upon goal for mitigating global warming in the second half of the century, net zero refers to a state in which the greenhouse gases going into the atmosphere are balanced by removal out of the atmosphere. It's easy to confuse with absolute zero. But, unlike absolute zero, net zero includes a removal rate so that any emissions produced are offset. Net zero is deemed important because this is supposedly the state at which global warming is maintained (it does not disappear though!). Taken from a textbook, this is correct: if global warming is proportional to cumulative greenhouse gases in the atmosphere, then removing all that we produce from a certain point in time will keep historically accumulated levels of GHGs stable, maintaining global warming levels.

I find it useful to break the term up into its constituents: "net" and "zero" to understand what it actually means. The "net" in net zero implies (and by extension admits) that greenhouse gases will continue to be created (although to a lesser extent) and the "zero" means that any emissions produced are removed from the atmosphere. Indeed, the "net" in net zero is important because it will be very difficult to reduce all emissions to zero on the timescale needed. The essence of this approach is on minimizing the rate at which emissions are produced and leveraging available removal strategies to balance any remaining emissions.

The 'net' in net zero is important because it will be very difficult to reduce all emissions to zero on the timescale needed.

What does achieving net zero status look like? Let’s assume a particular country has done all it can to minimize its emissions to 100 megatons per year, and it maintains this rate each year in the foreseeable future. The country would qualify as net zero at the specific point in time it starts removing emissions at an equivalent 100 megatons per year. This could be in two, five or ten years time, but it's the moment production equals removal - that's net zero. "Hard" or "permanent" net zero refers to this state of balance being sustained over subsequent matching time scales. In this instance the country would maintain the same production and removal rates each year for a number of years into the future and the result is that they cancel each other out. Importantly, it does not refer to any removal of the country's historical emissions inventory. Until the point in time when the rate of production equals the rate of removal, marginally more emissions will be produced and subsequently released into the atmosphere - not ideal. Using our bathtub analogy, net zero on a global scale means to slow the flow of water from the tap, increase the size of the outlet plug, and maintain the water levels short of spilling over. Until we get there however, the tap will continue to flow faster than we can increase the size of the outlet plug, adding to the bathtub effect. In reality, we will never reach true net zero and most likely get "near net zero". This is the most realistic and practical approach we have right now because it gives entities room to improve relative to their circumstances.

But time is of the essence - the bathtub is filling up...

GHG neutral

The term "GHG neutral" is similar to net zero but places emphasis on removal - implying an acceptance of unavoidable emissions. This applies to entities that, for some reason or another, cannot reduce the rate at which they produce emissions and use mechanisms like offsets to neutralize what they emit. The key point here is: a commitment to GHG neutrality does not require (or even necessarily imply) a commitment to reduce overall GHG emissions. A GHG-neutral business needs only to offset the GHG emissions it produces – even if those emissions are increasing - which opens up questions about the quality and accuracy of offsets - a topic for part 3.

A commitment to GHG neutrality does not require (or even necessarily imply) a commitment to reduce overall GHG emissions

In this state, the bathtub continues to fill up - rapidly - so the success of this approach is heavily dependent on maximizing the size the outlet plug using scientifically verifiable offset mechanisms that make a tangible difference to the state of atmospheric concentrations.

Carbon negative

Only after any of the above states have been reached, can an entity have the opportunity or start thinking about becoming carbon negative (or from a GHG perspective, "net negative"). It's a state in which the rate of emissions being removed is larger than the rate of emissions being produced. This is where the outlet plug drains water faster than water flows in. Sustaining a net negative state over time to reduce both present and historic lifetime emissions is top prize for any country or organization, not only because global warming is marginally reversed over time, but because entities removing and storing additional emissions can sell those on the market in the form of carbon credits to other entities who can offset their unavoidable emissions and buy themselves time.

Next up

In part 3, we will look at drivers - ways to influence the rate at which emissions are reduced or removed. This is where tangible change occurs because drivers are the actions entities can take to alter the state of emissions. But before we take action, we need to think about identifying and locating sources of emissions, a challenging and complex task considering how woven GHGs are into the fabric of our lives.