Why the obsession with “Net Zero”?

Why are we obsessed with extracting the last drop of carbon emissions? The zero approach is neither necessary nor desirable.

During the Industrial Revolution, humans began to use large quantities of fossil fuels. Those fuels are the product of the photosynthesis of plants and algae that removed carbon dioxide from the atmosphere millions of years ago.

The emission of carbon dioxide by burning, its sequestration by photosynthesis, absorption in the ocean, and reactions that combine CO₂ with rocks are a natural cycle that has been happening for millions of years.

By burning carbon that was sequestered millions of years ago humans have upset the balance of CO₂ in the atmosphere. The natural removers of CO₂ cannot keep up with the rate of emission, so the amount of CO₂ in the atmosphere increases.

CO₂ is a greenhouse gas, it absorbs radiation from the earth and reflects some of it to the earth, acting like a blanket to keep the earth warm. Without this blanketing effect, the earth’s average temperature would be close to zero degrees Celsius and life as we know it would not exist.

A group of scientists have attempted to model this effect using sophisticated computational techniques that most of us don’t understand, and they have come up with forecasts that claim the earth’s average temperature will rise if we continue to burn fossil fuels. There appears to be less agreement on the degree to which the temperature will rise. Models with different assumptions lead to very different predictions, but there is a consensus that forecasts a rise in the earth’s average temperature.

Temperature measurements over the past 150 years or so have identified a slow warming trend, but there is no way to reliably determine how much of that warming trend is a result of the human-caused increase in CO₂ emissions. However, the baseline for those temperature readings is the mid-nineteenth century which is known to have been an unusually cold period sometimes referred to as the Little Ice Age.

Most of the developed world has responded by committing to cutting carbon emissions. Several countries have committed to a target of “Net Zero” emissions by the year 2050. To achieve those targets, they will have to spend vast sums of money replacing fossil fuel-based heating systems, rebuilding electricity generation and distribution networks, modifying industrial processes, and replacing fossil-fueled transportation.

The relationship between the cost of reducing carbon emissions and the emissions eliminated is not linear. The tree has low-hanging fruit that can be plucked while standing on the ground, and there is fruit at the top of the tree that can’t even be reached with the longest ladder.

Take, for example, electricity generation. In a sunny climate, it is a simple job to supply 30% of your electricity from solar panels. Getting from 30% to 60% is much more expensive, you need to store electricity generated during the day and use it at night, and storage is expensive. Getting from 60% to 90% is even more expensive, you must overbuild so that you have enough supply in winter, and you need high-volume long-term storage that will include converting the electricity to chemical energy and back with massive loss of efficiency.

Similarly, private cars can easily be electrified but long-haul trucks are more difficult, and decarbonization of air transport will be very expensive.

The final 10% of the energy transition will probably be an order of magnitude more difficult and costly than the first 10%. But it won’t provide ten times the benefit.

At some point, there must be a cut-off where the costs exceed the benefits.

Climate scientists are telling us that the earth has become 1.5 degrees C warmer than it was in the middle of the nineteenth century. But even now, more people are killed by excessive cold than excessive heat.

Humans live and thrive in a wide range of climates. Can anyone say, definitively, that the climate is worse overall for the human race now, than it was in 1850? I think most of us would prefer today’s climate over that of the Little Ice Age.

Is anyone able to tell us what is the optimum average earth temperature for humans to thrive? A resident of Saudi Arabia may have a very different opinion compared to a resident of Siberia.

About 50% of the human-caused CO₂ emissions are removed naturally every year. The earth is now greener, plant growth has increased because there is a higher concentration of carbon in the atmosphere. Tomato growers have known about this phenomenon for many years, they inject carbon dioxide into their greenhouses to promote plant growth.

The natural sequestration of carbon is also increasing. Like many natural systems, the rate at which carbon is removed from the atmosphere increases when there is a higher concentration of CO₂.

If we were to stop emissions of CO_2, the concentration in the atmosphere would gradually return to the levels seen before the industrial revolution. The earth would get colder, plant growth would slow, and fewer people would die of heat, but more would die of cold.

Is that what we really want? Or would we prefer something closer to today’s weather?

The International Panel for Climate Change (IPCC), widely regarded as the leading authority on the subject, publishes progress reports and predictions for policymakers. You might be surprised to find that the latest report (AR6) does not require the complete elimination of carbon emissions by 2050 to maintain the earth’s average temperature within a range that is acceptable for human living. Here’s a chart from that report.

That chart shows that limiting global warming to 2^oC above the baseline still allows for emissions in 2050 to be about 20 GtCO₂ equivalent per year, or about 35% of existing emissions.

In business, there is a rule known as the Pareto principle, which says that 80% of the benefit of an action comes from 20% of the effort (or something to that effect). Whether the 80/20 split applies to decarbonization or not is arguable, but it is quite clear that the last 20% of emission reduction will be more difficult to achieve and more costly than the first 20%.

Instead of blathering on about Net Zero and Just Stop Oil, would it not be better to set achievable targets that could be attained at a reasonable cost? Is the Net Zero approach a case of letting the perfect be the enemy of the good?