Can We Reach Net-Zero Carbon Emissions?
We are merely delaying the inevitable. What would it take to actually stop global warming?
Earth is rapidly approaching a temperature limit that it should never reach. We are already functionally at 1.5 °C above preindustrial levels, and we are headed toward a 2 °C rise. That would result in more droughts, famines, species loss, sea-level rise, and flooding, and in more intense hurricanes. We do not want to go there.
And to be quite clear, we humans are the cause. We have been burning fossil fuels (coal, oil, and natural gas) at ever-higher rates, polluting the air with excess carbon. Through the years, this carbon has accumulated in the atmosphere, driving temperatures upward.
Perhaps some of you reading this will dispute that. You might claim that the Earth is not heating, or, if it is heating, it is not caused by us, or, even if we are causing it, it isn’t so bad. If that is your argument, and you have an open mind, you can read more about climate change here, here, here, here, here, here, and here. The rest of us will move on.
We should commit to never going above that 2°C limit. To do that, the Global Carbon Project estimates that we need to either limit total net future emissions to less than about 300 GtC (billion tonnes of carbon) [1] or somehow remove any carbon we release beyond that amount. That is a big task. Currently, burning fossil fuels and producing cement adds about 9.8 GtC of additional carbon to the environment each year. Also, changes in land use, such as deforestation, add an additional 1.4 GtC.
In total, we are adding about 11.2 GtC per year. Quick math says we would reach our budgeted 300 GtC in about 27 years. That’s 2053.
The Global Carbon Project has been tracking our condition. The chart below shows the rate at which we have been adding carbon through fossil fuel and cement processing emissions (shown in gray), and the rate at which emissions from land-use changes such as deforestation have contributed (shown in orange). The bottom of the chart shows that this carbon ends up in the atmosphere, the land, and the oceans.
The transfer of carbon to the land and sea is complex. The Global Carbon Project concludes that the rate at which the sea absorbs carbon from the atmosphere is remarkably constant, at about 27% of all new carbon we add to the air. The land also absorbs carbon at a “broadly constant” rate of 23% of all new carbon added. But the land sink varies considerably.
It is tempting to look at the carbon budget figures above and conclude that, if we only reduce our output in half, the land and sea will absorb all that we put into the atmosphere. That is not what the Global Carbon Project concludes. Rather, if we added carbon at half the current rate, the land and sea would absorb it at about half of that rate. So, knowing that about half of the carbon we add will remain in the atmosphere, and knowing the limit of what we can leave in the atmosphere, we can budget the total we can safely add.
Let’s suppose that, after an ambitious program to reduce carbon output, we cut our annual output in half. Yeah! But, unfortunately, even if we lower that 11.2 GtC figure to 5.6 GtC, all we have done is double the number of years it takes to reach the somewhat arbitrary 300 GtC limit. Is it a good thing to delay the pain from 27 years to 54 years? Yes. But what we really need to do is to bring that emission rate down to zero. Any number that makes the rate of change of carbon in the atmosphere significantly higher than 0 eventually drives us to the limit.
Putting on the Brakes
Here is a chart showing the rate at which we have been releasing carbon in the last 65 years.
Notice that we are not only adding carbon, but each year we add carbon at about 0.07 GtC/year faster than the year before. In other words, we not only accumulate carbon, but we are accelerating the rate at which we accumulate carbon. If we continue to increase our emission rate, we will reach the 2 °C temperature rise even faster than the previously mentioned 27-year timeframe.
But there is some good news. In 2025, for the first time, the increase in alternative electricity generation exceeded the increase in electricity demand. Environmentalists cheered. That was good, yes. But keep it in perspective. We did not reduce the cumulative carbon in the air that came from years of generating electricity. In fact, we even continued contributing carbon from electricity generation at about the same rate as the previous year.
But we stopped accelerating.
If you are driving at full speed toward a bridge that has just collapsed, then decreasing the acceleration rate is not that helpful. You need to actually slow down. You need to hit the brakes.
And if you hit the brakes, you may or may not stop before you get to that collapsed bridge. Can we stop in time? That, my friend, is the question before us. Hence, this post.
A Carbon Reduction Plan
In 2024, we released about 11.6 GtC into the environment. Let’s say we hold that rate steady through the end of 2027, and then, beginning in 2028, we reduce the emissions rate by 0.25 GtC per year. We would then reach net zero in about 48 years after having released 285 GtC. That’s not great, but at least it should keep us from exceeding the 2 °C threshold.
We could perhaps keep on track to meeting this goal by using a global cap-and-trade program. Every month, each person on Earth would get an equal amount of carbon credits, allowing them to release that amount of carbon that month. If they don’t use their budgeted amount, a payment equal to the market value of those carbon credits would go to their bank account. Other people could then buy those unused credits at the going market price. Power companies and manufacturing facilities would need to buy these credits to run their businesses.
An immediate issue is that this creates an enormous wealth transfer, in which the richest countries would be forced to pay the poorest countries so that the wealthiest could continue to release high amounts of carbon. Most rich countries would never accept such a plan.
Perhaps we could somehow change the carbon credits so that people were awarded credits based on current usage. Countries that currently use a lot of carbon would get more credits for future use. Poor countries, of course, would find this proposal enormously unfair. Could we ever find basic limits that nations would agree with?
And if countries found it advantageous to opt out, could we ever enforce the plan? If we can’t enforce it on everybody, what does it accomplish?
A variation of the cap-and-trade scheme is a fee-and-dividend system, which charges a fee for producing the fossil fuels that cause carbon pollution, with the income then distributed to the people. It has the same basic effect: those responsible for large carbon releases end up paying those who release less, encouraging conservation. But again, we end up with a massive wealth transfer from the rich to the poor.
Perhaps instead of a global system, we simply establish limits for each country, and it would be up to each to find a way to keep its emissions below that limit. The leaders could, perhaps, set up their own cap-and-trade system within their country. If a rich country wanted to use more than it had been allotted, it could perhaps buy the right to emit carbon from poorer countries that could sell it credits.
But we run into the same problem. If carbon emission limits are based on population, industries in wealthy countries would be forced to make an enormous wealth transfer to poorer countries. And poor countries do not want to be told they get fewer carbon credits, which could force them to give up many benefits of industrial life.
On the other hand, the need to limit fossil fuels might get forced upon all of us. The war in Iran has shut down the Strait of Hormuz and destroyed much energy infrastructure. Meanwhile, the war in Ukraine is resulting in serious damage to Russian energy infrastructure. We are facing looming shortages that will probably force us to cut back on the fuel we burn. These shortages may lead to a long-term reduction in fuel availability. So, paradoxically, this war may be helping save our planet.
But this forced shortage, if it continues, can lead to a recession. It is not what most people prefer.
Wealth Reduction
Another way to look at our carbon emissions is to examine the year-to-year change in the emission rate, as shown in the chart below. Yes, in the past 100 years, there were some years when we emitted less than the year before. Shall we cheer? Yes, but notice that, in each such year, there was an economic downturn, such as the 2008 financial crisis or the COVID-19 pandemic. And so, we find we can reduce carbon emissions when bad things happen to the economy. What we want to do is reduce carbon emissions in years when the economy is going well. Can we do that?
Source: Friedlingstein et al 2025; Global Carbon Project 2025, in GCP CarbonBudget 2025 slides at Global Carbon Budget | GCB 2025
We do not like emission reductions that are caused by recessions. Rather, we would like to change a few light bulbs, install better home insulation, and mount a few solar panels, finding that we then emit sufficiently less carbon. But how could we ever do enough such changes to reach a net carbon output of zero? That is what we want: net-zero.
The solutions to global warming that we will look at here all have some unpleasant ramifications. It becomes a matter of choosing the least of all evils.
We must leave no option off the table. The first option I just presented, global wealth reduction, would be hugely unpopular. But, as we will see, all options have negative ramifications. And so, we must leave no option off the table.
Did I just put an economic downturn on the table as something to consider? Reluctantly yes. We must consider this if we find nothing better.
But enough said. Let’s quickly move on.
Alternative Energy
Yes, we can build solar panels and windmills, and yes, costs are coming down. The use of alternative energy in electricity generation has expanded exponentially. As a result, fossil fuels for electricity have leveled off (gray area in chart below), while renewables accounted for all growth in electricity last year (green area below).
But clean energy has a dirty problem. To get the materials we need, we are bulldozing paradise and destroying glaciers. A dark mountain casts its shadow over human progress. Perhaps we are saving people from dangerous heat, but we are also leaving deep scars on the Earth.
We are not mining with renewable energy. Instead, we mine with diesel-powered equipment. Yet we are seeking to become carbon neutral. If it requires diesel equipment to produce alternative energy devices, that is not net-zero. The process releases carbon. The carbon footprint for the same amount of end-use energy is lower when we use renewables, but it is not net-zero.
We won’t always have cheap diesel fuel. Solutions that rely on diesel fuel may work in the short term, but they cannot be the long-term solution. Petroleum will not last forever. And it will not be long until we see diesel shortages. Building renewables without this diesel power is a much harder problem. Without abundant oil, can we even transition to a new economy?
In the carbon budget I suggested above, I show it level through 2027, and then we reduce. Part of the reason for that 2-year delay is that it will take a lot of energy to build alternative energy systems. We would end up with less usable energy for other things, for we would be committing a lot of energy to building alternative energy.
Even with today’s supply of diesel fuel, we are not keeping up with all we would need to do to build an alternative energy system.
For instance, one estimate says that the U.S. requires 5000 miles of additional high-voltage lines annually. But from 2022 through 2025, we have built only 392 miles total. We are nowhere close to the effort it would take to do renewables right.
Renewables require a lot of copper. But we already face a copper bottleneck that could derail the energy transition. Other materials are also in short supply, including aluminum, lithium, steel, coal, and silver. Are we reaching the peak of everything?
We have been adding renewable energy to service the new demand for electricity. New demand means more income. New customers can pay those costs for new solar panels. But now, we have the less easily justified task of retiring existing generating capacity and replacing it with renewables. That does not have the advantage that the new generators had when they were paid for by increases in revenue stream.
The chart above was just for electricity. Now compare that with the chart below for transportation. See that tiny blue area at the top? That is the fraction of transport power that comes from electricity. All the gray area represents burning fossil fuels directly to power transport.
Uh oh.
We still rely on fossil fuels as our main power for transportation. Sure, there are some electric cars, but there are few electric long-haul trucks, ships, airplanes, farm tractors, or construction machines. These needs are dominated by fossil fuels, and we are still a long way from electrifying them. And even the electricity used to power electric cars comes largely from fossil fuels.
The chart below shows our overall energy picture. We still rely on fossil fuels. We use more each year. Renewables are handling some of the growth, but renewables are not causing us to use less fossil fuel.
Nuclear Power
Nuclear power has stalled, with little new growth since 2000. The global share of electricity from nuclear power keeps dropping.
Few new plants are being built, and many existing plants are nearing retirement. Per the World Nuclear Industry Status Report 2025, nuclear plant closures (shown in brown below) are expected to exceed planned new construction (shown in blue).
Surely entrepreneurs must know that we will be desperate for clean energy solutions in the coming decades. So why aren’t they building more nuclear facilities?
One reason is that nuclear power simply costs too much. Solar and wind power are less expensive.
The above estimate of the rate at which we will be retiring old plants could be wrong. Perhaps we will push to keep old plants in service longer. But old nuclear plants are subject to many scheduled and unscheduled outages. This makes it difficult for power companies to maintain grid reliability.
For instance, the Palisades nuclear plant in Michigan was retired in 2022. Now the power company is trying to restart that plant but is finding it much harder than expected. This illustrates the problem with aging plants. If we find it is not practical to keep them running, and we retire them at the rate the World Nuclear Industry Status Report predicts, where is the effort to replace them with new plants? If we cannot even replace what exists, how is nuclear going to become a game-changer in the future energy balance?
Nuclear power plants often take more than 10 years to build. Even if we started planning new sites today, it would be a long time before new plants could help us. If we want to replace plants that will soon be retiring, we should have started thinking about it 15 years ago.
One cause of nuclear energy’s problems that I constantly hear is government regulations. Which regulations?
Get Merle, ret. P. E.’s stories in your inbox
Join Medium for free to get updates from this writer.
Government is good. So I don’t buy the assertion that all regulations are bad. My take on regulations is that where they are beneficial, we should keep them; where they are not, we should drop or change them.
Given the urgent need for power that doesn’t release more carbon, I agree with reviewing regulations and seeing whether they still make sense in light of that demand. When we look at the path forward in energy, we are often forced to choose the least of many evils. In many cases, nuclear energy may be the least evil. So, we must make sure we are not unnecessarily hindering nuclear power.
Another reason power companies may hesitate to build nuclear plants is waste disposal. Plants have not been able to find a place to accept the waste, so they store it on-site in pools or sealed in steel containers in vaults. This has not caused any major problems so far, but it is an accident waiting to happen. Electric companies may be hesitant to build nuclear plants, knowing that they will be saddled with the liability of dangerous nuclear waste for centuries after the fuel has outlived its usefulness.
Energy Storage
Electrical power supply and demand need to always be kept in balance. If the supply exceeds the demand, generators speed up, resulting in overvoltage. If the supply cannot meet the demand, generators slow down, resulting in a voltage decrease. Both conditions change the line frequency, which may then go out of spec. So, we need some way to balance things out.
Much of the alternative energy in use today simply supplements the existing electrical grid. Thus, we have fossil-fuel-powered plants we can throttle, including specific peaking power plants. These serve as backup for when the wind stops blowing on the windmills or the sun doesn’t shine on the solar panels. And we can keep nuclear plants running at close to full power overnight (because that is how nuclear facilities are most efficiently run), even though overnight demand for that power might be low. Nuclear and renewable energy don’t do a good job of balancing supply and demand. So instead, we throttle fossil fuel plants to control the grid power.
But if we try to go carbon neutral and get all our electricity from renewables, then we need special plans to balance supply and demand without natural gas plants.
We can add large flywheels to handle variations on the millisecond timescale, batteries on the minute timescale, and pumped hydro on the day timescale.
But batteries are expensive and require large quantities of materials. Most batteries use graphite, which is usually made from petroleum. So, if we use a large amount of petroleum to make our batteries, we are not truly carbon neutral.
Pumped hydro is an interesting solution. When too much power is generated, the excess is used to pump water into a high mountain reservoir. If too little power is available, water runs down a pipe from the mountain and drives generators. The costs are huge, but they still have potential for maintaining an alternative energy grid. Building all these reservoirs and equipment is a non-trivial undertaking.
If we come to rely heavily on renewables, these concerns about maintaining grid reliability become much more critical and require funding.
Industrial Heating
High-temperature industrial heating is a huge concern. We rely heavily on burning coal, natural gas, and oil to heat our ovens and furnaces. We don’t even have the equipment to do much of this with electrical power.
Electrical power has a major drawback for high-temperature heating. When fossil fuels are converted to electricity, only about 1/3 of the heat energy can power the generator. The rest is wasted heat. But even with that inherent energy loss, fossil fuels are still competitive with alternative energy for generating electricity.
But when fossil fuels are burned directly in high-temperature heating applications, virtually all of the heat energy in the fuel can be used to heat the process. Thus, a flow of oil that could generate the same electricity as a solar panel facility will produce about three times as much high-temperature heat energy in a furnace compared with the alternative energy plant.
Even China, with its massive alternative energy program, finds it needs to use ever-increasing quantities of coal. Its industrial heating applications simply have not given up their hunger for coal.
Studies of future industrial heating compare options and often conclude that electric heating is often impractical, and the best carbon-neutral solution is to burn fossil fuels and somehow capture the resulting carbon and bury it. But carbon capture has its own problems.
Carbon Capture and Storage
The fallback plan always seems to come around to carbon capture. We keep burning fossil fuels as long as we can and bury the exhaust carbon underground. But this is an expensive option. Only a small fraction of our carbon is currently being buried underground. Most carbon capture projects to date have not met their targets. About 70% of plants scheduled to be open by 2020 were never implemented. The largest plants have the most problems.
Further, carbon poses the risk of escaping from underground tombs, potentially resulting in a life-threatening return to the atmosphere.
Many have come to believe that carbon storage is just a distraction.
And yet plans to mitigate climate change by reaching net-zero tend to include carbon capture. After all, if we continue to add even a little carbon, that is not net-zero. If natural sinks are not sufficient to remove the small amount of carbon we are adding, we have a problem. So, proposals keep coming back to carbon capture as a key part of the solution. Let us hope for the best. We shall see how that works.
Reforestation
Part of the problem is that we keep cutting down trees to make farmland. This results in net carbon being released into the environment. Here is a chart showing the decline in global forest area.
Many of these trees are cut down to make ranches so we can have more beef. The UN predicts the population will grow from 8 billion people to over 10 billion this century. That is 25% more mouths to feed. And those people living in poorer countries are going to want a better diet. All of that will demand more farmland, much of which will likely come from cutting down forests.
We can dream that we will just do some reforestation, and that this will help the climate problem while also doing the seemingly contradictory step of creating more farmland from other forests. I find little hope that trees will save us. We will likely have less forest area in the future.
But yes, let’s plant trees.
Sunshades in Space
Let’s think outside the box. Why don’t we put up a big shade between Earth and the Sun to block out some of the sun and cool the planet? This has been seriously proposed. But a quick scan of this Wikipedia page shows me that this is an unlikely option. One study listed there, for instance, estimates it would take 20 million rocket launches into deep space to get the required materials in place. This option seems to ignore the true cost of space flight.
Why Worry?
The solutions discussed above seem unlikely to bring us to net-zero. Will humans ever commit to a plan to reach net-zero, and thus resolve climate change? It will be costly.
One could be tempted to just let the climate warm 2 °C or even 3 °C. But if we don’t eventually reach net-zero, we’ll only make things continually worse until we finally stop. Once we stop adding carbon, the carbon we’ve already released will take a long time to leach out of the atmosphere. It will stay in the air for many centuries unless we intervene. It would be better to saddle future generations with a 2° rise than a 3° rise.
Not only will our carbon stay in the atmosphere for many centuries, but locked-in effects will slowly increase temperatures even after we stop adding carbon. The chart below shows the results of a simulation of the effects of added carbon. Temperatures rise on the transient black line on the left until we stop adding carbon, that is, until we hit net zero. On the right side of the graph, lines show the continued rise in temperature even after we stop adding carbon. If, for instance, we stopped at a 2 °C increase, temperatures would continue to rise for another thousand years along the dark orange line as shown below.
We could be in even greater peril than the Global Carbon Budget predicts. As NASA’s James Hansen has pointed out, the carbon we release has been changing cloud cover in ways that are amplifying the effects of the added carbon. At the same time, the increasing amount of aerosol particles we put in the air has affected clouds in a way that cools the planet. These two effects have largely canceled each other out.
But, unlike carbon, the cooling mask quickly drops out if it is not continuously being replenished. When we finally cut back on fossil fuels and greatly reduce the rate of aerosol release, we would lose the aerosols’ cooling benefits. We would then see the full, amplified heating effect of cumulative carbon emissions without that cooling effect.
And we have now run an “experiment” which indicates Hansen was right. Recent laws requiring increased sulfur restrictions in ship fuel have lowered the sulfur content of ship exhaust. This, in turn, has changed cloud cover over the major shipping lanes, reducing the cooling effects of the sulfur. Global temperatures have started rising far above prior mainstream science expectations, just as Hansen had predicted. All of this means that the true effect of carbon emissions may well be much worse than prior calculations had predicted.
You might wonder why, if aerosols are so effective at cooling the planet, we don’t just put more into the air. The answer, of course, is that these aerosols would likely have negative consequences. But when we find ourselves faced with choosing between painful options, the painful option of aerosols such as sulfur in the air might not be much worse than the other available options.
We must try to leave as many options on the table as we can.
The optimists
In 2014, the IPCC Fifth Assessment Report presented Representative Concentration Pathways that the world might choose to follow. For instance, pathway RCP8.5 was the worst-case business-as-usual case, with a predicted temperature rise of 2.6 to 4.5 deg C. But pathway RCP2.6 had a temperature rise of only 0.3 to 1.7 deg C. The hope was that we could follow RCP2.6, or at least something more moderate like RCP4.5, which predicted a temperature rise of 1.1 to 2.6 deg C.
But here is what happened:
The goal was to keep this total greenhouse gas forcing near the RCP2.6 line. But actual greenhouse forcings have instead been running very close to the worst-case RCP8.5 pathway. Did we overestimate human resolve?
Nevertheless, hope springs eternal that, in the future, we will avoid past failures. This time, we will address the problem seriously.
For instance, the UK’s Seventh Carbon Budget details a plan with many of the concepts listed above, which they claim can make the UK carbon-neutral by 2050. They also have a detailed financial analysis saying that, by 2040, the net-zero approach would break even when the costs and benefits are compared with the business-as-usual plan. I won’t get into the details, but if this is true, it still requires an immense upfront financial commitment before we finally break even and see a predicted profit. Do the people have the will to do that? And the technical challenges are great. The plan relies on many concepts that have not been proven to scale, such as hydrogen systems, synthetic fuels, and CCS (carbon capture and storage). And there is always the question of how we are going to power all the equipment with looming diesel fuel shortages, and what all the associated mining does to the planet.
The Seventh Carbon Budget plan also calls for increasing the percentage of the UK that is woodland. Ok, great, but meanwhile, the UK government has issued a national security assessment saying that “Ecosystem degradation is occurring across all regions. Every critical ecosystem is on a pathway to collapse (irreversible loss of function beyond repair)”. In response to this warning about future collapse, the report says the UK needs “significant increases in UK food system and supply chain resilience” to “maintain food security” since “global ecosystem degradation and collapse threaten UK national security and prosperity.” That, to me, looks very serious. World food supply is going to be in short supply, and even prosperous countries had better have more of their own food, since they might not be able to buy what they need elsewhere. In other words, you folks had better start planting more farmland and gardens.
And that national security assessment clearly states that these are not just guesses of some wild worst-case possibility. The authors say they have high confidence that these things are true.
And somehow, while people are supposedly creating this additional farmland in the UK, the Seventh Carbon Budget also expects to see an increase in woodland. Something doesn’t seem to be adding up.
I appreciate the optimism. On the other hand, the concerns we are facing are quite serious.
Conclusion
Back to our question: Can we realistically reach net-zero in carbon emissions? Perhaps, but maybe not.
We could set limits with some sort of cap-and-trade scheme that would make those people who pollute with carbon pay enough that emissions get sufficiently reduced. Faced with that cost, people would initiate efficiency measures. They would use more solar, wind, nuclear, and other alternatives. They would build massive power grids with batteries and pumped hydro to keep the lights on without fossil fuels. And, where they needed to burn carbon, they would perhaps bury it in the ground, keeping their fingers crossed that it stays there. And perhaps, we would start putting aerosols in the air to keep us cooler. And we would plant trees. And thinkers would come up with ideas nobody has mentioned yet. But all that comes at enormous expense and effort, with many side effects.
Sooner or later, we need to do something. We could set out to hit net-zero quickly, as many have planned, and then avoid the worst of climate change. Or we could wait until it gets worse and then strive to hit net-zero. Or we could just keep burning all the oil, coal, and natural gas we can find, and let the future worry about it.
Serenity
In closing, I remind you that people have long asked for the serenity to accept the things they cannot change, the courage to change the things they can, and the wisdom to know the difference. That is so important today.
We need the wisdom to know what we can change. This will come only if scientists, engineers, technicians, entrepreneurs, politicians, and everyone else work together to fully understand what we can do to change what we can.
And then we need the courage to act on what we know.
And we also need the serenity to accept the things we cannot change.
In 1859, John Brown was sitting on a coffin — his own coffin — on a wagon that was taking him to his execution. He had led an unsuccessful slave revolt and had been condemned to death for doing that. On the way to the gallows, he noticed the beauty of the passing Blue Ridge Mountains. He said, “What a beautiful country you have…This is the first time I have had the pleasure of seeing it.” He was sitting on a coffin — his own coffin. And yet he still managed to see beauty. That’s serenity.
We are in a better position than John Brown. But we still face challenges that seem overwhelming. If John Brown could see beauty in his situation, then you and I can surely see beauty in ours.
We have a world of unfathomable beauty. We have built a civilization that allows us to experience the fullness of understanding and enjoying the world. The human enterprise is definitely worth doing. But it comes at a cost.
As we address today’s problems, may we all have the serenity to sometimes stop, to smell the roses, to see beauty we never saw before, and enjoy what life has to offer.
And then let us face this challenge with wisdom, courage, and serenity.
=====================
Notes:
- Many sites use GtCO2 (Gigatonnes of Carbon Dioxide) instead of GtC (Gigatonnes of Carbon). Each carbon atom combines with two oxygen atoms to form carbon dioxide in the atmosphere. The resulting CO2 weighs 3.664 times as much as the emitted carbon. Since my reference deals with all carbon, not just CO2, it uses GtC as the measure. To convert GtCO2 to GtC, divide by 3.664.
