By Kevin Trenberth*
When politicians talk about reaching “net zero” emissions, they’re often counting on trees or technology that can pull carbon dioxide out of the air. What they don’t mention is just how much these proposals or geoengineering would cost to allow the world to continue burning fossil fuels.
There are many proposals for removing carbon dioxide, but most make differences only at the edges, and carbon dioxide concentrations in the atmosphere have continued to increase relentlessly, even through the pandemic.
I’ve been working on climate change for over four decades. Let’s take a minute to come to grips with some of the rhetoric around climate change and clear the air, so to speak.
What’s causing climate change?
As has been well established now for several decades, the global climate is changing, and that change is caused by human activities.
When fossil fuels are burned for energy or used in transportation, they release carbon dioxide – a greenhouse gas that is the main cause of global heating. Carbon dioxide stays in the atmosphere for centuries. As more carbon dioxide is added, its increasing concentration acts like a blanket, trapping energy near Earth’s surface that would otherwise escape into space.
When the amount of energy arriving from the Sun exceeds the amount of energy radiating back into space, the climate heats up. Some of that energy increases temperatures, and some increases evaporation and fuels storms and rains.
Because of these changes in atmospheric composition, the planet has warmed by an estimated 1.1 degrees Celsius (2 F) since about 1880 and is well on the way to 1.5 C (2.7 F), which was highlighted as a goal not to be crossed if possible by the Paris Agreement. With the global heating and gradual increases in temperature have come increases in all kinds of weather and climate extremes, from flooding to drought and heat waves, that cause huge damage, disruption and loss of life.
Studies shows that global carbon dioxide emissions will need to reach net-zero carbon emissions by midcentury to have a chance of limiting warming to even 2 C (3.6 F).
Currently, the main source of carbon dioxide is China. But accumulated emissions matter most, and the United States leads, closely followed by Europe, China and others.
What works to slow climate change?
Modern society needs energy, but it does not have to be from fossil fuels.
Studies show that the most effective way to address the climate change problem is to decarbonize the economies of the world’s nations. This means sharply increasing use of renewable energy – solar and wind cost less than new fossil fuel plants in much of the world today – and the use of electric vehicles.
Unfortunately, this changeover to renewables has been slow, due in large part to the the huge and expensive infrastructure related to fossil fuels, along with the vast amount of dollars that can buy influence with politicians.
What doesn’t work?
Instead of drastically cutting emissions, companies and politicians have grasped at alternatives. These include geoengineering; carbon capture and storage, including “direct air capture”; and planting trees.
Here’s the issue:
Geoengineering often means “solar radiation management,” which aims to emulate a volcano and add particulates to the stratosphere to reflect incoming solar radiation back to space and produce a cooling. It might partially work, but it could have concerning side effects.
The global warming problem is not sunshine, but rather that infrared radiation emitted from Earth is being trapped by greenhouse gases. Between the incoming solar and outgoing radiation is the whole weather and climate system and the hydrological cycle. Sudden changes in these particles or poor distribution could have dramatic effects.
The last major volcanic eruption, of Mt. Pinatubo in 1991, sent enough sulfur dioxide and particulates into the stratosphere that it produced modest cooling, but it also caused a loss of precipitation over land. It cooled the land more than the ocean so that monsoon rains moved offshore, and longer term it slowed the water cycle.
Carbon capture and storage has been researched and tried for well over a decade but has sizable costs. Only about a dozen industrial plants in the U.S. currently capture their carbon emissions, and most of it is used to enhance drilling for oil.
Direct air capture – technology that can pull carbon dioxide out of the air – is being developed in several places. It uses a lot of energy, though, and while that could potentially be dealt with by using renewable energy, it’s still energy intensive.
Planting trees is often embraced as a solution for offsetting corporate greenhouse gas emissions. Trees and vegetation take up carbon dioxide though photosynthesis and produce wood and other plant material. It’s relatively cheap.
But trees aren’t permanent. Leaves, twigs and dead trees decay. Forests burn. Recent studies show that the risks to trees from stress, wildfires, drought and insects as temperatures rise will also be larger than expected.
How much does all this cost?
Scientists have been measuring carbon dioxide at Mauna Loa, Hawaii, since 1958 and elsewhere. The average annual increase in carbon dioxide concentration has accelerated, from about 1 part per million by volume per year in the 1960s to 1.5 in the 1990s, to 2.5 in recent years since 2010.
This relentless increase, through the pandemic and in spite of efforts in many countries to cut emissions, shows how enormous the problem is.
Usually carbon removal is discussed in terms of mass, measured in megatons – millions of metric tons – of carbon dioxide per year, not in parts per million of volume. The mass of the atmosphere is about 5.5x10¹⁵ metric tons, but as carbon dioxide (molecular weight 42) is heavier than air (molecular weight about 29), 1 part per million by volume of carbon dioxide is about 7.8 billion metric tons.
According to the World Resources Institute, the range of costs for direct air capture vary between US$250 and $600 per metric ton of carbon dioxide removed today, depending on the technology, energy source and scale of deployment. Even if costs fell to $100 per metric ton, the cost of reducing the atmospheric concentrations of carbon dioxide by 1 part per million is around $780 billion.
Keep in mind that the carbon dioxide concentration in the atmosphere has risen from about 280 parts per million before the industrial era to around 420 today, and it is currently rising at more than 2 parts per million per year.
Tree restoration on one-third to two-thirds of suitable acres is estimated to be able to remove about 7.4 gigatons of carbon dioxide by 2050 without displacing agricultural land, by WRI’s calculations. That would be more than any other pathway. This might sound like a lot, but 7 gigatons of carbon dioxide is 7 billion metric tons, and so this is less than 1 part per million by volume. The cost is estimated to be up to $50 per metric ton. So even with trees, the cost to remove 1 part per million by volume could be as much as $390 billion.
Geoengineering is also expensive.
So for hundreds of billions of dollars, the best prospect with these strategies is a tiny dent of 1 part per million by volume in the carbon dioxide concentration.
This arithmetic highlights the tremendous need to cut emissions. There is no viable workaround.
*Kevin Trenberth, Distinguished Scholar, NCAR; Affiliated Faculty, University of Auckland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
80 Comments
It's nice to see some numbers around CCS. So $1.4 trillion per year to remove all our carbon emissions, assuming magically the price thirds in short order.
Some more facts: The sea has absorbed around 90% of the total extra heat since the 1800s. It's running out of capacity to absorb more, which means atmospheric temperatures will increase at a faster rate once peak absorbance is reached.
Do more reading - and more math.
'Scenarios set out under the UN Climate Panel (IPCC) show human welfare will likely increase to 450% of today's welfare over the 21st century. Climate damages will reduce this welfare increase to 434%.'
https://www.sciencedirect.com/science/article/pii/S0040162520304157
The latest report by the Intergovernmental Panel on Climate Change, focusing on oceans and the cryosphere, points out that mangroves, salt marshes and seagrass meadows can store up to 1,000 tonnes of carbon per hectare—much higher than most terrestrial ecosystems.
Not sure whether NZ has taken up this mitigation activity - many other countries have;
The potential for seagrass in nationally determined contributions is significant, as some 159 countries have seagrass on their shores. An analysis soon to be published by GRID-Arendal, a Norwegian foundation working with the United Nations Environment Programme (UNEP), found that 10 countries have included seagrass in existing nationally determined contributions. Five countries refer to its conservation and restoration in mitigation actions, while eight plan to use it in adaptation.
https://www.unep.org/news-and-stories/story/seagrass-secret-weapon-fight-against-global-heating
KT has said that cumulative emissions are important
I disagree as it is what happens in the future that is more important than what has happened to date - which regardless of the right or wrong cannot be undone
A focus on the past may be useful if you want a blame game which does seem to be a big part of the UN's position
TL;DR - we're boned
The sum of our efforts to date has not lowered CO2 levels - in fact they are increasing and accelerating each year. It will take some drastic action at huge cost to make a difference. I can't see that happening until it is forced on us by the environment, by which time it will likely be too late.
What efforts to date? We really haven't done anything and are still adding fossil fuel burning plants in India/China regularly, why would C02 use be falling? IMO, if we are serious about reducing C02 we need Nuclear now and hopefully hydrogen if and when the tech enables it.
The Kyoto Protocol was agreed in 1995.
Nuclear is a good option. Hydrogen is not an energy source but more like a really inefficient battery. You don't find hydrogen, you create it using energy then convert it back into a third of the original energy again later. For most applications, it is better to use electricity directly.
I realise what hydrogen is, relatively inefficient energy storage. EV's are not the final solution, most need to hit 80 to 100 thousand Km's to break-even over the ICE equivalent. Battery's lose storage capacity over time as well and are so expensive to replace many cars will be scrapped at 10y to 15y. Great for the wealthy in cities but not going to make a difference.
Thankfully Auckland Council/Transport has just won a court case to decide that it doesn't really have to take climate change seriously enough to actually do anything differently or less oriented around individual use of fossil fuel-heavy transport. Dinosaurs trying to make sure we all keep burning dinosaurs as much as and for as long as possible.
Nobody seriously thinks nuclear is remotely appropriate for New Zealand right? Remember Fukushima? NZ has safe alternatives like abundant hydro, geothermal, wind & solar power, we've also got our own coal and gas. Battery tech gets better and cheaper all the time. There's mature tech to convert our methane to electricity on a megawatt scale.
I was going to say that having nuclear reactors in NZ is about as insane as giving experimental mrna covid vaccines to all the children in the country for no reason at all, but there are probably quite a few people out there that think both are a great idea.
Sorry but if you want nuclear now you had to start building 10-15 years ago.
Under current laws it takes at least 10 years to build a nuclear plant.
To replace 1/2 of the coal power plants in the United States - this is only half, and in 1 country - will require 123 nuclear power plants to be built.
That is 1 per month for 10 years. It takes 10 years to build, so they will start coming on line 2032 at the earliest - if there's no delays.
I don't think the united states has the capacity, or the locations, to build 123 nuclear plants.
The only way out of this mess is by lowering living standards. Which is exactly what inflation is doing.
I've come to the same conclusion. We will only stop burning fossil fuels when they run out and become prohibitively expensive. In a relative sense given the likely associated inflation you mention.
Its almost certain it will come with wars of some sort (hello Ukraine!)
It would be nice if the world could come together to actually force change at the pace necessary without being compelled to by physical constraints...
TK - wrong (I tend to expect this, then work backwards, your whole ethos is flawed).
You might do some homework:
https://www.thegreatsimplification.com/episode/19-simon-michaux
https://www.renewableenergyworld.com/storage/hydrogen-hype-49540/
Renewable tech is coming up against the 2nd Law and Carnot - batteries are going on fire, sure indicator they're near the limit. And they're orders of magnitude less energy-dense than a cupful of petrol. We are between a rock and a hard place; overshot population, overconsuming per capita, failing to address the entropic results (including CO2). We need to learn to live (much) less-consumptive lives. I don't see you leading that move....
We cannot and will not talk about real measures including population control.
When it becomes a real disaster, when it is too late for good outcomes, then the governments of the day will do something.
Future generations will inherit an Earth that has been stripped of its best assets and will need to do all the hard work of social and ecological re-engineering.
Technology will be our only way out of the worst of it but this in itself will only make the leaps it needs to when real money starts to get spent.
Why jump to the most extreme? Simply limiting immigration would be enough to reduce population of most countries. and ccc could recommend that people have two or less children to do their part to help the climate. I know I’d rather have two kids growing up in the first world than 4 in 3rd world conditions.
Obviously it's impossible to reduce the current population, but what should be done, is widely broadcast the predicament humanity finds itself in, remove subsidies for reproduction and ring fence those refusing to adjust behaviour. A UN sponsored child free year could get the ball rolling. The public education part, needs to be in conjunction with abandoning the advertiser funded media sector we currently have. Anything less and later this century life will more resemble the stone age than techno utopia.
Agree, and this is where some of these academics start to lose the confidence of the people. Why do they feel the need to have these sly jabs at the US? Just state what the facts are right now, and what we need to do to fix them - which in reality is that we somehow need to convince China to jump onboard, or we need to get ourselves off the very addictive "made in china" drug very very quickly. If we could also stop producing so many humans that would be great too - particularly in 3rd world countries where climate change is a lot further down the priority list than feeding hungry mouths and lining the pockets of corrupt officials.
Really?! I strongly doubt that. They weren't burning coal that much back then and the population was not that great.
I suppose if you factor land use change in that would up the numbers but I still doubt it would catch up with Britain unleashing the coal powered revolution
Does each person or each country have the right to make emissions? Should Kiwis be allowed to emit at double the rate of the Chinese? Should the rich be allowed more emissions than the poor?
I suggest we start by looking at ourselves
Visualizing Global Per Capita CO2 Emissions (visualcapitalist.com)
We are looking at ourselves - plenty of action happening in this space in NZ. I'd argue that most business in NZ have "sustainability" ranked somewhere near the top of the list on their strategic priorities, and most households are aware of their footprint and are thinking of ways to reduce it.
If you are seriously concerned about climate change, then I would be much more concerned about the lack of progress in China.
No, that is a complete waste of time. We need to focus on why they are being produced. They are being produced because people in poorer countries see how much we're using and want the same thing. Telling others to change their behaviour while we do nothing is a stupid approach to fixing this. I requires leading by example
Every author of these articles hammers China but the country is about a fifth of earth's population, obviously it will be a large emitter by nature of that fact. Also the Chinese have a declining population so managing emissions downwards will be a piece of cake for them, all they have to do is tread water.
On the other hands high per capita emitters with growing populations, like New Zealand, will have to work much harder to even stand still on emissions.
I don't know many Kiwi families having more than two kids - any growth in the population is coming from immigration. If China gets a free pass from you because they have a lot of people, do we get a free pass because we feed lots of people (including many in China)?
NZ is actively trying to reduce emissions - no more permits for exploration etc. and yet we have China opening up new coal mines every other week. They are a major problem in this battle and you can't simply gloss over it.
The real issuer is the grossly excessive per capita emissions from the very wealthy, including the billionaire in the US who are also corrupting democracy and setting up an oligarchy in the failed state of the USA.
All you are doing is saying 'la, la, la, look over there'.
Here's a working playbook which assumes markets and businesses' willingness and ability to deliver:
- Get educated on reputable climate science and real options https://drawdown.org/solutions/table-of-solutions
- Survive flooding whilst reading that storms carry 7% more energy and precipitation for each additional degree C of warmth
- Brush up on dynamic equilibrium of systems, energy return on investment and the Limits to Growth by the Club of Rome
- Existential crisis when you realise that most members of ecosystems can't move, so many become unviable as the local climate changes, save for human intervention
- Existential crisis when you read that ocean acidification from excess atmospheric CO2 may have an even greater effect than climate change, and add to its magnitude and severity
- Take back agency, get help, connect with people who are doing meaningful work on viable ecosystems and liveable climates
- Work up a marginal abatement cost curve for your area of consideration - organisation, city, region, nation, planet.
- Flip the MACC y axis so it becomes a marginal abatement value curve, and target those options which show marginal abatement value with current settings and market conditions
- Double down on investing to get maximal benefit from negative emissions to shift marginal technologies into net value creators e.g. carbon dioxide removal and https://www.scionresearch.com/about-us/about-scion/corporate-publicatio…
- Social crisis when there is a collective realisation that some industries overtake others with small changes in the price of carbon, while you realise that net zero in NZ will be about $272/tonne but the price of carbon has not risen sufficiently to induce mass behaviour change
- Realise social crises are opportunities for creative change
- Brush up on business model innovation and social change models
- Hard graft working with people to understand the magnitude impacts of climate change and respond proactively
- Social crisis where we come up against Limits to Growth and need to choose between diminishing returns of resource per unit of energy vs lifestyle and economic change to degrowth, which ends up converging on a conversation about forced vs approached degrowth
- Crowdsource climate change playbook again from Interest.co.nz contributors in 2023
How would you slow and reverse climate change? What would you add or prioritise?
It's clear to me the world will do too little too late to save ourselves. Tragedy of the commons. It seems dramatically reducing population is the only scenario that would actually achieve the goals in the real world we live in.
I would be surprised if there aren't scientists somewhere developing a virus that targets certain people based on their DNA/ethnicity, or anyone not vaccinated against it. There will be a few governments that would love to have that technology in the bottom drawer. But maybe I have just seen 1 too many Bond films.
Lets not forget the impact of methane hydrates, essentially pockets of frozen liquid methane in cold arctic areas, Siberia, Canada and also in the deep oceans. A bit of warming and these hydrates turn to gas, and bubble up into the atmosphere, where methane is so much more harmful than CO2, and further magnify the problems.
The coastal flooding must not be underestimated. At its worst there's a potential 80m rise in sea levels.
Most of our towns and infrastructure is coastal. Entire cities lost under the sea, with those entire populations forced to relocate onto higher (and probably steeper) ground. Yet they'll be faced with needing to rebuild under a seriously lower carbon input (ie less fossil fuel usage). So no cement for foundations, maybe no steel for roofing, maybe very limited resources for any rebuilding, save for scavanging materials from inundated coastal properties, or combing the beaches for washed up materials from homes that have been abandoned and taken by the seas.
Yes, homes will be abandoned, and the new shorelines will be littered with their debris. If you think ocean pollution is bad now, just wait till the homes and workplaces of a billion people are swallowed up and are churning with the tides.
Northland (NZ) becomes a series of islands. Good luck maintaining deliveries of goods, electricity etc from whatever is left of the mainland when there's the issue of transporting stuff (in a low carbon way) from island to island. In fact, at 80m the mainland begins from around Hamilton. Everything north of there is just a series of islands.
Our level of existing infrastructure will be savagely reduced, and the costs to replace it (without the advantage of abundant fossil fuels) will be so much higher.
Roads might be no more than bricks, cobblestones or mud.
Humanity might get knocked back a century in terms of development and infrastructure, and the rebuild will not be easy.
What? From the IPCC Sixth Assessment Report;
By 2050, sea level is expected to rise an additional 10–25 cm whether or not greenhouse gas emissions are reduced (FAQ 9.2, Figure1). Beyond 2050, the amount by which sea level will rise is more uncertain. The accumulated total emissions of greenhouse gases over the upcoming decades will play abig role beyond 2050, especially in determining where sea level rise and ice-sheet changes eventually level off.
From https://www.ipcc.ch/report/ar6/wg1/resources/frequently-asked-questions/
See link under Chapter 9, FAQ 9.2 | How Much Will Sea Level Rise in the Next Few Decades
Thank you for providing evidence in support of my statement, that 6m is more likely than 80m by 2050.
I was silent on whether 6m itself was likely. Just more likely than 80m.
Note that I was replying to someone who was specifically talking about runaway climate change from methane clathrates that push the climate over a tipping point.
No, Kate. There are no math for feed-back loops - remember we are well ahead of ANY IPCC projection (Euro/Aussie fires, ice retreat, albedo loss...
but I don't think CC will get us first. I've got an old dog with an arthritic back end - but his recent jaw cancer will beat the arthritis. I think we'll see WW3 over resources, before we even get to 1 metre SLR.
we are well ahead of ANY IPCC projection
That's just categorically wrong from a sea-level rise perspective from what I've read of their work. If actual sea level rise to-date was higher than their projections they would account for that by incorporating that actual data.
In actual fact in the recent (2021) AR6 report, the earlier highest (e.g., worst case IPCC scenario) RCP8.5 has been determined to be implausible due to the fact that fossil energy (particularly coal) use is tracking well behind its base assumptions.
https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario/
Perhaps it's better to say, we are are ahead of older projections in most areas. Of course as data is added, the uncertainty bars reduce in the nearest future projections. Coal use has declined as electricity has switched to gas fired thermal. The next step would logically be to switch from gas to non fossil fuelled generation. This is the step that challenges most. Personally I believe it can only be achieved beside a massive reduction in human industrial activity. A switch back to coal is as likely as any future scenario. IPCC models don't factor in sudden changes in human behaviour, such as wars and economic factors, such as industry/investor reluctance to fund a revival of the US fracking sector. I'm not actually sure if IPCC modelling even account for the amount of FFs actually potentially burnable. I guess this is nearly impossible, due to the fact reserves are seen as sensitive information and routinely lied about. In short, we can't know what we will burn, but I'm pretty sure if it's available, someone will burn it.
I agree with all of that - whilst capitalism/GDP growth is the benchmark economic indicator of a country's "success" we will likely fish the last fish and burn the last bit of fuel available. It's not like it hasn't happened within certain societies gone before.
We need far more inspirational economic theorists/thinkers who propose/show/direct an alternate way of social organisation.
Seems the human species and the planet are in an even worse situation than Marx ever predicted we would get to under a capitalist system before transitioning to the next historical stage.
Trenberth is clearly in the man made CC alarmist category. A few years ago he removed from his website a link to a known skeptic. No doubt concerned that his academic colleagues would cancel him.
The sky is not about to fall in any time soon, certainly not in the next 50 years, if few or no measures are taken to reduce CO2.
This article strangely gives me hope.
For $2.73 trillion per year (3% of global GDP), we can carbon capture our current emissions, and take 1ppm of C02 out of the air.
This technology can be expected to reduce in price as it matures and scales.
Being able to be gluttons, while making progress, for 3% of GDP, sounds pretty good.
Continued GDP growth based on fossil fuel consumption is not possible. Or any resource overuse. But yes generally growth per person must slow. Of course investors need growth to make money, so they can't allow that to happen.so the best we can do is sustainable growth. Public transport instead of cars etc.
Apocalyptic scenes
When New York and Shanghai start to sink, the great powers might act. Kiribati would have disappeared under the waves.
Wild weather devastates wheat, corn and rice fields. Cassava becomes the only food in the tropics.
By the time the World reacts, its too late.
"When New York and Shanghai start to sink" To me sinking is that the land mass is sinking, not sea level rising. With MSM regurgitating some scientists sea level rise predictions that may be the predominant cause, but I doubt it. On the other hand the land mass sinking may be more predominant. I don't know in these specific cases.
I've been reading all sorts of good comments here. However the main problem is that the way politics works, the incentives to actually do anything real is not there at a political level. We need to do less, consume less and charge more for carbon to make a real difference to CO2 levels. This is politically unpalatable.
Some of the climate change denying commentators here might want to read this to see where the true conspiracy is...
https://www.bbc.com/news/science-environment-62225696
I think the IPCC science has since successfully countered any/all denialist claims. It now comes down to whether or not the powers-that-be at the highest levels of government the world over are prepared to address CO2 pollution.
Given Biden's recent plea to the Saudi's to pump more oil and our own Labour government's extension of the excise tax reductions on petrol and diesel... it's perfectly clear to me they do not want higher costs at the pump to drive that change.
There is a blind-spot in terms of fossil fuel scarcity - just like there is a blind-spot in terms of declining fisheries and so on and so forth.
Yep the $2+ trillion a year climate change industry gravy train sure is a juggernaut. Gotta keep those doomy predictions coming.
"Interest in climate change is becoming an increasingly powerful economic driver, so much so that some see it as an industry in itself whose growth is driven in large part by policymaking.
The $1.5 trillion global “climate change industry” grew at between 17 and 24 percent annually from 2005-2008, slowing to between 4 and 6 percent following the recession with the exception of 2011’s inexplicable 15 percent growth, according to Climate Change Business Journal."
"and November's presidential election brought committed environmentalist Al Gore into the White House as vice-president. It was clear the new administration would try to regulate fossil fuels"
.As soon as I saw Al Gores name I stopped reading. He of Michael Man's original discredited hockey stick chart/graph
How has the hockey stick been discredited and by whom?
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