Arguments
Why children must emit eight times less CO2 than their grandparents
Posted on 14 August 2020 by Zeke Hausfather
This is a re-post from Carbon Brief
Global emissions of CO2 need to decline precipitously over the next few decades, if the world is to meet the Paris Agreement goals of limiting global warming to “well below 2C” and, ideally, below 1.5C.
If these goals are to be met, young people would have to live the greater part of their lives without contributing significantly to global emissions. Essentially, they would have fewer “allowable” CO2 emissions during their lifetime, compared with older generations.
To determine just how much smaller their personal CO2 limits would be, Carbon Brief has combined historical data on emissions and population with projections for the future. In a world where warming is limited to 1.5C, the average person born today can emit only an eighth of the lifetime emissions of someone born in 1950.
The interactive tool, below, shows the size of each person’s “carbon budget” during their lifetime – based on when and where they were born.
It looks at two different scenarios: one where the world limits warming to well below 2C above pre-industrial levels by 2100; and one were warming is limited to 1.5C.
It also considers two different ways of sharing future allowable emissions: one where each country tracks “optimal” pathways taken from models; and another, focused on equality, where each person can use the same portion of future emissions, no matter where they live.
In all cases, younger generations will have to make do with substantially smaller lifetime carbon budgets than older generations, if the Paris limits are to be respected. This is because most of the allowable emissions have already been used up, meaning young people will not have the luxury of unmitigated emissions enjoyed by older generations.
The idea for this analysis was first proposed to Carbon Brief by Dr Ben Caldecott at the University of Oxford. The methodology used – and its limitations – are explained in detail at the end of this article. Carbon Brief is now working to further develop the analysis with Dr Caldecott and his colleagues.
The global picture
Global emissions must peak in the next decade and quickly decline for the world to stay below its Paris Agreement limits, according to the UN. In the scenarios examined in this article (see methodology at the end for details), global emissions peak around 2020, decline around 50% by 2045 and then fall below zero around 2075 in order to hold global warming to below 2C.
Emissions have to fall even faster for warming to be kept below 1.5C – falling around 50% by 2030 and to below zero by 2055. In the 1.5C scenarios examined here, large amounts of negative emissions are deployed by the end of the century, removing carbon from the atmosphere equivalent to roughly a third of today’s emissions.
These emissions pathways can be divided up into average “lifetime carbon budgets” that depend on an individual’s year of birth. This allocation is based on the changing global population and emissions during each individual’s lifetime.
The figure below shows the global average lifetime carbon budget for people born in each year between 1900 and 2017, in scenarios where warming is kept below 1.5C (dark blue) or 2C (light blue).
Global average lifetime carbon budgets per-capita by birth year for 1.5C and 2C scenarios, assuming a lifespan of 85 years. Based on historical emissions data from the Global Carbon Project, historical and future projected population from the United Nations and global emission projections from MESSAGE-GLOBIOM. Generation birth years shown at the bottom from the Pew Research Center. See the methodology section for details. Chart by Carbon Brief using Highcharts.
As the chart above shows, if warming is limited to well below 2C the global average lifetime carbon budget for someone born in 2017 is 122 tonnes of CO2, only about a third as large as the budget for someone born in 1950. If warming is to be limited to 1.5C, the remaining budget is only 43 tonnes of CO2 and the difference is eight times as large.
Current per-capita global emissions are around 4.9 tonnes per person per year. This means that the lifetime carbon budget of someone born today is equal to 25 years of current emissions if warming is limited to well below 2C – and only nine years of current emissions if warming is limited to 1.5C.
Divvying up emissions
The analysis above uses a global average carbon budget. However, in reality, there is no such thing as a “global average” person and each country’s emissions will follow a slightly different trajectory in “well below” 2C and 1.5C worlds.
In general, emission reductions will need to be proportionally larger in developed, wealthier countries, such as the US, where per-capita emissions are very high. Developing nations, such as India, already have much lower per-capita emissions.
To put the difference into perspective, the average Indian had emissions of 1.9 tonnes of CO2 in 2017, whereas the figure in the US was 16.9 tonnes of CO2.
Moreover, historical emissions vary greatly between countries, with the likes of the US and UK responsible for a far larger share of cumulative emissions since the industrial revolution. This poses an open question as to how the fixed global carbon budgets set by the Paris Agreement should be divided between different countries.
There are lots of different ways to allocating future emissions between countries. Integrated assessment models (IAMs) – energy system models that examine what mix of different technologies and choices are needed to meet climate targets – provide one set of budget allocations, reporting future emissions for each region of the world.
The figure below is based on the allocations in 1.5C scenarios from IAMs. It shows how lifetime carbon budgets vary based on birth year, for four major countries and regions that are responsible for the bulk of global CO2 emissions. These are the US (light blue line), Europe (dark blue), China (red), and India (yellow).
Lifetime carbon budgets by birth year based on historical emissions and future IAM 1.5C scenarios, assuming a lifespan of 85 years. Based on historical emissions data from the Global Carbon Project, historical and future projected population from the United Nations and regional emission projections from MESSAGE-GLOBIOM. Generation birth years shown at the bottom from the Pew Research Center. See the methodology section for details. Chart by Carbon Brief using Highcharts.
If the remaining carbon budget is divided up in this way, based on IAM pathways, then national allowable lifetime emissions are much more similar for someone born in 2017 than in 1950 – but there are still large differences between countries.
For example, someone born today in the US would still be allocated a lifetime carbon budget some 15 times larger than someone born in India. Their budget would be four times larger than someone born in China and around twice as large as in Europe.
The table below shows the lifetime carbon budget in a 1.5C world (2C world) both globally and by major country/region, broken down by generation:
| Pre-Boomer (pre-1946) | Boomers (1946-1964) | Gen X (1965-1980) | Millennials (1981-1996) | Gen Z (1997-2012) | Post-Gen Z (post-2012) | |
|---|---|---|---|---|---|---|
| Global | 275 | 325 (348) | 276 (322) | 202 (264) | 118 (191) | 56 (134) |
| US | 1494 | 1464 (1530) | 1191 (1342) | 846 (1052) | 472 (709) | 238 (489) |
| Europe | 686 | 698 (733) | 582 (668) | 398 (521) | 218 (363) | 105 (259) |
| China | 119 | 255 (291) | 256 (334) | 220 (326) | 151 (279) | 71 (213 |
| India | 38 | 64 (71) | 61 (74) | 52 (69) | 23 (54) | 18 (39) |
Lifetime carbon budgets in tonnes of CO2 by birth year based on historical emissions and future IAM 1.5C (and 2C) scenarios. Pre-Boomer generations have identical 1.5C and 2C carbon budgets. Using generation periods from the Pew Research Center and averaging the lifetime budget of all the birth years of each generation.
This approach raises obvious questions about equity, as it implies that countries with high historical emissions will also receive a larger share of the proverbial pie in the future. There are lots of different ways to define equity – and little agreement – regarding which approaches would be both possible and “fair” for allocating future emissions.
One alternative would be to allocate the remaining budget equally between all people, wherever they live. This might be hard to achieve in practice as, say, per-capita US emissions would need to fall rapidly towards the global average while those in India would immediately rise.
But it provides a useful thought experiment that can be contrasted to the lifetime carbon budget allocation set out above. Even this might not be truly equal, is it neglects responsibility for historical emissions.
The figure below shows the effect of this allocation on lifetime carbon budgets by birth year for the same four major countries and regions. It is based on historical per-capita emissions and equal per-capita shares of the remaining carbon budget from 2018 onwards, in a scenario where warming is limited to 1.5C.
Same as the prior figure, but using global emission projections from MESSAGE-GLOBIOM to calculate future global per person emissions. See the methodology section for details. Chart by Carbon Brief using Highcharts.
The chart above shows that lifetime carbon budgets converge much more quickly when future emissions are divided equally, even though historical differences between countries remain. As a result, someone born in 2017 would have a similar lifetime carbon budget no matter where they are born.
Some limitations
Calculating lifetime carbon budgets is necessarily imperfect and relies on a series of unrealistic assumptions. Every person is different and, in practice, individual emissions will be strongly affected by income, behaviour and other factors.
While the average 1.5C lifetime carbon budget of someone, say, born in the US around 1995 might be 696 tonnes of CO2, people in that generation will, in practice, have widely varying individual emissions.
The approach taken here – dividing national emissions by population – also glosses over the fact that a sizable portion of emissions for some countries are the result of industrial and commercial activity producing goods for trade that are not consumed at home. These “consumption footprints” can differ significantly from national emission estimates, as Carbon Brief has previously examined.
For simplicity, a constant lifespan of 85 years is assumed when calculating lifetime carbon footprints. This is higher than the current average lifespan in most countries, but may be more realistic for younger generations today given expected advances in medical science and access to healthcare. However, in practice, lifespan differences between countries will likely persist into the future and could impact these calculations.
Finally, this approach assumes that emissions in a given year can be assigned equally across the population regardless of age. In reality, people are probably responsible for considerably lower emissions when they are children than adults, as they are not, say, driving cars and are often consuming less.
That said, this analysis provides a first look at how lifetime carbon budgets vary by age. It suggests that the allowable lifetime emissions for young people today is a fraction of that of previous generations, as the global budget for avoiding warming of 1.5C or 2C has already been mostly used up.
Methodology
Lifetime carbon budgets were calculated by adding the historical and projected future per-capita emissions for each year that an individual is expected to live – assuming a constant lifespan of 85 years since a given birth year for simplicity. This is higher than the current global average lifespan (it is typical of Japan today), but may be more typical for the lifespan of younger people today given continuing medical advances.
For example, if someone were born in the year 2000 in India, their lifetime carbon footprint would be the sum of historical per-capita emissions in India from 2000 to 2017, plus forecast per-capita emissions in India between 2018 and 2085.
The end of 2017 serves as the demarcation between historical and future emissions because 2018 emission and population values are not yet available for all countries.
Carbon budgets were calculated for all possible birth years from 1900 to 2017 for major countries and each of the world regions where UN population projections were available: Africa, Europe, Latin America and the Caribbean, North America, Oceania and Asia.
Historical CO2 emission estimates for each country from 1751-2017 were obtained from the Global Carbon Project. Historical population data from 1950-2017 and future population projections from 2018-2100 were obtained for each country from the UN World Population Prospects 2017. The “medium” scenario was chosen for future population projections, as it matches reasonably well with the population assumptions in the Shared Socioeconomic Pathway (SSP2) world used for IAM emission scenarios.
Future emissions by country for both 1.5C and 2C targets were based on IAM runs from the International Institute for Applied Systems Analysis (IIASA) MESSAGE-GLOBIOM model using the SSP2 world. SSP2 is a world where current economic and population trends broadly continue and MESSAGE-GLOBIOM was the model chosen to represent SSP2. MESSAGE-GLOBIOM emissions by region – and globally – were taken from the IAMC 1.5C Scenario Explorer.
As IAM runs in recent years lack country-specific values, regional emission estimates were used to estimate country-specific trajectories by scaling current country emissions by the percent reduction in regional emissions from the IAM runs. For example, if the IAM runs showed OECD countries reducing emissions by 50% by 2040 in a 1.5C scenario, emissions in each OECD country were estimated to decrease by 50% by 2040.
Net future emissions were used for per-capita emission estimates. This means that in many countries future per-capita emissions go negative in the second half of the 21st century, particularly in 1.5C scenarios. The distribution of negative emissions in MESSAGE-GLOBIOM varies regionally, with a particularly high concentration of negative emissions in Latin America and the Caribbean.
Finally, as both emission and population projections are only available through to 2100, but people born after 2015 will still be alive post-2100, per-capita emissions are assumed to remain constant at 2100 values in subsequent years.
Two future emission allocation scenarios are provided: one based on the regional MESSAGE-GLOBIOM emission pathways and one where the global MESSAGE-GLOBIOM projected emissions are distributed evenly to every country on a per-capita basis after 2017. The latter shows how a more equitable distribution of remaining emissions would affect lifetime carbon budgets, compared to the allocation in IAMs.
The countries featured in the interactive tool are a subset of those with the largest populations. However, major regions are also included, so if there is a country not featured on the list its region should provide a reasonable estimate. The “North America” region is not shown as all member countries appear on the list.
So you calculate your carbon budget. Its going to be a very difficult exercise for the average person to take this number and work out the implications for making lifestyle changes. I would wager that virtually nobody is going to do this, let alone get it right. So what is the point of this carbon brief article?
It would be more useful for the experts to give people a lifestyle prescription budget. You actually have to spell out what cars they can drive, what household appliances to own, where they should set thermostats, how many kms they can fly each year, how many grams of meat per day is acceptabale, etcetera. Obviously it would be for some mythical average person but it creates a starting point, and individuals can adjust things.
Just saying fly less, eat less meat and eat more greens doesn't mean a lot. You have to get precise and quantitative. Otherwise most of the population will have no idea what's really expected of them.
Nigelj,
What you are saying sounds great, but it is useless. It's not the amout of electricity you use, but rather how that electricity is produced that matters. Use all you need if it is produced by wind or solar.
Same goes for meat and veggies. It's not what you eat, but rather how that food was produced and transported/stored that matters. Local regenerative production of both meat and veggies can be done in a carbon negative manner. If it is, then eat all you want.
Guidelines like you propose assumes we can't actually fix the unsustainable systems that support our societies to sustainable systems. We can, and we must. This is why the changes you have called for are nearly impossible to implement and definately wont reverse AGW.
Carbon budgets are not for individuals. They are a way for policy makers to gage timelines for rebuilding there infrastructure to support sustainable systems.
Red Baron @2, there are a couple of problems with your ideas. Most places dont have much zero carbon electricity and are unlikely to hit 100% before 2050 Paris Accord time frames. We don't have zero carbon fuels for aircraft, apart from very limited ethanol blends, and may never have at 100% level, and we dont have regenerative agriculture at scale and scaling it will not be quick or easy, and we dont have zero carbon cements, etcetera. So we have to look at how much we reduce our relevant personal consumption, at a point in time. It will vary over time obviously.
Not saying its easy to calculate, and it will vary depending on place and generation systems etcetera, and it cant be punishing, but its possible to calculate. It will have to be an intelligent guesstimate based on what technology can reasonably be expected to solve. Its called reducing your personal carbon footprint. Refer to the IPCC reports for some details and ideas.
And the problems can't all be solved simply by making pain free substitutions. Sometimes its about consuming less. Its not me saying this. Its what we are being told to do by the expert groups. So I dont see how you have rebutted what I said. People need some idea of how much to do, as well as what to do, surely?
And I didnt "propose" any guidelines. I referred to ideas typically promoted by the IPCC and various expert bodies, to illustrate a point. "If" we are to fly less, surely we need guidance on just how much less with some specificity? If you dont like the "guidelines" take it up with those scientific bodies, not me.
A more appropriate way of dividing the carbon budget would be to make it inversely proportional to wealth - allow zero carbon budget for the wealthiest people and give the highest carbon budget to the poorest people.
Of course the shape of the distribution could be debated. But the richest should not get any of the carbon budget. In fact, it could be argued that in addition to having to prove they are worthy of being the richest by setting the examples of how to live truly carbon-neutral, the very richest may also be required to assist the least fortunate develop to sustainable better living, helping to advance them faster so that they do not use up their carbon budget, especially if those richest grew up priviledged because of the carbon causing acquisitions of wealth and pleasue by their families.
That would be difficult, but doing the right thing should be expected to be harder rather than cheaper, easier or quicker.
Also note that this methodology should not be averaged into Nations with National Averages. Such averaging could hide the harmful inequities that could easily exist and be defended by the richest within any nation.
That would require an effective Global monitoring and enforcement system, something that the richest fight viciously against with appeals to Nationalism and the appealing demands for Freedom of Nations and people to do as they please (as long as it pleases the richest).
Clarifying and expanding my comment @4:
Though the shape of the distribution from poorest to richest is open to debate, there must be a constant decline in carbon budget as wealth increases.
Also, the point of zero-carbon budget is debatable, but it probably should not be a higher value than wealth of 100 million Euros. And an additional requirement could be a minimum level of 'truly negative carbon impact' for everyone with wealth higher than the zero point, with the required minimum negative increasing as wealth increases.
Thomas Piketty's recent book "Capital and Ideology" sets out a detailed basis for understanding the harmful propensity for inequity to grow. He also provides brackets for wealth to help clarify the problem of inequity.
Brackets could be 10% groupings of the bottom portion of the population personal wealth (all quite poor so not much difference between the brackets) and then 5% for each wealthier grouping up to 90%, then 1% brackets up to 99% and 0.1% brackets for the remaining wealthiest. That would allow a more limited number of 'Carbon budget' numbers to be applied rather than a painfully rigorous individual evaluation. That would be:
The important understanding is that all of the wealthier people need to behave better and be more helpful than the poorer people. Self-governing by individuals to limit selfish temptations would be the best solution. But some individuals will require external governing because of a lack of interest in being helpful (something that a wealthier person cannot logically be excused for compared to a poorer person).
Red Baron @2,
I was very pleased to see a post from you that I completely agree with!!
Regarding my earlier comments. They are meant to establish an understanding that, of course, is difficult to practically achieve by each person responsibly managing their individual budget (or each person being audited). As nigelj and Red Baron have been presenting Government over-sight and leadership action is required.
The people wealthier than the zero-carbon level of wealth can be monitored and audited individually with the oversight of national audits being performed by an international organization.
The lower levels of wealth would be harder to manage individually. What would make more sense is for nations and each of their regions to be assigned total carbon budgets based on the wealth levels and distribution within each regional population. The total impacts from the region would be monitored. And evaluators would investigate the evidence of measurable efforts to meet the intent of getting better behaviour from the wealthier people. Possible measures include comparing carbon impacts from registered vehicle use and home energy use with level of wealth with significant deterrent penalties for wealthier people if their impacts are higher than less wealthy people (competition to be lower impacting).
Regarding the ways for people to better understand how they can be less harmful and more helpful (in addition to the nigelj and Red Baron discussion on the issue), one simple action is for people to stop any recreational activity that involves fossil fuel use. Another is of course for people to be made aware of the better food options with measures implemented to make the better options less expensive than the currently developed popular and profitable food choices.
A last point is regarding the inter-generational reality of impacts. The lack of responsible corrective actions through the past 30 years has created the much more daunting challenge that the current day global community faces. And it has caused the harmful inequity of what the younger generation will be able to do (and, of course, there is regional inequity due to regions getting wealthy from harmful activity that affects regions that do not benefit).
It may be helpful to have retroactive penalties for wealthier and more influential people who misled and misinformed populations through the past 30 years. As a minimum, richer nations with leadership members who misled about the matter should face retro-active penalties as a deterrent to continuation of that harmful activity.
And penalties could even be considered for people who Optimistically promoted the idea that no corrections of behaviour were required because growing economic wealth with enlightenment would naturally produce the required solution through new technological developments that would be popular and profitable.
Necessity can powerfully drive innovation. And imposing restrictions and corrections that are unpopular, especially ones that are unpopular with the wealthiest, could be a very powerful motivation for helpful sustainable innovation.
I think we need to build sustainable systems, and I never said otherwise. But I think sustainable systems are highly unlikely to be sufficient to meet Paris 2050 time frames and so while we build them we also need to look harder at our per capita consumption of various things, and that means having some precise quantitative goals or its just meaningless.
Most climate organisations where I live promote reducing consumption of various things. Im not suggesting the sort of crazy stuff, and self flaggelating stuff M Morre came out with in his planet of the humans movie, but we can do some things. Looks like RB and MS are in fantasy land, or are looking for a free lunch :)
[BL] Please try to avoid inflammatory language, so we don't end up in another flame war.
Nigelj:
Please cite reputable sources to support your wild claims.
I have provided you many references that show it is possible to generate enough renewable energy to power the entire economy. Red Baron has provided references that show it is possible to reduce cfarbon emissions from agriculture.
[BL] Please try to avoid inflammatory language, so we don't end up in another flame war.
There are many news items about regenerative farming.
This CBC item is the latest I have come across "With better soil, farmers can fight climate change, make agriculture more sustainable".
The written article summarizes the longer radio conversation.
An important point made is that changing to regenerative farming is helpful, but the reduction of CO2 benefit eventually ends. So rapidly reducing the burning of fossil fuels is still required. Stopping rain forest destruction and stopping industrial farming are important helpful steps, but they are not lasting solutions.
The solution is for the highest consuming and impacting people to be low consuming and impacting people, and the richer they are the lower theiir consuption and impacts should be vbecxause richer people can afford to behave better.
That requires the combination of reduction of consuption that nigelj suggests along with corrrections of the consumption that occurs to only be sustainable activities like regenrative farming and renewable energy (not nuclear) done in a way that does not unsustainably consume materials, like the rare earth materials used in machines being fully recycled (no losses). It also requires external goiverning of the selfish among the population who will not responsibly self-govern to behave better than those who are less fortunate than they are.
M S Sweet @9 I never said otherwise. What I said simply summarised my view @2. Here it is again: "there are a couple of problems with your ideas. Most places dont have much zero carbon electricity and are unlikely to hit 100% before 2050 Paris Accord time frames. We don't have zero carbon fuels for aircraft, apart from very limited ethanol blends, and may never have at 100% level, and we dont have regenerative agriculture at scale and scaling it will not be quick or easy, and we dont have zero carbon cements, etcetera. So we have to look at how much we reduce our relevant personal consumption, at a point in time. It will vary over time obviously."
Do you disagree? If so why?
OPOF @10. thanks for understanding the issue is about levels of consumption, as well as building sustainable systems and making substitutions.
Correction to typo: "Most places dont have much zero carbon electricity and are unlikely to hit 100% by 2050"
Nigelj,
Jacobsosn et al 2018 and Connelly et al 2016 both show that it is entirely possible to build out a renewable energy system for ALL POWER by 2050 (not just electricity, All Power: electricity, heat, transportation, farming and industry). They include non fossil fuel for airplanes. The only thing required is political will power.
If everyone works hard to convince political leaders to get going we might have a chance.
Renewable energy has only been the cheapest option for about 5 years. It is now the cheapest option in about 2/3 of the world. In a few years it will be the cheapest option everywhere. Since fossil power plants take 10 years to plan and build they are still finishing plants started 10 years ago (like the Barakah nuclear plant in the UAE). If the USA takes a leadership position the change will be faster.
The Red Baron is more optimistic and informed about regenerative agriculture than I am. I think they will get something out of agriculture.
The unsupported opinion of a non expert who does not like to read the primary literature is not very valuable.
michael sweet @14
I have no doubt renewable energy is technically possible by 2050, and it wont be excessively stressful financially, and we have the economic capacity if theres a will to do it. That was never the point at issue.
You havent really answered my question. I will try rephrasing it. It seems unlikely we will meet the targets of solving all problems by 2050 with sustainable systems (including renewable energy), for various politicial reasons (using this widely) , so we should look at a plausible scenario, and make up the shortfall by making some level of reduction to our consumption of electricity, meat, flying, and so on (and various authorities promote the same, more or less). This in turn suggests we need to get a little bit more specific about quantities.
So do you agree or disagree ? Surely scientists can manage a simple clear cut yes or no? You can of course qualify things with as many or few '"buts" as you want.
Its just that by agreeing fully with RB you were by simple logic appear to be disagreeing pretty fully with what Ive just said.
I have already put some energy into trying to convince politicians and others to adopt renewable energy programmes. I dont specifically promote nuclear power very often at all, but I just dont see it as an option worth opposing.
Nigelj,
You are putting words in Brd Barons and my mouths.
[BL] The two of you seem to be going around and around in circles on this. Can all involved please try to restrict comments to new points and reasonable discussion?
M S Sweet, @16
"You are putting words in Brd Barons and my mouths."
No I'm not. I said you 'appear' to be dismissing my comments. There is a huge difference between this and saying "M S Sweet dismisses my comments.
And notice how when I respond to people I copy and paste what they say. This is how professionals do it. You just paraphrase and its not even slightly accurate.
And I asked you a clear question. You still havent answered it. Enginner Poet is right about you.