Carbon emissions must be reduced to avoid dangerous climate change. Economic growth will increase emissions unless production is decarbonised.
Can the world’s economy be decarbonised fast enough to allow growth that is also green?
Or must the world’s economy shrink?
The carbon intensity of production
The total production of the world economy is the combined production of all the countries in the world. It is called the gross world product (GWP). In dollar terms, this has been estimated as $87 trillion for 2013.
The amount of greenhouse gasses humans emit is determined partly by GWP. It is also also determined by how much greenhouse gas is emitted for each unit of GWP. Roughly 400 grammes of CO2 are emitted for each dollar’s worth of production. This the Carbon Intensity. It gives
Global_emissions_of_CO2 = Gross_World_Product*Carbon_Intensity
Global_emissions_of_CO2 in numbers is:
$87 trillion * 400 grammes CO2/$ = 35 billion tonnes
The goods and services the “average” person produces is the Personal_Product so
Gross_World_Product in numbers is:
6.8 billion people * $1300= $87 trillion
This means Global_emissions_of_CO2 is (1)
This helps us see that there are three ways of reducing carbon emissions:
- Reduce World Population
- Reduce Personal Product
- Reduce Carbon Intensity
Policies to reduce population will not be analysed here. Reducing Carbon_Intensity is what most policy makers emphasise. The big question is “What if it can’t be done fast enough?”
Supplimentary material will show some calculation for the decade ending 2013. During this time
- World Population increased by 12%
- Personal Product increased 60%
- Carbon Intensity reduced by 28%
- but … Carbon emissions increased by 30%
And during the three years up to 2013
- World Population increased by 3.5%
- Personal Product increased 17%
- Carbon Intensity reduced by 12%
- but … Carbon emissions increased by 7%
Carbon emissions are still increasing – boosted somewhat by an increased population; reduced substantially by a lower Carbon Intensity but swamped by increased Personal Product, the GWP per person.
Some, if not most, policy makers say that “Green Growth” is possible – and an increase in production can be counter balanced by a much lower carbon intensity so that carbon emissions fall fast enough to avoid dangerous climate change. The questions are
- Can the world decarbonise fast enough?
- Is Green Growth a fantasy?
Worldwide personal carbon budget
Carbon Brief reports the remaining carbon budget to give a 66% chance of keeping global warming below 1.5˚C is 243 billion tonnes. That means, if humanity emits 243 billion tonnes more of CO2e global temperature will rise to 1.5˚C above pre-industrial. Using the same calculations, the remaining carbon budget to keep below 2˚C is 843 billion tonnes.
World population was estimated recently at 7,317,801,293 by Worldometers. Dividing the remaining carbon budgets by the world’s population gives 33 tonnes of CO2e for a 1.5°C rise. For a 2°C rise this calculates as 115 tonnes per person.
UK emissions: 21 tonnes CO2e per person per year?
In a little noticed corner of a report by the Committee on Climate Change (the CCC), Reducing the UK’s carbon footprint, figure 1.8 shows the UK’s greenhouse gas emissions peaking at 1350 million tonnes of CO2e in 2007, just before the economic crash. That’s about 21 tonnes per person CO2e per year. Figure 1.8 also shows a fall of about 25% for 2009 as a result of the crash.
Figure 1.8, Greenhouse gas emissions associated with UK consumption (1993-2010), separates greenhouse gas emissions from the UK’s domestic consumption from emissions caused abroad in producing the UK’s imports. For all years after 1997 imported emissions exceed domestic emissions. The fall in emissions between 2007 and 2009 is largely the result of a fall in imported emissions (about 25%) rather than a fall in domestic emissions (just over 10%).
Figures given in a the UK’s Carbon Footprint 2007 to 2012 from DEFRA, gives similar figures for domestic consumption emissions as the CCC report but imported emissions are given as significantly lower – by about a third. However, the report does say
the uncertainty relating to the changes in the UK’s greenhouse gas footprint has not yet been researched and the estimates must therefore be treated with caution and have been classified as experimental.
For the examples below the lower values in the DEFRA report will be used.
Extracting carbon from the atmosphere is necessary
The latest IPCC reports the need for extracting carbon from the atmosphere towards in the second half of this century in order to keep within the 2°C rise in global temperatures. 2°C is the threshold for “dangerous climate change”.
In No option left but to suck CO2 out of air, says IPCC, the New Scientist reports
Keeping below a 2°C rise probably means keeping CO2 concentrations in the air below 450 parts per million. We are already up from a pre-industrial 280 ppm to 400 ppm. Most scenarios the IPCC examined overshot 450 ppm and required recovery through “negative emissions” – BECCS, or some other CO2-sucking technology – later this century. CCS could be risky, but we may have no choice, the IPCC says.
For a rudimentary sketch of a large scale BECCS project, see How Drax could be the greenest machine in the world. This looks at turning Drax Power Station in Yorkshire, the largest coal-fired power station in the country, into BECCS power station to extract CO2 from the atmosphere. This would not be easy – some might say impossible – but “we may have no choice”.
Green growth in the UK?
Can the UK eke out its remaining carbon budget until BECCS rescues the climate? Does “Green growth in the UK” mean that the UK’s remaining carbon budget lasts long enough for BECCS to work and at the same time grow the economy. For the sake of argument assume that BECCS begins to work seriously after 2050.
According to the UK’s Carbon Footprint 2007 to 2012, the carbon footprint of the UK for the year 2012 was 863 million tonnes of CO2e per year, measured on a consumption basis. That was 13.5 tonnes each. These emissions exceed the remaining carbon budget for a 1.5˚C rise in less than three years.
Can the UK to keep within the 115 tonne, 2˚C budget? Large reductions in emissions will be required. For example, reducing carbon emissions at a rate of 11% a year exhausts the budget by 2050. For “Green Growth in the UK” to be possible carbon intensity must decrease at rate of more than 11% a year, far higher than in the decade 2002 to 2012. In that decade it decreased by an average of 2.4% a year.
If that rate continued, production per person would have to fall by 8.6% a year to keep within budget.
“Green growth for the UK” probably is a fantasy.
Green growth for the world?
Worldwide, the numbers don’t seem quite as bad because the yearly emissions of green house gasses are just over 5 tonnes CO2e per person, much lower than in the UK. This breaks the 33 tonne, 1.5˚C budget in six years (See Carbon Brief’s Six years worth of current emissions would blow the carbon budget for 1.5 degrees). To eke out the 115 tonne, 2˚C budget until 2050 requires personal carbon emissions to fall at a rate of 4% a year.
For green growth to be possible for the whole world, the carbon intensity of production must fall by over 4% a year and large scale carbon extraction from the atmosphere must be possible after 2050.
“Green growth for the World” may be a fantasy too.
Now for the bad news
Bad news no 1. Missing carbon feedbacks.
It is known the climate models that the IPCC used to calculate these remaining budgets (the CMIP5 models) have missing feedbacks and their estimates of temperature rise were underestimates. POSTnote 454 from the Parliamentary Office of Science and Technology, Risks from Climate Feedbacks (POST-PN-454,January 2014) says
Compared to existing model estimates, it is likely that climate feedbacks will result in additional carbon in the atmosphere and additional warming. This is because the majority of poorly represented climate feedbacks are likely to be amplifying feedbacks. This additional atmospheric carbon from climate feedbacks could make it more difficult to avoid a greater than 2°C rise in global temperatures without additional reductions in greenhouse gas emissions. The strength of many amplifying feedbacks is likely to increase with warming, which could increase the risk of the climate changing state.
Some commentators suggest the uncertainties in our knowledge of carbon cycle and physical feedbacks may mean the Earth will warm faster than models currently estimate.
This means the carbon budgets discussed above are too generous.
Bad news no 2 A 2˚C temperature rise may not be safe.
The UK government is set on 2˚C as the threshold of dangerous climate change. Earlier this year Ed Davey, then Secretary of State at DECC said in a speech launching their Carbon Calculator
We need to help people focus on the solutions that work, that add up, that keep the global temperature rise within 2 degrees C. The UK’s approach has been to set in law an ambitious target to reduce emissions by 80% by 2050.
But is 2°C safe? Not according to James Hansen. A few days ago, on Australia’s RN breakfast, he said:
Two degrees is a prescription for disaster that’s actually well understood by the scientific community… This number was chosen because it was convenient. It was thought that will give us a few decades so we can set targets for the middle of the century. What the science tells us is that we have an emergency. This is actually a global crisis and the science for that is crystal clear.
Bad news No 3 The reduction in carbon intensity may be lower.
In the calculations above population data used is from the US Census Office, carbon emissions data from PBL Netherlands Environmental Assessment Agency and global production per person from Index Mundi, based on the CIA World Factbook. were calculated from these. For the years between 2007 and 2011, the average changes in carbon intensity was a fall of 3.7%..
Carbon intensity has also been been estimated by the US Energy Information Administration for these years. Their figures for carbon intensity are larger, partly explained by different units in measuring global production. The bad news is that for these years the EIA have the carbon intensity growing by an average of 0.9%.
With bad news on the climate appearing regularly, it’s hard to avoid this conclusion:
“Green Growth is a Fantasy”: Dangerous climate change cannot be avoided without reducing world consumption.
Note (1) : This is based on the Kaya identity.
Note (2): In the calculations for “Green growth in the UK?”, population is assumed to be rising at 0.6% a year. In “Green growth for the world?”, population is assumed to be rising at 1% a year.
Postscript 11 November 2015
Met Office doubts the IPCC
I attended a joint presentation of the Committee on Climate Change and the Met Office this week. Julia Slingo, Chief Scientist at the Met Office’s Hadley Centre, gave an illuminating presentation. If I remember correctly, she mentioned the wildfires in Indonesia as additional feedback cutting the climate budget.
I also picked up a Met Office handout which says “There is also a number of additional Earth system feedbacks that could affect the future budget, including the nitrogen cycle constraints on the carbon cycle, and emissions of greenhouse gasses from permafrost and methane hydrates. These are expected to place further limitations on the total global carbon budget.” (These feedbacks are also mentioned in Parliamentary POSTnote 454,“Risks from Climate Feedbacks”, January 2014),
I have always believed Myles Allen’s Trillion Tonne Hypothesis was too optimistic. This postulates that the amount of carbon emissions that would raise world temperatures to 2˚C above preindustrial to be 1 trillions tonnes of carbon (i.e. 3670 tonnes of CO2). The problem is that the computer models of climate, when the calculations were made, had missing feedbacks. (See “Myles Allen and the Trillion Tonne hypothesis” in The Committee on Climate Change: Letters and response.)
“These are expected to place further limitations on the total global carbon budget.” Is that a polite way of saying Myles Allen and the IPCC have been too optimistic and overestimated the remaining carbon budget?
Postscript 28 April 2016
Updates for the remaining carbon budgets
More than a year has passed since Carbon Brief’s calculation in November 2014. So reducing the carbon budgets by emissions since then (7 tonnes CO2 per peson) gives
The remaining carbon budget for a 66% chance of avoiding 1.5˚C is now… 26 tonnes CO2 per person. This requires a yearly rate of decarbonisation of 15%
The remaining carbon budget for a 66% chance of avoiding 2.0˚C is now… 108 tonnes CO2 per person. This requires a yearly rate of decarbonisation of 4%
(The following needs checking….)
However, these budgets are too high because this only accounts for the effects of CO2 and do not take account of other greenhouse gasses. The World Resources Institute says:
“one can argue for an even smaller budget and additional emissions constraints because non-CO2 gases are not included in 1 trillion tonne C figure. For example, short-lived greenhouse gases, such as methane, are not included in – nor necessarily appropriate for – the 1 trillion tonne C budget approach because they play a secondary role in influencing long-term warming.
However, when non-CO2 forcings are taken into account, the budget is reduced and that budget may depend on the scenario studied. For example, according to one scenario studied in the IPCC AR5 (RCP 2.6), when non-CO2 greenhouse gases are considered, the budget drops much lower to 790 PgC.”
That means that the effect of other greenhouse gasses reduces the overall budget to 79% of the original. The remaining carbon budgets are measured in terms of CO2 so, as a rough estimate they should be reduced by 21%. This now gives
The remaining carbon budget for a 66% chance of avoiding 1.5˚C becomes … 21 tonnes CO2 per person. This requires a yearly rate of decarbonisation of 24%
The remaining carbon budget for a 66% chance of avoiding 2.0˚C becomes… 85 tonnes CO2 per person. This requires a yearly rate of decarbonisation of 5%
But there are reasons these may be too optimistic.
Postscript July 2016: DEFRA seem to agree!
Email to DEFRA (9 June 2016)
I have updated the IPCC’s remaining carbon budgets elsewhere estimating the remaining budget for 2˚C as 115 tonnes of CO2e per person or alternatively 85 tonnes CO2.
Reply from DEFRA’s contractors via DEFRA (4 Jul 2016)
“The work confirms what many other academics have commented on – the reductions in demand that are required are severe in scale and we will not meet targets by tackling emissions intensity alone.”
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