All posts for the month October, 2018

Australian Beer Prices set to Double Due to Global Warming?

Earlier this week Nature Plants published a new paper Decreases in global beer supply due to extreme drought and heat. 

The Scientific American has an article “Trouble Brewing? Climate Change Closes In on Beer Drinkers” with the sub-title “Increasing droughts and heat waves could have a devastating effect on barley stocks—and beer prices”. The Daily Mail headlines with “Worst news ever! Australian beer prices are set to DOUBLE because of global warming“. All those climate deniers in Australia have denied future generations the ability to down a few cold beers with their barbecued steaks tofu salads.

This research should be taken seriously, as it is by a crack team of experts across a number of disciplines and Universities. Said, Steven J Davis of University of California at Irvine,

The world is facing many life-threatening impacts of climate change, so people having to spend a bit more to drink beer may seem trivial by comparison. But … not having a cool pint at the end of an increasingly common hot day just adds insult to injury.

Liking the odd beer or three I am really concerned about this prospect, so I rented the paper for 48 hours to check it out. What a sensation it is. Here a few impressions.

Layers of Models

From the Introduction, there were a series of models used.

  1. Created an extreme events severity index for barley based on extremes in historical data for 1981-2010.
  2. Plugged this into five different Earth Systems models for the period 2010-2099. Use this against different RCP scenarios, the most extreme of which shows over 5 times the warming of the 1981-2010 period. What is more severe climate events are a non-linear function of temperature rise.
  3. Then model the impact of these severe weather events on crop yields in 34 World Regions using a “process-based crop model”.
  4. “(W)e examine the effects of the resulting barley supply shocks on the supply and price of beer in each region using a global general equilibrium model (Global Trade Analysis Project model, GTAP).”
  5. “Finally, we compare the impacts of extreme events with the impact of changes in mean climate and test the sensitivity of our results to key sources of uncertainty, including extreme events of different severities, technology and parameter settings in the economic model.”

What I found odd was they made no allowance for increasing demand for beer over a 90 year period, despite mentioning in the second sentence that

(G)lobal demand for resource-intensive animal products (meat and dairy) processed foods and alcoholic beverages will continue to grow with rising incomes.

Extreme events – severity and frequency

As stated in point 2, the paper uses different RCP scenarios. These featured prominently in the IPCC AR5 of 2013 and 2014. They go from RCP2.6, which is the most aggressive mitigation scenario, through to RCP 8.5 the non-policy scenario which projected around 4.5C of warming from 1850-1870 through to 2100, or about 3.8C of warming from 2010 to 2090.

Figure 1 has two charts. On the left it shows that extreme events will increase intensity with temperature. RCP2.6 will do very little, but RCP8.5 would result by the end of the century with events 6 times as intense today. Problem is that for up to 1.5C there appears to be no noticeable change what so ever.  That is about the same amount of warming the world has experienced from 1850-2010 per HADCRUT4 there will be no change. Beyond that things take off. How the models empirically project well beyond known experience for a completely different scenario defeats me. It could be largely based on their modelling assumptions, which is in turn strongly tainted by their beliefs in CAGW. There is no reality check that it is the models that their models are not falling apart, or reliant on arbitrary non-linear parameters.

The right hand chart shows that extreme events are porjected to increase in frequency as well. Under RCP 2.6 ~ 4% chance of an extreme event, rising to ~ 31% under RCP 8.5. Again, there is an issue of projecting well beyond any known range.

Fig 2 average barley yield shocks during extreme events

The paper assumes that the current geographical distribution and area of barley cultivation is maintained. They have modelled in 2099, from the 1981-2010 a gridded average yield change with 0.5O x 0.5O resolution to create four colorful world maps representing each of the four RCP emissions scenarios. At the equator, each grid is about 56 x 56 km for an area of 3100 km2, or 1200 square miles. Of course, nearer the poles the area diminishes significantly. This is quite a fine level of detail for projections based on 30 years of data to radically different circumstances 90 years in the future. The results show. Map a) is for RCP 8.5. On average yields are projected to be 17% down. As Paul Homewood showed in a post on the 17th, this projected yield fall should be put in the context of a doubling of yields per hectare since the 1960s.

This increase in productivity has often solely ascribed to the improvements in seed varieties (see Norman Borlaug), mechanization and use of fertilizers. These have undoubtably have had a large parts to play in this productivity improvement. But also important is that agriculture has become more intensive. Forty years ago it was clear that there was a distinction between the intensive farming of Western Europe and the extensive farming of the North American prairies and the Russian steppes. It was not due to better soils or climate in Western Europe. This difference can be staggering. In the Soviet Union about 30% of agricultural output came from around 1% of the available land. These were the plots that workers on the state and collective farms could produce their own food and sell surplus in the local markets.

Looking at chart a in Figure 2, there are wide variations about this average global decrease of 17%.

In North America Montana and North Dakota have areas where barley shocks during extreme years will lead to mean yield changes over 90% higher normal, and the areas around have >50% higher than normal. But go less than 1000 km North into Canada to the Calgary/Saskatoon area and there are small decreases in yields.

In Eastern Bolivia – the part due North of Paraguay – there is the biggest patch of > 50% reductions in the world. Yet 500-1000 km away there is a North-South strip (probably just 56km wide) with less than a 5% change.

There is a similar picture in Russia. On the Kazakhstani border, there are areas of > 50% increases, but in a thinly populated band further North and West, going from around Kirov to Southern Finland is where there are massive decreases in yields.

Why, over the course of decades, would those with increasing yields not increase output, and those with decreasing yields not switch to something else defeats me. After all, if overall yields are decreasing due to frequent extreme weather events, the farmers would be losing money, and those farmers do well when overall yields are down will be making extraordinary profits.

A Weird Economic Assumption

Building up to looking at costs, their is a strange assumption.

(A)nalysing the relative changes in shares of barley use, we find that in most case barley-to-beer shares shrink more than barley-to-livestock shares, showing that food commodities (in this case, animals fed on barley) will be prioritized over luxuries such as beer during extreme events years.

My knowledge of farming and beer is limited, but I believe that cattle can be fed on other things than barley. For instance grass, silage, and sugar beet. Yet, beers require precise quantities of barley and hops of certain grades.

Further, cattle feed is a large part of the cost of a kilo of beef or a litre of milk. But it takes around 250-400g of malted barley to produce a litre of beer. The current wholesale price of malted barley is about £215 a tonne or 5.4 to 8.6p a litre. About cheapest 4% alcohol lager I can find in a local supermarket is £3.29 for 10 x 250ml bottles, or £1.32 a litre. Take off 20% VAT and excise duty leaves 30p a litre for raw materials, manufacturing costs, packaging, manufacturer’s margin, transportation, supermarket’s overhead and supermarket’s margin. For comparison four pints (2.276 litres) of fresh milk costs £1.09 in the same supermarket, working out at 48p a litre. This carries no excise duty or VAT. It might have greater costs due to refrigeration, but I would suggest it costs more to produce, and that feed is far more than 5p a litre.

I know that for a reasonable 0.5 litre bottle of ale it is £1.29 to £1.80 a bottle in the supermarkets I shop in, but it is the cheapest that will likely suffer the biggest percentage rise from increase in raw material prices. Due to taxation and other costs, large changes in raw material prices will have very little impact on final retail costs. Even less so in pubs where a British pint (568ml) varies from the £4 to £7 a litre equivalent.

That is, the assumption is the opposite of what would happen in a free market. In the face of a shortage, farmers will substitute barley for other forms of cattle feed, whilst beer manufacturers will absorb the extra cost.

Disparity in Costs between Countries

The most bizarre claim in the article in contained in the central column of Figure 4, which looks at the projected increases in the cost of a 500 ml bottle of beer in US dollars. Chart h shows this for the most extreme RCP 8.5 model.

I was very surprised that a global general equilibrium model would come up with such huge disparities in costs after 90 years. After all, my understanding of these models used utility-maximizing consumers, profit-maximizing producers, perfect information and instantaneous adjustment. Clearly there is something very wrong with this model. So I decided to compare where I live in the UK with neighbouring Ireland.

In the UK and Ireland there are similar high taxes on beer, with Ireland being slightly more. Both countries have lots of branches of the massive discount chain. They also have some products on their website aldi.co.uk and aldi.ie.  In Ireland a 500 ml can of Sainte Etienne Lager is €1.09 or €2.18 a litre or £1.92 a litre. In the UK it is £2.59 for 4 x 440ml cans or £1.59 a litre. The lager is about 21% more in Ireland. But the tax difference should only be about 15% on a 5% beer (Saint Etienne is 4.8%). Aldi are not making bigger profits in Ireland, they just may have higher costs in Ireland, or lesser margins on other items. It is also comparing a single can against a multipack. So pro-rata the £1.80 ($2.35) bottle of beer in the UK would be about $2.70 in Ireland. Under the RCP 8.5 scenario, the models predict the bottle of beer to rise by $1.90 in the UK and $4.84 in Ireland. Strip out the excise duty and VAT and the price differential goes from zero to $2.20.

Now suppose you were a small beer manufacturer in England, Wales or Scotland. If beer was selling for $2.20 more in Ireland than in the UK, would you not want to stick 20,000 bottles in a container and ship it to Dublin?

If the researchers really understood the global brewing industry, they would realize that there are major brands sold across the world. Many are brewed across in a number of countries to the same recipe. It is the barley that is shipped to the brewery, where equipment and techniques are identical with those in other parts of the world. This researchers seem to have failed to get away from their computer models to conduct field work in a few local bars.

What can be learnt from this?

When making projections well outside of any known range, the results must be sense-checked. Clearly, although the researchers have used an economic model they have not understood the basics of economics. People are not dumb  automatons waiting for some official to tell them to change their patterns of behavior in response to changing circumstances. They notice changes in the world around them and respond to it. A few seize the opportunities presented and can become quite wealthy as a result. Farmers have been astute enough to note mounting losses and change how and what they produce. There is also competition from regions. For example, in the 1960s Brazil produced over half the world’s coffee. The major region for production in Brazil was centered around Londrina in the North-East of Parana state. Despite straddling the Tropic of Capricorn, every few years their would be a spring-time frost which would destroy most of the crop. By the 1990s most of the production had moved north to Minas Gerais, well out of the frost belt. The rich fertile soils around Londrina are now used for other crops, such as soya, cassava and mangoes. It was not out of human design that the movement occurred, but simply that the farmers in Minas Gerais could make bumper profits in the frost years.

The publication of this article shows a problem of peer review. Nature Plants is basically a biology journal. Reviewers are not likely to have specialist skills in climate models or economic theory, though those selected should have experience in agricultural models. If peer review is literally that, it will fail anyway in an inter-disciplinary subject, where the participants do not have a general grounding in all the disciplines. In this paper it is not just economics, but knowledge of product costing as well. It is academic superiors from the specialisms that are required for review, not inter-disciplinary peers.

Kevin Marshall

 

by manicbeancounter on 18/10/2018  •  Permalink
Posted in Climate Change Economics, Costing, Economics, Global Warming, Science & Non-science, Science - the Boundaries
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Posted by manicbeancounter on 18/10/2018

https://manicbeancounter.com/2018/10/18/australian-beer-prices-set-to-double-due-to-global-warming/

IPCC SR1.5 – Notes on Calculations and Assumptions

Given that my previous post was about failing to reconcile the emissions estimates for 1.5°C and 2.0°C of warming in the IPCC fifth assessment report (AR5), I was intrigued to see how the new IPCC “special report on the impacts of global warming of 1.5 °C above pre-industrial levels” would fare. However, that will have to wait for another post, as first there are some “refinements” from AR5 in how results are obtained. From my analysis they would appear that key figures on temperatures and climate sensitivities are highly contrived.

Isn’t 1.5°C of warming already built in? 

Chapter 1 Page 24

Expert judgement based on the available evidence (including model simulations, radiative forcing and climate sensitivity) suggests that if all anthropogenic emissions were reduced to zero immediately, any further warming beyond the 1°C already experienced would likely be less than 0.5°C over the next two to three decades, and also likely less than 0.5°C on a century timescale.

This basically states that if all emissions were stopped now there is more than a 50% chance that warming would not exceed 1.5°C. But using previous assumptions 1.5°C should be already be built in. 

If ECS = 3.0 (as in AR5) then that implies the net effect of all GHGs and all aerosols is less than 396 ppm, despite CO2 on its own in September 2018 being 405.5 ppm (1.6°C of eventual warming). Further, in 2011 the impact of all GHGs combined was equivalent to 430 ppm, or an extra 40 ppm more than CO2 on its own. On that basis we are at the around 445 ppm or fractionally about the 2.0°C warming level. However, in AR5 it was assumed (based on vague estimates) that the negative human impacts of aerosols exactly offset the addition of other GHGs (e.g. methane) so that only CO2 is considered. Even then based on ECS = 3.0 without further emissions 1.5°C will be eventually reached.

But ECS has been lowered.

From Chapter 1 Annex Page 11

…Equilibrium Climate Sensitivity (ECS) of 2.7°C and Transient Climate Response (TCR) of 1.6°C and other parameters as given in Millar et al. (2017).

This raises the CO2-eq level to achieve 1.5°C of warming by 15-16 ppm from 396ppm and the CO2-eq level to achieve 2.0°C by 23-24 ppm from 444 ppm. Mauna Loa CO2 levels in September averaged 405.5 ppm. With ECS = 2.7 this is equivalent to just 1.44°C of eventual warming compared to 1.60°C  when ECS = 3.0. What is more significant is that if ECS were 2.8 eventual warming of 1.50°C would be in the pipeline sometime before the end of the year. ECS = 2.7 is the highest ECS that us currently compatible with the statement made above if CO2 alone is taken into account. Consider this in the light of 2013 AR5 WG1 SPM, which stated on page 16

Equilibrium climate sensitivity is likely in the range 1.5°C to 4.5°C

And in a footnote on the same page.

No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.

 In AR5 they chose ECS = 3.0 as it was in the middle of the range. A range unchanged since the Charney Report of 1979. I am not aware of any that establishes ECS is a range that would justify ECS = 2.7 that is not contradicted by other research. For instance Lewis and Curry 2018 gives a median estimate for ECS of 1.66.

Transient Climate Response (TCR)

But how does the Transient Climate Response (TCR) of 1.6°C fit into this? Some context can be had from the very start of the Summary for Policy-Makers SPM-4

A1.1. Reflecting the long-term warming trend since pre-industrial times, observed global mean surface temperature (GMST) for the decade 2006–2015 was 0.87°C (likely between 0.75°C and 0.99°C)

With TCR = 1.6°C for a doubling of CO2 levels what is the warming generated from a rise in CO2 levels from 280 to 400.83 ppm? That is a rise in CO2 levels from pre-industrial times to the average level in 2015. I calculate it to be 0.83°C. Make TCR = 1.7°C and that increases to 0.88°C. It is effectively assuming that both 100% of the rise in average temperatures in over 150 years is due to CO2 alone (consistent with AR5), and there has been no movement whatsoever from the short-term Transient Climate Response to the long-term Equilibrium Climate Sensitivity. However, if TCR is a variable figure derived from a calculation from revealed warming and CO2 rise, it becomes meaningless nonsense unless you can clearly demonstrate the other assumptions are robust. That is (1) 100% of past warming was due to human emissions (2) the impact of GHGs other than CO2 are effectively cancelled out by aerosols etc. (3) natural factors are net zero (4) the average temperature data anomaly is without any systematic biases. For instance, when measured CO2 levels were about 390ppm, the AR5 WG3 SPM stated in the last sentence on page 8

For comparison, the CO2-eq concentration in 2011 is estimated to be 430 ppm (uncertainty range 340 to 520 ppm)

It seems a pretty shaky foundation to the assumption that negative impact of aerosols (with uncertainties) will offset the combined impact of other GHG increases.

Summary and Concluding Comments

On the estimates of climate sensitivity, it appears to be set so that the IPCC can still claim that if emissions stopped tomorrow then there would be a greater than 50% chance of 1.5°C warming never been exceeded. The ECS value of 2.7°C is set at the maximum value, given the assumptions. But ceteris paribus, this will not hold if

  • One waits 3 years and CO2 levels continue increasing at a rate of the last few years.
  • ECS is slightly higher but still well within the accepted range of estimates. Indeed if ECS = 3.0, as in AR5 and AR4 in 2007, then 1.5C of warming was exceeded 5 years ago.
  • The impact of all GHGs together is slightly more than the offsetting impacts of other aerosols.
  • 0.06°C, or more, of the observed rise on temperature since 1850 is not due to GHG emissions.

Then there is the Transient Climate Response (TCR) which appears to be little more than taking the historical temperature change, assuming all of is down to human GHG emissions, and calculating a figure. Including rises in CO2 a century or more ago is hardly transient.

Based on my calculations, the results are highly contrived. They appear as a very fine balance between getting the maximum values for human-caused warming possible and not admitting that 1.5°C or even 2°C is already passed. There is a huge combination of empirical assumptions that are as equally valid as the ones used in the SR1.5 that go one way or the other. Rather than being a robust case, empirically it is highly improbable one.

Finally there is a conundrum here. I have calculated that if ECS = 2.7 and the starting level of CO2 is 280 ppm, then in round numbers, 1.5°C of warming results from CO2 levels of 412 ppm and 2.0°C of warming results from CO2 levels of 468 ppm. With CO2 levels in September 2018 at 406 ppm for 2.0°C of warming requires a rise in CO2 ten times greater than for 1.5°C of warming. So how can the IPCC claim that it is only about twice the amount of emissions? In my previous post I could not find an explanation, even though the emissions numbers reconciled with both past data and future emissions to generate 2.0°C of warming given certain assumptions. In the next I hope to provide an answer, which fits the figures quite closely, but looks pretty embarrassing.

Kevin Marshall
by manicbeancounter on 09/10/2018  •  Permalink
Posted in Climate Change, Science & Non-science
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Posted by manicbeancounter on 09/10/2018

https://manicbeancounter.com/2018/10/09/ipcc-sr1-5-initial-notes-on-calculations/

Why can’t I reconcile the emissions to achieve 1.5C or 2C of Warming?

Introduction

At heart I am beancounter. That is when presented with figures I like to understand how they are derived. When it comes to the claims about the quantity of GHG emissions that are required to exceed 2°C of warming I cannot get even close, unless by making some a series of  assumptions, some of which are far from being robust. Applying the same set of assumptions I cannot derive emissions consistent with restraining warming to 1.5°C

Further the combined impact of all the assumptions is to create a storyline that appears to me only as empirically as valid as an infinite number of other storylines. This includes a large number of plausible scenarios where much greater emissions can be emitted before 2°C of warming is reached, or where (based on alternative assumptions) plausible scenarios even 2°C of irreversible warming is already in the pipeline.  

Maybe an expert climate scientist will clearly show the errors of this climate sceptic, and use it as a means to convince the doubters of climate science.

What I will attempt here is something extremely unconventional in the world of climate. That is I will try to state all the assumptions made by highlighting them clearly. Further, I will show my calculations and give clear references, so that anyone can easily follow the arguments.

Note – this is a long post. The key points are contained in the Conclusions.

The aim of constraining warming to 1.5 or 2°C

The Paris Climate Agreement was brought about by the UNFCCC. On their website they state.

The Paris Agreement central aim is to strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius. 

The Paris Agreement states in Article 2

1. This Agreement, in enhancing the implementation of the Convention, including its objective, aims to strengthen the global response to the threat of climate change, in the context of sustainable development and efforts to eradicate
poverty, including by:

(a) Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change;

Translating this aim into mitigation policy requires quantification of global emissions targets. The UNEP Emissions Gap Report 2017 has a graphic showing estimates of emissions before 1.5°C or 2°C warming levels is breached.

Figure 1 : Figure 3.1 from the UNEP Emissions Gap Report 2017

The emissions are of all greenhouse gas emissions, expressed in billions of tonnes of CO2 equivalents. From 2010, the quantity of emissions before the either 1.5°C or 2°C is breached are respectively about 600 GtCO2e and 1000 GtCO2e. It is these two figures that I cannot reconcile when using the same  assumptions to calculate both figures. My failure to reconcile is not just a minor difference. Rather, on the same assumptions that 1000 GtCO2e can be emitted before 2°C is breached, 1.5°C is already in the pipeline. In establishing the problems I encounter I will clearly endeavor to clearly state the assumptions made and look at a number of examples.

 Initial assumptions

1 A doubling of CO2 will eventually lead to 3°C of rise in global average temperatures.

This despite the 2013 AR5 WG1 SPM stating on page 16

Equilibrium climate sensitivity is likely in the range 1.5°C to 4.5°C

And stating in a footnote on the same page.

No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.

2 Achieving full equilibrium climate sensitivity (ECS) takes many decades.

This implies that at any point in the last few years, or any year in the future there will be warming in progress (WIP).

3 Including other greenhouse gases adds to warming impact of CO2.

Empirically, the IPCC’s Fifth Assessment Report based its calculations on 2010 when CO2 levels were 390 ppm. The AR5 WG3 SPM states in the last sentence on page 8

For comparison, the CO2-eq concentration in 2011 is estimated to be 430 ppm (uncertainty range 340 to 520 ppm)

As with climate sensitivity, the assumption is the middle of an estimated range. In this case over one fifth of the range has the full impact of GHGs being less than the impact of CO2 on its own.

4 All the rise in global average temperature since the 1800s is due to rise in GHGs. 

5 An increase in GHG levels will eventually lead to warming unless action is taken to remove those GHGs from the atmosphere, generating negative emissions. 

These are restrictive assumptions made for ease of calculations.

Some calculations

First a calculation to derive the CO2 levels commensurate with 2°C of warming. I urge readers to replicate these for themselves.
From a Skeptical Science post by Dana1981 (Dana Nuccitelli) “Pre-1940 Warming Causes and Logic” I obtained a simple equation for a change in average temperature T for a given change in CO2 levels.

ΔTCO2 = λ x 5.35 x ln(B/A)
Where A = CO2 level in year A (expressed in parts per million), and B = CO2 level in year B.
I use λ = .809, so that if B = 2A, ΔTCO2 = 3.00

Pre-industrial CO2 levels were 280ppm. 3°C of warming is generated by CO2 levels of 560 ppm, and 2°C of warming is when CO2 levels reach 444 ppm.

From the Mauna Loa CO2 data, average CO2 levels averaged 407 ppm in 2017. Given the assumption (3) and further assuming the impact of other GHGs is unchanged, 2°C of warming would have been surpassed in around 2016 when CO2 levels averaged 404 ppm. The actual rise in global average temperatures is from HADCRUT4 is about half that amount, hence the assumption that the impact of a rise in CO2 takes an inordinately long time for the actual warming to reveal itself. Even with the assumption that 100% of the warming since around 1800 is due to the increase in GHG levels warming in progress (WIP) is about the same as revealed warming. Yet the Sks article argues that some of the early twentieth century warming was due to other than the rise in GHG levels.

This is the crux of the reconciliation problem. From this initial calculation and based on the assumptions, the 2°C warming threshold has recently been breached, and by the same assumptions 1.5°C was likely breached in the 1990s. There are a lot of assumptions here, so I could have missed something or made an error. Below I go into some key examples that verify this initial conclusion. Then I look at how, by introducing a new assumption it is claimed that 2°C warming is not yet reached.

100 Months and Counting Campaign 2008

Trust, yet verify has a post We are Doomed!

This tracks through the Wayback Machine to look at the now defunct 100monthsandcounting.org campaign, sponsored by the left-wing New Economics Foundation. The archived “Technical Note” states that the 100 months was from August 2008, making the end date November 2016. The choice of 100 months turns out to be spot-on with the actual data for CO2 levels; the central estimate of the CO2 equivalent of all GHG emissions by the IPCC in 2014 based on 2010 GHG levels (and assuming other GHGs are not impacted); and the central estimate for Equilibrium Climate Sensitivity (ECS) used by the IPCC. That is, take 430 ppm CO2e, and at 14 ppm for 2°C of warming.
Maybe that was just a fluke or they were they giving a completely misleading forecast? The 100 Months and Counting Campaign was definitely not agreeing with the UNEP Emissions GAP Report 2017 in making the claim. But were they correctly interpreting what the climate consensus was saying at the time?

The 2006 Stern Review

The “Stern Review: The Economics of Climate Change” (archived access here) that was commissioned to provide benefit-cost justification for what became the Climate Change Act 2008. From the Summary of Conclusions

The costs of stabilising the climate are significant but manageable; delay would be dangerous and much more costly.

The risks of the worst impacts of climate change can be substantially reduced if greenhouse gas levels in the atmosphere can be stabilised between 450 and 550ppm CO2 equivalent (CO2e). The current level is 430ppm CO2e today, and it is rising at more than 2ppm each year. Stabilisation in this range would require emissions to be at least 25% below current levels by 2050, and perhaps much more.

Ultimately, stabilisation – at whatever level – requires that annual emissions be brought down to more than 80% below current levels. This is a major challenge, but sustained long-term action can achieve it at costs that are low in comparison to the risks of inaction. Central estimates of the annual costs of achieving stabilisation between 500 and 550ppm CO2e are around 1% of global GDP, if we start to take strong action now.

If we take assumption 1 that a doubling of CO2 levels will eventually lead to 3.0°C of warming and from a base CO2 level of 280ppm, then the Stern Review is saying that the worst impacts can be avoided if temperature rise is constrained to 2.1 – 2.9°C, but only in the range of 2.5 to 2.9°C does the mitigation cost estimate of 1% of GDP apply in 2006. It is not difficult to see why constraining warming to 2°C or lower would not be net beneficial. With GHG levels already at 430ppm CO2e, and CO2 levels rising at over 2ppm per annum, the 2°C of warming level of 444ppm (or the rounded 450ppm) would have been exceeded well before any global reductions could be achieved.

There is a curiosity in the figures. When the Stern Review was published in 2006 estimated GHG levels were 430ppm CO2e, as against CO2 levels for 2006 of 382ppm. The IPCC AR5 states

For comparison, the CO2-eq concentration in 2011 is estimated to be 430 ppm (uncertainty range 340 to 520 ppm)

In 2011, when CO2 levels averaged 10ppm higher than in 2006 at 392ppm, estimated GHG levels were the same. This is a good example of why one should take note of uncertainty ranges.

IPCC AR4 Report Synthesis Report Table 5.1

A year before the 100 Months and Counting campaign The IPCC produced its Fourth Climate Synthesis Report. The 2007 Synthesis Report on Page 67 (pdf) there is table 5.1 of emissions scenarios.

Figure 2 : Table 5.1. IPCC AR4 Synthesis Report Page 67 – Without Footnotes

I inputted the various CO2-eq concentrations into my amended version of Dana Nuccitelli’s magic equation and compared to the calculation warming in Table 5.1

Figure 3 : Magic Equation calculations of warming compared to Table 5.1. IPCC AR4 Synthesis Report

My calculations of warming are the same as that of the IPCC to one decimal place except for the last two calculations. Why are there these rounding differences? From a little fiddling in Excel, it would appear to me that the IPCC got the warming results from a doubling of 3 when calculating to two decimal places, whilst my version of the formula is to four decimal places.

Note the following

  • That other GHGs are translatable into CO2 equivalents. Once translated other GHGs they can be treated as if they were CO2.
  • There is no time period in this table. The 100 Months and Counting Campaign merely punched in existing numbers and made a forecast ahead of the GHG levels that would reach the 2°C of warming.
  • No mention of a 1.5°C warming scenario. If constraining warming to 1.5°C did not seem credible in 2007, which should it be credible in 2014 or 2017, when CO2 levels are higher?

IPCC AR5 Report Highest Level Summary

I believe that the underlying estimates of emissions to achieve the 1.5°C or 2°C  of warming used by the UNFCCC and UNEP come from the UNIPCC Fifth Climate Assessment Report (AR5), published in 2013/4. At this stage I introduce an couple of empirical assumptions from IPCC AR5.

6 Cut-off year for historical data is 2010 when CO2 levels were 390 ppm (compared to 280 ppm in pre-industrial times) and global average temperatures were about 0.8°C above pre-industrial times.

Using the magic equation above, and the 390 ppm CO2 levels, there is around 1.4°C of warming due from CO2. Given 0.8°C of revealed warming to 2010, the residual “warming-in-progress” was 0.6°C.

The highest level of summary in AR5 is a Presentation to summarize the central findings of the Summary for Policymakers of the Synthesis Report, which in turn brings together the three Working Group Assessment Reports. This Presentation can be found at the bottom right of the IPCC AR5 Synthesis Report webpage. Slide 33 of 35 (reproduced below as Figure 4) gives the key policy point. 1000 GtCO2 of emissions from 2011 onwards will lead to 2°C. This is very approximate but concurs with the UNEP emissions gap report.

Figure 4 : Slide 33 of 35 of the AR5 Synthesis Report Presentation.

Now for some calculations.

1900 GtCO2 raised CO2 levels by 110 ppm (390-110). 1 ppm = 17.3 GtCO2

1000 GtCO2 will raise CO2 levels by 60 ppm (450-390).  1 ppm = 16.7 GtCO2

Given the obvious roundings of the emissions figures, the numbers fall out quite nicely.

Last year I divided CDIAC CO2 emissions (from the Global Carbon Project) by Mauna Loa CO2 annual mean growth rates (data) to produce the following.

Figure 5 : CDIAC CO2 emissions estimates (multiplied by 3.664 to convert from carbon units to CO2 units) divided by Mauna Loa CO2 annual mean growth rates in ppm.

17GtCO2 for a 1ppm rise is about right for the last 50 years.

To raise CO2 levels from 390 to 450 ppm needs about 17 x (450-390) = 1020 GtCO2. Slide 33 is a good approximation of the CO2 emissions to raise CO2 levels by 60 ppm.

But there are issues

  • If ECS = 3.00, and 17 GtCO2 of emissions to raise CO2 levels by 1 ppm, then it is only 918 (17*54) GtCO2 to achieve 2°C of warming. Alternatively, in future if there are assume 1000 GtCO2 to achieve 2°C  of warming it will take 18.5 GtCO2 to raise CO2 levels by 1 ppm, as against 17 GtCO2 in the past. It is only by using 450 ppm as commensurate with 2°C of warming that past and future stacks up.
  • If ECS = 3,  from CO2 alone 1.5°C would be achieved at 396 ppm or a further 100 GtCO2 of emissions. This CO2 level was passed in 2013 or 2014.
  • The calculation falls apart if other GHGs are included.  Emissions are assumed equivalent to 430 ppm at 2011. Therefore with all GHGs considered the 2°C warming would be achieved with 238 GtCO2e of emissions ((444-430)*17) and the 1.5°C of warming was likely passed in the 1990s.
  • If actual warming since pre-industrial times to 2010 was 0.8°C, ECS = 3, and the rise in all GHG levels was equivalent to a rise in CO2 from 280 to 430 ppm, then the residual “warming-in-progress” (WIP) was just over 1°C. That it is the WIP exceeds the total revealed warming in well over a century. If there is a short-term temperature response is half or more of the value of full ECS, it would imply even the nineteenth century emissions are yet to have the full impact on global average temperatures.

What justification is there for effectively disregarding the impact of other greenhouse emissions when it was not done previously?

This offset is to be found in section C – The Drivers of Climate Change – in AR5 WG1 SPM . In particular the breakdown, with uncertainties, in table SPM.5. Another story is how AR5 reached the very same conclusion as AR4 WG1 SPM page 4 on the impact of negative anthropogenic forcings but with a different methodology, hugely different estimates of aerosols along with very different uncertainty bands. Further, these historical estimates are only for the period 1951-2010, whilst the starting date for 1.5°C or 2°C is 1850.

From this a further assumption is made when considering AR5.

7 The estimated historical impact of other GHG emissions (Methane, Nitrous Oxide…) has been effectively offset by the cooling impacts of aerosols and precusors. It is assumed that this will carry forward into the future.

UNEP Emissions Gap Report 2014

Figure 1 above is figure 3.1 from the UNEP Emissions GAP Report 2017. The equivalent report from 2014 puts this 1000 GtCO2 of emissions in a clearer context. First a quotation with two accompanying footnotes.

As noted by the IPCC, scientists have determined that an increase in global temperature is proportional to the build-up of long-lasting greenhouse gases in the atmosphere, especially carbon dioxide. Based on this finding, they have estimated the maximum amount of carbon dioxide that could be emitted over time to the atmosphere and still stay within the 2 °C limit. This is called the carbon dioxide emissions budget because, if the world stays within this budget, it should be possible to stay within the 2 °C global warming limit. In the hypothetical case that carbon dioxide was the only human-made greenhouse gas, the IPCC estimated a total carbon dioxide budget of about 3 670 gigatonnes of carbon dioxide (Gt CO2 ) for a likely chance3 of staying within the 2 °C limit . Since emissions began rapidly growing in the late 19th century, the world has already emitted around 1 900 Gt CO2 and so has used up a large part of this budget. Moreover, human activities also result in emissions of a variety of other substances that have an impact on global warming and these substances also reduce the total available budget to about 2 900 Gt CO2 . This leaves less than about 1 000 Gt CO2 to “spend” in the future4 .

3 A likely chance denotes a greater than 66 per cent chance, as specified by the IPCC.

4 The Working Group III contribution to the IPCC AR5 reports that scenarios in its category which is consistent with limiting warming to below 2 °C have carbon dioxide budgets between 2011 and 2100 of about 630-1 180 GtCO2

The numbers do not fit, unless the impact of other GHGs are ignored. As found from slide 33, there is 2900 GtCO2 to raise atmospheric CO2 levels by 170 ppm, of which 1900 GtC02 has been emitted already. The additional marginal impact of other historical greenhouse gases of 770 GtCO2 is ignored. If those GHG emissions were part of historical emissions as the statement implies, then that marginal impact would be equivalent to an additional 45 ppm (770/17) on top of the 390 ppm CO2 level. That is not far off the IPCC estimated CO2-eq concentration in 2011 of 430 ppm (uncertainty range 340 to 520 ppm). But by the same measure 3670 GTCO2e would increase CO2 levels by 216 ppm (3670/17) from 280 to 496 ppm. With ECS = 3, this would eventually lead to a temperature increase of almost 2.5°C.

Figure 1 above is figure 3.1 from the UNEP Emissions GAP Report 2017. The equivalent report from the 2014 report ES.1

Figure 6 : From the UNEP Emissions Gap Report 2014 showing two emissions pathways to constrain warming to 2°C by 2100.

Note that this graphic goes through to 2100; only uses the CO2 emissions; does not have quantities; and only looks at constraining temperatures to 2°C.  To achieve the target requires a period of negative emissions at the end of the century.

A new assumption is thus required to achieve emissions targets.

8 Sufficient to achieve the 1.5°C or 2°C warming targets likely requires many years of net negative emissions at the end of the century.

A Lower Level Perspective from AR5

A simple pie chart does not seem to make sense. Maybe my conclusions are contradicted by the more detailed scenarios? The next level of detail is to be found in table SPM.1 on page 22 of the AR5 Synthesis Report – Summary for Policymakers.

Figure 7 : Table SPM.1 on Page 22 of AR5 Synthesis Report SPM, without notes. Also found as Table 3.1 on Page 83 of AR5 Synthesis Report 

The comment for <430 ppm (the level of 2010) is "Only a limited number of individual model studies have explored levels below 430 ppm CO2-eq. ” Footnote j reads

In these scenarios, global CO2-eq emissions in 2050 are between 70 to 95% below 2010 emissions, and they are between 110 to 120% below 2010 emissions in 2100.

That is, net global emissions are negative in 2100. Not something mentioned in the Paris Agreement, which only has pledges through to 2030. It is consistent with the UNEP Emissions GAP report 2014 Table ES.1. The statement does not refer to a particular level below 430 ppm CO2-eq, which equates to 1.86°C. So how is 1.5°C of warming not impossible without massive negative emissions? In over 600 words of notes there is no indication. For that you need to go to the footnotes to the far more detailed Table 6.3 AR5 WG3 Chapter 6 (Assessing Transformation Pathways – pdf) Page 431. Footnote 7 (Bold mine)

Temperature change is reported for the year 2100, which is not directly comparable to the equilibrium warming reported in WGIII AR4 (see Table 3.5; see also Section 6.3.2). For the 2100 temperature estimates, the transient climate response (TCR) is the most relevant system property.  The assumed 90% range of the TCR for MAGICC is 1.2–2.6 °C (median 1.8 °C). This compares to the 90% range of TCR between 1.2–2.4 °C for CMIP5 (WGI Section 9.7) and an assessed likely range of 1–2.5 °C from multiple lines of evidence reported in the WGI AR5 (Box 12.2 in Section 12.5).

The major reason that 1.5°C of warming is not impossible (but still more unlikely than likely) for CO2 equivalent levels that should produce 2°C+ of warming being around for decades is because the full warming impact takes so long to filter through.  Further, Table 6.3 puts Peak CO2-eq levels for 1.5-1.7°C scenarios at 465-530 ppm, or eventual warming of 2.2 to 2.8°C. Climate WIP is the difference. But in 2018 WIP might be larger than all the revealed warming in since 1870, and certainly since the mid-1970s.

Within AR5 when talking about constraining warming to 1.5°C or 2.0°C it is only the warming which is estimated to be revealed in 2100. There is no indication of how much warming in progress (WIP) there is in 2100 under the various scenarios, therefore I cannot reconcile back the figures. However, for GHG  would appear that the 1.5°C figure relies upon a period of over 100 years for impact of GHGs on warming failing to come through as (even netting off other GHGs with the negative impact of aerosols) by 2100 CO2 levels would have been above 400 ppm for over 85 years, and for most of those significantly above that level.

Conclusions

The original aim of this post was to reconcile the emissions sufficient to prevent 1.5°C or 2°C of warming being exceeded through some calculations based on a series of restrictive assumptions.

  • ECS = 3.0°C, despite the IPCC being a best estimate across different studies. The range is 1.5°C to 4.5°C.
  • All the temperature rise since the 1800s is assumed due to rises in GHGs. There is evidence that this might not be the case.
  • Other GHGs are netted off against aerosols and precursors. Given that “CO2-eq concentration in 2011 is estimated to be 430 ppm (uncertainty range 340 to 520 ppm)” when CO2 levels were around 390 ppm, this assumption is far from robust.
  • Achieving full equilibrium takes many decades. So long in fact that the warming-in-progress (WIP) may currently exceed all the revealed warming in over 150 years, even based on the assumption that all of that revealed historical warming is due to rises in GHG levels.

Even with these assumptions, keeping warming within 1.5°C or 2°C seems to require two assumptions that were not recognized a few years ago. First is to assume net negative global emissions for many years at the end of the century. Second is to talk about projected warming in 2100 rather than warming as a resultant on achieving full ECS.

The whole exercise appears to rest upon a pile of assumptions. Amending the assumptions means one way means admitting that 1.5°C or 2°C of warming is already in the pipeline, or the other way means admitting climate sensitivity is much lower. Yet there appears to be a very large range of empirical assumptions to chose from there could be there are a very large number of scenarios that are as equally valid as the ones used in the UNEP Emissions Gap Report 2017.

Kevin Marshall
by manicbeancounter on 03/10/2018  •  Permalink
Posted in Climate Change Analysis, Climate Change Economics, COP21 Paris, Global Warming, Uncategorized
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Posted by manicbeancounter on 03/10/2018

https://manicbeancounter.com/2018/10/03/why-cant-i-reconcile-the-emissions-to-achieve-1-5c-or-2c-of-warming/