Friday, February 7, 2020

Climate 2020: Still on a glide-path to diaster, part three ("Peak Coal")

In Parts One & Two, I illustrated how the probability of ongoing exponential economic growth makes RCP8.5 (or something even worse) a quite plausible future. But what are the arguments against RCP8.5 as a plausible future?

Thus Zeke Hausfather in Carbon Brief:

One particular aspect of both the RCP8.5 and the new SSP 8.5 scenarios that has drawn quite a bit of criticism from energy researchers are their assumptions around future coal use. Reaching the CO2 emissions in these scenarios requires a large-scale increase in coal use – with 6.5 times more coal use in 2100 than today.…

With global coal use having declined slightly since its peak in 2014, it is hard to envision a world where coal expands this dramatically in the future even in the absence of new climate policies. This is particularly true given the falling prices of alternative energy technologies in recent years. A forthcoming “expert elicitation” – where energy experts were asked to assess the likelihood of various outcomes – gives RCP8.5 only a 5% chance of occurring among all the possible no-policy baseline scenarios.

Argument I: Coal use peaked in 2014 [or 2013, depending on the source], and is likely to continue to decline, making the expansion of coal use posited in RCP8.5 implausible.

 Truly, it's hard to dispute that, just look at this graph of global coal consumption annually:

Not Really

 No, I'm only kidding! That's part of a graph of global temperatures:

 Here's the real data on annual coal consumption:

Except I'm obvisously still kidding, because I've just taken the September Arctic sea ice area and inverted it:

This is -- I promise, joke over, the real thing -- global annual coal consumption:


You can see that the record-highest annual coal consumption was in 2013. This is true, just as it is true that the record-highest average temperature of the Earth was in 2016, and the record-lowest September Arctic sea ice extent was in 2012. But we cannot say coal consumption "peaked" in 2013 any more than we can that global temperatures "peaked" in 2016. What we can say is that 2013 had the highest coal consumption on record, and the second highest was -- 2018 (the last year for which we have data. We also can say that the last eight years of the data (2011-2018) contained the eight highest coal-consuming years.

When it comes to short-term noise in a long-term trend, climate realists have been round and round this bend before. All the good-faith voices on the climate know the the denialist short con of "no warming since [insert current warmest year on record.] I would suggest we apply the same skeptical attitude to "peak coal."

Certainly these trends are not exactly analogous. We know the temperature record will be broken again (and again, and again) because of the remorseless laws of atmospheric physics. No law of human behavior is half so ironclad. It may be that after the false spring of 2017 & 2018 (when coal consumption appeared to resume its upward march) will be a blip, and 2013 truly will stand as the peak, as the rest of the world follows the United States and Western Europe in aggressively phasing out coal. But is that really the most likely scenario here?

The primary reason for the decline in coal consumption from 2014-2016 (it doesn't sound that impressive when we put dates on it, does it?) was that the rapid growth in Chinese consumption abated and their consumption was steady, not rapidly rising, over the past decade:

This coupled with the continued reduction in coal use in the United States and Europe accounts for coal's modest decline. Will this decline spread rapidly to the rest of the world? Or, to put it another way, is China's transition a function of their increasing wealth and sophistication (intolerance of air pollution, desire to be a leader on climate change, need to develop clean energy exports) or is it a function of global structural change (perhaps caused by inexpensive renewables) which will spread to all corners of the globe BEFORE said corners are as wealthy and powerful as China?

A definitive answer to that question is beyond my powers, but we can check in on some of the large, poor countries who, if they emulate China and the United States, could easily push coal consumption to the levels seen in RCP8.5.

Let's start with India, soon to be the most populous country in the world, currently averaging 6-7% GDP growth annually.
Not much sign of a coal phase-out there. How about in Africa? Data for the whole of Africa or Sub-Saharan Africa as a region is hard to come by (if you have a source, put it and your thoughts about my poor research skills in the comments.) The largest country in terms of population is Nigeria, is coal declining there?
It doesn't seem so. If anything, it seems like it's just getting revved up. Another fast-growing economy, neglected by Western pundits doubtless due to the long shadows of CHina and India, is Indonesia, with a population of 264 millions and average annual GDP growth of 4-6% over the last 20 years. How is the post-coal future unfolding on the great Pacific archipelago?
India has another important neighbor besides China, their former compatriots and current mortal enemies, the Pakistanis. Unfortunately, though they have their share of differences, in regards to burning the dirtiest fuel on Earth, they seem to be of one mind.
You can see a similar pattern in other large developing countries like Brazil, Bangladesh, the Philippines, and Vietnam (all with rapidly growing economies and with over half a billion people between them):

I have probably contributed substantially to global warming with the bits consumed by all of these graphics, but the point is this: the decline in coal consumption from its "peak" was short-lived, was almost entirely driven by the decisions/economic circumstances of a few wealthy countries and one huge middle-income country (and aspiring superpower) (China.) The trend, if it can even be called that, is not nearly enduring enough, dramatic enough, or widespread enough to lead us to abandon the default assumption that more growth leads to more energy use, and more energy use, in the absence of strong collective political action, means burning more coal.

Thursday, February 6, 2020

Climate Change 2020: Still on a glide-path to disaster, Part Two


In Part One I created a simple model to illustrate how easily the world could reach or exceed the emissions projected by RCP8.5: (Long-term GDP growth) x (smaller annual improvements in emissions intensity) = way too much CO2.

In Part Two, as promised, I'm going to look at some of the "ground truth" of global development that makes those rising emissions in my very simple model plausible.

First, the goal posts: RCP8.5 projects 88Gt/year of CO2 emissions in 2100. Without fussing too much about the area under the curve, if a scenario gives us >88Gt/year of CO2 emissions in 2100, we can conclude that RCP8.5 is realistic, presuming said scenario is realistic. Make sense? So our first data points:

RCP8.5, Co2 emissions in 2100: 88Gt

RCP8.5, CO2e: 120Gt

Current CO2 emissions (2019): 37Gt 
We're going to ignore CO2-equivalents for now, because the non-CO2 forcings are largely short-lived, more easily reversible problems, such as methane, which are less relevant on the century scale.

If I were asked to sum up in a single phrase the reason RCP8.5 cannot be ruled out, and is, in fact, highly plausible, it would be "economic growth."

Leaving aside the bright spot of the Great Depression -- sarcasm very much intended -- and the hangover from WWI and the 1918 influenza pandemic, the world has not seen less than 3% growth over any five-year period for the past hundred years.

It is hoped that population growth will continue to slow in the coming decades, but that is unlikely slow economic growth overall -- if anything, the relationship between economic growth and population growth tends to be the inverse of that.

Even 3% growth, sustained over the next 80 years, leads to a world where the average person is richer -- far richer -- than the average American is today: ($170k/year at purchasing power parity.)

What might such a world look like in terms of greenhouse gas emissions?

We had better hope they don't emit like Americans, because that would be the ball game:

US carbon emissions per capita: 16.5 tons/year

If the world in 2100 emits like the US: 181.5Gt/year

So to put the question in a deliberately stringent way, for RCP8.5 or something worse to NOT unfold over the next 80 years, either long-term GDP growth needs to fall precipitously, which would be a vast crisis of human suffering in its own right, and which virtually no one thinks is just or even sane, OR the population must fall dramatically, OR we are positing a world in which 11 billion people are 2-3 richer than present-day Americans, but produce nothing remotely resembling an American's average greenhouse gas emissions.

Note that this is just another, hopefully slightly more concrete and accessible, way of talking about carbon intensity and the "decoupling" of economic growth: finding a way for 5-10 billion people to be richer than Americans without producing anything remotely like the GHG emissions we do.

I wish "not remotely" were a rhetorical flourish, but it isn't. Doing 20%, 30%, 50% better than we do in terms of CO2 per unit of production is not enough.

Germany, for example, has invested a vast amount in renewable energy, grid improvements, and conservation. The exact figure is debated, but the total investment to date is generally agreed to be on the order of hundreds of billions of dollars. So let's imagine a wealthy world that invests heavily in renewables and makes the progress Germany has made.

German CO2 emissions: 11 tons/year per capita

If the world in 2100 emits like Germany: 121Gt/year

 Again, our simple thought experiment blows past the RCP8.5 scenario and into uncharted territory. The same thing happens in a world that emits like China (although with 3% growth, said world would be an order of magnitude richer than China, $170k/year per capita vs $17k):

China: 8.5 tons

If the world in 2100 emits like China today: 93.5Gt

Just to be clear, this thought experiment imagines a world where carbon intensity is vastly improved, producing ten times as much per unit of CO2 emitted compared to China today. It's not enough. RCP8.5 is still on the table.

These thought experiments illustrate why (Long-term GDP growth) x (smaller annual improvements in emissions intensity) is such a menacing equation. Since the advent of modern capitalism and the Industrial Revolution, two of the most predictable things about human history is that people will make more people and those people will strive to get rich. And eventually, in more or less time depending on things like the level of governmental dysfunction, frequency of wars and revolutions, and availability of capital, people do get rich (compared to where they or their parents started.)

So when assessing the likelihood of RCP8.5 or worse, we can break it down to several simple wagers:
  • The population in 2100 will be dramatically lower than today: bad bet.
  • Economic growth, averaged over decades, will halt or reverse itself, in contradistinction to the entirety of human history since the beginning of the Industrial Revolution: bad bet.
  • Vastly richer and more numerous human societies will, without significant exception, produce vastly more goods and services per unit of emissions: Unknown (policy dependent.)
Given one of these bets must pay off to have any hope of avoiding RCP8.5 or worse, can we really say RCP8.5 is "implausible"?

In Part Three, I'll discuss the four main lines of reasoning offered to justify playing down or ruling out RCP8.5, and why I think these rhetorical mountains are practical molehills.

Wednesday, February 5, 2020

Climate Change 2020: Still on a glide-path to disaster, Part One

In the last few years, some climate analysts have underlined the fact -- which was never in doubt, but was arguably under-emphasized -- that RCP 8.5 was designed more as a worst case than as the shortest-odds bet.

As anyone might anticipate who has spent more than five minutes interacting with climate deniers or lukewarmers/inactivists, numerous bad-faith actors took this as their cue to one the one hand exaggerate the importance of RCP 8.5 to the climate literature and on the other to claim it has been admitted to be impossible.

I only wish I were kidding. Eric Roston's screed is representative:

To justify relegating the "nightmare scenario" to the "dustbin," Rosten cites the following Nature editorial:

RCP8.5 was intended to explore an unlikely high-risk future2. But it has been widely used by some experts, policymakers and the media as something else entirely: as a likely ‘business as usual’ outcome. A sizeable portion of the literature on climate impacts refers to RCP8.5 as business as usual, implying that it is probable in the absence of stringent climate mitigation. The media then often amplifies this message, sometimes without communicating the nuances. This results in further confusion regarding probable emissions outcomes, because many climate researchers are not familiar with the details of these scenarios in the energy-modelling literature.

This is particularly problematic when the worst-case scenario is contrasted with the most optimistic one, especially in high-profile scholarly work. This includes studies by the IPCC, such as AR5 and last year’s special report on the impact of climate change on the ocean and cryosphere4. The focus becomes the extremes, rather than the multitude of more likely pathways in between.

Happily — and that’s a word we climatologists rarely get to use — the world imagined in RCP8.5 is one that, in our view, becomes increasingly implausible with every passing year5. Emission pathways to get to RCP8.5 generally require an unprecedented fivefold increase in coal use by the end of the century, an amount larger than some estimates of recoverable coal reserves6. It is thought that global coal use peaked in 2013, and although increases are still possible, many energy forecasts expect it to flatline over the next few decades7. Furthermore, the falling cost of clean energy sources is a trend that is unlikely to reverse, even in the absence of new climate policies7.
 The first problem here is that, by definition, implausible is not impossible. And when dealing with "nightmare scenarios," identifying them as implausible is far from making the case we should "say goodbye" to the possibilities.

But the major problem with this thinking, in my view, is that RCP 8.5 is quite plausible, and those who say it isn't -- to say nothing of deniers screaming about "the RCP 8.5 fraud" -- are overreacting to short-term trends and politicians' promises.

The case against RCP8.5, in broad strokes, is this:

*Coal use peaked in 2013, and is likely to continue to decline, making the expansion of coal use posited in RCP8.5 implausible.
*Clean energy options (solar and wind) have dramatically fallen in price, making a return to dirter energy unlikely.
*The amount of coal required to make RCP8.5 a reality may not even exist on earth -- certainly it will not be cost-effective to extract it.
*The pledges by the vast majority of the world's governments in the Paris accords and elsewhere suggest a "business as usual" path far below that of RCP8.5.

Before addressing these points one by one, let's construct a simple model to illustrate why RCP8.5 is still quite plausible.

There are two overwhelming important long-time drivers of GHG emissions: population growth, and economic growth. Both can be captured by a single metric: total (not per capita) global GDP, sometimes called Gross World Product (GWP.)

While it is possible to decouple economic production from GHG emissions, in practice this is a slow, halting, process. Since 1980, carbon intensity (emissions per unit of GDP at purchasing power parity) has fallen slowly, by less than 1.5% per annum:

Helpfully, carbon intensity worldwide fell by roughly 50% from 1970 to 2015, making calculations easy: .985 ^ 45 = .51. It's a pretty steady decline. Global GDP was $12 trillion in 1970 and $78 trillion in 2014, yielding an average annual growth rate of 4.2%.

The simplest possible model would just extend these trends into the future. Each year we have 4.2% more GDP, causing 1.5% less emissions per unit. Since 4.2% is quite a bit greater than 1.5%, our uber-simple model projects emissions will continue to grow: .985 (emissions intensity) x 1.042 (GDP) = 1.2637 (CO2 emissions grow by 2.6% per year.)

If you start with the current numbers, plug in the growth rate of 2.6%, and look at 2100, you don't get RCP8.5 -- you get something far, far worse. RCP8.5 projects a leveling off of emissions growth and emissions of less than 30GtC of carbon annually, compared to 10GtC today.

2.6% growth, on the other hand, would see us over 75GtC in 2100 -- more than double RCP8.5. That's without incorporating carbon-cycle feedbacks or assuming any turn for the worse in terms of climate policy. It's just a straight-up extrapolation of current trends. And while I am not a modelling expert, and extrapolating current trends is far from the only way to guess at the shape of the future (and obviously depends heavily on which trends you project forwards) nevertheless, "Things continue as they are" is always a scenario we should give serious consideration to, lest we outsmart ourselves like the political analysts who fail to seriously consider "Person leading in the polls wins" when predicting the outcome of an election.

In Part Two, I'll look at the trends that make continued exponential growth in carbon emissions a frighteningly plausible prospect (Spoiler alert: it's population growth and economic growth, plus a dash of human perversity.

In Part Three, I'll look at the 4 points offered as cause for optimism regarding RCP8.5, and how there's less there than meets the eye.