Can we get to 350 ppm? Yes, we can

In a recent post, I made the optimistic argument that, despite all the obstacles thrown up by rightwing denialism, the world is on track to reduce CO2 emissions to zero by 2050, on a trajectory that would hold atmospheric concentrations of greenhouse gases below 450 ppm. On current models, that gives us a 67 per cent chance of holding the long term increase in global temperatures below 2 degrees. Warming of 2 degrees would not be cataclysmic for humanity as a whole but it would be a disaster for many people and also for vulnerable ecosystems such as coral reefs. That’s why 350.org wants to reduce concentrations to 350 ppm from current levels above 400 ppm.

Is that even possible?
And, what would it mean for global warming?

In this post, I’ll argue that the answer to the first question is definitely yes. I’m going to start with the assumption (based on this post) that we can reduce emissions from fossil fuels to zero by 2050, and keep concentrations below 450 ppm at that point. What are the options to reduce concentrations over the following fifty years? In the absence of some new technological fix (not implausible, but there’s nothing in sight as of 2017), there are three main possibilities

* Reducing methane emissions and concentrations. Methane emissions arise mainly from agriculture (paddy rice and ruminants), with some possible addition from fracking. It appears feasible, though not trivial, to greatly reduce these sources at fairly low cost. And because methane has a short residence time, a reduction in emissions will lead fairly rapidly to a reduction in concentrations. The conversions are very tricky, but the radiative forcing associated with methane is currently about 0.5 watts, compared to 1.94 for CO2. So, if methane concentrations were reduced by 40 per cent, that would be equivalent to a 10 per cent reduction in CO2, or about 40 ppm.

* Natural absorption. Only around 50 per cent of the CO2 we emit (the so-called atmospheric fraction) ends up as increase in atmospheric concentrations, with the rest being absorbed by oceans. After that initial addition to sink, CO2 stays in the atmosphere for a long time. However, there is still some additional absorption by sinks. Yale Climate Connections suggests that around 50 per cent is absorbed in 50 years, and around 70 per cent in 100 years. So, by 2100, an additional 20 per cent or so of the CO2 emitted around now will have been absorbed by sinks. A rough estimate would be 0.2*(450-280) or 35 ppm, where 450 is the peak concentration and 280 the stable pre-industrial level. Of course,this is far from an ideal solution, since CO2 contributes to acidification of oceans and therefore to coral reef decline.

* Reforestation and other land use changes. Land use change is currently a big net contributor to global warming, but a systematic program of reforestation could turn this around. The potential has been estimated at 85 ppm.

Against these possibilities, there is currently a net cooling effect, equivalent to around 50 ppm, from aerosols associated with air pollution. Hopefully, pollution will be reduced over the coming century, but that makes the task of stabilizing the climate a bit more difficult.

A question I haven’t yet been able to find a good answer on is: how much warming would a trajectory peaking at 450 ppm and declining to 350 ppm ultimately produce? If anyone can point me to a good source, that would be great.

Finally, at least some of the pollutants we’ve emitted over the past century will, on our current understanding, stay there for hundreds or thousands of years, leading to long term problems of sea level rise. But if we can get to 2100 without destroying the planet through climate change or nuclear warfare, I’m sure our great-grandchildren will work out some way of cleaning up what’s left of our mess.

Sense and senselessness in transport policy

I’ve been doing various pieces of work on transport. Here’s a quick update:

* I’ll be speaking at a one-day seminar organised by the Institute for Sensible Transport in Sydney on 8 August. It should be a good event for those with a professional interest in road pricing and related topics.

* For those with a general interest, I have a section over the fold from my book-in-progress, Economics in Two Lessons. Comments and criticism much appreciated.

* While I was a Member of the Climate Change Authority, I put a lot of work into a report the Authority did on vehicle fuel efficiency standards. With the rejection of just about every other policy measure to reduce CO2 emissions in Australia, this was the government’s last chance to do something useful. Naturally, Turnbull and Frydenberg went to water the moment the denialists who dominate the LNP raised an objection. Perhaps, now that the laws of mathematics have been subordinated to Australian law, Turnbull can solve our problems by simply decreeing a change of sign, so that an increase in emissions becomes a decrease.

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Census crowdsource (repost)

In 2012, I crowdsourced an analysis of the census results, looking at the extent to which the increase in religion was driven by changes in stated affiliation from religious to non-religious, as opposed to the demographic replacement of older more religious cohorts by younger, less religous ones. A couple of wrinkles on this

* I didn’t mention immigration last time. It appears (unsurprisingly) that those born overseas are more likely to be religious, but less likely to be Christian, than the Australian born.

* As the ABS notes

The religious pattern of those under 18 is most similar to the 35-49 year olds, suggesting the form may be completed with their parents’ beliefs.

It seems likely that when they report for themselves, these young people will be more like the 19-34 age group. It’s hard to say whether we should call this an affiliation change or a cohort effect.

I’d like to ask again for a crowdsourced analysis. It may be useful to read the comments thread to my previous request.

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Are the Nationals a political party?

I’ve made this point before, but I’m constantly reading articles about the rising share of “protest” votes going to “minor parties” in which the set of minor parties excludes the National Party. The reason is, of course, that the Nationals are a long-established party which, with a few state-level exceptions, operates in permanent coalition with the Liberals.

But, for all practical purposes, the same is true of the Greens. Roughly speaking, Labor and the Greens are in the position the Liberals and Nationals (and previously the Country Party) were for most of the 20th century. They fight three-cornered contests, often bitterly, and do a lot of agonising about preference swaps, coalitions and so on. But, when push comes to shove in terms of forming governments, they almost always line up together, whether in a coalition, with a formal agreement, or with informal support.

The most important difference between the two is that the Greens get more votes from a wider range of electorates. The difference that drives the spurious analysis of “protest parties” is that the coalition between Labor and the Greens is less formal and more fractious than that between the Liberals and Nationals.

If you count Labor and the Greens as a coalition, then the rise of protest parties in Australia appears primarily as a crackup of the political right. We’ve seen a profusion of rightwing protest parties, with only
the Xenophon group in the centre, and nothing much at all on the left. That differs from the situation in some other countries, where social democratic parties have embraced austerity and collapsed (Greece, Netherlands) or where the established leadership has been pushed aside (UK and possibly soon US also). I have some ideas about this, but I’ll have to write about them later.

But, coming back to the main point, a consistent analysis should treat both the Nationals and Greens as minor parties, or else neither of them.

Technology to the Rescue ?

There’s been a fair bit of buzz about an article in New York Magazine with an apocalyptic picture of climate change over the next century. I’ll for a more complete response later. But as it happens, I was already thinking about a much more optimistic post.

From the Climate Change Authority, of which I was a Member until recently, here’s a set of emissions trajectories consistent with a 67 per cent probability of limiting warming to 2 degrees.

There’s a pretty good case to be made that we are on the blue trajectory, and that, with decent political outcomes, we will be able to go below it and hold warming to the Paris aspirational target of 1.5 degrees. That would still have plenty of negative effects, for example on coral reefs, but it would not be an existential threat to humanity.

The points that are critical in the blue trajectory are a peak in emissions, right about now and a drop to zero net emissions by 2050. The first looks to have been achieved. As for the second, we are already seeing commitments to this goal from developed countries and jurisdictions, and there’s every reason to think it can be achieved at low cost.

As an economist, this is about the outcome I would have expected given a global commitment to an emissions trading scheme with a carbon price on a rising trajectory to $US100/tonne or so. In fact, we’ve seen nothing of the kind. There has been no real global co-ordination, and where carbon prices have been imposed, they have been low and limited in scope.

Instead, we’ve had a series of favorable technological surprises of which the most striking have been the plummeting cost of solar photovoltaics, and advances in battery technology allowing both low-cost electricity storage and affordable electric vehicles. There’s no reason to think these advances have run out, or that any of the remaining problem areas (air transport, cement manufacture and so on) will prove insuperable.

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