Category Archives: Climate Change

Marching Against a Tail (and All Those Who Don’t Get Risk)

This Saturday 7th March, I will be joining the Time to Act Climate March, which seeks greater government action to prevent climate change. Why? Because of RISK! To remind everyone: Risk jpeg Something can be risky even if it has a low probability as long as the impact is high. Imagine a game of Russian roulette. You put a revolver against your head with one loaded chamber–and then you pull the trigger. Feeling lucky? I now offer you $1 million to play the game once. Remember, an ordinary revolver usually has six chambers, one of which is loaded. Do you take the bet? What about a pistol with 100 chambers? A thousand? With 1,000 chambers, the probability that you blow your brains out is 0.1%. Is that a good bet?

In statistics, that 0.1% likelihood outcome is firmly in the ‘tail’ of the probability distribution. When outcomes cluster around a central estimate, they may not have significant tails; others, have long or fat tails. This is important since generally the tail is where bad stuff happens. In my example above, something really horrible happens in the tail: death. As impacts go, that is pretty bad. So despite the low probability of an adverse outcome and the $1 million potential pay off, putting a 1,000 chamber pistol against your head with only one bullet is still a very risky bet.

So is frying the planet.

And this is why I think scientists like Judith Curry and Nic Lewis don’t really get risk. They argue that doubling atmospheric CO2 isn’t much to worry about because we may only warm a little. Yes, we may warm only a little; but then again we may not. Here is the climate sensitivity table from a recent paper by the two (click for larger image):

Curry and Lewis jpeg

ECS refers to equilibrium climate sensitivity and TCS to transient climate sensitivity. Simplistically, the former has a longer time horizon than the latter.

On the back of this paper, Curry was welcomed with open arms by the Wall Street Journal to do an op-ed (which you can find on Curry’s personal web site here) and feted by climate skeptic blogs across the world. In the op-ed, Curry takes an extract from the table:

Nicholas Lewis and I have just published a study in Climate Dynamics that shows the best estimate for transient climate response is 1.33 degrees Celsius with a likely range of 1.05-1.80 degrees Celsius. Using an observation-based energy-balance approach, our calculations used the same data for the effects on the Earth’s energy balance of changes in greenhouse gases, aerosols and other drivers of climate change given by the IPCC’s latest report.

And then goes on to make a policy recommendation:

This slower rate of warming—relative to climate model projections—means there is less urgency to phase out greenhouse gas emissions now, and more time to find ways to decarbonize the economy affordably. It also allows us the flexibility to revise our policies as further information becomes available.

Now ‘likely’ used in the WSJ op-ed means the 17-83% range. She has 17% of the outcomes in the good tail–warming below 1.05 degrees Celsius–and 17% in the bad tail–above 1.80 degrees Celsius. But from the table we also see that there for a 5-95% range, the outcome of a doubling of CO2 may be above 2 degrees Celsius of warming–2.5 degrees to be exact.

Some rough back of the envelope calculations. The pre-industrial revolution level of atmospheric CO2 was 280 parts per million (ppm). We are now at 400 ppm, so to double from pre-industrial concentrations, we would need to get to 560ppm. Co2 concentrations are also rising at around 2.25-2.50 ppm per annum. So if climate sensitivity to a doubling of CO2 were 3 degrees Celsius, we would get 2 degrees of global warming if CO2 concentrations reached around 450 ppm, which will be in about 20-30 years time. Two degrees of warming is considered (somewhat arbitrarily) to be the borderline for dangerous climate change.

Now Curry and Lewis see a non-negligible risk, that is 5%, that the sensitivity is 2.5 degrees. If right, the current rate of CO2 emissions would lock us into a 2-degree warmer world maybe 10 years later than the consensus, say in 2050. And then we come to the tail.

What is going on further into the tail. I want to know about this low-probability tail risk. It is important. This is the chamber containing the one bullet. If you wouldn’t play Russian roulette at very low odds, how about permanently damaging the planet at such odds?

How deeply do we have to get into the tail before we hit catastrophic climate change of 4 to 6 degrees of warming (remember that this particular risk is a composite of how much carbon we put in the atmosphere and how sensitive climate is to that amount of carbon). Let’s suppose we have a 99% confidence interval that we remain outside of the disastrous outcomes. Now we have 0.5% in the really bad upper tail. That’s odds of one in 200. Are you happy ignoring a disaster movie outcome if it only has odds of one in 200?

Moreover, if we ignore this tail risk of climate sensitivity and feel “there is less urgency to phase out greenhouse gas emissions now”,  isn’t there the possibility that due to fossil fuel infrastructure lock-in, we commit ourselves to a more than doubling of atmospheric CO2?

It gets worse. What if their climate sensitivity numbers are wrong. Curry and Lewis use one particular approach to reach their figures, but there are others. Michael Mann sets out the alternative approaches and the resulting climate sensitivity numbers in a Scientific American article here (click for larger image). In general, they are nearly all higher than those of Curry and Lewis. So Curry and Lewis’ disastrous climate change tail risk, with odds perhaps measured in the hundreds, may actually be a tail risk with odds measured in the tens. We can’t really be sure at this stage.

Solid Line of Evidence jpeg

Finally, going on a march would appear a quixotic act in the face of the wicked problem of climate change. But one can take a risk approach similar to that of extremely unlikely, but very harmful, events here as well. Voting, demonstrating and lobbying may have only a very small chance of changing the probability of the final outcome. But the potential impact of altering an outcome–through in this case encouraging more aggressive Co2 emission mitigation–is monumental. This is reverse Russian roulette, where the chamber with the bullet becomes the benign outcome. And so I march.

Chart of the Day, 4 March 2015: Arctic Stories

Arctic sea ice extent is one of the most iconic indicators of climate change, but we usually give it most attention during the summer melt months. Nonetheless, I try to do a quick catch-up around the beginning of March, which marks peak extent. And this is what we see (Source: National Snow and Ice Data Center here; click for larger image):

Arctic Sea Ice Extent jpeg

Generally, winter ice is not a good predictor of summer ice extent, so I wouldn’t read too much into the fact that we are currently hitting new historical March lows in terms of what will happen this coming summer. That said, what we see in the above chart is still part of the general picture of new climate records being made across the board–especially in northern latitudes where warming is amplified.

The NSIDC is also hosting a series of stunning animated NASA satellite images that illustrate the changing nature of Arctic snow cover, vegetation and frozen ground as well as sea ice extent.  The frozen ground page has this inset chart showing the general thaw (click for larger image):

Nonfrozen Ground Anomalies jpeg

This, in turn, is increasing fears relating to methane release, although as I blogged about here, I still see this as a lesser risk than general CO2 emissions. The Global Carbon Project also has a good backgrounder on methane (here), including a methane budget showing sinks and sources (click for larger image):

Methane Graphic jpeg

At present, we have more to fear from ruminants, rice, landfills and fossil fuels, than from hydrates and thawing peat bogs.

Returning to sea ice, the ‘go to’ site is Neven’s “Arctic Sea Ice Blog” I’ll be checking in regularly to see if what we are seeing now with Arctic sea ice is just a blip or harbinger of another big melt season. Neven has also just highlighted a disturbing Ocean Geographic Magazine photo essay by Jenny Ross that is worth checking out. It’s a surreal and unnerving experience to witness the planet change dramatically before our eyes.

Climate Change Pledge: Credit, Where Credit Is Due

In my last post (here), I was somewhat rude about Prime Minister David Cameron. Or rather I was rather rude about the vacuous drivel he spouted about competitiveness. But credit where credit is due. Of the three party leaders who signed a pledge in mid-February to combat climate change regardless of the outcome of the May election, it was Cameron who had the most political capital on the line.

First, here is the pledge (credit also to The Green Alliance, who brokered it) and for the whole one page document see here (click for larger image).

Climate Change Pledge jpeg

The Climate Coalition‘s “Show the Love Campaign” also helped created sufficient momentum to secure the joint pledge. (The Climate Coalition brings together 100 organisations whose interests relate to climate change; for membership, see here.) Indeed, the full pledge document was actually badged with the “For the love of” logo:

for the love of jpeg

Overall, the press coverage has been positive. Even the generally climate skeptic friendly Daily Mail gave the announcement a positive spin (here). And The Financial Times highlights the courage that Cameron has shown:

The deal is likely to infuriate numerous Tory rightwingers, such as Owen Paterson, the former environment secretary, who believes that climate change has been “consistently and widely exaggerated” in scientific forecasts.

Mr Paterson has argued that the UK should scrap the Climate Change Act, which binds the country to cutting greenhouse gas emissions.

Others who have urged Mr Cameron to tone down the green rhetoric include Lord Lawson, the former chancellor, who has criticised the UN Intergovernmental Panel on Climate Change, seeing it as “alarmist”.

The Carbon Brief also suspends cynicism and takes on board the positive aspects of the pledge.

The UK probably hasn’t witnessed a similar show of cross-party political unity on climate change since parliament voted to pass the UK Climate Change Act in 2008, with the support of all the main party leaders and only five votes against.

The joint pledge is, therefore, domestically significant for what it rules out, rather than what it rules in, because it reduces the chance that the next government could weaken the UK’s stance on climate change.

And they also highlight what to me is the most important part of the pledge: that climate change does not have to be a wedge issue. You can be passionate about countering climate change regardless of which part of the political spectrum you occupy.

In broader political terms, the cross-party UK climate pledge is already being used as an example to others. In Australia, a Nobel laureate says his country’s political leaders should follow the UK lead. In the US, the Washington Post compares UK leaders’ unity to Republican and Democrat disagreement over climate.

So three cheers for the pledgers, and special kudos to Cameron. But I’m greedy, and I hope that whoever wins the next election will kick it up a notch and be even more aggressive over countering climate change. Here’s hoping.

Collapse Comes of Age

Not long ago, the study of human collapse and extinction was the preserve of cranks (or Hollywood). True, a few maverick scholars have taken on the topic, Joseph Tainter and his book “The Collapse of Complex Societies” springs to mind. Yet little academic infrastructure existed to give collapse studies depth. But just as with happiness studies, another topic covered by this blog, the situation has now changed.

In the UK, our two oldest universities, Oxford and Cambridge, have both set up institutes that probe into the greatest risks faced by mankind. In Oxford, we have the Future of Humanity Institute (FHI), and in Cambridge the Centre for the Study of Existential Risk (CSER). To get a taste of the FHI and its founder Nick Bostrom I recommend you read this in-depth article by Ross Andersen of the magazine Aeon here.

Like this blog, Bostrom’s principal concern is risk; that is, the probability that an event will occur combined with the impact should that event occur.

Risk jpeg

However, Bostrom extends this concept to take in scope: whether a particular risk is limited to a locality or whether it is all encompassing. This produces a risk matrix like this (source for the following analysis his paper here; click for larger image):

Typology of Risk jpeg

The X in the grid marks what Bostrom calls “existential risks”, which he defines thus:

A risk where an adverse outcome would either annihilate Earth-orginating intelligent life or permanently and drastically curtail its potential.

Bostrom then goes on to subdivide such existential risk into four categories:

Bangs: Intelligent life goes extinct suddenly due to accident or deliberate destruction.

Under this category we get traditional disaster movie scenarios of asteroid impact, nuclear holocaust, runaway climate change, naturally-occuring modern plague, bioterrorism, terminator-style super-intelligence and out-of-control nanobots.

Crunches: Society resets to a lower-level of technology and societal organisation. 

This includes bang-lite scenarios that don’t quite kill off intelligent life but rather just permanently cripple it.  Crunches also cover resource depletion and ecological degradation whereby natural assets can no longer support a sophisticated society. Crunch could also come from political institutions failing to cope with the modern world–subsequent to which emergent totalitarian or authoritarian regimes take us backwards.

Shrieks: A postmodern society is obtained, but far below society’s potential or aspirations. 

This is a rather nebulous category since the measuring stick of our potential is against something that we may not be able to understand–a reflection of Bostrom’s philosophical roots, perhaps.

Whimpers: Society develops but in so doing destroys what we value. 

Under this scenario, we could pursue an evolutionary path that burns up our resources or we bump up against alien civilisations that out-compete us. Over the time scale that this blog looks at–the lifespan of our young–this existential threat can be ignored.

Building on many of Bostroms preoccupations, a joint report by FHI and the Global Challenges Foundation has just been published under the title “Global Challenges: 12 Risks That Threaten Human Civilisation”. The Executive Summary can be found here and the full report here.  The report is again concerned with existential risks, but approaches this idea somewhat differently than Bostrom’s earlier work.

The focus of the report is on low probability but high impact events. The logic here is that low probability events are generally ignored by policy makers, but when such events occur, they could have catastrophic consequences. Accordingly, policy makers should be duty bound to plan for them. From a probability perspective, what we are talking about here is the often-ignored right tail of the probability distribution.

Existential Probability jpeg

The 12 risks falling into the right tail of the distribution highlighted in the report are:

  1. Extreme climate change
  2. Nuclear war
  3. Global pandemic
  4. Ecological collapse
  5. Global system collapse
  6. Major asteroid impact
  7. Super volcano
  8. Synthetic biology
  9. Nanotechnology
  10. Artificial intelligence
  11. Unknown consequences (Rumsfeld’s unknown unknowns)
  12. Future bad global governance

As an aside, finance is one of the few disciplines that takes these tails seriously since they are the things that will blow you up (or make you a fortune). The industry often doesn’t get the tail-risk right (incentives often exist to ignore the tail) as the financial crisis of 2008 can attest. However, the emphasis is there. A lot of science ignores outcomes that go out more than two or three standard deviations; in finance, half your life is spent trying to analyse, quantify and prepare for such outcomes.

Returning to the Global Challenges report, the emphasis of the analysis is on dissecting tail risks, with the goal of provoking policy makers to consider them seriously. One of the most interesting proposals within the report if for a kind of existential risk early warning system, which I will look at in a separate blog post.

Finally, I will finish this post with a chart dealing with severe climate change (click for larger image or go to page 64 of the report), a risk that I hope will be at the centre of the upcoming COP 21 climate talks in Paris in December. The fact that our top universities are seriously studying such risks will, I hope, prevent them being seen as the preserve of cranks and disaster movies in future.

current climate risk jpeg


Chart of the Day, 17 February 2015: How Scary Is Methane?

A doomer commentary on methane has been doing the rounds on social media. Pictures of  methane bubbles certainly look scary, but the overall atmospheric concentration of methane has been showing only a mild rise. From the Advanced Global Atmospheric Gases Experiment (AGAGE) data series:

AGAVE CH4 jpeg

Moreover, the current climb is far slower than that seen in the 1980s. From a paper by Kirschke et al (click for larger image).

Methane jpeg

Although methane is a very powerful greenhouse gas (about 20 times as powerful as CO2), it presently makes up a little under 2 parts per million (ppm) of the atmosphere compared to around 400 ppm for CO2.

Critically, methane’s atmospheric life is short, about 12 years, after which it converts into CO2 (and thus becomes 20 times less potent). For this reason, it doesn’t accumulate easily. Keeping this in mind, a post by David Archer on the Real Climate blog looked at chronic versus catastrophic methane releases (click for larger image).

Chronic versus catastrophic methane release jpeg

So, in order to recreate a disaster movie scenario, we either need to see a massive and sustained release of methane or a ginormous spike in methane emissions. Where would this come from? The candidates are generally given as methane hydrates or other sources of trapped methane at high northern latitudes. But to see how realistic such places are as a source, we need to see where the methane is coming from at present (source here; click for larger image).

Methane Sources and Sinks jpeg

As you can see, anthrogenic sources such as wet-field rice cultivation, fossil fuel extraction and animal-rearing over-shadow other sources such as hydrates. Indeed, to get hydrates to become the principal driver of atmospheric methane concentrations we would need to see a 10 to 100-fold rise, and this would then need to be sustained for a long period of time.

According to scientists such as David Archer and Gavin Schmidt, such emission scenarios don’t look plausible (for more detail see here). In short, they see little evidence of a methane bomb ready to explode.

Simplistically, the difference between methane and CO2 is that the latter stays up in the atmosphere once put there while the former doesn’t. In sum, CO2 provides plenty of disaster movie material; we don’t have to look further afield to scare ourselves senseless.

Chart of the Day, 13 February 2015: Dr. Spencer’s Temperature Record

It’s a while since I posted on  the University of Alabama-Huntsville (UAH) temperature data, or more precisely on the global average lower tropospheric temperature anomaly as measured by satellite. The anomaly refers to the difference between the current temperature reading and the average reading for the period 1981 to 2010 as per satellite measurements.

The official link to the data at UAH can be found here, but most months we get a sneak preview of the release via the climatologist Dr Roy Spencer at his blog here.

Spencer, and his colleague John Christy at UAH, are noted climate skeptics. They are also highly qualified climate scientists, who believe that natural climate variability accounts for most of recent warming and any manmade contribution is minor. If they are correct, then we should see some flattening or even reversal of the upward trend within the UAH temperature time series over a long time period.

The last reading was for January 2015, and showed an anomaly of 0.28 degrees Celsius. This is the forth hottest temperature recorded for any January since the satellite record was started in December 1978 (37 January observations). To get a sense of the trend, see the chart here (click for larger image):

UAH Sat Temp Jan 15 jpeg

The climate skeptic community has made much of the fact that 2014 was not the hottest year on record according to satellite data. This contrasts with the time series recorded by both NASA and NOAA, which show 2014 taking the record. This is how the top 10 stack up according to UAH (taken from Spencer’s site here):

Annual Global Temp Anomalies jpeg

In the same post, Spencer highlights the statistical error surrounding the terrestrial hottest year claim for 2014. This is true. The reported temperatures are best estimates and sit within confidence bands. So newspaper articles should have read: “best estimate of temperature makes 2014 hottest year on record”. This doesn’t, however, make such good newspaper copy.

More important is the fact that one year’s worth of temperature is really just weather, while a decade or two is climate. Spencer has something to say about this as well:

Roy Spencer Text jpeg

The red flag here is “13 calendar years”. Why not ’20’? We are talking about climate after all. Critically, the 13 years takes us back to 2002 and produces the flattest line possible through the data in the chart shown above. If, by way of contrast, you take the UAH data set and compare the average temperature anomaly for the 10 years through 2014 with the average anomaly for the 10 through 2004, you see a rise of 0.13 degrees Celsius. The equivalent 20o4 to 1994 decade comparison is 0.22 degrees Celsius. So we have a slowdown, but it is far less pronounced and we still have a lot of warming.

Further, the 37 year UAH data record is still short, so a plateauing stands out. For the longer terrestrial data series, as I blogged about here, alternate fast and slow warming phases are nothing unusual. A hiatus is just that: a pause not a stop.

Critically, Spencer believes that the recent period of slow warming is evidence of low climate sensitivity to the ongoing rise in atmospheric CO2. Unfortunately, the only way he will be proved wrong about this (since he doesn’t accept consensus theory) if for the planet to undergo significant warming. This is an augment regarding which the consensus will likely be proved right, but which is far from a cause for celebration.

Chart of the Day, 8 February 2015: The Primordial Soup of US Renewables

If you like charts (as I do), and you are interested in all things energy and climate change, then the annual Bloomberg New Energy Finance‘s “Sustainable Energy in America Factbook” is an absolute treat. The 2015 edition came out last week.

While the United States does not have a Climate Change Act like the UK, it does have top-end academic research, government-backed blue sky thinking (via the Advanced Research Projects Agency for Energy), lots of entrepreneurial zeal, a deep well of venture capital funding and a multitude of innovative state-led renewable initiatives. Just as the primordial soup of complex molecules on early earth once gave rise to the chemical combinations that we call life, so we hope that the US renewable melting pot will also give birth to something transformational.

Of course, we are not there yet. And Voldemort is well represented in the US care of the anti-science Congress and a fossil fuel lobby that makes the tobacco giant lobbying of the 60s and 70s look like amateur time. But let’s stay upbeat. For a start, King Coal does appear to be in full retreat (click for larger image on all charts).

Electricity Generating Capacity by Fuel Type jpeg

Further, investment continues to pour into the renewable space at a rate 10 times higher than a decade ago:

Renewable Investment jpeg

With the exponential explosion in solar capacity particularly encouraging.

US Solar Roll Out jpeg

I could go on.

Nonetheless, for the US to lead the world into a post-carbon age before we are committed to extremely dangerous climate change still requires a step change upward in renewable investment. But the building blocks for a renewable revolution are there, they just need to be put in the right order.