Uncharted Territory

January 23, 2016

Greater Interannual Seasonal Temperature Variability in a Warming World?

Filed under: Agriculture, Global climate trends, Global warming, Science, UK climate trends — Tim Joslin @ 5:42 pm

You attempt to use the correct scientific jargon and then realise that sometimes the English language is insufficiently precise.  What I mean by the title is to ask the important question as to whether, as global warming proceeds, we will see a greater variation between summers, winters, springs and autumns from year to year.  Or not.

My previous two posts used Central England Temperature (CET) record data to show how exceptional the temperatures were in December in 2010 (cold) and 2015 (warm) and highlighted two other recent exceptional months: March 2013 (cold) and April 2011 (warm).  I speculated that perhaps, relative to current mean temperatures for a given period, in these examples a calendar month, both hot and cold extreme weather conditions are becoming more extreme.

What prompted today’s follow-up post was an update from the venerable James Hansen, Global Temperature in 2015, to which a link appeared in my Inbox a few days ago.  This short paper documents how 2015 was by a fair margin globally the warmest year on record.  But it also includes a very interesting figure which seems to show increasingly greater variability in Northern Hemisphere summers and winters:

160120 More variable summer and winter temps

I’ve added a bit of annotation to emphasise that the bell curves for both summer and winter have widened and flattened. That is, not only have the mean summer and winter temperatures increased, so has the variance or standard deviation, to use the technical terms.

If true, this would be very concerning. If you’re trying to grow food and stuff, for example, it means you have to worry about a greater range of possible conditions from year to year than before, not just that it’s getting warmer.

I was about to suggest it might be time to panic. But then it occurred to me that there must surely have been some debate about this issue. And sure enough Google reveals that Hansen has written about variability before, and more explicitly, such as in a paper in 2012, titled Perception of climate change, which is free to download.  Hansen et al note “greater temperature variability in 1981-2010” compared to 1951-80.

Trouble is Hansen et al, 2012 was vigorously rebutted by a couple of Harvard boffs.  Andrew Rhines and Peter Huybers wrote to the Proceedings of the National Academy of Sciences, where Hansen et al had published their paper, claiming that Frequent summer temperature extremes reflect changes in the mean, not the variance [my stress].  They attributed Hansen’s flattening bell curves were due to various statistical effects and asserted that mean summer and winter temperatures had increased, but not the standard deviation, and therefore the probability of relative extremes.

That left me pretty flummoxed, especially when I found that in Nature that another bunch of eminent climate scientists also claimed, No increase in global temperature variability despite changing regional patterns (Huntingford et al, Nature 500, p327–330, 15 August 2013).

Just so we’re clear, what the guys are saying is that as global warming proceeds – not even when we reach some kind of steady state – temperatures will just on average be shifted up by a certain amount.

I have to say I find this very difficult to believe, and indeed incompatible with the fact that some parts of the world (continental interiors, say) warm faster than others (deep oceans) and the observation that the wind blows in different directions at different times!

Furthermore we’ve just seen, between Decembers 2010 and 2015 in the  CET record, a much greater spread of temperatures than in any comparable period (actually in any period, period, but we’re concerned here with variability over a few years – less than a decade or two, say – when the climate has had little time to change) in the previous 350 years.  I take the liberty of reproducing the graph from my previous post:

160114 Dec 2015 related CET analysis slide 2a

December 2015 was 10C warmer than December 2010, 2C more than the range between December temperatures in any other era.

And I also recollect figures like this one, showing the freakishness of summer 2003 in Switzerland, where, like the UK, there is a long history of weather records:

160120 More variable summer and winter temps slide 2

This appears on the Climate Communication site, which shies away from any mention of increased variability.  But the original Nature paper in which it appeared, Schär et al, 2004 is very clear, and is even titled The role of increasing temperature variability in European summer heatwaves. The synopsis (which is all I can access – pay-wall) notes that:

Instrumental observations and reconstructions of global and hemispheric temperature evolution reveal a pronounced warming during the past approx 150 years. One expression of this warming is the observed increase in the occurrence of heatwaves. Conceptually this increase is understood as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small. Here we show that this framework fails to explain the record-breaking central European summer temperatures in 2003, although it is consistent with observations from previous years. We find that an event like that of summer 2003 is statistically extremely unlikely, even when the observed warming is taken into account. We propose that a regime with an increased variability of temperatures (in addition to increases in mean temperature) may be able to account for summer 2003. To test this proposal, we simulate possible future European climate with a regional climate model in a scenario with increased atmospheric greenhouse-gas concentrations, and find that temperature variability increases by up to 100%, with maximum changes in central and eastern Europe. [My stress].

Hmm. Contradictory findings, scientific debate.

My money’s on an increase in variability. I’ll keep an eye on that CET data.


January 22, 2010

Interestingly, Volcanoes can Trigger El Ninos

Filed under: Agriculture, ENSO, Geoengineering, Global warming, Science, Volcanoes — Tim Joslin @ 6:24 pm

Once again, I’m starting this post as I’m halfway through another one that may or may not see the light of day. I was trying to put together a rant following the Royal Society’s (RS’s) panel discussion on geo-engineering (available on royalsociety.tv), which I attended on Tuesday evening. The meeting followed a report issued by the RS last September.

Rather than rule out most of the possibilities, the RS boffins recommend further research. A cynic might suggest this was self-serving; I couldn’t possibly comment.

There are numerous problems with many of the geo-engineering approaches. But I wanted to be original and see if I could find evidence to support my hypothesis (noted in a previous post) that trying to cool the planet by injecting sulphur dioxide (SO2) into the stratosphere where it would produce reflective particles would block a disproportionate amount of sunlight striking the atmosphere at a shallow angle (i.e. more tangentially). More sunlight would therefore be blocked at the ends of the day, high latitudes and in winter.

In fact, the boffins noted on Tuesday that a disproportionate effect in the Arctic could be “beneficial”. This doesn’t stop them apparently relying on a computer modelling study that simply plugs in “a reduction in global mean insolation of 1.84%”.

The RS study repeatedly discusses recent volcanic events in order to assess possible effects of the geo-engineering plan.

Having looked into the matter, I can say this is bordering on a waste of time.

Drs Strangelove want to fire enough SO2 into the sky to block out around 2% (on average) of the sunlight, their sums suggesting this would counterbalance a doubling of CO2 levels.

But this interesting graph (courtesy of WIkipedia) shows what volcanoes do:

Mauno Loa observations of atmospheric transmission of sunlight

Wow! They don’t block 2% of solar radiation, rather 10 to 20% on a regular basis, and presumably even more when a real biggie goes off.

And this is enough to cause real disruption.

First off, the boffins worry about affecting the monsoon and other aspects of the hydrological cycle, citing the effects of the Pinatubo eruption in 1991. But Pinatubo caused massive short-term cooling. Monsoons rely on the land becoming warmer than the oceans, leading to rising air, drawing moist air towards the landmass. Obviously, if you reduce sunlight by 10% or so, the land will warm much slower and could remain too cold, relative to the ocean (which is kept warm by stored heat), for a healthy monsoon.

Second, I noted in a comment on a previous post that El Chichon was followed by a strong El Nino. As can be seen from the graph I gave at the time, there was a weaker one after Pinatubo. “Could they possibly fit together?”, I found myself wondering. Yesterday, via Realclimate, I came across a paper suggesting that yes, indeed they could (pdf).

The point, of course, is that El Ninos occur when warm surface water flows (unusually) east across the Pacific (see also Wikipedia). The warm water builds up in the first place because the initial flow (ultimately due to the rotation of the Earth) creates, in turn, an atmospheric warm zone to the west (around Indonesia), and a cooler region near South America. Lower pressure maintains a significant difference in the surface level between the west and the east of the ocean (maybe 60cm!). But the feedback relies on maintenance of the temperature (and hence atmospheric pressure) differential and eventually breaks down, typically in December (when the sun is not overhead at the Equator) and the whole thing collapses like a lop-sided souffle in an unevenly heated oven. Warm waters temporarily flow east with significant effects on the global climate for a year or two.

Fairly obviously, a general cooling event, such as a volcanic eruption, is likely to trigger an El Nino.

As an aside, it might be worth noting that a warming period is likely to lead to a strong El Nino, as observed in 1997-8, for example. The warming will reinforce the feedback creating the original imbalance. 1982-3 was also a strong El Nino event:

El Chichon anomaly (1983-4 temperatures compared to 1980s)

Maybe the cooling caused by the 1982 eruption of El Chichon enhanced an El Nino that was anyway ready to take place. Or maybe it was always going to be a big one.

At the risk of trying to read too much into limited evidence, it might be possible to surmise that the 1997-8 El Nino was so strong because the global warming trend leading up to it was reinforced by recovery from the Pinatubo cooling event. Similarly, to stretch the point even further, 1972-3 is listed as a strong El Nino, and followed the recovery after the Agung eruption, though that was 10 years before and not so large as El Chichon and Pinatubo (though a graph over at SkepticalScience gives a different impression). Fascinating stuff – no wonder climate scientists can’t wait for another major eruption!

Incidentally, because we mainly measure the temperature at the surface of the planet, El Ninos show as spikes in the data, because warm surface water covers cooler layers over a large area of ocean (and in turn affects temperatures on land). When a volcano triggers an El Nino, the cooling caused by the volcano is therefore partially obscured by the El Nino. An eruption when we were already in an El Nino state would consequently likely appear to have a greater effect on global temperatures than one that triggered an El Nino.

The geo-engineering plan is entirely different to the case of intermittent volcanic forcings. The plan involves a semi-permanent sunscreen to block 2% of sunlight. The problems will be entirely different. Relying on the historical record of the effects of volcanic eruptions won’t allow us to predict all the effects of the geo-engineering proposal.

Logic tells me that an SO2 sunscreen will disproportionately affect high latitudes, where sunlight is a highly valued commodity. Politically, it would of course be next to impossible to achieve broad agreement to go ahead with the geo-engineering plan. Furthermore, in a warmer world, with increased tropical desertification, we may be relying on food production in more northerly areas. Blocking sunlight might not be a bright idea.

Nevertheless, I carried on surfing for a bit for evidence that volcanic forcings could affect high latitudes more. The best I could come up with was the Russian famine of 1601-3, likely triggered by an eruption in Peru.

October 27, 2009

Scientific American’s Sustainable Future

Scientific American’s customer management is appalling. When I first subscribed to the print edition, the magazine’s online presence was trumpeted as one of the benefits. I therefore understood I would also obtain access to the Scientific American Digital (how quaint!). Nope. I got no more online access than I had previously and ended up paying a Scientific American Digital subscription on top of the print subscription. Someone should call the Advertising Standards Authority! (Annoyingly my online subscription has now expired, and, I see from the correspondence page – which publishes letters on topics in the edition, I kid you not, 4 months earlier, like we’re still in the 1950s – that I appear not to have received the July issue at all).

Just lately – in the midst of a UK postal strike – I can find no way to notify my address change or even log on at http://www.scientificamerican.com. The site recognises none of the several numbers on the address labels of the magazines I’m sent. The contact email address intl@scientificamerican.com simply doesn’t work. Mind-blowing. Scientists, eh? Hardly surprising there were dodgy solder-joints at the LHC, was it?

Nevertheless, I persist with Scientific American. It’s worth it for the quality of the articles. And, I have to say, its old-fashioned feel.

The lead article in the November issue is titled: “A Plan for a Sustainable Future”, by Mark Z Jacobson and Mark A Delucchi . It discusses how the entire world could be powered by wind, water and solar power by 2030. And it’s well worth a read.

The authors note that building “millions of wind turbines, water machines and solar installations” is not without precedent. For example, “during WWII the US retooled automobile factories to produce 300,000 aircraft”. For clean energy the numbers are feasible: the list includes 490,000 tidal turbines, 3,800,000 5MW wind turbines, 49,000 concentrated solar power (CSP) plants and 40,000 solar PV plants.

I’m afraid I have some quibbles:

  • The authors quote a US Energy Information Administration projection of 16.9TW of global energy demand in 2030, compared to 12.5TW now.  I suspect 16.9TW will prove to be a massive underestimate.  As well as a greater population and higher living standards, there’ll be new sources of demand in 20 years, for example, for large numbers of desalination plants to produce fresh water.  I’d be amazed if we aren’t using twice as much energy by 2030 as we are now.
  • On the other hand, ruling out wind and solar power production “in the open seas” is suspect: I would have thought there was a lot of scope to generate power there, e.g. on floating islands, which I’ve seen proposed, probably in Scientific American itself.
  • Nuclear power is dismissed because of the “carbon emissions” caused by “reactor construction and uranium mining and transport”, but no explanation is given as to why these activities couldn’t be powered by clean energy.
  • Interestingly, the authors are concerned about all forms of pollution, so rule out carbon capture and sequestration (CCS) and biofuels on the grounds of air pollution other than CO2. I’d have liked to see at least a nod to the other problems with these primitive technologies: principally the difficulty of capturing all the CO2 in a coal-fired plant, the cost of burying the carbon and the risks; and, for biofuels, the land use problems – not just food vs fuel, but that the land would store carbon quicker if left alone!
  • I doubt that geothermal energy is “renewable”.  There may be a lot of it, but the rocks will reheat only very slowly.
  • The authors suggest that we deploy 1,700,000,000 – yeap, 1.7 billion – “rooftop photovoltaic systems”.  I think this is nuts.  First off, I’m really struggling with the numbers – the 0.003MW – or 3kW – size of each system must refer to average (mean) output to be consistent with the rest of the article.  But, according to my mate David MacKay (print edition, p.40), 20W/m2 is going some for solar PV in the sort of countries where there are a lot of roofs. So these systems would have to be 150m2 each. They have big roofs in America, I guess. But my more fundamental objection is that the output of 100,000 of these babies only adds up to 1, yes one, of the 40,000 PV power plants. What’s easier, do you think, fit solar panels on every roof in a medium-sized town, such as Southampton where I come from, or stick them all in a big field outside of town (perhaps a long way outside, like in North Africa, where funnily enough you need far fewer panels)? I’ll give you a clue: let’s be pessimistic and say it takes 1/2 hour to put a panel in a standardised array in a field and optimistically 2 days to put the scaffolding up so you can get on the roof without a health and safety violation – before you start the pretty much bespoke installation process. Barmy idea, isn’t it? I worry that the inclusion of the rooftop PVs owes more to some kind of philosophical belief in the virtues of localism than to sound scientific (or economic) reasoning. And of course the article concludes by advocating the dreaded feed-in tariffs. What better way of transferring money to those with big roofs from those, um, without big roofs?

Nevertheless, notwithstanding a few hints that it may be informed by countercultural ideology, I recommend taking a look at “A Path to Sustainability by 2030”.

But the November 2009 Scientific American is worth buying for another article alone. No, not more minute analysis of the “Hobbits of Indonesia” (not read that one yet, but – to go all Iain M Banks for a moment – does the obsessive human interest in the details of our family tree perhaps represent some kind of species-level insecurity?), but “The Rise of Vertical Farms” by Dickson Despommier. The author should perhaps have credited “The World Without Us“, but he makes the point that we should farm indoors and leave nature to absorb the excess carbon we’ve been stuffing into the atmosphere.

The key argument is that you can grow so much – so much less riskily too – in controlled climate conditions indoors: “4 growing seasons, double the plant density, and 2 [or more, surely, of many crops – judging by a photo I once saw in the Guardian of a hydroponic indoor vegetable farm in Tokyo] per floor”, so that, excusing the quaint American units, a “30-story building covering one city block [5 of these ‘acre’ things] could … produce 2,400 acres of food”!

Despommier worries about how his vision can be made to happen, but in fact it’s simple. As soon as a realistic price is put on ecosystem services, there’ll be a huge economic incentive to invest in “vertical farms”.

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