Our very own hockey stick

Everyone with even the slightest interest in climate change has heard of the ‘hockey stick’ which showed in 1998 that recent warming is unprecedented in human history (the background is here, on wikipedia, if you want it).

What we may not have been particularly aware of was that it was based primarily on Northern hemisphere data. In hindsight, that meant there was the ghost of a hope that the temperature trend didn’t apply to Australia, but a team led by Joelle Gergis of Melbourne University has just laid that phantasm to rest: we now have our very own hockey stick.

Temperature reconstruction graph
Fig. 4 from Gergis et al.

The temperature reconstruction uses 27 proxy records, relying equally on tree rings and coral cores, and concludes that summer temperatures in the post-1950 period were warmer than anything else in the last 1000 years at high confidence, and in the last ~400 years at very high confidence.

RealClimate introduces the study here (that’s where I found out about it, in case you hadn’t guessed).

Update, 25 March 2013: A reader recently alerted me to the fact the Gergis et al’s paper was withdrawn before publication. It appears that there were technical flaws in it which meant it didn’t meet the expected standards of proof.

As far as I can determine, however, its conclusions were still probably correct – as one would expect, given that it was only extending northern hemisphere records into the southern hemisphere and one would not expect to find any great north-south difference.

Update 2, June 2020: The original paper seems to have been replaced in 2016 by another by the same authors, Australasian Temperature Reconstructions Spanning the Last Millennium.  Their conclusions are essentially the same:

Regardless, the most recent instrumental temperatures (1985–2014) are above the 90th percentile of all 12 reconstruction ensembles (four reconstruction methods based on three proxy networks—R28, R3, and R2). The reconstructed twentieth-century warming cannot be explained by natural variability alone using GISS-E2-R. In this climate model, anthropogenic forcing is required to produce the rate and magnitude of post-1950 warming observed in the Australasian region.

 

Science, entertainment or misinformation?

A friend suggested a few days ago that I ‘may be interested in this (forthcoming) ABC TV show Climate Change – Can I Change your Mind?

It is indeed the sort of programme I watch so I thanked him and looked further. I didn’t have to look much further, actually, since a pre-review was also on the ABC’s excellent website: I can change your mind about science on the ABC. In it, Stephan Lewandowsky is scathing about the lack of scientific comment and, in fact, scientific balance in the programme. The Sydney Morning Herald coverage (dare I say even the SMH coverage?) shares some of those concerns. I see no reason to disbelieve Lewandowsky, an acknowledged expert in how people arrive at their opinions, especially since his criticisms match the concerns which the programme information raised in my own mind.

While it is refreshing that the ABC willingly publishes such a negative opinion piece about one of its own programmes, that programme seems to have been disappointingly, frustratingly, ill-conceived in the first place. An ill-balanced pair of debaters, male authority-figure vs young female, in which the authority figure is mis-educated and plain wrong, is a poor start; and ‘equal time’ to pro and anti is an outright injustice in the face of the well-understood science of the subject.* Are they going to give ‘equal time’ to a flat-earther next week? On this basis, they might as well.

So … I will turn the TV on tomorrow evening but I will make sure, for the sake of the screen, that there are no heavy objects within reach.

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* The way conservative media misrepresented ‘equal time’ as ‘fairness’ is something Oreskes covered at length in Merchants of Doubt. A fair balance is one which leaves the viewer/reader/listener with an accurate idea of the relative strengths of the two sides. Graham Readfearn has a detailed critique of the defects of the process on his blog.

Grab bag: the art of climate change

Climate change is a science-heavy issue with enormous social and political implications so it makes sense that responses to it come from all sorts of people in all sorts of media. This little collection looks at visual art.

There was an excellent exhibition of art inspired by climate change in Melbourne a couple of months ago. It was reported on ABC TV’s 7.30 and that report is now available as video and transcript at http://www.abc.net.au/7.30/content/2012/s3416543.htm. (The video is also on YouTube.) Metro Gallery’s page about its show, here, doesn’t add much but does mention a film of the project, which could be worth tracking down, too.

Looking for it a few minutes ago, I came across an American sculptor, Nathalie Miebach,  who translates climate numbers into colourful artworks which look more like intriguingly complicated toys than anything else. Read the article here and, if you like, click through to the associated photo gallery.

I have known the work of street artist Banksy for quite a long time but I haven’t mentioned it on Green Path before. Here is his graphic comment on global warming.

Political cartoons are also art, of a kind, and that is my excuse for squeezing Climatesight’s collection of cartoons http://climatesight.org/image-collection/ into this post. Here’s a sample from it to encourage you to investigate further:

Cartoon: people queuing for "A Reassuring Lie" and bypassing "An Inconvenient Truth"

P.S. (27.3.12) Just found a couple more here – scroll down to the bottom of the page.

Remembering the floods

I wrote about extreme weather events and their connection to global warming two and a half months ago and a small coincidence leads me to revisit the topic. Today has been chosen as the day of remembrance for the disastrous SE Queensland floods a year ago, and a link on RealClimate took me yesterday to a paper by eminent climate scientist James Hansen which touches on something I’ve been thinking about for some  time: the fact that climate change should already be apparent to ordinary people.

First, the floods. Wikipedia has a good overview here with plenty of links to further information and the ABC has put together a terrific gallery of flood photos here. There’s not much point in trying to add to that coverage here. The floods certainly qualify as an ‘extreme weather event’ and were recognised as such in the major global report State of the Climate in 2010 from NOAA and the Bulletin of the American Meteorological Society. 

Hansen’s paper, Climate Variability and Climate Change: The New Climate Dice (November 2011) (pdf here) begins thus:

The “climate dice” describing the chance of an unusually warm or cool season, relative to the climatology of 1951-1980, have progressively become more “loaded” during the past 30 years, coincident with increased global warming. The most dramatic and important change of the climate dice is the appearance of a new category of extreme climate outliers. …

The greatest barrier to public recognition of human-made climate change is the natural variability of climate. How can a person discern long-term climate change, given the notorious variability of local weather and climate from day to day and year to year?

This question assumes great practical importance, because of the need for the public to appreciate the significance of human-made global warming. Actions to stem emissions of the gases that cause global warming, mainly CO2, are unlikely to approach what is needed until the public perceives that human-made climate change is underway and will have disastrous consequences if effective actions are not taken to short-circuit the climate change.

He goes on to show two kinds of systematic change in climate: the averages have shifted and, at the same time, the odds of extreme events occurring have increased dramatically. This, of course, is the significance of his title: the climate dice have been loaded (biased) by global warming. He presents details of the changes which have already occurred and notes that, “The climate dice are now loaded to a degree that the perceptive person (old enough to remember the climate of 1951-1980) should be able to recognize the existence of climate change.” In particular, people should be noticing that extreme weather is far more common than it ever used to be.

He doesn’t quite ask, “Why don’t they notice?” but the question hovers there, waiting for an answer.

I have been trying to answer it myself since a random conversation a year ago. I was chatting to a youngish, intelligent person with a degree in natural sciences and a job in  GBRMPA, which looks after the Great Barrier Reef. I was quite surprised to find that she had not actually observed the effects of climate change. Then I found that she had spent her first ten years on a Pacific island, her next eight in Sydney, and another eight or so here in Townsville, so she hadn’t actually been anywhere long enough to notice a change in that location.

As I thought about that, I realised that she has lots of company. There are far fewer people who might reasonably be expected to notice climate change than we might at first think. A quick estimate goes like this:

  • Age group really has to be 40+, since anyone under ten in the early 1980s won’t remember the old norms. Change has occurred in the last thirty years, but it is the comparison with the pre-1980 baseline which makes it stand out strongly. That rules out more than 50% of the world’s population and perhaps even more than 50% of the world’s voters.
  • But also, those people have to have been living in the same general area for 40+ years, or have returned to it after some time away, because no-one in California will say, “It wasn’t like this when I was a kid,” if they grew up in Normandy, Queensland or even Virginia. How many Westerners are that stable? 50%?
  • Furthermore, the closer we live to nature, the more likely we are to notice its changes – but more and more of us are urbanised. Europe, Australia and the US are all more than 80% urbanised according to UN stats, while China, India and most of the developing nations are less than 40% urbanised. How many of the 50% of 50% are therefore likely to qualify as “perceptive”? Less than 50% in the West, certainly; perhaps more than 50% in less urbanised countries.
  • That leaves less than 10% of the world’s population in a position to recognise climate change from personal observation. And (unfortunately for the debate) most of those 10% are the rural poor of developing nations, the most frequent victims of climate change not the opinion-makers of industrialised nations.

Of course, Hansen’s statistics show that extreme weather events are going to increase very rapidly in number and severity as global warming continues. More and more of us will notice the effects in our daily lives. But that is not really good news.