Understanding Climate Risk

Science, policy and decision-making

Posts Tagged ‘warming

Time to stop hiding behind warming trends

with 12 comments

Time to stop hiding behind warming trends

By Roger Jones, Victoria University

Dr Rajendra Pachauri, head of the IPCC, has reportedly acknowledged to Graham Lloyd of The Australian, that there is a “17-year pause in global temperature rises”, a fact that apparently has been suppressed in Australia. Dr Pauchauri endorses debate, saying that people had a right to question the science, whatever their motivations.

But according to Lloyd, Pachauri’s views contrast with arguments in Australia that views outside the orthodox position of approved climate scientists should be left unreported.

Am I an “approved” climate scientist? because I don’t hold that view, nor do I know any who does. What we would like, though, is for science to be reported as science and for opinion to be reported as opinion. And for all reporting to be accurate.

Lloyd makes this claim: unlike in Britain, there has been little publicity in Australia given to recent acknowledgement by peak climate-science bodies in Britain and the US of what has been a 17-year pause in global warming. Britain’s Met Office has revised down its forecast for a global temperature rise, predicting no further increase to 2017, which would extend the pause to 21 years.

This is the Met Office’s latest five-year forecast shown below. Skeptical Science reports the Met Office saying: the latest decadal prediction suggests that global temperatures over the next five years are likely to be a little lower than predicted from the previous prediction issued in December 2011. We’re in the midst of a period of La Niñas, which have a slight cooling effect, as do rising sulphate emissions in Asia. But look at the blue line – do my eyes deceive me? Is it level with the previous black line? It’s warmer? Perhaps Lloyd’s computer has a tilt to the right that makes increases look level.

Observed (black, from Hadley Centre, GISS and NCDC) and predicted global average annual surface temperature difference relative to 1971-2000. Retrospective predictions starting from June 1960, 1965, …, 2005 are shown as white curves, with red shading representing their probable range, such that the observations are expected to lie within the shading 90% of the time. The most recent forecast (thick blue curve with thin blue curves showing range) starts from November 2012. All data are rolling annual mean values. The gap between the black and blue curves arises because the last observed value represents the period November 2011 to October 2012 whereas the first forecast period is November 2012 to October 2013. UK Met Office

The Met Office predicts record global mean temperature over the next five years – now that’s news.

News Corporation sells roughly 70% of the newspapers in metropolitan Australia, and its readers are subject to this kind of fudging on a regular basis. It’s no wonder some “approved” scientists are frustrated.

But that’s not the only thing that frustrates me. It is also time to challenge what Lloyd calls the orthodox position of climate science.

Climatology needs to stop hiding behind long-term trends and explain what is in plain sight, and why variations in the rate of warming might be important. I’m working with colleagues at the moment on a National Climate Change Adaptation Research Facility project called Valuing Adaptation to Rapid Change and we’re looking at the economics of rapid change. Non-linear behaviour in climate driving extreme events has the potential to really hurt us.

The first thing to bear in mind is that a trend line is a model. A warming trend is not a theory of how climate changes. If a complex, non-linear system fails to follow a trend, look at the model to see whether it represents the theory sufficiently well.

In a nutshell, the theory says greenhouse gases act like a blanket, trapping heat near the surface. This creates a radiation imbalance at the top of the atmosphere. The earth system warms to return this balance by increasing the heat escaping from the top of the atmosphere so that energy out equals energy in. This is a slow process, taking centuries, because the ocean has to warm sufficiently to support a hotter atmosphere. The scientific confidence in this aspect of climatology is extremely high. A simple trend line is sufficient to measure this process.

But on decadal time scales, the trend-line model fails. Most of the heat trapped in the earth system goes into the oceans. The top 700m of ocean increased in heat content from 3 x 1022 Joules in 1997 to 10 x 1022 Joules in 2010, in a highly non-linear manner, due to mixing rates between the surface and deep ocean. The atmosphere holds as much heat as the top 3m of ocean, about 0.4% of the heat content above. Why on earth then, with highly non-linear processes in the ocean, would we expect a gradual warming trend in the atmosphere?

A paper I published last year shows that most of Australia’s warming occurred in two episodes, one in the late 1960s to early 1970s, when south west WA rainfall also decreased, and the other in 1997-98. The other finding was that most of this warming was anthropogenic. On decadal timescales, step and trend is a much better model for explaining warming than simple trends.

To me, the graph above makes perfect sense: mild trends separated by an instantaneous rise of about 0.3°C. By ignoring non-linearity and projecting future climate change as simple trends, orthodox science is doing us a great disservice. We have not yet woken up to the recent non-linear increases in heatwaves and fire danger in Australia let alone planning for more such changes in the future. The same goes for floods.

Observed and projected percentage area experiencing an exceptionally hot year: Queensland as an example. Note the recent rapid increase (source: K. Braganza, Bureau of Meteorology)

Days above high fire danger, average of 9 Victorian sites, showing statistically significant rapid increase (site data from Bureau of Meteorology)

It’s time to stop defending orthodox science by hiding behind simple trends and come to grips with the fundamental non-linearity of climate change. That’s the risk we need to mitigate, adapting to changes that can’t be avoided.

Roger Jones receives funding from the National Climate Change Adaptation Research Facility. He is affiliated with Climate Scientists Australia and the IPCC.

The Conversation

This article was originally published at The Conversation.
Read the original article.

Antarctic Peninsula warms – The Australian spins

with one comment

Interesting ice-core temperature results from James Ross Island on the Antarctic Peninsula (AP) that points to recent and rapid warming that is unusual and of concern (sourced from Crikey who find its unusual nature alarming). The Australian reports (via Graeme Lloyd) that while unusual, the warming is not unprecedented relative to natural variation. Lloyd also includes a quote that is neither in the paper or the press release, and a bogus assertion arising from a misunderstanding of the purpose of the research. I have enquired from the authors if they were the source of Lloyd’s quote. Update – they have replied: see below.

So, how concerned should we be about the results? From the press release:

Results published this week (Nature paywall) by a team of polar scientists from Britain, Australia and France adds a new dimension to our understanding of Antarctic Peninsula climate change and the likely causes of the break-up of its ice shelves. Read the rest of this entry »


with 2 comments

Last Friday the global climate conspiracy erected another plank dressing up the façade that is record of warming record in Australia. At an extra-ordinary nerdfest held the Victorian State Library, the cruel manipulations of temperature records by the Bureau of Meteorology were described. ACORN-SAT, I mean, really! Lies dressed up as statistics were outlined to an audience who hung on every word. The conspirators have done such a good job that the Australian record so closely resembles the tricked up records from Hadley-CRU, the Goddard Centre for Space Studies and NASA, that they all have to be made up. There’s no way that independent analyses of measurements of something we can’t see – air – can be so accurate.

Well, that’s the objections of the denialati out of the way.

The BoM did release The Australian Climate Observations Reference Network – Surface Air Temperature (ACORN-SAT) data on Friday and it looks excellent. Today I’m downloading some of the data for a project I’m involved in, so it’s good to have. The data were also used in the recent State of the Climate 2012 released by the Bureau and CSIRO.

Part of the impetus to get this done was a barely coherent set of assertions on how Australia’s climate records were being massaged by the Bureau. These assertions were formally submitted (pdf) as a request to audit climate records to the Attorney-General in February 2010. Co-signees were Senator Cory Bernardi, Joanne Nova (an alias), Andrew Barnham, Anthony Cox, James Doogue, Chris Gillham, Ken Stewart and Dr David Stockwell. They also alleged that BoM and CSIRO advice on climate change was misleading. This follows up similar fishing expeditions in New Zealand and the US yielding similar results. Not only were the records validated, quality control methods and subsequent adjustments improved those data giving us even more confidence that the record of warming they contain is unimpeachable.

Improved methods, external international review and a more comprehensive coverage have led to the Bureau to claim they have the some of the best quality records of temperature of any country. I think they’re right.

Read the rest of this entry »

Written by Roger Jones

March 28, 2012 at 10:56 am