Archive for the ‘Abrupt change’ Category
By Roger Jones, Victoria University (reproduced from The Conversation)
With fires still burning across New South Wales, it’s time to have a look at the role climate change might have played. Are the conditions we’re seeing natural variation, or part of a long term trend?
In fact, it doesn’t have to be one or the other.
Has bushfire risk increased due to climate change?
In research I did with colleagues earlier this year we looked at the Fire Danger Index calculated by the Bureau of Meteorology, and compared how it changed compared to temperature over time in Victoria.
South-east Australia saw a temperature change of about 0.8C when we compared temperatures before 1996 and after 1997. We know that it got drier after 1997 too.
We then compared this data to the Forest Fire Danger Index, to see if it showed the same pattern. We analysed fire data from nine stations in Victoria and did a non-linear analysis.
We found that fire danger in Victoria increased by over a third after 1996, compared to 1972-1996. The current level of fire danger is equivalent to the worst case projected for 2050, from an earlier analysis for the Climate Institute.
While it’s impossible to say categorically that the situation is the same in NSW, we know that these changes are generally applicable across south-east Australia. So it’s likely to be a similar case: fire and climate change are linked. Read the rest of this entry »
The following statements are typical of the gradualist adaptation narrative:
- Within limits, the impacts of gradual climate change should be manageable.
- Therefore, climate change adaptation can be understood as: (a) adapting to gradual changes in average temperature, sea level and precipitation.
- Gradual climate change allows for a gradual shift in the mix of crops and to alternative farming systems.
So why are Gauss and Newton in the bath and Ed Lorenz in the hot tub?
Global warming has caused SAM and ENSO to divorce according to Guojian Wang and Wenju Cai, published in Nature Science Reports on June 20. This is having major impacts on Australia and has contributed to the warm and dry conditions over the southern part of the continent since the late 1960s.
SAM is the Southern Annular Mode surrounding Antarctica, a band of wind and water that distributes hot, high pressure and cold, low pressure lobes around the Southern Ocean. This transfers atmospheric mass (pressure) between the mid and high latitudes. The positive phase is highly correlated with a positive phase of ENSO (the El Niño-Southern Oscillation), La Niña. A positive phase of SAM forces westerlies further south in autumn-winter, but in summer allows the easterly trades greater access, bringing in more moisture from the tropics and enhancing La Niña summer rainfall.
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.
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.
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.
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 »
Warmer oceans, tropical species being found further south, decline in temperate species, the first signs of CO2 effects on shell production in Australian waters …
These are a few of the headlines from the Marine Climate Change in Australia, Impacts and Adaptation Responses 2012 Report Card (download pdf). Put together by the Marine Biodiversity and Resources Adaptation Network (NCCARF), Fisheries Research and Development Corporation, and CSIRO’s Climate Adaptation Flagship. The reporting comprehensive, covering the report card itself and six chapters on marine climate and thirteen on marine biodiversity. Alistair Hobday, summarising the report card on The Conversation.
Here’s a summary with some of my own conclusions about observed and projected changes. The latter you can take or leave as they’re based on my personal views about how climate changes. For recent and near future changes, I place a greater emphasis on how climate is likely to change rather than by how much. This places the emphasis more on the diagnosis and understanding of change rather than prediction. There’s a fair bit in doing this, so amongst other things I’m into today (like gardening, cooking and cleaning), I’ll update these sections as I go (Sunday 11 am, SST; Wednesday, SLR). Read the rest of this entry »
Rapid warming in SE Australia challenges plans to adapt gradually
Step changes in warming of a few tenths to 1°C can produce rapid changes in risks such as extreme heat and fire danger. Yet, adaptation-planning that follows the dominant model of smooth climate change makes gradual adjustments to keep up with small changes in extremes. In these circumstances, a rapid change can catch sensitive systems out. Poorly planned responses may also lead to maladaptation.
Studies of prehistoric climate change in Victoria’s western lakes imply that future changes might not be smooth. Dacre Smith's painting of Lake Gnotuk, from Views of Victoria in the steps of von Guerard.