Understanding Climate Risk

Science, policy and decision-making

Archive for the ‘Climate observations’ Category

Climate shifts and extremes

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This posts looks at how climate shifts affect extremes using the example of heat extremes in SE Australia. We had another burst of hot weather this week, which led to rolling power blackouts in South Australia. These are becoming more common, as our electricity bills rise to pay for network infrastructure. In every year but one since 1997, the Laverton, Victoria climate record has registered at least 1 day above 40°C. For those of you interested in how the science of detecting and projecting extremes is carried out, there is a comprehensive background on methods. For those who are just interested in results, page down to the results section. Read the rest of this entry »

IPCC SREX released

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The Summary for Policymakers (SPM) for the IPCC Special Report Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) was released late last night our time. The final plenary was held in Kampala Uganda, finishing on the 17th before the release yesterday. As usual, it is gone through line by line by IPCC country member representatives and the co-ordinating lead authors to craft a document that contains key policy messages while retaining true to the science in the report.

The SPM is complex and has already been given a number of interpretations in the press. The ABC news says extreme weather to worsen with climate change. The Australian focuses on the uncertainty Climate change effects unknown: IPCC report. A quick survey of Google news suggests that most outlets are focusing on extremes to worsen, or the qualified some extremes to worsen.

The Australian is different. Its header says:

GREAT uncertainty remains about how much of an impact climate change will have on future extreme weather events, the world’s leading climate scientists have found.

While there has been an increase in warm days and a decrease in cold nights, the likely impact on future weather events would not be evident for decades because of natural variability, the scientists say in a key review prepared for the UN’s Intergovernmental Panel on Climate Change.

This completely ignores the thrust of the report, which is to address the risks of extreme climate-related events and disasters and manage changing risk through adaptation. The great value of the report is not so much in its headline findings, which are complex but are in bringing the climate, adaptation and disaster communities together. These two communities had a hard time of it in the writing of the report bringing together different language, concepts, views of risk and methods of assessing vulnerability and adaptation. Read the rest of this entry »

Written by Roger Jones

November 19, 2011 at 7:59 pm

Sunday Age 10 Questions on Climate Change – the final two

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The Sunday Age – OurSay readers questions on climate change are down to the last two:

  1. ”THE claim ‘the science is settled’ is plainly false due to the many problems with the AGW [anthropogenic global warming] hypothesis (e.g. global temperatures have not risen since 1998 despite rising CO2 levels; alarmism is based on flawed models that do not reflect empirical measurements.)” 
  2. ”Why is the Australian public asked to swallow the ‘carbon dioxide is a dangerous climate-changing pollution’ crap when science shows no observed relationship between global climate and atmospheric carbon dioxide? There is no physical evidence showing a relationship between temperature and CO2, only computer models which give different answers according to whatever assumption data you put in. But there is a very close relationship between temperature and solar activity … Why, when thousands of respected scientists signed a petition saying they don’t agree there is a problem, are we being forced to give up billions in tax dollars to waste on trying to stop carbon dioxide emissions?” 

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Sea level rise. Part II – tide gauge analysis

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Sea level rise Part I covered the stoush resulting from a paper on long-term tide gauge records for Australasia. The author was Phil Watson of the NSW Department of Environment, Climate Change and Water and the paper was published in the Journal of Coastal Research in March. Tamino has pointed out the limitations of the statistical methods used, showing that the conclusion of decelerating sea level cannot be sustained. Tamino removed the annual cycle then used 20-year and lowess smoothing to show that the opposite conclusion – recent sea level rise is accelerating – is probably true for the Australasian region. A conclusion I strongly support.

It’s generally accepted that long-term climate records are analysed using trend analysis; either as a linear or non-linear trend, usually quadratic. The use of a particular statistical method assumes a specific model of how a system behaves. That model can be made explicit but if not, there is still an assumed model being used. Sometimes the assumption won’t be declared because it’s a widely accepted paradigm.

So what is the model sitting behind trend analysis – measured as either a straight line or a curve – and what paradigm of change process does it support? By analysing single tide gauge records, I am asking “How does sea level respond to externally-driven warming at a given location?” Read the rest of this entry »

Written by Roger Jones

August 4, 2011 at 4:39 pm

Sea level rise. Part I – the stoush

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A stoush on Australiasian sea level rise has erupted in the press and the blogosphere since the publication on July 22 of a story in The Australian covering a paper analysing long tide gauge records in Australasia. The details are covered comprehensively by Deltoid. The paper, by Phil Watson of the NSW Department of Environment, Climate Change and Water was published in the Journal of Coastal Research in March. It concluded that:

The analysis reveals a consistent trend of weak deceleration at each of these gauge sites throughout Australasia over the period from 1940 to 2000. Short period trends of acceleration in mean sea level after 1990 are evident at each site, although these are not abnormal or higher than other short-term rates measured throughout the historical record.

The Australian misprepresented this conclusion by calling in question 21st century projections of sea level rise (SLR). There is a very simple reason as to why this is not the case. The projections are about current and future ocean budgets, whereas the tide gauge records are more about process. Sea level budgets are known well enough to provide very high confidence that SLR will accelerate throughout the 21st century. The process of sea level rise at a site as measured by tide gauges is complex. Watson’s conclusions as emphasised by himself, his employers and real experts do not call into question the basic science about future SLR budgets.

However, as to the process of SLR I think the statistics currently being used don’t tell the full story. In part I, I summarise the story to date and in Part II, I will show an alternative method for analysing long-term tide gauge records. Read the rest of this entry »

Written by Roger Jones

August 4, 2011 at 9:11 am