Dr Pete Ridd has responded to my latest response to his comments. Given that he raises a few issues of fact, I think it is useful to explore his conjectures point by point in a final post. Some of these conjectures are easily dispelled which I think will be useful to the wider audience. I do think, however, that we will draw the line under the "Swindle" issue after this post.

Dear Peter,

Thank you for your recent comments. I will list my response to your comments (which are in bold) point by point.

2 Corals and Cockroaches
I think there is no major disagreement between Prof H.G and myself on the analogy between cockroaches and corals. We seem to agree that both organisms are tough but not indestructible. Corals have certainly done it tough over the ages – especially during cool periods.

The problem lies not with the cockroach but with the canary. Clearly from the scientific viewpoint the canary analogy is useless except in terms of spectacular colour. It is much less appropriate than the cockroach analogy. Canaries are invoked primarily for publicity purposes to persuade the public of the dangers of global warming on climate change. It is an emotive argument, not based in any facts, and gives the wrong impression of the sensitivity of corals to change.

Respectfully, we may have to agree to disagree on this. In terms of geological time scales, as you quite rightly point out, I have no issues with the analogy between cockroaches and corals – corals have persisted over geological timescales. The "cockroach" analogy holds true over broad geological timescales – coral organisms have persisted since the Cambrian period (542 million years ago) yet as you are well aware have fluctuated in both diversity and abundance. This analogy alone would imply that corals are "bombproof" and that any projected temperature increases would have little impact on the world’s coral reefs, which is clearly not the case. Coral reefs as they exist today are sensitive to change, as we are witnessing in mass bleaching events and subsequent mortality of reefs on a global scale, therefore as emotive as this issue may be, it is based upon fact.

The key to this, of course is the difference between species extinction and ecological ‘extinction’. While coral species may survive over geological time frames, the reefs and reef ecosystems may disappear (for long periods of time). And the latter is the issue of most importance to people.

The canary / coal mine analogy originated from canaries in cages acting as an ‘early warning system’ for increases in odourless methane gas – if present, the canary would die (or at least fall off its perch), alerting miners to its presence. This analogy is similar to corals (irrespective of their colour, I feel you are being a little too literal here Peter) in that coral reefs do act as an early warning system for increases in temperature – they are sensitive to thermal stress and bleach / die as a direct response of this. The effect on corals is dramatic and has served to warn us of the impending problems that other ecosystems, as well as coral reefs, may face as rapid climate change ensues.

3 Some like it hot.

I do not dispute that at a particular location and time, there is a clear hard cut-off where corals will bleach. This has been one of the major successes of the science in this area and Prof H.G has obviously been at the forefront of this research. The argument comes down to whether they can change rapidly enough to cope with warming and whether the warming we have so far seen is actually faster than what has occurred in the near past. On this we clearly disagree (see below)

I have posted on this before at Climate Shifts – (Barrier Reef ‘can adapt’ to warmer times). The evidence of rapid changes in the thermal tolerance of corals or their symbionts is scant within the published scientific literature.

4 Climates have changed before.
Prof H.G refers to the wrong part of the geological record and also to the wrong time scale when he looks at rates of change. Certainly the general rise in temperature (averaged over a few hundred of years) at the end of the little ice age was slow (though Prof H.G has considerably exaggerated this in his figures), but a feature of geological climate records is that they are often highly variable at all time scales. It would be brave to presume that the temperature rose at the end of the last ice age by a nice and gentle steady rate. (http://en.wikipedia.org/wiki/Ice_age).

The time scale of interest is over decades. A look at modern temperature proxies and even instrumental proxies indicate that a temperature change rate of 0.010C/year (rise or fall) is common, if not the norm. Such a rate of temperature change is in the same order as we presently see.
http://www.climateaudit.org/pdf/mcintyre.mckitrick.2003.pdf
http://en.wikipedia.org/wiki/Medieval_Warm_Period
http://www.globalwarmingart.com/wiki/Temperature_Gallery

Prof HG may not believe the proxy records that show the rapid temperature fluctuations associated with the little ice age and the medieval warm period (see above sites) as it has become a hotly disputed topic that goes to the heart of the IPCC claims about climate change.

You mix two statements in here – firstly the last ice age (by which I am assuming you mean the last glacial period in the Pleistocene, ~12-110ka) and the "little ice-age" prior the medieval warm period, which is (I assume) why you infer that I am referring to the wrong part of the time scale:

"Last ice-age"

I recommend that you download the Vostok core data and run a trend analysis through it. If you do this, there are no sections of the record (even those that go up or down) where the rate comes even close to what we have seen over the last hundred years. And logically, you can have too many periods at which the rate came close to 0.01°C per year, given that the overall difference between temperature difference between glacial and interglacial periods is only 8-10°C. That is, you achieve that in 800-1000 years and these transitions took more than a few thousand years.

To illustrate this numerically, I went and looked at the rate of change within the Vostok temperature data (obtaining the slope slope over 200 years periods; 8-10 points from the data set). When I do this I get:

Slope over 8-10 points (~200 yrs)
Rate of change
°C per 100 years
Mean -0.0028
Min -0.8505
Max 0.7726
Points examined: 330 data sets from over 420,000 years of record

That is the highest rate of change (up or down- these are outliers really) in the past 420,000 years is less than 0.01°C per year. Most telling is the average rate of change during this period which is 0.000028 °C per year. Quite sobering really given that rates exceed that over the past 100 years and given that we are headed toward a period in which we will change the earth’s temperature at the rate of 0.04 °C per year!

"Little ice-age"

The evidence you present here is somewhat thin on the ground – the McIntyre & McKitrick paper quoted here is a correction to the northern Hemispheric average temperature series, which bears little relevance to tropical regions and the GBR. Temperature records extracted from isotope records of massive Holocene corals on the GBR may be more regionally relevant to the discussion on the little ice age (Hendy et al [2003] Science 295 1511-1514). Between 1565-1700, temperatures on the GBR were ~0.2-0.3C cooler than the long term average (over a 420yr record). After this, above average sea surface temperatures persisted through most of the 18th and 19th centuries, and average temperatures cooled to a minimum in the early 20thC . A significant rise in temperature was also recorded between 1900-1980 (0.7 – 1.0C), consistent with an 80yr dataset from the United Kingdom Meteorological Office (Global Sea-Ice and Sea Surface Temperature data set, GISST2.2).

A recent paper (Calvo et al[2007] Palaeogeography, Palaeoclimatology, Palaeoecology 248 190-201) entitled "Interdecadal climate variability in the Coral Sea since 1708 A.D." details temperature records from Sr/Ca isotpe ratios from a Porites coral extracted from Flinders reef (see Fig 5). Indeed, an increase in SST increased from a mean of ~25.0C in 1830 to just below ~26.0C in 1870 – a time period of 50 years (even greater than 0.010C/year) – which I agree with you is a slow rise in temperature following the little ice-age. However, note that the last data point in 1980 shows an increase to 26.75C – higher than at any point in time since the beginning of the coral record in 1700. This rise in temperature towards the current thermal threshold is of considerable concern.

But we need not go into that debate here as the instrumental records show a very similar rate of warming in the early part of this century (1900 to 1940) as it did in the latter part of the century. Considering that the CO2 production in the early part of the 20th century was far less than at the end of the century it is quite possible (I believe probable) that most of the warming in the early 20th century is natural and running at the standard 0.010C rate (see http://www.search.com/reference/Instrumental_temperature_record

Your logic is fatally flawed here Peter – Using the same reference you provided above (http://www.globalwarmingart.com/wiki/Carbon_Dioxide_Gallery), CO2 production in the early part of the 20th century is far greater than at the end of the century, not less as you quoted. This somewhat negates your statement that it is either ‘possible’ or ‘probable’ that warming in the early 20thC is natural.

From this I think it unreasonable to conclude that the rates of temperature change we have thus far seen are anything extraordinary and I would further suggest that the absolute temperatures are not unusual considering the Holocene climatic optimum and the medieval warm period.
That brings us to the future and if the high end predictions of the IPCC are correct. I agree that Prof H.G’s figure of 4 degree in 100 years would cause significant damage, at least in the short term to the GBR, though I would not be surpised if in a few hundred years after, the GBR would be in better shape than it is today particularly if sea level rise covered the reef flats such as shown in Prof HG’s photograph in this post.

As I have blogged here on Climate Shifts and written in the scientific literature, there is a distinct lack of a physiological mechanism by which corals will magically "adapt" to these increases in temperature. An increase of as little as 1-2oC above today’s maximum summer temperatures is enough to cause serious bleaching of coral reefs. As blogged before, this is the basis for the very successful satellite detection programs (this wouldn’t work if these thresholds were variable!).

A 4 degree rise in 100 years (particularly when combined with other anthropogenic impacts such as increases in nutrients, sediment, overfishing that are impacting Indo-Pacific reefs) is likely to be devastating (indeed, show me one piece of published literature that contradicts this). Whilst I defend your right to an opinion, it is reckless to suggest or imply otherwise with no scientific grounding, particularly using your academic credentials as a scientist and a "scientific advisor"

The point is that with a 4 degree rise in 100 years, the damage to the GBR will be the least of our environmental, social and economic concerns. It will be the system that will get through the best. It is an open system not bounded by natural and unnatural borders.

Peter, again, you have provided no evidence that this will be the "system that will get through best" – if this an opinion, you are welcome to express it, but the science you are using to support your opinion is non-existant.

5 Have we been swindled
I was interested that Prof H.G agrees that the GBR is one of the best preserved ecosystems in the world. This seems at odds with the view that the public has now got. The general public have been told repeatedly that not only is the GBR to be completely wiped out in the coming couple of decades, but that it is already seriously degraded. The paper by Pandolfi eta l (2003) I quoted previously is a case in point, but there are numerous examples of this exaggeration in the public arena.

Pandolfi et al (2003) state that "The best-protected reefs in the world, on the Great Barrier Reef, are the closest to pristine… but are also one quarter to one third of the way to ecological extinction". Please note that there is a distinct difference here between "preserved" and "protected" – the paper of Pandolfi et al (2003) detailing global trajectories of the long-term decline of coral reef ecosystems should serve as a wakeup call to politicians, managers and the public alike – whilst the GBR is well managed and protected in comparison to other reef systems around the world, it still faces many issues of degradation and future impacts – this is far from exaggeration.

In this sense the public have been swindled into believing the GBR is in much worse state that it really is. Perhaps I would in retrospect avoid the word swindle and replace it with misinformed (both deliberate and otherwise) I would not mind if these exaggerations only occasionally surface, but it seems to be a continuous stream and much of it is deliberate. Prof H.G’s recently publicity about the cold water bleaching event is a case in point. It is remarkable that Prof HG blames this on climate change and thus implies that not only are the corals going to die because it is too hot, but also they will die from the cold. In reality this is just an unusual event and by itself says nothing about climate. It says much more about our limited understanding of corals, their ability to cope with extremes, and our lack of knowledge of the response of corals to previous extreme events.

We actually know a lot about the sensitivity of corals to both hot and cold conditions. Like all organisms, corals have a comfort zone outside of which they are stressed. I have written a couple of peer-reviewed articles on be phenomena of cold stress and speculated in those articles that this is probably a natural event. I suggest you read those peer-reviewed scientific articles as opposed to newspaper articles on the topic.

The pair of photo’s Prof H.G uses at the beginning of this post is another example of willful manipulation of the science. We could just as easily show pictures showing regeneration of coral. Such a pair would not show that the reef is in great shape. In highly variable systems these single data points are meaningless as science but powerful P.R tools.

The paired photographs are from published scientific literature – in terms of highly variable systems and single data points, I will be posting an article mid week regarding coral decline in the Indo-Pacific that will go a long way to correcting your statement here.

By the way Peter, I challenge you to produce just one matched pair of photos showing the reverse situation. That is a photo from 1900 or so without coral on the inshore GBR matched up to one from the same site where coral now flourishes (from the past 10 years).