You have publicly asserted that human-caused global warming is a grave threat to the future survival of large parts of the GBR. However, the underlying global warming trend (Trend) in SST’s are less than 0.1 0C/decade which is relatively slight compared with the annual volatility. It is thus meaningful to analyse that volatility, and that is best done after detrending the data.
Figure A) is derived from this BoM source and it removes the distraction of Trend, given that there is much evidence that the modest Trend is not adaptively stressful to the holobionts.
This shows most notably in 1973 and at the end of WW2 that there were greater ± extremes in the past than when the four mass thermal bleaching events were reported. The beginning of significant awareness of bleaching and the availability of resources for the GBR to detect such was marked by this 27-year study by De’ath et al of 2012.
It has been found globally that some corals have survived severe mass bleaching events that resulted in greater thermal tolerance because of changes in their symbiont “algae” mix. However, there does not seem to be any evidence that such responses have permanence. Any subsequent lessening of thermal/PAR stress seems likely to result in reversion to symbiont mixes having other benefits. Furthermore, immediately prior to the 1998, 2002 and 2016 mass bleaching events, the SST’s were notably cool, inferring that the corals were likely to be badly conditioned for the coming shocks.
Thus, the critical metric is in the relatively massive annual swings that are measured in degrees; and not the underlying global warming trend of less than 1/100 0C/year.
Figure B) shows SST day-anomalies on 18/June/2017 and indicates the primary driver of the volatilities seen; arising from the poorly understood ocean circulation variability:
Firstly, notice that at the highlighted locality on the GBR it was slightly below average on that day whereas off SW WA it was significantly warmer than average. In comparison, back on 21/March/2017 the same GBR locality had a very hot spike of +3.5 0C whereas off most of WA it was cold at down as low as -3.1 0C.
Figure C): The figure above suggests a quasi-opposite phenomenon between the east and west of Australia, so it is appropriate to examine the long-term BoM data as follows:
This reveals a long history of quasi-opposites that relate to ocean circulation changes (notably ENSO).
Returning to figure B, there was also a Brazilian hotspot anomaly at an extreme +7.1 0C while contrastingly in ENSO regions 1 & 2 off Ecuador and Peru, it was in La Nina at -2.1 0C. A fuller study has revealed that there is also a quasi-opposite east to west oscillation around that continent too (in the short-term data at least).
These poorly understood ocean circulation oscillations have resulted in alternating hot and cold localities, and they have occurred centennially with quite uniform magnitude and frequency.
It has been opined that global warming results in increasing climate change extremes, but there is no evidence of this in the BoM/NOAA SST time series data.
Figure D) demonstrates a secondary co-variable in ‘the weather’; notably wind, cloud cover and rainfall, (well correlated with ENSO). An extreme example was with tropical cyclone Debbie which evidently wedged very warm water before its path* and created a massive hot spike that was unprecedented anywhere on the GBR during 2017 (frame b below).
On the other hand, there were anomalies higher than on the GBR in the lower Tasman where the East Australian current is somehow blocked and mostly diverts east while generating strong surface eddies. This is apparently because of a period of unexplained high strength in that current.
*The maximum SST impact of Debbie is shown here on 28/march/2017. This is an interactive site; click any spot for SST and surface current speed. Click earthto open menu to find different dates and other parameters.
Frame (c) reveals that El Nino was strong in region 2 during the 2017 hot season on the GBR (Region 1 was similar). This is further indication of globally continuing ocean circulation instability in 2017.
None of these phenomena are predictable in magnitude, frequency, or regionality (e.g. every El Nino is different and the impacts are not consistent). However, they clearly have varying correlations with ocean circulations. Neither are tropical cyclones (or hurricanes) predictable in magnitude, frequency, or regionality, and there is no evidence that they have a worsening trend, rather the opposite.
Your claims that the GBR is seriously threatened by global warming are invalidated by THE DATA.
I can expand on this brief analysis if you concerned. But, are you interested in properly advising the public as to the real threats and the highest management priorities for the GBR?
Bob Fernley-Jones (Mechanical engineer retired….engineers do data BTW)
PS I have no interests in the fossil fuel industry, or any friends or relatives that do.