Friday, October 19, 2012
Another piece of research using climate proxies has cast some light on the recent evolution of sea surface temperature in a region of the Atlantic.
The researchers, from the National University of Mexico and the Woods Hole Oceanographic Institution in the USA, writing in the journal Paleoceanography, point out that accurate low-latitude sea surface temperature records that predate the instrumental era (post-1850) are needed to put recent warming in the context of natural climate variability and to understand what they describe as the possible influence of anthropogenic climate change on this variability.
They obtain a most interesting 235-year-long sea surface temperature reconstruction based on annual growth rates of coral (Atlantic coral Siderastrea sidereal) at three sites in Mexico located within the Atlantic Warm Pool (AWP). The point out that AWP surface temperatures vary in concert the Atlantic Multidecadal Oscillation (AMO) – a basin-wide, quasiperiodic (60–80 years) oscillation of North Atlantic sea surface temperatures.
They find that the annual growth rates of all colonies are significantly, inversely correlated to regional sea surface temperatures. The temperature data they obtain shows an additional multidecadal sea surface temperature cycle prior to instrumental record that suggests that AWP multidecadal variability, and likely AMO variability, persisted since at least 1775 AD with an amplitude comparable to that of the instrumental era.
The sea surface temperature reconstruction shows that it remained within 1 deg C of recent values during the past 225 years, consistent with previous reconstructions.
The graph they produce is fascinating. It shows a decline in sea surface temperature from 1773 to 1860, then a peak at 1880 which then declines to 1910. The year 1910 is a significant one for those studying rises in sea level as it is from 1910 that the gradient of recent sea level rise changes and persists that that rate of increase to the present day.
The rise in sea surface temperature since 1910 is qualitatively the same as the rise in global surface temperature over this period, a rise between 1910 – 40, a slight decline to about 1980 and a rise thereafter.
SOURCE (See the original for links)
Wednesday, October 10, 2012
The Great Barrier Reef is doomed again. A recent widely publicised scientific study reports the dramatic finding that it has lost half its coral in the last 27 years. Forty-eight precent of the loss is attributed to storm damage, with bleaching and crown-of-thorns starfish being responsible for 10% and 42% respectively. The average annual rate of coral loss over the 27-year period was estimated to be 3.38% and growth was put at 2.85%, leaving a net decline of 0.53% per year. Further effort and research on starfish control is suggested to be the most promising means of reversing the decline. Elimination of the loss due to starfish would leave a net gain of 0.89%.
While the news reports present the appearance of scientific precision and certainty, examination of the study itself reveals a number of doubtful assumptions, undisclosed conditions and instances where strong conflicting evidence is unmentioned. Examples of this include:
* The margin of error in visual surveys of coral cover is high and unassessed; yet, they are presented to hundredths of a precent without any qualifying explanation, as if they are precisely accurate. Coral cover is highly variable between reefs and over different areas or at different years on the same reef. Visual estimates of the percentage of coral cover can differ significantly, depending on where, when and by whom the observations were made. Also, many of the observers doing the surveys upon which this study is based were inexperienced students primed by learned expectations of threats to the reef.
* The reef is vast and in any given year surveys sample only a small portion. The reported sudden decline in coral cover in the last couple of years is almost certain to have been exaggerated by surveys made to assess the damage from severe cyclones crossing the reef in 2009 and 2011, with few or no surveys in unaffected areas in those years.
* The study states, “Cyclone intensities are increasing with warming ocean temperatures….”
This statement is unsubstantiated and contrary to available evidence. The most definitive recent studies find no increase in tropical cyclone frequency or intensity. On the GBR severe cyclone activity for the past century has also been well below the level for the preceding century. The study also states:
“The recent frequency and intensity of mass coral bleaching are of major concern, and are directly attributable to rising atmospheric greenhouse gases.”
No evidence exists for this claim. The mass-bleaching events of recent decades have coincided with surface water warming resulting from periods of extended calm associated with strong El Niño events. This impedes normal evaporative cooling as well as wave driven mixing. There is no evidence of any increase in the frequency or strength of El Niño events, and climate models project increased wind speeds from warming, not more calms. The report further states:
“Water quality is a key environmental driver for the GBR. Central and southern rivers now carry five- to ninefold higher nutrient and sediment loads from cleared, fertilized, and urbanized catchments into the GBR compared with pre-European settlement.”
No actual measurements of pre-European sedimentation rates exist. These are only estimates and extrapolations from unverified proxies which may or may not represent what is claimed. What is certain is that the inshore areas of the GBR are heavily blanketed in sediments that have accumulated over thousands of years and turbidity in coastal waters is overwhelmingly governed by re-suspension of these sediments through wave action, not by current day runoff from the land.
The most widely cited study purporting to show a large increase in sedimentation after European settlement was based on an increase in barium in coral skeletons just after 60,000 head of cattle were introduced into the Burdekin area in 1870. This was attributed to an increase in erosion caused by the cattle. But this period also coincided with the ending of an extended period of extreme drought and no explanation has ever been offered for why the barium level has subsequently decreased despite the million head of cattle now in the same catchment.
The assumption that levels of turbidity in flood runoff events are almost entirely attributable to farming and grazing is unwarranted, and it is readily observable that runoff turbidity from crop and grazing areas is often markedly less than from undisturbed natural areas. Crops and grasses are simply better at retaining soil than is either the rainforest or open eucalypt woodland they have replaced. Sediment-trapping by dams and cessation of the widespread annual burning practiced by the pre-European inhabitants of the area can also be expected to have reduced sediment outflows.
There is good reason to expect that agriculture and grazing may well have resulted in a net reduction in levels of sediment discharge, compared to pre-European condition. The claims of multi-fold increases in sedimentation are simply speculation wrapped in techno-waffle and presented as fact.....
The core claim is that the reef has lost half of its coral in the past 27 years and that: “Without significant changes to the rates of disturbance and coral growth, coral cover in the central and southern regions of the GBR is likely to decline to 5–10% by 2022.”
If this is true, the implications for future research and management are profound. It means that the current condition of the GBR is essentially no better than that of the heavily exploited and effectively unmanaged reefs of the Caribbean or SE Asia. It means all the money and effort that has gone into management and research has been an abject failure. It means that the promised “resilience” to environmental impacts that was the major justification for greatly expanded green zones and sundry other stringent and costly restrictions on productive usage have achieved nothing, and that the vaunted resilience has been just another theoretical academic fantasy. It means that the claims of having the best managed reefs in the world have been only a self-serving delusion. It means that all the past assertions of successful management have been untrue and the research supposedly supporting it has been either grossly incompetent or a deliberate misrepresentation.
Worse still, this all took place when, for nearly three decades the reef, was supposedly dying off in clear view of all the experts and they even had the surveys to confirm it. Were they too slack to look at their data until now or did they hide it because it didn’t suit their agenda at the time? If they were that incompetent or dishonest in the past, why should we now believe them now?
On the other hand, if the whole business of threats to the reef has simply been grossly exaggerated then it is also time to end the charade. In addition to rent-seekers there is abundant evidence of a variety of other unhealthy influences being involved as well. These include media sensationalism, political pandering for green votes, postmodern scientific corruption, “noble cause” corruption, ill-informed eco-evangelism and bureaucratic empire building.
Regardless of the reef-salvation industry’s industry’s motives, its efforts can only be viewed as either honest but incompetent or duplicitous and self-serving. It is time to severely cut the funding for this elaborate and costly farce. By their own reckoning the reef saviours have failed miserably and we can no longer afford them.
Personally, I suspect that the surest way to save the reef would be to cut funding for management and research by half and link future cuts or increases to the balance of economic and environmental outcomes. I have little doubt that would soon effect a miraculous recovery.
Much more HERE