(he continues this is still min 8 of 15..and I started at 6min)

but at that RS meeting in 2009 I saw the first time that we had run out of road.
The geological record was unflinching.
"Coral reefs flourish best at 350 parts per million or less of atmospheric carbon dioxide"
(..hmm AFAIK that is an extraordinary claim, without any extraordinary evidence
Corals have been around for millions of years, during which time the earth's gases have been all over the place
and at the same time we don't know precisely what they were in any given decade
..so to start talking about such a precise sweet-spot sounds ridiculous
Just look at how prior to 1960 CO2 was at 314ppm, is he seriously saying that they know coral had lower growth that time , compared to 350 in 1988 ? )

We broke thu that level in 1988
(It is wrong to assert that have never happened before
even if you think in the 2 million year history of man it's always been below 350)
By 2009 it was 387ppm and CLIMBING FAST !
(Remember the measure he is talking about are not the daily measurement which varies greatly from Winter to Summer, but the annual average)
No wonder reefs were in trouble , we'd already overshot !
To secure a healthy future for coral we'd have to somehow catch that CO2 and put it underground

.. (whoa ...we seem to have gone into a game of Chinese whispers
His argument is that
#1 peak El Nino's lead to coral bleaching ..that's PARTIALLY true
#2 That the global temp is rising ..that's true in general, but NOT new
#3 That CO2 is the proxy for increasing temp .. 'a hand on the thermostat'
Except no one says that rising temps are 100% due to CO2
Most say that temperature rise has 2 components : the general rise as we come-out of an ice age and a possible component from GREEHOUSE gases effect..remember CO2 is only 1 GHG with water vapour being the main one,
And there is discussion about the proportion contributed by those 2 components.

#3 That rising temps will kill coral and it will not recover
But there are two things there are many types of coral living at many different temperatures
So when you say Coral X won't like a 2C temperature rise, people will say that Coral Y a few hundred miles nearer the equator already lives at a temp 2C warmer than coral X

#4 ..Now he has leapt to a new assertion that even if we stop producing CO2 we have to catch existing CO2 to drive it back down to 350ppm
but we know that CO2 is NOT the only driver of temp
That coral at location-1 will have been living at a lower temperature 100,000 years ago
and will probably without man be living at a different temp 100,000 years in the future with possible drift into new location
Most people would say he has jumped a few steps there
First you have a growing trend-in-CO2 emissions , so an aim would be to stabilise that
that would mean ppm would still increase but at a stabilised rate
then you'd look to stabilise actual emissions so that the growth in ppm-trend would start to fall
then you look to cut emissions below today's levels, but ppm would still increase
However if you got some new magic energy source, say fusion then you stop all CO emission and ppm would become static
Then you could use that new energy to such CO2 out of the atmosphere
..However even if you get ppm back to 350 then the temp in location1 will still be rising but just due to natural factors.
Of course if nature throws up some super volcanoes in that time, then the dust from them would reduce the planets temperature.

May 21, 2018 at 10:48 AM | stewgreen

1. Coral bleaching is the result of coral dying, and does not have to be due to temperature change.

2. Coral has always died. Dead coral is an ideal home for new coral to grow.

3. It is time for the coral experts to identify the survivable temperature range of corals.

4. Then they can list the other reasons why coral bleaching events are not unprecedented:

https://www.nature.com/articles/365836a0?error=cookies_not_supported&code=3f6af5da-8502-461c-9239-b76dd835ac96

"EPISODES of coral bleaching resulting from dissociation of endosymbiotic algae (zooxanthellae) from host coral tissues have occurred with increasing frequency over the past decade on reefs throughout the tropics1,2. These episodes have usually been attributed to increases in sea water temperatures3–10, but the mass bleaching events that occurred throughout the Caribbean during 1987 and 1990 were not readily explained by temperature alone11,12. An additional factor that may have contributed to these bleaching episodes is ultraviolet radiation in the 280–400-nm band. At many localities where bleaching occurred in 1987 and 1990, sea conditions were described as extremely calm with exceptionally clear water13. In the absence of suspended organic and inorganic matter in the water column, higher than average intensities of ultraviolet radiation probably reached all depths within the photic zone for several consecutive months. Evidence for a possible link between ultraviolet radiation and coral bleaching has not been forthcoming2. Here we report results of a field experiment showing that, irrespective of high water temperatures, short-term (three weeks) increases in ultraviolet radiation of a magnitude possible under calm, clear water column conditions can readily induce bleaching in reef-building corals."

Yeah, cos a Travel and Tourism website is always gonna tell it like it is, right?

Very severe coral bleaching affected all these islands in 2005, when abnormally warm water temperatures exceeding 29°C and up to 31°C sat over the coral reefs from mid May to mid November. Many island states reported that more than half of their corals bleached with a large proportion of these subsequently killed;
zx In 2006 many corals were still bleached or were infected with coral disease, such that coral losses continued, with many countries reporting losses of about 50% of their previous coral cover;

Status of coral reefs of the Lesser Antilles: The French West Indies, The Netherlands Antilles, Anguilla, Antigua, Grenada, Trinidad and Tobago

Click

Excellent program, I thought. Looking forward to tomorrow.

I was struck by the fact that there was - from a so-called scientist - a singular lack of scientific evidence, and a hyperbole of sentiment. Pathetic, I thought.

Well, it was billed as a personal response by a scientist, not a scientific response by a person, the science is clearcut and well-supported and he referenced it more than enough: 19% of reefs lost globally and 60% under threat. Warm water reefs at the top of their thermal tolerance, bleaching events becoming more frequent, and likely to be annual before long. Pretty grim, for the science, you could do worse than start here:

Despite their importance, coral reefs are facing significant challenges from human activities including pollution, over-harvesting, physical destruction, and climate change. In the latter case, even lower greenhouse gas emission scenarios (such as Representative Concentration Pathway RCP 4.5) are likely to drive the elimination of most warm-water coral reefs by 2040–2050. Cold-water corals are also threatened by warming temperatures and ocean acidification although evidence of the direct effect of climate change is less clear. Evidence that coral reefs can adapt at rates which are sufficient for them to keep up with rapid ocean warming and acidification is minimal, especially given that corals are long-lived and hence have slow rates of evolution. Conclusions that coral reefs will migrate to higher latitudes as they warm are equally unfounded, with the observations of tropical species appearing at high latitudes “necessary but not sufficient” evidence that entire coral reef ecosystems are shifting. On the contrary, coral reefs are likely to degrade rapidly over the next 20 years, presenting fundamental challenges for the 500 million people who derive food, income, coastal protection, and a range of other services from coral reefs. Unless rapid advances to the goals of the Paris Climate Change Agreement occur over the next decade, hundreds of millions of people are likely to face increasing amounts of poverty and social disruption, and, in some cases, regional insecurity.

https://www.frontiersin.org/articles/10.3389/fmars.2017.00158/full

Which part of '50% loss' is giving you the problem Stew? Meanwhile, we lost 30% of some of the most important corals on the Great Barrier Reef in 2016 …

Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them. Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016, corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3–4 °C-weeks. After eight months, an exposure of 6 °C-weeks or more drove an unprecedented, regional-scale shift in the composition of coral assemblages, reflecting markedly divergent responses to heat stress by different taxa. Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs comprising the world’s largest coral reef system. Our study bridges the gap between the theory and practice of assessing the risk of ecosystem collapse, under the emerging framework for the International Union for Conservation of Nature (IUCN) Red List of Ecosystems, by rigorously defining both the initial and collapsed states, identifying the major driver of change, and establishing quantitative collapse thresholds. The increasing prevalence of post-bleaching mass mortality of corals represents a radical shift in the disturbance regimes of tropical reefs, both adding to and far exceeding the influence of recurrent cyclones and other local pulse events, presenting a fundamental challenge to the long-term future of these iconic ecosystems.

https://www.nature.com/articles/s41586-018-0041-2

“When corals bleach from a heatwave, they can either survive and regain their colour slowly as the temperature drops, or they can die,” Hughes said. “Averaged across the whole Great Barrier Reef, we lost 30% of the corals in the nine-month period between March and November 2016.”

From <https://www.theguardian.com/environment/2018/apr/19/great-barrier-reef-30-of-coral-died-in-catastrophic-2016-heatwave>

Alarming, not alarmist.

So, RR, the corals are going to evolve themselves out of trouble?

Riiiiiight.

As usual you present tertiary skewed interpretations of work from avowed catastrophists.

Au contraire, you present ad hominem arguments against a prominent and distinguished academic recognized by Nature in 2016 as one of the “10 people who mattered this year” while I gave direct and relevant quotes from several peer-reviewed journals. Primary sources. It is abundantly clear that nearly a third of the GBR died off in 2016, the warming trend is unlikely to decelerate, bleaching events will become more common and warm water corals are in dire trouble.

The bleaching database you admire is curated by Simon Donner, who clearly has no issue with Hughes' methodology:

I wish I could say that this widespread death of corals comes as a surprise. It doesn’t. Scientific research, including my own, has been warning for almost two decades that the fate of the world’s coral reefs depends on actions to slow global warming. A look back at some old work on the subject shows just how critical a time this is for the climate, for coral reefs, and for scientists.

http://blogs.ubc.ca/maribo/2017/03/16/the-great-barrier-reef-and-the-voice-of-scientists-in-the-trump-era/

And here is Donner's 'elevator pitch' on AGW

http://www.comprehendingtheclimatecrisis.com/tag/elevator-pitch/

Do you a new smear for him? Not alarmist, just alarming.