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Coral's 2°C limit is wrong!

By Dave Armstrong - 18 Sep 2012 18:48:11 GMT
Coral's 2°C limit is wrong!

Coral reef image; Credit: © Shutterstock

As IUCN publish the first of their expert verdicts in various reefs, another nail in the coffin of corals looks likely as the formal 2°C global warming limit is being broken. The Canadian, Australian and German collaboration here produced a useful paper in the journal, Nature: Climate Change.

Only two thirds are safe, even if the 2°C limit above pre-industrial levels is not broken. Katja Frieler of the Potsdam Institute's eminent Climate Impact Research Group further emphasises, "Without a yet uncertain process of adaptation or acclimation, however, already about 70% of corals are projected to suffer from long-term degradation by 2030 even under an ambitious mitigation scenario." That ambitious mitigation would involve instant cutting of coal, oil and gas emissions for a start. Not likely, is it?

Even worse scenarios appear next. At a mere 1.5°C rise, half of the coral reefs would still disappear. So many figures tend to blur the point. What is appearing more and more are the most accurate figures, after the most recent research. Old research tended to appease groups who were uncertain about the actual climate change. Now we are certain that the planet is much warmer than expected. Coral bleaching was reported elsewhere last week but here is used to stress again the temperature effect rather than any unknown disease. The temperature for 32,000 possible years( up until 20600) was exhaustively diagnosed, producing quite definite and indisputable results to push the point 16% of corals actually disappeared under the giant and prolonged heating stress that oceans experienced of 1998.

coral reefs and climate change

Credit: © Nature Climate Change

Above: Thermal tolerance at 1.0 °C (a), 1.5 °C (b) and 2.0 °C (c) of global mean warming. Colour scale indicates the average of the 19 frequencies calculated at each coral reef grid point. Green points represent frequencies below 0.2 yr−1 and yellow to red points represent frequencies above that critical limit for long-term degradation. (d), Corals at risk of long-term degradation for constant 2 °C. The average across 19 AOGCMs (thin blue lines) is shown as a thick grey line. (e), Fraction of the world's coral reef cells (coloured areas) at risk of long-term damage due to frequent coral bleaching events, depending on global mean temperature (xaxis) and assumed thermal threshold (y axis). A constant 2°C×month thermal threshold is indicated by the horizontal dashed line.

With all of that stress, the acidification problem only pours oil on the literal flames. It's the greenhouse gas,CO2 , again, but this time forming carbonic acid in the water. Rather like limestone cave formation, the coral superstructure of calcium carbonate cannot be formed. Malte Meinshausen, now at the University of Melbourne, comments on the window of opportunity that we have just for the moment: "We close this window, if we follow another decade of ballooning global greenhouse-gas emissions."

500 million people are closely affected by the coral reefs' one million species and their own "wellbeing." That in itself causes all kinds of overfishing, pollution, disease and water quality problems, but our universal global warming now proves the killer link for almost all of these people and corals. This research will soon be appearing even faster, although the great efforts in man-hours ad scientific "nous" will be completely wasted unless the less ignorant of our politicians see the blatant message written on the reefs.

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Topics: Climate / Coral