Monday, November 07, 2005

Coral and global catastrophes

Here's an elevator speech for this project:

Tropical corals reefs may be first entire ecosystem to be eliminated as a result of climate change, in combination with other factors. Is this alarmism? Half-truth? What – really – can and should be done? Reefs are vital to the lives hundreds of millions of people. Public understanding and awareness are at a very low level. A popular, accessible but serious publishing project, including a book, that reaches large numbers of people can help.

There is no shortage of people ready to doubt and discourage, or to say there will be little interest in this endeavour. Well, we’ll see.

Even if the threats to coral reefs are serious, how high should they rank on a list of global priorities?

The distinguished climatologist Hans Joachim ("John") Schellnhuber does not, for example, include them in his map of "Earth System Tipping Points" (see summary at Oops). I recently wrote to ask him why. He said:

"I fully agree with you that the tropical coral reefs are endangered by global warming and - very important - ocean acidification. The reason why I did not include them as an "Earth System Tipping Point" is the fact that there is no clear analysis available yet how their destruction would affect the planetary machinery as a whole (or how their decline would at least impact on a regional scale). It is obvious that there will be local effects like coastal destabilization.

If you have good arguments for expecting large-scale impacts, please let me know. My tipping points map is a living beast anyway that changes all the time because of pertinent input such as yours".

I answered that I did not know any good arguments for expecting large-scale impacts on the "planetary machinery as a whole", and sent John’s comments to Tom Goreau of the Global Coral Reef Alliance. Here are extracts from Tom’s response:

"I very much like John's mode of thinking and am delighted that this is reaching the popular press.

…the current generation of climate models appear to be missing the vast bulk of positive feedback mechanisms that MUST exist in the Earth climate system [and] whose existence is revealed by analysis of the long term empirical climate data (ice cores, deep sea cores, etc.) which is why I trust data far more than models. We all agree qualitatively that things will get worse much faster than models suggest, but we really don't know how high they will get and how long this will take, due to uncertainty about the actual rates.

…For example our global coral reef [sea surface temperature] database shows that there are already important changes in ocean circulation taking place in every part of the ocean. These have profound effects on climate change, but are not included in the models. We are seeing an increase in the flow of heat in the Gulf Stream and Kuroshio systems, and big increase in the Antarctic circumpolar current, for example, two of [John’s] key areas. The Amazon is in fact changing faster than recognized, witness the unprecedented drought now underway. Most Caribbean corals are now dying of high temperature.

…While I agree with [Caspar] that coral reefs should be listed in ALL global compendia of major tipping points because it is the richest ecosystem in the sea and the first which will be effectively destroyed by global warming with devastating environmental and economic consequences to over 100 countries from loss of biodiversity, fisheries, shore protection, tourism, etc.

[But] John is right that this does not trigger global environmental changes. Coral reefs account for half of the limestone burial in the sea, and although many naively think this is a CO2 sink, it is in fact the major natural net source of CO2 to the atmosphere...the net amount of CO2 added to the atmosphere by coral reef growth is 50 times LESS than we put in from fossil fuels, which gives you an idea how anthropogenic effects have overwhelmed natural processes. The bottom line is that loss of coral reefs will be a catastrophe for almost all tropical marine countries, but it does not in itself trigger various global climate feedbacks. That is to say this is a major tipping point RESPONSE, rather than being a DRIVER of future changes".

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