Sunday, September 30, 2012

Through a Reef Darkly

Simon Donner provides a gliss on the fate to come of coral reefs in a warming world, and, to be frank, it ain't pretty.  The reefs are toast in a 2 C warmer world.  Commenting on Freiler, Meinshausen, Golly, Mengel, Lebek, Donner and Hoegh-Guldbergs' paper "Limiting global warming to 2 C is unlikely to save most coral reefs", Simon points to the obvious, if 2 C is an average, then the extremes are worse, and it is the extreme hot spells that doom the reefs.

Frieler et al. relates the projected frequency of heat stress events – what I often call ocean “heat waves” – in coral reefs worldwide – that can cause coral bleaching to global mean temperature change, the metric discussed so often in policy circles, the public and the press.  In past studies, including several of my own (Donner et al., 2005, 2007), we estimated the frequency of bleaching events under different future greenhouse gas scenarios. In those studies, we are able to show the difference in the outcome for coral reefs between futures with different levels of atmospheric carbon dioxide (and other greenhouse gases). For example, my “Coping with Commitment" (open access) paper concludes  with a discussion of the level of atmospheric CO2 necessary to avoid one definition of "dangerous" impacts to coral reefs.

In those past analyses, though, if you wanted to know what the coral reefs picture looked like under some specific global mean temperature increase – like, say, the proposed 2 deg C threshold – you’d need to take apart the results and find the point in the emission scenarios were global average warming reaches (or, depending on your question, stabilizes) at that level. In response to a request in advance of the UN Copenhagen climate summit in 2009, a group of colleagues and I did that analysis (pdf) for the Caribbean and found a clear difference between the coral reef outcomes in +1.5 C and a +2 C world. Frieler et al is the first paper to do a comprehensive analysis of coral reef outcomes under different temperature thresholds for the whole planet.
Now some, not Eli to be sure, might point out how useful proper framing could be in this matter.  Eli is simply depressed.


J Bowers said...

What did marine life ever do to us to deserve all this? In related news:

Fish to shrink by up to a quarter due to climate change, study reveals
"Scientists predict 14-24% reduction in fish size by 2050 as ocean temperatures increase"

Shrinking of fishes exacerbates impacts of global ocean changes on marine ecosystems. Cheung (2012)

Anonymous said...

Language warning for bunnies with twitchy, delicate ears.

I know that for the last little while I've been a scratched record (remember vinyl?), but we're fucked.

Well, our kids and theirs are fucked, and we don't give a shit that they are.

But what is more amazing is that we don't even want to minimise how much we fuck up things for our decendants and that the natural world doesn't rate a second thought let alone a first one.

That's even more fucked.

Bernard J. Hyphen-Anonymous XVII, Esq.

David B. Benson said...

Well, help to advocate beginning on

Irrigated afforestation of the Sahara and Australian Outback to end global warming
(The full paper pdf is open access.)

david lewis said...

Donner wrote a blog post discussing the study in more detail here.

"In the end, perhaps what’s most striking about the study is that despite many methodological differences from previous work, the results are not surprising. In that sense, the paper shows how robust the overall climate forecast is for coral reefs"

Sou said...

@David Benson - Australia is the world's second driest continent after Antarctica. Where do they plan to get the water from to irrigate the outback?

I hope they weren't thinking of pumping water hundreds of miles inland from the already fragile Murray-Darling system!

The outback is huge and doesn't get much rain.

I have to say that I really dislike these sort of suggestions. It devalues the existing (dry) habitat, which is very precious IMO.

Sou said...

Hope it's not too late for the Great Barrier Reef - half the coral has reportedly disappeared in the past 27 years.

J Bowers said...

Ex-GOP Party Office, Michael Satfford's piece is worth some exposure: Spring and Fall: To a Climate Change Denier

As is his piece on: Why I Gave Up On Being a Republican