Threatened staghorn coral invades Fort Lauderdale!

Last week I was visiting FIU and talking with Lionfish guru Zack Judd when the topic of the Acropora range shift came up.  He and Laura Bhatti wanted to take me to do something fun on my last day in Miami.  So we decided on snorkeling off the beach on the world famous Fort Lauderdale strip to see one of the local coral reefs.  Seriously.  I was skeptical. First, because this is what the shoreline looks like: GaltMile-aerial1 Close up of a typical coastal habitat: 2007573-Elbo_Room_Fort_Lauderdale The thing is, I had heard from my buddy Bill Precht that Acropora cervicornis (AKA staghorn coral) is moving northward along the Florida reef track in response to global warming. Precht and Aronson have a great paper in FEE (2004) “Climate flickers and range shifts of reef corals” that outlines all of this. i1540-9295-2-6-307-ex1 Though now rare throughout their Caribbean range (mainly due to white band disease), staghorn corals appear to be moving northward into Palm Beach County: i1540-9295-2-6-307-f03.jpg But still, I didn’t think these new populations would be, literally, right off the strip, in pretty shallow water (3-5 m depth). And I didn’t imagine how massive they would be. They were huge and the thickets were fairly thick, even though hurricane Sandy recently rolled over them. Check out these photos Zack took: OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA


I know of other persisting or new staghorn thickets elsewhere in Caribbean (Bill and I documented one such example in Jamaica in 2003) but nothing quite this large. This is really good news. And it is in agreement with my growing sense that climate change is going to be more about change (range shifts, altered composition, new players, etc.) than outright destruction and extinction. We will have some of that, but the science to date suggests that species are changing their distribution and phenological timing in response to warming much more than they are simply dying out and going extinct.  They aren’t giving up quite yet.

The case study also emphasizes the over-dispersion of many marine species and the huge role of abiotic factors, like temperature, in limiting distributions. (I think in general, we are way to concerned about connectivity in the ocean – there seems to be plenty of that.)

Listen, Acropora cervicornis and palmata for thousands of years were two of the dominant reef-building corals  in the Caribbean. Their populations were decimated regionally in the 1980s and their loss radically changed countless aspects of coral reef communities. Their expansion into South Florida does not mitigate that regional loss. It also does not mean future threats won’t wipe them out. And they can’t keep moving forever; there is no shallow water hard bottom habitat to settle on too far north of Florida and other environmental factors, like water sediment and nutrient load, would probably prevent colonization anyway. Range shifts will not save all species. Many, like Australia seaweeds will range shift into oblivion (e.g., the southern ocean). But I think it is still pretty cool to see species like this continue to bounce back. It gives me hope. And I think it should be teaching us some broader lessons.

One is that local impacts and local human population density in general has very little to do with the loss of corals. Look at the shoreline these corals are colonizing! There is nowhere in the Caribbean with such high urbanization and yet here they come. The presence of people per se is not driving coral loss or limiting recovery.

When sponges take over

Below is a guest post by UNC student Kati Moore:

Overfishing, pollution, and most of all, climate change, are destroying corals, causing the collapse of ecosystems and fishing industries around the world.

“Corals are the backbone of the entire ecosystem,” said Emily Darling, a marine and climate change researcher at the University of North Carolina at Chapel Hill.

When corals die, sponges often take over the reefs, which causes drastic changes in reef ecosystem dynamics.

Think of an ecosystem like a city. Some cities are lively and diverse, have great restaurants and an eclectic music scene. Reefs with corals at their base are like this. Corals are colorful and vibrant, and most importantly, support a diverse group of plants and animals, including fish people eat.

Some cities are dull. Life in these cities is monotonous, there is little diversity, and there is absolutely nothing to do on a Friday night. These are reefs without corals. When corals die, other organisms such as sponges take over. Corals are “really critical for biodiversity,” said Elizabeth McLeod, climate adaptation scientist for The Nature Conservancy.

Global warming is making the oceans hotter and saltier, which destroys the tiny algae that live inside corals and give corals their bright colors. Without these algae, corals die. This process is called coral bleaching because killing the algae removes all color from the corals, leaving them white and “bleached.” Coral bleaching is “one of the most critical climate change impacts,” McLeod said.

Bleached coral on the Great Barrier Reef. Image by J. Roff (CC BY-SA 3.0). 

Human actions that release carbon dioxide into the air, such as burning fossil fuels, also release carbon dioxide into the oceans. More carbon dioxide lowers the water’s pH, making it more acidic, a stressful state for most corals. More carbon dioxide in the water also means less carbonate, which corals need to build their skeletons.

Overfishing is another important threat to corals, McLeod said. Overfishing removes fish at the top of the food chains in coral reefs. Without these fish to eat organisms further down the chain, the food chain breaks down, and the reef ecosystem, including the corals, collapses.

When corals die, they leave behind open space for other organisms such as sponges, urchins and certain species of algae. Most marine researchers once thought algae to be the most likely contender for taking over when corals die. New research shows sponges may have a better chance than previously thought.

In a paper published in the May 2013 issue of Global Change Biology, James Bell, marine ecologist at Victoria University of Wellington, cited cases in Belize, Puerto Rico, Indonesia and at Palmyra Atoll in the Central Pacific Ocean where the area covered by coral had decreased while the number of sponges increased.

One sponge whose takeover has been better documented than most is a brown, bulbous sponge called the chicken liver sponge. In 1998, oceans reached record temperatures, destroying a record number of corals through coral bleaching. Some types of corals experienced greater than 90-percent mortality. Scientists refer to this as the mass bleaching event of 1998.

The chicken liver sponge, Chondrilla nucula. Image by Esculapio (CC BY-SA 3.0). 

Richard Aronson, professor and head of biological sciences at the Florida Institute of Technology, conducted research in Belize around this time and found the chicken liver sponge almost completely covered the sea floor which had once been dominated by corals. The chicken liver sponge’s success was due to how fast it grows (many times the rate of most corals), and the smelly toxins it produces to ward off predators.

Researchers have documented similar takeovers by sponges across the Caribbean and Pacific Ocean where corals have died as oceans got hotter, more acidic and more polluted. Sponges have survived these changes mainly because they are less sensitive than corals.

When sponges take over, the ecosystem becomes a dull city. “It’s not like it’s a wasteland,” said John Bruno, marine ecologist at the University of North Carolina at Chapel Hill, “but I doubt that [sponges] are going to support fish populations in the way that corals will.” This means lower diversity overall as well as fewer edible fish.

“It’s hard to see any real benefits either ecologically or economically” when sponges take over, said Bell, author of the journal article on sponge dominance.

Interview with Abel Valdivia about lionfish and biotic resistance

I LOVE this interview PeerJ just posted (and excerpted below) with Bruno lab PhD student Abel Valdivia about our new paper on lionfish and biotic resistance.  

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PJ: What were your motivations for undertaking this research?

AV: The invasion of lionfish into the Caribbean basin over the past ten years provides a unique possibility to study marine species invasion at a large geographical scale. Species invasion is one of the major threats the oceans face today, and can be closely related to issues such as fishing and climate change. With rising temperatures due to global warming, several marine species are shifting their geographical range; occupying new environments; establishing new ecological interactions with established residents, and therefore changing the community structure and composition of the invaded systems. Marine invasions due to human introductions or ocean warming are important to understand at a large spatial scale since it will be a very common phenomenon in the near future.

Lionfish have spread to every shallow and deep habitat of the Western Atlantic and the Caribbean, including coral reefs environments, seagrass meadows, mangrove root systems, estuarine habitats, and even depths over 90 meters. Lionfish have even been reported in the colder waters near Boston, Massachusetts. We are still investigating the negative impacts of this invader on all of these already disturbed ecosystems, but one thing is clear – their voracious appetite threatens small fish and juveniles of depleted fish populations including commercially and ecologically important species such as groupers, snappers, and herbivores.  The failure of the Caribbean region to constrain invasion success may be partially associated with the lack of native predatory capacity due to overfishing, or simply to weak biotic resistance by native predators and competitors to a novel predator.

PJ: How would you say your study is controversial?

AV: Over the past few years some studies have hinted that native groupers could potentially prey on invasive lionfish and therefore act as natural bio-control of the invader. There is one study that reported lionfish in the stomachs of at least two species of large groupers. However, it was not clear if the lionfishes were already dead when the groupers ate them. Another study found a negative relationship between the biomass of native Nassau grouper and lionfish at a relative small spatial scale in the Exuma Cays Land and Sea Park in the Bahamas. In fact, we were excited to test the generality of this negative relationship in a paper published last year. Unfortunately, we did not find any evidence that grouper or any other predators (including sharks) or competitors (same size native predators) were negatively related to lionfish and concluded that other physical environmental variables and culling were the main drivers of lionfish distribution and abundance.

Our current study expands on those findings by adding new factors that are known to affect fish abundance (e.g., fishing and reef structural complexity). We also tested whether lack of native predatory capacity was an issue across the Caribbean. While some reefs actually had a low abundance of native predators due to overfishing, other well-protected reefs with high abundances of sharks, groupers and snappers exhibited a high abundance of lionfish. Therefore, the lack of predatory capacity does not limit the control of the invader. In general there is actually little to no evidence that abundant native predators can constrain the distribution and abundance of invasive predators. For example, the expansion and proliferation of the invasive Burmese python in the Florida Everglades was never constrained by the abundant native American alligator.

Read the rest here

Coral reef resilience: a biogeographic perspective

GBR_corals-590x400Coral reefs are affected by a large range of disturbances including disease, bleaching, storms, and Acanthaster planci, also known as crown of thorn starfish (COTS) outbreaks.  There appears to be a lot of variation of how much coral cover is affected by physical and biological disturbances and in how quickly coral communities recover from it.  Those two ecological processes, resistance to and recovery from disturbance, make up “resilience” (although in some corners of coral reef science, the recovery component is emphasized and nearly synonymous with resilience).  Resistance and recovery (and the disturbance regime they are linked to) control ecological “stability” or the degree to which population or community state varies with time.

People have been quantifying coral community resilience in the field for many decades. Stoddart (1974) studied the effects of hurricane hattie on the near-pristine reefs of Belize in 1961 (when it was still part of the British Empire and called “British Honduras”) and Endean and Stablum (1973) documented the effects of the first of many COTS outbreaks on the Great Barrier Reef.

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And of course Joe Connell studied the waxing and waning of shallow water coral cover (and species richness) in response to disturbance on Heron Island, GBR for decades (and probably still is).  Connell (1997) was also the first person I know of to synthesize this literature, although exhaustive, he employed pre-meta-analysis “vote counting” and his effort wasn’t exactly quantitatively sophisticated:

Screen Shot 2014-03-28 at 7.02.28 PMGraham et al. 2011 sort of picked up where Connell left off with a meta-analysis of the recovery of coral communities around the world.  Surprisingly, they found that disturbance type, e.g., “physical” vs. “biological” disturbances, and other reef characteristics including connectivity had little effect on recovery rate.  Region did seem to affect recovery, with it being fastest in the western Pacific, i.e., the most diverse place:Screen Shot 2014-03-28 at 10.32.01 PM Human population density and management status also appeared to effect recovery rates, but not in ways that you would have expected! 

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Reefs with lower post-disturbance coral cover tended to recover more quickly:

Screen Shot 2014-03-28 at 10.40.48 PM I recently taught an undergraduate seminar class in which for a class project, we expanded on the Graham et al study and asked: Is coral species richness related to resistance to and recovery from disturbances?

More diverse communities are thought to be more stable—the diversity–stability hypothesis—due to increased resistance to and recovery from disturbances. For example, high diversity can make the presence of resilient or fast growing species and key facilitations among species more likely. How natural, geographic biodiversity patterns and changes in biodiversity due to human activities mediate community-level disturbance dynamics is largely unknown, especially in diverse systems. For example, few studies have explored the role of diversity in tropical marine communities, especially at large scales.

We contacted Dr. Nick Graham, he shared his database with us (thanks Nick!)(which you can download here). We synthesized the results of 41 field studies conducted on 82 reefs, documenting changes in coral cover due to disturbance, across a global gradient of coral richness. The students added the resistance / coral loss data (the original study just looked at recovery) and we used Veron’s coral richness maps to estimate local richness (at the sites of the disturbance studies). 

Our results (Zhang et al. 2014) indicate that coral reefs in more species-rich regions were marginally less resistant to disturbance and did not recover more quickly.  

Screen Shot 2014-03-28 at 6.40.00 PMCoral community resistance was also highly dependent on pre-disturbance coral cover, probably due in part to the sensitivity of fast-growing and often dominant plating acroporid corals to disturbance. Our results suggest that coral communities in biodiverse regions, such as the western Pacific, may not be more resistant and resilient to natural and anthropogenic disturbances. Further analyses controlling for disturbance intensity and other drivers of coral loss and recovery could improve our understanding of the influence of diversity on community stability in coral reef ecosystems. Read more here at PeerJ: Zhang et al. 2014.

Literature Cited

Connell, J.H. (1997). Disturbance and recovery of coral assemblages. Coral Reefs, 16, S101–S113.

Endean, R. & Stablum, W. (1973). The apparent extent of recovery of reefs of Australia’s Great Barrier Reef devastated by the crown-of-thorns starfish. Atoll Research Bulletin, 168, 1–41.

Stoddart, D.R., 1974. Post-hurricane changes on the British Honduras reefs: resurvey of 1972. In: Proceedings of the Second International Coral Reef Symposium, vol. 2, pp. 473–483

Recent and future impacts of ocean warming on marine biodiversity

I am a (relatively junior) member of an NCEAS/NSF funded international working group that is assessing how climate change is affecting ocean ecosystems.  Today, we published our third major paper (in Nature; Burrows et al. 2014), that predicts how ocean warming will affect global patterns of Biodiversity. Read a nice non-technical summary here and a nice summary by the editor:

To survive in a changing climate, a species may need to move in order to stay in an area with a constant average temperature. Such mobility would depend on an ability to keep pace with a moving climate — and on the absence of physical barriers to migration. These authors use the velocity of climate change to construct a global map of how ecological climate niches have shifted in recent decades and go on to predict changes in species distribution to the end of this century. The map indicates areas that will act as climate sources and sinks, and geographical barriers likely to impede species migration. The data show that geographical connections and physical barriers — mostly coasts — have profound effects on the expected ability of organisms to track their preferred climate. This work underlines the importance of migration corridors linking warmer and cooler areas as a means of maintaining biodiversity.

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Our first major paper came out in Science in 2012 (Burrows et al. 2012) in which we described the “velocity” of warming of the planet at relatively fine grains.

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Our second paper “Global imprint of climate change on marine life” - and really the primary output of our working group – was published last year in Nature Climate Change. Read my summary here at Skeptical Science and less technical summaries here and here.

We synthesized all available studies of the consistency of marine ecological observations with expectations under climate change. This yielded ametadatabase of 1,735 marine biological responses for which either regional or global climate change was considered as a driver. Included were instances of marine taxa responding as expected, in a manner inconsistent with expectations, and taxa demonstrating no response. From this database, 81–83% of all observations for distribution, phenology, community composition, abundance, demography and calcification across taxa and ocean basins were consistent with the expected impacts of climate change. Of the species responding to climate change, rates of distribution shifts were, on average, consistent with those required to track ocean surface temperature changes. Conversely, we did not find a relationship between regional shifts in spring phenology and the seasonality of temperature. Rates of observed shifts in species’ distributions and phenology are comparable to, or greater, than those for terrestrial systems.

Working group leader Mike Burrows and I (with Chris Harley) also summarized the output of our team and other literature in a new book chapter (Bruno et al. 2014) which I serialized here.

Top 5 Things I Learned at The Benthic Ecology Meeting 2014

Justin Baumann has a very nice piece on his first experience at the Benthic Ecology Meeting here.

I was really impressed by his insight and the general maturity of his post. I am on Justin’s committee but I haven’t interacted with him enough to get this clear a sense of what he is doing and thinking.  Like so many newish grad students, Justin is really into blogging and science outreach.  I worry sometimes about students putting time into outreach, but one clear benefit is that it enables them to communicate ideas and opinions with their mentors and community.  So go check out his piece and some of his other posts at his website or the superb grad-student-run Under-The-C-Blog.

1) Benthic Ecology Meeting is incredibly student friendly!

According to the official conference booklet, 67% of all oral and poster presentations were given by students. As a conference attendee, I would say that it was safe to assume that students outnumbered faculty by at least 2:1, if not more. There were students everywhere. I’ve never been to so many student talks. This conference is not ASLO Ocean Sciences, it’s smaller, more personal, and less overwhelming. It offers students (both undergraduate and graduate) a great platform for being introduced to a conference and for giving a presentation to a large group of peers without feeling extremely overwhelmed. As someone who gave their first major research presentation in front of a room of the most well known faculty in my field (International Coral Reef Symposium), I would say that coming to Benthics first would have been dramatically better. Plus, since most of the attendees are students, it is a great way to meet colleagues in the field and discuss ideas without being overly intimidated. If you are a marine science student and you have never presented at a conference or want to work on your presentation skills, I suggest that you give Benthics a try!

Read the rest here

NOAA to close key fisheries lab in Beaufort, NC

The excellent Fisheries Blog has a great piece on the proposed closing of the facility on Pivers Island.  I was shocked when I first heard this news.  Duke/UNC organized a congressional visit to the facility that could change minds.

Despite the incredible work done by the approximately 100 NOAA Beaufort Laboratory employees (see page 8), the recently proposed Fiscal Year 2015 budget by President Barack Obama surprisingly proposes closing the facility. That is right, it proposes closing shop on more than a century of research.

Read the rest here

Graph of the day: projected coral bleaching under different RCPs

From van Hooidonk et al. 2013 PDF. Learn about RCPs here.


Really Dumb Idea #247: Training sharks to eat dead lionfish

Below is a repost from the graduate student-written Under The C blog by Serena Hackerott. 

Since the lionfish invasion hit the news, people have suggested that native predators will eat and control invasive lionfish. For more information check out our previous posts The Great Debate: Predators vs Lionfish and Who’s “Lyin’” about Lionfish?. But with current evidence suggesting that the current level of predation by native predators is not enough to control lionfish (Hackerott et al. 2013 and Raymond et al. 2014) people have started to suggest “training” native predators to eat lionfish by feeding speared lionfish to sharks, grouper, barracuda, eels, and other predators.  A recent paper reports that individual lionfish that were tethered in place on reefs where divers frequently spear lionfish (and presumably feed them to the local predators) were eaten by native predators. Authors claim this is evidence that native predators can in fact be “trained” to eat lionfish. However, there has been an unfortunate consequence of divers attempting to “train” predators to eat lionfish. It seems that instead of learning to associate lionfish with food, predators like sharks and barracuda are associating divers with food. This is leading to uncharacteristically aggressive behavior towards divers as seen in the video above. As a SCUBA diver with over 10 years of experience, I am very comfortable diving with sharks in a natural setting. Personally, though, I would not like sharks to start expecting me to bring snacks every time I enter the water.  (more…)

New report: what we know about climate change

Below is a guest post by Dana Haine, a K-12 Science Education Manager at the Environmental Resource Program (ERP) here at UNC.

A new report on climate change was released by AAAS yesterday.  According to the New York Times, “the language in the 18-page report, called “What We Know,” is sharper, clearer and more accessible than perhaps anything the scientific community has put out to date.”

Also, today, according to the New York Times, the President will unveil a website,, “that will try to turn scientific data about global warming into mapped digital presentations.”

This afternoon at 5PM the White House will host a high-level forum on plans to make the United States more resilient to climate change. John Podesta will lead an event that includes Dr. John Holdren (Office of Science and Technology), Kathryn Sullivan (NOAA), Mike Boots (Council on Environmental Quality), Ellen Stofan (NASA), and Rebecca Moore (Google’s Earth Engine).  The discussion should highlight “new announcements” from agencies and the private sector to help communities shore up infrastructure and respond to the impacts of climate change.

Live: Wednesday, March 19th– 5:00pm Eastern (2pm Pacific)

Watch it here:

Congress considers Magnuson-Stevens

Note, below are materials for a guest lecture I am giving tomorrow in Dr. Elizabeth Havice‘s Geography 435: Environmental Politics class (at UNC).  

Congress is currently considering reauthorizing (and tweaking) the Magnuson-Stevens Fishery Conservation and Management Act.  A National Academy of Science report found that the law has worked relatively well (e.g., in reducing the number of “overfished” stocks). So reauthorization is supported by most environmental NGOs like Pew, many scientists and fisheries agencies, and some trade and lobbying groups representing fisheries interests.

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However, there are some in congress that want to weaken the law in the name of (bogusly) enabling flexibility (which already exists):  (more…)

How can we represent complex results in transition journals?

Below is a cool piece, reposted from the Wares Lab.  I run into this issue too and I think the answer is modern journals like PeerJ that allow movies plugged right into the paper.   

When I first started doing science, visualization of our data and results was a bit easier. Sequence a gene from 20-30 individuals, generate a phylogenetic hypothesis, make it look pretty, Figure 1. As we have moved to information from more and more loci (or greater numbers of samples, or any other factor of additional complexity), there have been ways developed to summarize the results visually for the purposes of proving to the audience of a journal article that you are on the right track in terms of interpretation. For example, former postdoc (and now faculty at Texas A&M – Galveston) Ron Eytan used these images to show which parts of a phylogeny were consistently supported and which were not (an image that overlays many reconstructions of a phylogeny from the same data):  (more…)

The 10 warmest years on record globally have all happened since 1998


The dangers of data deficiency

Below is a guest post by Chris Mull, a PhD student in the Dulvy Lab at Simon Fraser University.  Chris studies shark biology and evolutionary neuroecology.  You can read more about his research here.

Over this past week science headlines have been flooded with the news that one-quarter of all chondrichthyans (sharks, skates, rays, and chimaeras) are threatened with extinction. This finding, according to a massive study by the International Union for the Conservation of Nature (IUCN) Shark Specialist Group, is alarming, and is helping to galvanize the already growing concern over the status and conservation of the world’s sharks and rays. However, lost amid the media frenzy over the headline statement is the equally disturbing finding that almost half of the world’s known chondrichthyan species are categorized as Data Deficient. This means we know so little about half of the world’s sharks and rays basic life history information, such as how quickly they grow or how often they reproduce, that it is extremely difficult to infer how their populations are faring, or how resilient they might be to the myriad of threats they face. This considerable gap in our basic understanding of sharks and rays may be the biggest unaddressed threat they face.


Ovik Banerjee 1989-2014

I regret sharing the devastating news that Ovik Banerjee passed away last Monday.  He was only 24.

Ovik worked in our lab in 2011. He and Amanda and Juan de spent the summer that year in Muisne Ecuador, working on a mangrove restoration – blue carbon project (DelVecchia et al. 2013).  This is what Ovik said about that summer:

During the summer of 2011 I was a field researcher in Ecuador studying Carbon Sequestration in Mangrove Forests. There were times where I spent days at a time on an island with only five permanent human residents, no electricity or running water, and countless mosquitoes. Despite the hard work (12 hour days), it was one of the best summers of my life.

I ran into Ovik last summer in Providence RI at Water Fire, and he was as happy and friendly and outgoing as ever.  That was the last time I saw him.  On Facebook as in person Ovik was passionate about issues like the environment and social justice.


Pipeline as you’ve never seen it before

Scientists as advocates and is climate change really bo-ho-horing?

There has been a broad, intense, and interesting discussion about science outreach sparked by Gavin Schmidt’s talk at AGU this year (below).

The Yale forum has a great piece on it, breaking down some of Gavin’s main points:

Scientists must be careful, however, and follow a handful of rules of engagement that will protect their integrity as a scientist as well as their rights as a citizen. Responsible advocacy is characterized by a handful of principles, Schmidt said. The individual should:

  • communicate his/her values fairly and truthfully;
  • make the connections between his/her values and policy choices explicit;
  • make sure to distinguish his/her personal conclusions from the scientific consensus;
  • acknowledge that people with different values would have different policy choices; and
  • be aware of how his/her values might impact objectivity, and be vigilant.

Irresponsible advocacy, on the other hand, can be recognized through a handful of clues. Among these:

  • Individuals misrepresent and hide their values.
  • The basis of their policy choices is unclear.
  • There’s an untested presumption that the individual’s personal scientific conclusions are widely held.

Sound reasonable? Does to me. Yet some scientists still disagree. (more…)

Just a green crab, doin green crab thangs

I love science rap.  Especially rap by Eric Axelman:

Do the facts matter?

 has an interesting piece on whether the climate change “consensus” is a useful policy approach. Is it changing the minds of people that formerly didn’t “believe in” climate change? And more broadly whether facts ever change minds.

As two top researchers studying the science of science communication—a hot new field that combines public opinion research with psychological studies—Dan Kahan and Stephan Lewandowsky tend to agree about most things. There’s just one problem. The little thing that they disagree on—whether it actually works to tell people that there’s a “scientific consensus” on climate change—is a matter of huge practical significance. After all, many scientists, advocates, and bloggers are doing this all the time. Heck, Barack Obama and Al Gore are out there doing it. And the central message that the United Nations’ Intergovernmental Panel on Climate Change sought to convey with its latest report, that scientists are now 95 percent certain that humans are driving global warming, is a message about scientific consensus. from here

97_piechart_med  Read the full piece here

Q: What does the new IPCC report say about sea level rise?

A: Nothing good. See the plot below of observed past and predicted future sea level (rise). Note the two plotted future scenarios are based on the new Representative Concentration Pathways (RCPs): plausible trends in atmospheric CO2 (and other greenhouse gases) concentration named for the corresponding additional heat retained by 2100 in W m-2. For the past, proxy data are shown in light purple and tide gauge data in blue. For the future, the IPCC projections for very high emissions (red, RCP8.5 scenario) and very low emissions (blue, RCP2.6 scenario) are shown. Source: IPCC AR5 Fig. 13.27. From RealClimate:

Let us jump straight in with the following graph which nicely sums up the key findings about past and future sea-level rise: (1) global sea level is rising, (2) this rise has accelerated since pre-industrial times and (3) it will accelerate further in this century. The projections for the future are much higher and more credible than those in the 4th report but possibly still a bit conservative, as we will discuss in more detail below. For high emissions IPCC now predicts a global rise by 52-98 cm by the year 2100, which would threaten the survival of coastal cities and entire island nations. But even with aggressive emissions reductions, a rise by 28-61 cm is predicted. Even under this highly optimistic scenario we might see over half a meter of sea-level rise, with serious impacts on many coastal areas, including coastal erosion and a greatly increased risk of flooding.

As this graph makes clear (look at the lower panel) the observed rate of sea level rise is increasing. Fig. 3. Modelled versus observed global sea-level rise. (a) Sea level relative to 1900 AD and (b) its rate of rise. Source: IPCC AR5 Fig. 13.7.

“For an unmitigated future rise in emissions (RCP8.5), IPCC now expects between a half metre and a metre of sea-level rise by the end of this century. The best estimate here is 74 cm. By 2300, for unmitigated emissions IPCC projects between 1 and more than 3 meters of rise.”

On the low end, the range for the RCP2.6 scenario is 28-61 cm rise by 2100, with a best estimate of 44 cm. Now that is very remarkable, given that this is a scenario with drastic emissions reductions starting in a few years from now, with the world reaching zero emissions by 2070 and after that succeeding in active carbon dioxide removal from the atmosphere. Even so, the expected sea-level rise will be almost three times as large as that experienced over the 20th Century (17 cm). This reflects the large inertia in the sea-level response – it is very difficult to make sea-level rise slow down again once it has been initiated. This inertia is also the reason for the relatively small difference in sea-level rise by 2100 between the highest and lowest emissions scenario (the ranges even overlap) – the major difference will only be seen in the 22nd century.

Although estimates for sea level rise through 2100 in the new report (AR5) are about about 60% greater than in the previous edition (AR4), they are still considered quite conservative and probably exaggerate uncertainty at the lower range. Read the whole piece here