It’s mid-winter and time for a sober look at the state of our planet, and at the state of our human enterprise. What on earth is happening to the Arctic? Is the bleaching of coral reefs as bad as it has been reported? Is humanity beginning the correction that most environmental scientists believe is long overdue? And does discussing any of this really matter in a post-truth world where people believe any story which validates their preconceptions?
Contrary to what some readers may believe, posts to blogs do not just happen. They take time to craft. Or at least, on this blog they take time to craft, perhaps because writing does not just come naturally to me. There was a bit of a hiatus in the final months of 2016 – the process of moving house and overseeing ‘minor’ renovations took more time than I had intended, and the US political scene took a turn which left me wondering whether it was now time for the big sleep. But it is a new year, and today I feel energized. I am committing to produce about two posts a month, to focus on environmental issues, but to occasionally comment on political issues when they pertain to our interaction with the rest of the biosphere. I’ll continue a healthy marine and tropical bias since that may help me stay close to topics I know something about. If readership dwindles, I’ll shut up.
Each day we hear more about the people Donald Trump is selecting for his cabinet. Anyone who thinks this is going to be “just another Republican presidency” has not been watching closely. We could be at the beginning of a radically changed world, and I do not mean in a good way. Rather than spew frustration by talking about his picks, I will use this post to talk instead about Arctic sea ice, glacier melt, and coral reefs. All have been in the news of late, and both provide disturbing evidence of how seriously humanity is altering this planet. We definitely are in the Anthropocene.
A Radically Warmer Arctic
Something very strange is happening at the top of the world. On 16th November, a graph posted on Twitter caught my eye. It showed total global sea ice area (Arctic and Antarctic combined) for every day of the year, plotted for every year since 1978. Here is that graph, and an update of it to January 3rd, 2017.
Graph as posted on Twitter by Zack Labe, a Cornell student, using data downloaded from the National Snow and Ice Data Center (NSIDC) in Boulder CO. It shows a trace of total sea ice extent (Arctic + Antarctic) for every year from 1978. The trace for 2016 is consistently low, and appears to have gone onto a completely different path starting in late August.
The graph as currently available on the web, with data extended through 3rd January 2017.
In truth, the image I saw on Twitter is more alarming than the more recent one, and both exaggerate the extent to which the 2016 data diverge, because of the truncation of the Y-axis (there is also something wrong re the Y-axis of the first graph). NSIDC has routinely published data using a Y-axis extending down to 0 km2. Also, by combining what is happening in the Arctic with what is happening in the Antarctic, when the two regions operate on approximately opposite cycles of ice growth and retreat, is a strange analysis. We do not know from this graph whether the Arctic is failing to freeze up in the Fall, or the Antarctic is melting more rapidly during Spring, or both. In fact, it’s a little bit of both.
In November, when the discrepancy in global sea ice between 2016 and previous years was at its greatest, Antarctic seas contained 14.54 million km2 of ice, the lowest amount on record for that month, and more than twice as far from average coverage as was seen in the previous lowest year. In the Arctic, sea ice extent was 9.08 million km2, nearly two million km2 below average for November, caused by what the Guardian referred to as a triple whammy of continued warm waters, a warm atmosphere, and winds which concentrated this warmth over the Arctic. This year is not like any previous year. It will be interesting to follow trends in 2017.
Continental Ice Sheets
While loss of sea ice may have profound impacts on the rate of global warming, and loss of Arctic sea ice may prove a bonanza for international trade and for fisheries and mineral exploitation in that ocean, the loss of continental ice causes sea level rise. Given the human penchant for living by the sea, sea level rise may become one of the most important of all the changes we lump as climate change. Scientists who study ice are learning a lot, but a lot remains to be learned concerning how quickly, and by what mechanisms, the major continental ice sheets in Greenland and Antarctica will respond to our steadily warming climate. During 2016 there were several significant advances in understanding the behavior of the west Antarctic ice sheet reported in the technical press. I blogged about a couple of them in July, and talked briefly about the strange ways glaciers melt in November. At the end of the year, we learned something more about the behavior of the much larger east Antarctic ice sheet, and got some contradictory messages about the Greenland ice sheet (showing just how much there is to learn).
In December, Stephen Rintoul, University of Tasmania, and six colleagues published a report in Science Advances dealing with the mechanisms of melting in the east Antarctic ice sheet. They studied the Totten ice shelf which forms the terminus of the largest glacier on east Antarctica, the Totten glacier.
Antarctic glaciers extend out from shore as immense blocks of ice grounded on the sea bed hundreds of meters below sea level, and towering several meters above sea level. As they push outwards the calving of icebergs at their seaward edges adds to the sea ice that extends the ice shelf as a floating ice mass out across the surrounding ocean. Melting of the sea ice does not, itself, lead to sea level rise – it is floating already – but its melting permits further transport of ice from the glacier and that does raise sea level. Glaciologists have long considered the east Antarctic ice sheet to be more stable than the smaller west Antarctic ice sheet because its geography makes it less exposed to ‘warm’ waters, however observations in recent years have revealed that the Totten glacier is thinning at a faster rate than expected if surface melting alone were responsible. Were it to continue, this melting could result in substantial sea level rise as ice moved down from the continent behind.
Australian research vessel, Aurora Australis, at the edge of the Totten glacier. This mass of ice is grounded on the rocky subtidal coast, with a floating ice shelf usually extending out further into the ocean. A rare opportunity of open water at the edge permitted access to the front of the glacier. Photo © Paul Brown, Australian Maritime College.
Rintoul and colleagues had the opportunity, because fortuitous winds opened a passage adjacent to the inner edge of the sea ice (close to the seaward edge of the grounded ice) and they were able to secure ship-based measurements of ocean conditions there. Their investigations revealed that, as in parts of the west Antarctica ice shelf, underwater geography and movement of ocean waters were combining to transfer considerable quantities of ‘warm’ water deep beneath the otherwise grounded ice along a canyon more than a kilometer deep. (I am using ‘warm’ to denote that this ‘Circumpolar Deep Water’ is hardly warm – it remains below 0oC – but at about -0.4oC it is significantly warmer than the prevailing ocean temperature in the region. At the pressure typical for water a kilometer deep, this water is a couple of degrees above the freezing point and can certainly melt ice.) Rintoul and colleagues calculated that this warm water flowed in towards the grounded ice at about 220,000 m3 per second, resulting in heat transfer sufficient to melt somewhere between 63 and 80 billion tonnes of ice from the bottom of the glacier per year. This amount conforms to previous satellite estimates of the rate of thinning.
What Rintoul and colleagues have done is to confirm, and provide the first quantitative estimates for, significant melting from beneath the Totten glacier. They’ve revealed that this largest glacier in east Antarctica is very dynamic, and being melted by the same mechanisms at work in the west Antarctic ice sheet. The long-held idea that the vast masses of ice locked up in the east Antarctic ice sheet are unlikely to melt significantly unless the world becomes a lot warmer is no longer true, and as that ice melts, sea levels must rise.
Nature’s issue for 8th December contained three papers which together provide an exemplary illustration of how science really progresses, while also telling us more about glacier melting. Those who think that science is all about proclaiming inviolate truths, and those who believe science is merely opinion and speculation illustrated with complex graphs and tables and as likely to be wrong as right, could do well to take a look.
The core papers, one by Joerg Schaefer of Columbia University and colleagues, and the other by Paul Biermann of University of Vermont and colleagues were published back to back, and preceded in Nature’s ‘news & views’ editorial section by a forum (really two short commentaries) discussing them. The commentaries were by French scientists Pierre-Henri Blard and Paul Leduc, and by UK scientist Neil Glasser. The reason for discussing the papers together is that they use similar methods to reveal probable events in the deep past on the Greenland ice sheet, and draw diametrically opposed conclusions. Neither paper is obviously ‘wrong’, yet both cannot be completely ‘correct’.
Biermann and Schaefer are both primarily interested in assessing the stability of the Greenland ice sheet during the Pleistocene. Understanding its behavior back then, when a varying climate cycled the world into and out of successive glaciations, should help us gauge its likely behavior over the next few decades. In the absence of a time machine, both teams turned to the generation by cosmic rays of 26Al and 10Be, isotopes of Aluminum and Beryllium respectively. Cosmic rays impinging on surface bedrock generate these isotopes only within the top few meters. Deeper rock, or rock buried under many meters of soil or ice, is not so altered. The two isotopes decay, but at differing rates, so that changes in the ratio of 26Al to 10Be can inform how long ago a particular rock sample was at the surface and exposed to cosmic rays. This ratio, plus the concentrations of each isotope can inform for how long that rock was being bombarded at the surface.
Biermann and colleagues examined isotopes in sediment cores retrieved from oceanic sites off the Greenland coast that were subject to a rain of sediment from melting glacial ice. Schaefer and colleagues looked at isotopes in a core drilled through the Greenland ice sheet and into the rocky terrain near the summit. But they got different answers. Biermann’s group found evidence that the Greenland ice sheet began to develop about 7.5 million years ago, and was essentially a permanent structure during the last 2.7 million years surviving through several interglacial periods. Schaefer’s group found evidence of extended, or more likely repeated, shorter periods during the last 2.5 million years when the ice sheet was not present at the core location. Either the ice sheet has been very stable for a considerable period of time, during which climate varied from glacial to interglacial on multiple occasions, or the ice sheet has been far more dynamic in its response to climate and has melted and reformed one or several times. Both commentaries suggest possible ways to reconcile the two sets of observations, and Glasser appears to favor an eventual conclusion that the ice sheet is more dynamic than we have suspected previously. His commentary concludes,
“These new papers throw down three immediate challenges. First, we must seek ways to reconcile the two seemingly contradictory records of the ice sheet’s past behaviour. Second, we must try to understand the dynamical processes of the ice sheet that make possible the required huge and rapid variations in the size and volume of the [Greenland ice sheet]. And third, we need to assess whether such variations could happen again in the near future, with all the attendant social and economic consequences that would accompany a rapid rise in global sea level.”
Science is a process of throwing up hypotheses, finding data that will support or refute them, and throwing up new hypotheses to replace them when they are found wanting. Science is also seldom easy. The papers by the Biermann and Schaefer teams advance our understanding a little bit, but it is going to take further work, by them or others, to sort out what the real history was. And, as Glasser states, there are potentially significant consequences for our own time if a more dynamic behavior is confirmed. We do live in interesting times.
Sea Level Rise
Make no mistake, sea level rise is one of the more important consequences of climate change. It is slow and inexorable, but it usually reveals itself suddenly when a storm leads to more flooding than expected or more erosion from storm surge. Everything seems to be fine, and then the next storm causes billions of dollars losses because of unanticipated damage. Reading back through the IPCC reports, it is clear that sea level rise is one of the consequences of warming that has been consistently underestimated. Rates and extent by 2100 have been ratcheted up in each successive report.
Unanticipated complexities in the melting of ice are perhaps the primary reason for scientists’ relatively feeble ability to project likely rates of sea level rise. While significant advances in understanding of ice behavior are being made (as witness the reports discussed here), there are very likely to be new surprises to be discovered in the future. What concerns me is a nagging feeling that these surprises will generally be ones that lead to an upward revision in the likely extent and/or rate of sea level rise in the future. Remember, the warming we have already caused will ensure sea level rises for the next two or three hundred years – the time delays built into the mechanisms that connect CO2 emissions, through atmospheric and oceanic warming, to ice melting and sea level rise take that long. And the pattern of melting may be such that far more of it will take place for a given cumulative rise in CO2 emissions than we currently suspect. The work of scientists interested in ice sheet behavior over the next few years will be critical in helping to define realistic levels of risk.
Piazza San Marco, Venice, at high tide. Photo © Andrea Pattaro/AFP/Getty
If climate change is a wicked problem, because it happens too slowly to attract the attention of a naked ape selected for skill in avoiding charging predators, sea level rise is an even more wicked consequence. It will proceed slowly and inexorably. Our attention will be drawn to it intermittently when infrastructure fails, at great cost, during particular storms, and we will focus on the symptoms rather than the disease. We will spend fortunes on sea walls, pumping systems, and other infrastructure to protect built landscapes, almost certainly underestimating the full extent of local need on each occasion. Far better to recognize the inevitability, do the science to pin down the extent and rate, and plan the retreat to higher ground. Venice is a great city, but our world does not need multiple Venices, and the money built on new Venices could be far better spent on decarbonizing our global economy.
On the other hand, perhaps the Donald will simply fix sea level rise while he is draining the swamp and building the wall. Time will tell. Cartoon © Toles/Washington Post.
Meanwhile Coral Reefs
An assessment of the global impacts of the recent el Niño on coral reefs is a big enough topic to deserve space in my next post. Instead, I want to focus here on the continued lack of traction of the coral reef story. I’ve talked about this before, but, briefly, there are sizeable numbers of reef scientists who feel that the message concerning human impacts on coral reefs is simply failing to be received by a wider audience with the gravity it should get.
For many of us, the 1997-8 global bleaching event was the first of repeated wake-up calls that our warming of the planet was going to have major implications for the long-term sustainability of these iconic ecosystems. Most of us recognized that substantial degradation of coral reef systems would have important direct and indirect, economic, esthetic, and cultural impacts on humanity, particularly on the 1.36 billion of us who reside within 100 km of a tropical coast. Many of us also recognized that if global warming was having such severe impacts on coral reef systems when temperatures had not yet risen 1Co, we should anticipate serious impacts on other, less sensitive ecosystems in the future. Global mass bleaching was a canary in a mineshaft, falling off its perch, and the real significance of what was happening concerned long-term sustainability not just of reefs, but of the biosphere that sustains our lives.
The succession of bleaching events around the world has been widely documented and widely reported in the international media. In Canada, in the depths of dark December, 2016, about a week before Christmas, I saw yet another update on the severe bleaching of the Great Barrier Reef, complete with underwater footage of stretches of bleached and dying corals, as one of just 7 stories included in CBC’s national news program that evening. But like the overwhelming majority of such reports, this one dealt with the story as a tragic environmental incident far away in Australia. True, it was presented as part of a global phenomenon, but it was a coral reef phenomenon, an environmental story. There was no hint that it might be a sign that we were exceeding one more of the planetary limits that will govern the sustainability of our own civilization.
The coral reef science community has struggled for some years now with the failure of the story to resonate. We have criticized our tendency to focus on doom and gloom. We have argued that we must tell this doom-laden story by focusing on points of light, hotspots, and #oceanoptimism. One result is lots of images and video in the media showing beautiful reefscapes, and wonderful examples of the complexities of form, function and behavior that make coral reefs so wonderful.
For most people, knowing that there are some wonderful coral reefs out there becomes evidence that the concerns expressed by scientists are probably exaggerated. Time to worry about reef demise later, when new images of wonderfulness are harder to find. The call to focus on the positive can easily become a call to enjoy the beautiful evening with the moonlight glinting off the ice and the water, while standing on the deck of the Titanic, racing headlong towards the iceberg. We do not need Pollyanna, although we do need to offer whatever hope we can, while describing as compellingly as possible, what appears to be happening to reefs across the tropics.
One former coral reef scientist, Randy Olson, has recently provided a relatively unhelpful diatribe on his blog criticizing the coral reef science community for its inability to tell stories simply, following his ABT (and, but, therefore) mantra, and using words of no more than one syllable. Yes, he had a point. An important one. Many of us have never learned how to tell an engaging story about our science, able to capture the attention of people other than environmental geeks. Without engaging the unconverted it is impossible to build a groundswell of understanding and engagement with what is surely an important issue for our times. We should work hard to tell the story far more effectively. But Olson already has the skill to tell good stories; he apparently feels that the coral reef story is no longer his to tell.
(In an e-mail exchange, Olson assured me he has not given up on reefs or reef scientists, but he wants the reef science community to provide a singular narrative about what is happening to coral reefs. I’m sorry, Randy, the story is more nuanced than that, and if there is no room for nuance in modern story telling we really are in a strangely illiterate world, a Trumposphere perhaps. I still think people can understand complex stories – such as what is happening to coral reefs – though I agree we scientists need to work harder at telling these stories well.)
It’s also true, as in any ‘science’ story, that there are differences of opinion among the members of the reef research community. I don’t believe any of my colleagues looks at the evidence of coral bleaching in recent years and considers it ‘normal’, or ‘the way things have always been’. Nor do I believe any of us thinks human CO2 emissions are not the ultimate cause. But we do differ in our assessments of the severity of what has happened to reef ecosystems in recent years, or, even more, the severity of what is likely to come in the next few decades.
Some among us still cling to the belief that ‘it won’t be too bad, long-term’, either because they are convinced that mutation and natural selection will confer resilience to heat stress in time for corals to flourish once more in warmer future seas, or because they think that, somehow, we will manage to cool off the planet quite soon despite all the evidence pointing to a likely failure to keep warming under 2oC. I still hope they are correct, but I don’t think the available evidence gives their beliefs much support.
Others see the demise of coral reefs bringing with it a massive reduction in ocean biodiversity. The claim that 25% of marine species live on coral reefs is too often used to suggest that 25% are absolutely dependent on coral reefs. They are not, although substantial loss of reefs will lead to some loss of biodiversity as reef specialists succumb. The world’s ocean ecosystems are not going to collapse because coral reefs disappear. And exaggeration of this type is not helpful. Still others really do focus on the tragedy that the substantial loss of coral reef ecosystems represents for the planet – but they view the story as an environmental/ecological one, and fail to make the connection to the wider story of the risks we are building for our own future. These scientists may criticize the views expressed by other reef scientists who recognize the link to our future, and think the story is not really about corals or even about reefs at all. In my view, reef scientists who think the demise of reefs is a ‘reef’ story are missing the real point – it really is about us. Here is a recent interview with CCTV, Washington, in which I attempted, not fully successfully, to get the focus shifted from reefs to the wider picture.
I personally believe we need to make the reef story about us if we want the wider public to care. We have little likelihood of convincing the wider community of the importance of acting to sustain coral reefs if we fail to connect flourishing reefs with a biosphere that sustains our own species and civilization. Coral reefs, by themselves, are just not that important to the bulk of people who have never seen one, and whose lives, so far as they are aware, are unaffected by whether or not reefs thrive. (I accept that among reef scientists there will be some who believe we should focus on communicating the science about coral reefs, because our role is not to comment on broad political issues such as the need to move humanity off fossil fuels. I disagree with them.)
A recent article in Anthropology Now, by Irus Braverman, University of Buffalo, explores the various threads of this discussion within the reef science community. While I think she has painted a far more combative dialog than is really taking place, there is some truth in her assessments. Some of us, depressed by the continuous drip-drip-drip of bad news, do view coral reefs as ‘probably doomed’ over the next few decades, and in unguarded moments are likely to use expressions like ‘basket case’, ‘up the creek’, or just plain ‘fucked’ when describing future reefs. Others really do refuse to face the fact that if warming episodes are wiping out vast tracts of coral, small-scale cultivation of fragments for out-plant on small patches of dead reef is just another way of rearranging chairs on the Titanic – it fills time, makes you feel useful, but has no realistic possibility of solving the problem. Still others, with genetic interests and expertise, are exploring the possibility of selective rearing of corals to build heat resistant strains for use in reseeding efforts. I welcome the latter efforts. I also despair at the fact that humanity seems far less capable of local management that effectively deals with some of the ‘simpler’ stressors – overfishing, pollution, inappropriate coastal development – because we have difficulty building the will to act. There is reason for reef scientists to be both angry and depressed by what is going on in far too many reef locations around the world. And if we want to engage the public, we have got to use that anger and depression to communicate effectively with them.
As I was completing this post, a new article appeared in Scientific Reports. Written by Ruben van Hooidonk from NOAA’s Atlantic Meteorological and Oceanographic Laboratory in Miami, and eight colleagues from the USA, Thailand, French Polynesia, Guam, the UK and Australia, this paper reports an attempt to provide a global projection of coral reef bleaching into the future. Specifically, van Hooidonk and colleagues have used projections of sea surface temperature out to 2100 to compute times when thresholds for coral bleaching were exceeded for all coral reef regions. By combining model projections derived from the IPCC CMIP5 dataset, with higher resolution climatology derived from NOAA’s Pathfinder v 5.0 series, they were able to identify dates when bleaching would be likely, at a spatial resolution of 4km2. They used these results to map the year when severe bleaching was likely to become an annual event for each reef location, under two scenarios: a business-as-usual one comparable to what is likely if humanity continues to dither over whether or not to decarbonize our economy (IPCC RCP8.5), and a more optimistic one (RCP4.5) representing the successful implementation of efforts to reduce carbon emissions that are 50% more intense than currently committed to by nations under the Paris accord.
Histograms showing the global distribution of 4 km2 reef locations with reference to the year in which each is likely to start experiencing annual severe coral bleaching. The left panel shows results assuming we follow a business-as-usual approach to CO2 pollution. The middle panel shows some slight improvement in that onset of annual bleaching is delayed by about 11 years. The right panel shows the improvement in number of years delay for each reef. Figure 4 from van Hooidonk’s paper in Scientific Reports.
Under business-as-usual, they project that over 99% of coral reef locations will experience severe bleaching annually before 2100, but there is wide variation among and within reef regions. On average, reefs will experience annual bleaching by 2043, but 5% of reefs will experience such conditions before 2033, and 11% of reefs will not experience annual bleaching until after 2053 if their projections are confirmed. Under more aggressive greenhouse gas mitigation efforts (represented by RCP4.5), the average reef does not experience annual severe bleaching until 2054, but 32% of reefs see less than 10 years delay in onset of annual bleaching, while 7% of reefs see a reprieve of more than 25 years.
While these results are based on projections of model results out to 2100, and may depart from reality especially in later decades, they permit three important conclusions: First, the pattern of warming we have set in train is likely to create conditions favoring annual recurrence of severe bleaching in all reef locations during this century, and for many locations within the next three decades. Second, effort to mitigate CO2 emissions does improve the future for reefs, although what has been committed to so far, under the Paris accord, buys the average reef less than a decade. Third, and most important, there are substantial differences among and within locations in the likelihood of severe bleaching. This makes it possible to rank coral reefs in terms of their relative risk of severe bleaching near term, and plan conservation actions accordingly.
I fear there is also a fourth conclusion that needs to be drawn from this paper. Those of us within the reef science community who have talked about the ‘loss’, the ‘demise’, the ‘disappearance’, or even the ‘extinction’ of coral reefs as we knew them in the 1950s or 1960s seem to be much closer to the likely reality than those who have been more optimistic, assuming that, somehow, things won’t be as bad as all that. We really are doing a number on coral reefs, and we will discover there are other ramifications of our CO2 pollution.
Putting the coral reef and the ice melt stories together, there is a fifth conclusion to draw. We are having profound effects on this planet – ones that will impact our lives severely in the near future. Will our descendants look back on this time as one in which we realized our errors and made a concerted effort to correct them? Think about that as you watch the clowns parade.