It’s shocking for me (Robert) to accept that my home could be wiped out by greatly rising seas. That’s because I live on a hill north of San Diego, 45 feet above sea level and more than a mile inland from the coast. Equally shocking to me (Dan) is that the current coastline of my beloved Mendocino County, California, could largely disappear, a place where I spend weekends with my daughters exploring rivers that run inland, deep into wine country. These inundations won’t happen this century, but that is little solace. At the rate the world is going, land so dear to our hearts could slip under the sea and stay there for thousands of years. That hurts. Most of us believe our homes, our towns, our cities will be here for centuries and millennia to come. And why not? In Europe and across Asia millions of people live in cities that are thousands of years old. Indeed, inspired by European permanence, Robert’s family built garden walls from stone and fondly looked forward to passing on the land to hoped-for-grandchildren, and theirs, and so on. That idea, however, now seems flawed to both of us writing this article. Strong, new research indicates that anyone or anything tens of feet above the sea today may one day face an unbeatable force, whether a country home near San Diego or a skyscraping condo in Miami. Although shorelines are forever evolving, these changes can be predicted directly, and are due to needlessly excessive carbon dioxide (CO2) emissions from a relatively brief, recent period of time. How has the public not been made clearly and painfully aware of this? Why does fierce debate over climate miss so glaring a threat? The misperception, the widespread disbelief and the fallacy are rooted in a grave error in our thinking about time.


The many models that have projected scenarios about future climate change generally forecast only to the year 2100, or at times merely to 2050. As a result, public discussions have been mostly about “X degrees of warming” or “Y feet of sea level rise” to the end of this century. We have accidentally but notably limited our thinking, causing us to miss striking impacts that arise beyond this limited and artificial, specific time horizon. It is fair to say that citizens and politicians intend for Miami, and indeed the whole State of Florida, to exist well beyond 2100. Same for New York City, Boston, Washington D.C., London, Shanghai, Amsterdam, Mumbai and so on. Yet the same people discount staggering losses these places face beyond 2100. That’s wrong, and immoral too. That’s because a crucial fraction of airborne carbon from the industrial revolution, plus that coming this century and next, will persist for tens to hundreds of thousands of years. The CO2 stemming from just 150 years ago to a mere two centuries ahead may commit the world by inertia to tens of thousands of years of impacts. Anything going on for tens of thousands of years ahead essentially means “forever” on human time scales. These new data imply that we’re creating a kind of forever legacy, one that potentially can’t be ever forgotten, or fixed, no matter how far ahead we conceive of humanity. We are doing ourselves a dreadful disservice by consistently framing 2100 as essentially the last, final year of impacts. We’re thinking in a blinkered way decades out, while our foot is pressing hard on a warming accelerator that has serious impacts centuries out. How, then, can we think about climate and seas in truer time frames? An admirable new paper by Peter Clark and colleagues in Nature Climate Change, titled “Consequences of Twenty-First-Century Policy for Multi-Millennial Climate and Sea-Level Change,” illuminates the issue and helps point a way ahead. It addresses sea level rise in a longer term from a scientific perspective. The authors first analyze data that show how a major rise in CO2 and warming from 20 millennia ago brought Earth out of an ice age. Air temperatures continued to rise over a long period from the Ice Age to the near-modern climate that began some 11 millennia ago. From that time onward, CO2 levels and air temperatures sharply leveled off. Sea levels, which were 400 feet lower than today, did not stop rising, however. They continued rising long past when air temperatures reached their plateau, rising for another 8,000 years, climbing another 150 feet up to today’s height. The oceans did not achieve the near-current state that we all know as modern coasts and maps until roughly 3,000 years ago. The mere sliver (in geologic time) of climate stability in the last 10 or so millennia has dearly helped human societies and cultures to flourish. But the lesson is that seas are acutely sensitive to CO2 and temperatures, and they can have inertia lagging the carbon cycle and climate system. That means today’s oceans could go on rising very long after CO2 might be steadied—even if humanity takes determined action to slow rises in CO2worldwide, or even decrease emissions. This thorny fact is not widely appreciated. As Clark and his co-authors note, one-fifth to half of the airborne CO2released by human industry so far and in the next 100 years will still be present in the atmosphere by the year 3000. Combine CO2 persistence with the inertia of seas and it can mean sea level rise might go on at least 10 or more millennia—the unimaginable. There is no easy off switch to halt the rising of seas, no matter how much future societies might wish it to end. The opportunity to go on ignoring this basic dynamic is now vanishingly small. There’s already been a well-accepted 1.5 degree Fahrenheit increase in global temperatures since 1900. That change alone seems to come close to the greatest variations that have occurred over the previous 10,000 years. The current rate of change is just as concerning. It had taken a long period, from some 21 millennia to 12 millennia ago, for atmospheric concentrations of CO2 to jump by 80 parts per million (ppm), from about 190 to 270 ppm. In that time span global temperatures rose by an average of 7 degrees F. We are on track to repeat that kind of increase over a much shorter period. Keep in mind what that scale of change means. A difference of 7 degrees F separates today’s “ideal” climate from the extreme conditions of an ice age. For a refresher, the Ice Age built ice sheets over Canada, New England, parts of the Midwestern U.S., Northern Europe and Northern Asia. The Great Lakes were born when those sheets retreated. The meltwater retreat created Long Island in New York, and Cape Cod. Huge impacts were thus wrought by 7 degrees F; ice stood two miles tall over parts of North America, and shaped the elevations of a continent we know today. Just imagine if there’s another 7 degrees F of global warming ahead. Certainly that would alter land, sea and ecology in scales and ways hard to fathom. By looking back to Earth’s more distant past we know that with a temperature rise of “only” 2 degrees to 5 degrees F warmer, seas could rise 15 to 65 feet, a level that would drown so much today. For a thought experiment, adding 5 degrees F of warming is very imaginable, given current trends of increasing CO2. So it is reasonable to imagine seas 60 feet higher. That would render all of Florida a memory, almost all of New York City, much of the Eastern seaboard, parts of the Western U.S. and Gulf Coasts—and (Robert’s) acre of San Diego land that today is a mile from the present shore. Mechanisms by which this happens are easy to fathom. Greenland’s ice sheet stores only 22 feet of potential sea level rise, possibly ongoing for some 10 millennia. However, the Antarctic ice sheet stores around 150 feet of potential rise in that same time frame. Ironically, over the last dozen years, the East section of the Antarctic ice sheet annually has gained some 175 trillion pounds of ice. But West Antarctic annually has lost much more, some 275 trillion pounds of ice. (Greenland has averaged 600 trillion pounds of ice lost yearly, which is equivalent to10 billion trucks a year carting ice away). We may be heading quite outside of conditions known in human recorded history. Earth might even begin to exhibit changes of states that only can be guessed at. A new study, for instance, shows that net melting is causing Earth to slightly change how it moves on its polar axis. Days are getting just very slightly longer as ice melts at poles and redistributes that mass as water towards the equator. A very tiny change in Earth’s spin may not be troubling, yet it helps to show the magnitude of changes possible from CO2. Even distant earthquakes conceivably can grow in size or frequency, as unburdening crust rebounds after losing trillions of tons of ice. That in turn also could mean increased volcanism and tsunamis worldwide. These threats may be on long timescales but there’s an acute need for scientific knowledge, measured in and across millennia, to seep into our global discussions. August 2016 was the planet’s warmest month on record, by a lot. It was the 16th month in a row that a monthly heat record fell, way beyond any such streak in 137 years of record keeping. Arctic temperatures were an eye-opening 20 degrees F above normal. With relatively extreme levels of heat covering the Arctic, ice levels in the winter there were the lowest ever recorded. Nights have stayed warmer worldwide, too, making heat waves tougher to endure. This happened alongside the largest, single-year jump in atmospheric CO2 concentrations ever recorded. The level is now over 400 ppm and rising. And the global ocean reached record warmth as well. So what does all this mean for sea level rise? An international panel in 2013 had given scenarios for rise in this century mainly based on straightforward expansion of warming oceans. They only allowed for a small influence from marine ice-sheet instability, known as MISI, primarily on the assumption that Antarctic ice sheets were too stable and vast to irreversibly shrink this century. The report presented an optimistic lower-end CO2 scenario that assumed strong actions would be taken later this century to reduce CO2 emissions, and which predicted an estimated 1 foot of rise (0.3 to 0.6 meters) by 2100. The higher-end estimate, based on current trends continuing and little strong action this century to reduce CO2, led to 3 feet of rise by 2100, with the rate increasing rapidly to between one third to over half of an inch (8 to 16 millimeters) per year during the last two decades of this century. Such a rate only a century hence could be up to 10 times the 20th century average rise and might possibly approach what had occurred around end of the Ice Age, when seas rose rapidly. In the three years since that major report, three new papers on ice-sheet dynamics have shown that our prior understanding was incomplete, and that MISI mechanisms may be much more extensive across the Antarctic. The enormous Pine Island Glacier in Antarctica, for example, is thinning and retreating at a quickening rate. Mechanisms in newer models show that mass loss from unstable retreat may potentially become significant, sooner than expected. Some early collapse may be starting at the Thwaites Glacier now. Unexpected collapse of the Antarctic marine ice sheet could cause previous upper estimates of sea level rise to be exceeded not long after the end of this century. Although the timescale is uncertain, more rapid collapse could occur in a relatively short time period of two to nine centuries.
NASA’s DC-8 flies over the crack forming across the Pine Island Glacier ice shelf on Oct. 26, 2011. Credit: NASA GODDARD SPACE FLIGHT CENTER, FlickrCC BY 2.0
Furthermore, an important paper released in 2016 notes marine ice cliffs may be becoming instable, another mechanism for yet more rapid retreat through 2100. A different paper, out in March, shows sea levels could start to rise much more than was forecast in the prior lower-end scenarios. It indicates that more than 40 feet of rise may potentially come just from Antarctica by 2500, in accord with higher-end scenarios for CO2. The point here is that 2100 shouldn’t be regarded as a terminal year. To do so is folly, a fallacy in thinking. Life goes on, people do not end there, and seas will not suddenly halt their rise then. Scientists are natural skeptics, not prone to dramatize their findings. But cause for abundant hope is fading. That ought to stretch our thinking. Listening to the sea and this emerging science should mean adjusting ideas about what’s wise. The paleoclimate record indicates that in periods of meltwater, or termination of the last glacial period, seas possibly might have risen at an astounding rate of a foot per decade, or 10 feet per century. There is no reason to say it can’t happen again, or rise by faster rates. Given aggressive CO2 trends, it must be considered. Will such ideas lead to sound policy decisions? They should, but probably will not. Consider that likely levels of CO2 could make a folly of putting billions or trillions of dollars into armoring coastlines. One can imagine an enormously long and expensive wall, say 10 feet high, being topped in a century or two. And one can’t even imagine seawalls able to handle oceans going 50 feet higher and rising. Costly walls might make slightly more sense if rising seas could be counted on to stabilize, or retreat from knowable heights, and do so in a year meaningful to our species. Since neither is the case, capital that might be spent on armoring might instead be deployed in smarter ways. Arguably, rather than spending enormous yet finite capital on costly “hardening,” it would be better to put resources into avoiding CO2emissions, and growing renewable energy in the first place. Prevention rather than cure. That brings up the next part of this story: What, then, should we do?


One recently celebrated initial step was the Paris climate agreement, spelled out in December 2015. Although pundits thought it would take years to ratify the accord, by October 2016 the needed threshold of 55 nations that also represented 55 percent of global emissions had ratified it, putting it into effect. Moving from hope to real and difficult action has undermined prior aspirational agreements, however, such as the Kyoto Protocol. Paris is an important start, as is a recent amendment expanding the Montreal Protocol to cover hydrofluorocarbons, but the world is critically short on time and the means to verify reductions, and on finance for the necessary actions to achieve those reductions. Paris, moreover, isn’t binding. It is no treaty, and it lacks penalties. And perhaps most importantly the formal goal of 2 degrees Celsius (3.6 degrees F) for an “upper limit” on “allowable” warming is in truth a legal fiction, a mere balm for present leaders, since the planet is on a clear path to blow right past it. Furthermore, science suggests this 2 degrees C of warming is far more dangerous than the negotiators seem to think. Warming with much higher seas for millennia can be already baked in, even at a hoped-for 2 degrees. That is why the Paris Accord left many scientists shaking their heads in despair. There is an enormous gap between how quickly the science says carbon emissions must fall to stay within 2 degrees C, and what global agreements like that from Paris may aim to require. International equity is important, too. Western nations have already burned through much of the world’s total allowable carbon budget—the amount of carbon the world can burn before the planet is likely to cross the 2-degree threshold. This is profound, and vexing. Developing nations like China and India bear little blame for fuels burned for a century till now, and they may unsurprisingly argue for growth based on carbon-spewing industry of their own. Yet repeating our same carbon-path is now unaffordable given the global carbon budget. The physical carbon ceiling is wholly unyielding. The chemistry and physics of warming can’t be bargained with or pled to. Therefore, although the Paris climate accord is good as a first step, the need now is for ongoing real action and a strong, continuing commitment to progress to a 1.5 C target. If we act as if Paris and the Montreal Protocol amendment are the major endpoints, not a beginning, that will put off real solutions until it is too late. There are also pitfalls along the way if we don’t make climate solutions an ongoing process. “Cap-and-trade” systems for carbon emissions in theory can begin a transition to market-based mechanisms but they have already been gamed by many participants because caps are not rigorous and diminishing. A very hard look is needed at how natural gas is implemented: Can a plant be built today and be decommissioned by 2050? So-called “clean coal” is expensive, untested, unwieldy and unworkable, yet it is raised as a panacea. (Lost coal jobs are indeed a concern worthy of much attention, however). Nonstarters like geoengineering are suggested in some desperation, at least in the long term, yet they defy morality and could worsen a spiraling ocean acidification. Today, opportunity lies in implementing clean, green economies of solar and wind power, and energy efficiency, and geothermal and hydropower when ecologically friendly. The challenges of ocean acidification, fragile ecosystems and climate-induced migration all point to the need to scale up the truly clean energy economy at an exceptional pace. We suppose that possibly we all could close our eyes and hope that, say, leaders in China go even bigger on clean energy while dropping coal entirely. But China is cutting back on its ambitious solar goals. We could hope for “negative emissions” by sucking CO2 from the air and sequestering it into stone far below ground. That's technically feasible in certain basaltic rock regions, but the process is extremely expensive, and it is difficult to see this being implemented at a global scale. And that is where the rub is: CO2 dumping is free, today, and CO2 sequestration is costly. There are steps that make sense. Carbon taxes—including revenue neutral ones where other taxes are reduced—can work because they send unambiguous economy-wide signals. Carbon accounting across the public sector, and for companies wishing to do business with local to national governments, can educate and start the movement to full carbon pricing. Strong crossover policies, such as those linking car purchases to low-carbon goals, also accelerate the process.  Financial divestment from fossil fuels—which has been a challenge to implement—is another natural place to begin. We must consider, then, opportunities that harness viable technology and economics. For example, a simple, transparent carbon tax could be key. It could help get us near where we’ve got to be and hasten green energy. Even many big businesses are now calling for a carbon tax. A simple tax that’s adopted widely could be very significant. But in the U.S. a carbon tax goes unmentioned in political debates. One way or another, if leaders are going to get real on climate, they have to end fossil fuel subsidies, then phase out fossil fuel use, all while implementing clean, renewable energy for electricity generation and transportation. We should do this for our grandchildren and for their grandchildren. And because it is patriotic, will make us stronger and is far less distorting to our interests than fossil fuel dependence. These moves are not burdens. They are opportunities. Getting closer to 100 percent renewables could be achieved more readily than most people say. It can make nations stronger and more resilient, and add jobs. In some places like California, China, Denmark, Germany, Kenya and Morocco, renewable energy is progressing faster than in others. But nowhere is it fast enough. We two authors have spent most of our careers advancing renewable energy and sustainability, addressing climate both in theory and practice around the world—in academia, the public sector, the private sector and as entrepreneurs. Yet nothing currently gives us great hope that very harsh scenarios for climate change and sea level rise, lasting for millennia, will be completely avoided. Looking at rates of CO2 emissions, and at international actions that lean toward lofty words about future cuts over real action with teeth today, optimism does not spring to mind. In a mere couple of centuries, humans will have committed Earth to new climate regimes and higher seas never seen in our history, that will potentially last millennia. And we will have done it all, knowing the likely consequences.


Capitalizing on Solutions that Can Make Ecological and Economic Sense. Robert J. Wilder in Journal of Alternative Investments, Vol. 7, No. 2, pages 80–84; Fall 2004.  Saving Marine Biodiversity. Robert L. Wilder, Mia J. Tegner, Paul K. Dayton in Issues in Science and Technology, Vol. 15, No. 3 (Spring 1999). Listening to the Sea: The Politics of Improving Environmental Protection. Robert J Wilder. University of Pittsburgh Press, 1998.