Deep Future

by Curt Stager

  These comments, though backed by years of experience, were so different from what I’d been hearing that I pressed further. Are our sugar maples really not seriously threatened by climate change?

  “Some things certainly could change here as it warms,” he explained. “We do see sap runs starting earlier in the season now, but that doesn’t hurt the trees any. The main risk would be if the summers become a lot drier, because maples can’t handle droughts very well.”

  That put the ball back in my court. I dug into my collection of Adirondack weather records to see what’s been going on with our summer rains and what may lie ahead. The last century saw no apparent long-term shift in drought frequency, and the last thirty years were slightly wetter than the previous eighty years, but with no significant trend one way or the other in summer rainfall. So perhaps there is nothing particularly worrisome in terms of climate for maples here after all, at least in the near future.

  NECIA used several computer models to predict that annual average temperatures will be as much as 12.5 degrees warmer in the Northeast by century’s end under an extreme-emissions scenario, and that annual precipitation totals could be 10 to 15 percent higher, but there’s no way to be sure how accurate such models are without waiting to see what really happens. Nonetheless, you can still run them through a few hoops to see how well they perform on a known playing field, and historical weather records are the best tools for that job. To meet the challenge, a model must run its predictive time clock backward and produce a curve that closely resembles the real records. NECIA tried that very thing—a process called “hindcasting”—and reported that their models did an acceptable job of reconstructing the last decades of overall warming, but they didn’t make nearly as strong a showing in the precipitation trials. A multiyear dry spell during the 1960s, what people back then called “the great northeastern drought,” cut a deep and memorable notch in regional rainfall records, but the computer reconstructions missed it entirely.

  The failure to reconstruct the 1960s drought properly isn’t very surprising, though. Rain and snow are more difficult to work with than temperature because they vary more in time and space. Greenhouse gases mix easily throughout the lower atmosphere and wrap the entire planet in a fairly homogeneous heat-trapping blanket, so it’s relatively easy for a computer model to simulate their effects on temperature. And even without our carbon pollution in play, temperatures tend to be more smoothly distributed over a landscape than precipitation is. On a hot summer day, for example, everybody in a given region will swelter more or less equally, but not everyone will necessarily be soaked by a thunderstorm that happens to pass through the area. Random turbulence or a bump in the terrain can lift and cool a bubble of humidity so it drenches one place while another goes dry, and plumes of precipitation from local lake effects or various colliding air masses can strike one place but miss another. To deal with such complexity, you have to average more wet-dry data together than you do when documenting temperatures, and even then you still need to treat the results with care.

  But the problems with predictive modeling can also run deeper than that. The brief ups and downs in simulations aren’t always linked definitively to particular dates, which makes the basic trends in their long-term forecasts more reliable than the shorter year-to-year fluctuations. In addition, different models are built around different assumptions that oversimplify or exaggerate various aspects of the climate system in unique and potentially conflicting ways. And perhaps surprisingly, zooming in on smaller subregions of the planet doesn’t necessarily simplify matters but instead can add even more complexity by forcing the models to deal with mountains, lakes, and other local weather-distorting features. Such downscaling also reduces the number of weather stations left within the study area to support the simulations with historical data, and it can magnify systemic errors that lurk within the global-scale models themselves. In a recent essay in Nature by correspondent Quirin Schiermeier, one expert grimly summed the situation up with “our current climate models are just not up to informed decision-making at the resolution of most countries.”

  One reasonable way to deal with this kind of uncertainty is to consider results from multiple sources rather than settling for just one. An excellent mechanism for doing this is Climate Wizard, a user-friendly online analysis engine that was developed by the Nature Conservancy, the University of Washington, and the University of Southern Mississippi. The website presents you with a map of the world that lets you focus on various regions of interest, and it allows you to harness any of sixteen well-known global climate models to predict temperatures and precipitation during the rest of this century. Climate Wizard’s impressive stable of models can yield a wide range of conflicting results if you ask for detailed predictions about a particular season, a short stretch of years, or certain small locales. But the broad-brush generalizations are remarkably consistent, as if the models prefer to “think big” rather than being forced to squint closely at an overly restrictive time or place. For example, all of them anticipate global-scale warming trends that become more intense the more CO2 we release, and most also anticipate somewhat wetter conditions in the northeastern United States by 2100 AD.

  So what does this tell us about the future of the temperate zone? If we follow a moderate, 1,000-Gton scenario, then both the models and common sense say that most of the temperate regions should warm several degrees further by 2100 AD, especially in the higher latitudes, and that precipitation will change in a more patchy fashion. According to the combined results from all the Climate Wizard models, most of North America, northern Europe, and central Asia will become wetter overall, while much of the American Southwest, Patagonia, southern Australia, and the Mediterranean region will become drier. The South African Cape, as one might expect after learning about the likely poleward drift of winter storm tracks there, is also on the list of future drier places.

  Progressively higher temperatures will reduce the duration and thickness of snow and ice cover in the northern United States, perhaps enough to make low-lying Lake Champlain totally ice-free but probably not enough to prevent the highest of the upland lakes from freezing in midwinter. The tips of the tallest Adirondack peaks might still turn white for a few months each year, and the skiing and snowmobiling industries might hang on longer here than in much of the rest of the Northeast, perhaps well into the twenty-second century and beyond. And one bothersome regional pollution problem may finally be solved when our fossil fuel consumption finally trails off. Coal-fired power plants and internal combustion engines will stop dumping so much acid rain here. Lucky us.

  If Adirondack forests once more become botanical equivalents of the Blue Ridge and Smokies as a result of moderate-scale warming, they won’t do it very quickly. Existing trees will take centuries to die of old age and to make room for different ones as the region slowly warms, and southern trees won’t move up here any faster than their seeds can. Then as now, the most abrupt changes will probably be caused not by climate change but by forestry practices, fires, and imported pests. Already, we’re losing our beeches to fungal infections as we’ve previously lost chestnuts and elms to foreign blights, and invasive emerald ash borers are just beginning to threaten ash trees all over North America. This also applies to animals, as well; white nose syndrome is rapidly decimating our local bat populations, yellow perch and golden shiners are driving native trout from our upland lakes, and imported zebra mussels are replacing native mussels in lowland waters.

  If somewhat wetter conditions also develop here as most models suggest, then the additional moisture may or may not help to keep local wetlands and forest soils from drying out during warmer summers, depending on how the seasonal inputs and evaporation balance out; seasonal-scale model projections of precipitation in the relatively small Adirondack and Champlain regions differ too much to be reliable, though most of the models predict annual-scale wetting trends here. Warming could make meltwater surges and ice jams more frequent in our rivers durin
g winter, but by keeping the snowpack and ice cover from building up as much it might also reduce the severity of those events in early spring. More precipitation could be a good thing for the Adirondacks in general, but it might not be so nice for cities downstream if river discharge continues to increase as well. As the ocean-linked level of New York Harbor slowly rises around the rim of Manhattan Island, episodic but potentially destructive river flooding may also occur there if more North Country runoff events push the Hudson over its banks.

  Some southern-type animals that are rarely seen in the high country today, such as opossums, may become more common here, while other rarities, like northern-type bog lemmings, may disappear. But most of our mammals, from bears and raccoons to otters and red foxes, are resilient enough to stick it out for the long haul, and all are widely distributed outside the Adirondacks. Even if lemmings and other boreal species no longer find suitable homes here, their disappearances will be local, not total, if future climatic shifts remain moderate, and their descendants may eventually return from more northerly regions after the thermal peak passes. Many of the maps of species ranges that U.S. residents consult show only blank spaces north of the national border, as if the vast climatic refuge of Canada doesn’t exist. Phrases such as “extinct within New York State” are human-centered constructs, and they need not represent true extinction at all. A more species-centered approach, rather than a state-or nation-centered one, may show that bog lemmings can continue to thrive in Canada and perhaps even expand the northern limits of their range as their southern limit drifts over and beyond our park boundaries.

  One often hears that global warming will cause disease-bearing insects and ticks to spread into higher temperate-zone latitudes and elevations as well. That may be true in some cases, but probably not very often in the case of mosquito-borne malaria. Claims that the tropical scourge will soon invade the United States, for example, fail to recognize that malaria is already endemic to North America. Outbreaks were common as far north as Canada during the nineteenth century, and New York City residents often suffered from it. I have an old field guide to camping in Maine, published in 1879, that warns tourists of the malarious “miasm” that was supposedly emitted by northern wetlands at night. Malaria was only recently extirpated in North America by aggressive human intervention, including the draining of breeding pools, the spraying of pesticides, the screening of windows, and improvements in health care. Similar preventive measures also drove endemic malaria from much of Europe and Scandinavia, and humans are very likely to keep it from returning to its original northerly haunts.

  But what if we take the 5,000-Gton path? According to Climate Wizard, the temperate zone as a whole may warm twice as much by 2100 A.D. as it would in the moderate B1 emissions scenario, but the distribution of changes in precipitation is expected to be similar, with the Mediterranean region, the American Southwest, Patagonia, southern Australia, and the South African Cape drying, while most other temperate regions become wetter, although the magnitudes of those changes will be greater than in the milder situation.

  The Adirondack Mountains are only a few million years old, so they’ve never been exposed to hothouse conditions as extreme as those of a PETM-like 5,000-Gton scenario. A super-greenhouse of that intensity could create conditions during the long centuries of thermal maximum that would be unlike any in local ecological history. Our highest lakes and peaks could become totally ice-free in winter, and rare alpine tundra plants such as dwarf willow and cushion-like Diapensia, which were originally pushed up to the tallest summits by postglacial warming, would be shoved the rest of the way upward into local extinction. In this case, the loss of boreal species from the Adirondacks might also be followed by total extinction if the Arctic heats up enough, too.

  Nonetheless, mountainous regions such as the Adirondacks will have a built-in advantage over other temperate-zone areas as far-future climates warm and then cool on the long tail of the CO2 curve. Many species will be able to migrate into new climatic settings simply by moving up or downhill rather than being forced beyond the boundaries of a wild refuge, as long as it doesn’t warm too much and their other ecological needs are also met in the new locations. But the outlook isn’t all rosy, either. Among the most vulnerable animals and plants will be those living at the tops of the highest mountains because they will have no place higher to retreat to. If our alpine tundra-style vegetation is lost to a 5,000-Gton super-greenhouse, it may not return to these peaks for hundreds of thousands of years.

  The factor that will play the most important role in determining the fate of future wild lands will, of course, be us. We’re the ones who introduce “invasive” alien species to their new territories, and people of the future will surely continue to help invaders spread into new territories whether by accident or design. And although strong, strictly enforced laws can keep forested islands like the Adirondacks afloat in a sea of development, not everyone wants to keep them that way, so there’s no telling what the next century’s legislative decisions might bring. Major reversals of what people can and cannot do with wild areas could easily cause more rapid and devastating changes than Anthropocene climate alone is likely to produce.

  Will our descendants love the landscapes of the deep future as much as we love them now when the vegetation changes and the mountains and lakes hold less snow and ice in winter? Even the fanciest computer models can’t tell us that. Seemingly wild places like the Adirondacks are already quite different from what they were in centuries past because of fires, logging, settlement, pollution, overhunting, invasive species, and disease. But most of us don’t complain much about such things; we like our home territories pretty much as we first encountered them, whatever the pedigree. We can only hope that later generations feel the same way about the artificially warmer landscapes that will await them as the Anthropocene continues to unfold.

  Epilogue

  What we need to invent … are ways in which farsightedness can become a habit of the citizenry of

  the diverse peoples of this planet.

  —Margaret Mead, Atmospheric Science Conference,

  North Carolina, 1975

  I’m traveling from the Adirondacks to midcoast Maine with my partner, Kary, in order to attend a joint celebration of July birthdays; my father’s, my mother’s, and mine. As the Grand Isle ferry chugs eastward across Lake Champlain, we take a breezy bench seat together on the observation deck between blue water and blue sky to watch the gray, wave-cut bluffs of the Vermont shoreline approach. It’s a familiar route for us, but my background research and writing for this book have helped to make simple journeys into living tours of the subjects discussed in these pages.

  Just before I set the emergency brake and switched our car’s engine off for the ferry crossing, the radio aired a short piece about how people throughout the world are becoming increasingly concerned about climate change. At the end of the broadcast Kary asked, “What would a book about the deep future have to say to those people?”

  Good question. If I had to boil it all down to one sentence, I’d consider saying, “Don’t panic and don’t give up!” Climate change is a troubling and complex issue, but it’s not going to kill us all off, either. During the last hour, Kary and I increased the total CO2 content of our lungs and raised the mean annual temperatures of our surroundings 3°F (2°C) simply by driving downhill from Paul Smiths to Plattsburgh, where the air is both denser and warmer. But the landscape, though changed, still looks healthy and prosperous. To paraphrase a recent comment by oceanographer Wallace Broecker, we need to think, speak, and act rationally if we’re going to deal successfully with the enormous environmental and social problems facing us.

  But I would also hasten to add that today’s carbon crisis is nevertheless a very troubling problem. The effects of our emissions on climates, oceans, and isotopes will last orders of magnitude longer than most people yet realize. They are already changing the world in important ways, and although our own species will survive those
changes, many others may not.

  As the ferry draws nearer to the layered cliffs, I remember telling my geology students that these rocks used to lie beneath a tropical ocean, and that some of the fossil reef deposits nearby are among the oldest in the world, even older than the fossil fuels that power our cars and ferries. During the last 450 million years, the thick plate of continental crust that now supports them has drifted far north of its former position, and what was once a thriving and colorful marine habitat is now a flat-lying tombstone with the stiff images of former inhabitants imprinted on it. The cinnamon roll spirals of ancient tropical snails are not only out of place on dry land half a hemisphere away from the equator; they don’t even exist anymore except in fossil form, and neither does the former ocean basin they once lived in. If those creatures had had enough brain capacity to think millions of years into the future, what would they have thought of this extreme turn of events? Would the associated localized cooling from tropical to temperate conditions and the demise of an entire ocean have seemed like an utter catastrophe, or would vibrant Burlington, the ferry, and our pleasant cross-country jaunt have reassured them that life could still be worth living in Anthropocene times?

  Farther down the road amid Vermont’s lovely Green Mountains, a fuel truck pauses to scope a railroad crossing, and it makes me change my message to “Stop, Look, and Listen.” A deeply historical perspective can make modern greenhouse heating seem no more outlandish than the natural PETM and Eemian warm periods of the distant past, and it can make post-whiplash cooling seem no more frightening than the long Cenozoic descent into repeated ice ages. But even so, it’s still wise to stem our carbon emissions as much and as rapidly as possible. Not because it would prevent climate from changing at all; we’ll still have to deal with things like the Arctic oscillation, solar cycles, and El Niño no matter what we do about carbon pollution. And not because warming is necessarily all bad, either; the formerly tropical Champlain snails certainly wouldn’t think so, and preventing the next ice age is a favor to future generations.