Graph of the four primary climate change factors from Lean and Rind 2009 (paper linked in the menu to the left). The right hand part of the curve is the L & R projection for future decades.
One of the responsibilities of teaching young people about climate change is that at some point you will be required to be to be able to describe, as accurately as you can, what will most likely happen. Students, quite rightly, want to know what their futures will be like, and will ask you to tell them. More than anything they will be seeking reassurance, some straw to grasp that things are not as bad as they seem. This is only human. If it's in your power to give some reassurance, you should. No young person deserves to spend their early years worried about some horrible event that may or may not come to pass. But you must also balance this with a realistic assessment of the facts, and some careful set of warnings so that they are prepared.
This important obligation is complicated by the fact that what will happen in climate change is simultaneously as much an economic and social problem as it is a problem for natural scientists. Few thinkers have a good grounding in all of these disparate areas, and so their expertise, and comfort level, begins to peter out as they approach disciplinary boundaries.
And the honest truth should always be, well, we don't quite know exactly what will happen. The future is full of uncertainty and subject to the influence of random events. In the case of climate change, the primary uncertainty is whether or not various currently hypothetical "feedback loops" will tip the system over some "threshold" to an entirely different equilibrium -- an entirely different planetary climate resulting in the dislocation of billions of people and their support systems. I'm not going to deal with feedbacks in this article, except to say that they may exist, may kick in, and have all the power they need to change the planetary reality beyond current comprehension. (This is one reason our class focuses on dynamic systems models -- so students can begin to understand feedback loops and how they can create exponential effects.)
Instead I will try to answer the easier question, "What will most likely happen if what has been happening for the past few decades continues to happen for a few more decades and there are no tipping points or fast feedbacks in that time-frame?"
I'm no world-class expert, but I have been puzzling over these social and natural science interactions in the sustainability arena for some twenty years now. Interdisciplinary problems like these were the focus of both my MS and PhD theses, particularly the PhD which focused directly on questions of social change with regard to climate change in American society. It was a similar concern that forced me out of my first (military) career with a crisis of conscience many years ago. I guess I would say that my main qualification would be that, yes, for better or for worse, this is actually a lot of what I think about, and have been thinking about for a few decades now. In addition to the expected books about climate science and renewable energy, my bookshelves are full of books on the history of great social upheavals, from the American revolution to the end of the Cold War.
It helps that I teach climate and sustainability classes each academic year and each semester. That keeps me in practice, and the students' interest gives me a reason to keep thinking.
Each year and indeed each semester I must therefore take a good stab at trying to describe for my students what I think will most likely happen, based on the most recent data and events. I always tell them that this is my best guess, based on the most recent data publicly available, and subject to change, perhaps dramatic change, as things unfold.
This is a responsibility I take seriously.
I use a two- to five-decade time horizon, and focus on the important periods in students' futures one to two decades out when they will be forming a career and a family and therefore need a reasonable economic situation, and then later, four or five decades out, when they will be thinking about their retirement, and therefore need society to be organized enough to support them.
Most recently, since it became available, I've used the 2009 Lean and Rind study "How will Earth’s surface temperature change in future decades?," which is linked to the side of this post, and which directly addresses this decadal problem. It also happens to use a statistical method that most third-year students have been taught already, and which can be easily replicated in class. I extrapolate the L & R projection based on the table of climate effects given on page 8 of the 2007 IPCC report Summary for Policymakers. (The "FAR SMP")
This seems to me to be a conservative set of starting points based on the low p-values in L & R, the high R-squared, and the consensus nature of the FAR.
Let's start with what will most likely happen with the planetary, North American and Maine climates, in that order.
There are four major factors to consider. Three major stochastic or cyclical natural factors, the El Nino/Southern Oscillation, volcanic effects, and the cyclical variance in total solar energy reaching the planet, compete to mask the combined anthropogenic effects of greenhouse gas emissions, land use changes, and black carbon pollution. (For the statistical exposition of their workings, see L & R 2009 posted to the right.)
The underlying temperature trend is, however, upwards, and this slope is correlated with the combined anthropogenic effects and statistically very significant, allowing us to rule out other hypotheses as to the cause (p < 0.01 for all four variables).
The coefficient of correlation in the L & R model is 76%, meaning that we have a good ability to predict what will happen to global temperature, if we know or can guess the future status of the four variables.
The 24% unexplained variation is definitely unsettling, but society routinely has to predict public and private policy based on far more unsettling uncertainties, for instance, the uncertainty of what the oil markets will do next week, or whether North Korea will use one of its nuclear bombs. The notion that we shouldn't do anything about climate change because we don't know how enough, with enough certainty, is nonsense, and mostly just a rhetorical tactic used by climate policy opponents who have some personal monetary stake in the outcome. We know plenty enough to act now.
(This is a slimy business, this climate denialism, and the people who practice it seem more and more reprehensible to me as time goes along. But, what goes around will come around. In particular, should the people that have been attacking climate scientists ad hominem expect any mercy when the public realizes just how utterly evil they have been, and how much they have been playing fast and loose with other people's lives and futures? But this is a matter for another discussion.)
So what will happen if, as seems very likely if not almost certain, the anthropogenic effects in L & R continue to increase?
More or less obviously, the planet will continue to warm as it has done for several decades. The recent flat spot in the five-year average warming was just that, a flat spot at the top of a long uphill incline, most probably due to a recent sunspot minima and the persistent presence of small amounts of volcanic aerosols, and the temperature trend will continue on up as soon as the eleven-year solar cycle picks itself up again and the skies clear of aerosols.
(Correction: I just received an email from Judith Lean, in which she cites persistent La Nina conditions as responsible, along with the solar cycle, for the recent sub-decadal moderation of the climb in global AAT.)
The result would be a year like 1998, only worse, because of the increase in the anthropogenic variable. L & R project such a year (labeled "B") in the right hand side of the graph. (They don't really know which year this might be, of course.)
The next decades warming may not be as abrupt as we had thought it would be five or six years ago, based on the recent projections for solar cycle 25. This seems to me a kind of Godsend of sorts. However, if at any time the sunspots return, the warming will accelerate.
The anthropogenic effects will continue to climb, even if the sunspots hesitate, and so the planet will continue to warm, just at a slower rate than was thought in, say, 2004. But the trend may also accelerate. Back then we were able to "look forward" to depleting oil supplies reducing pressure on the atmosphere, but with recent developments in domestic non-conventional supply this "hope" has evaporated.
(My quotes are deliberate. I understand perfectly well how bad oil depletion would have been, and how great it is that we now have better domestic supply. I'm relieved and even willing to celebrate that the new supplies allow us to get some of our (US and the west's) geopolitical power back with regard to the various petrostate dictators, especially China, Russia and the middle east. I just think that climate change is likely going to be worse for us than oil depletion would have been.)
The general addition of energy to the atmosphere, with the evaporation and churning that results, will mean increased extreme weather -- what Tom Friedman has called global "weirding" -- all over the planet, more droughts and desertification, more heavy monsoons and more ten, hundred- and even thousand-year flooding. Atlantic hurricanes may become more intense, but they may also become less frequent, or at least it may appear so because they may veer away from the eastern seaboard more easily. All this and more is provided on page eight of the FAR SPM or other references such as Kerry Emmanuel's work on hurricane intensity or frequency.
In La Nina years, according to L & R and the various expositions of ENSO effects given by NOAA, regional warming won't appear too strongly in Maine and other northern tier states, but the American south will be badly affected much as it has this year. In El Nino years, the entire continent will be much warmer and Maine will generally have a warm wet winter. There's usually quite a bit of snow with an El Nino Maine winter, or at least it seems that way to me after having lived through a few of them now, but the air temperature is warmer. If, as happened during this last winter (a strong La Nina), a strong southerly loop of the jet stream sets up for a good portion, the winter weather in Maine can become very changeable, as cool northerly and warm southerly air masses either side of the jet stream alternate overhead, and as the great storms that cause nor'easters run up from the southern waters, along the edge of jet-stream-following cold fronts.
A good volcanic eruption with significant cooling aerosols is enough to give us a much cooler year world-wide. Volcanoes are, or at least appear to be, random within this decadal viewpoint.
The general take-home message for the next few decades is gradual warming of one to two degrees Celsius, most likely just one degree before 2050 (this warming is less marked in predictions based on L & R 2009 than in the IPCC FAR because of the effect of the solar cycles), with random El Nino warmings and volcanic coolings from time to time along the way. But this is quite rapid warming from an ecosystem point of view. In the continental US under an L & R scenario, changes will most likely be gradual but climate zones will move steadily north "over" the tops of ecosystems, leaving those systems subject to high disease- and weather-related mortality, particularly of those native plants and animals that were at the edge of their range. An example is the dramatic pine beetle infestation in the western US. Invasive plants and animals will move in to replace natives. The people that live in these ecosystems, particularly farmers and gardeners and fishermen, will be required to work out new ways to live in relationship with the ecosystem. In the high arctic change will be more rapid.
It seems reasonable to me to expect that extreme weather events will worsen as the energy in the atmosphere increases. It seems unreasonable to expect different, especially after this year.
Understanding how all this impacts the economy and thus society requires a slightly different way of thinking. Economists understand that economic change occurs at the margin, because economic events such as recessions or booms in the business cycle or in specific sectors are the aggregate of thousands of small decisions made by individual consumers and suppliers.
Thus the aggregate demand for petroleum created the current North Dakota and Canadian oil booms. What was a shortage and high prices just about everywhere else, and a factor in the recession, created an economic boom and even an investment bubble and over-employment in the Albertan and North Dakotan oil patches.
At the margin, climate change will have impacts on the economy as some sectors and products are badly affected, while other sectors and products boom. I think Texas agriculture is in for a hard time, while Maine agriculture seems to be experiencing if not a boom, at least a partial resurgence of sorts, and the development of new crops and new markets. Likewise, continued high price even for the new oil supply means that Maine hardwood pellets are in demand, as are the stoves that burn them.
So, ceteris paribus (all things being equal), if we expect marginal change and if climate change continues much as it has done for the last few decades and as predicted in L & R 2009, an economic viewpoint will predict some proportion of Texan farms and ranches to lose output and go out of business one by one as time goes by, while some proportion of Maine farms will increase in output and a few more will come into business or increase the scale of their business every year.
Likewise, Maine maple businesses will go out of business one-by-one, while farm businesses in Maine that are experimenting with new crops, such as our new small vineyards and wineries will come into business one-by-on.
This is the inherent nature of marginal change.
It's only when a community is actually badly damaged by extreme weather events to the effect that civilization has to be rebuilt locally that this balancing economic effect is reduced. Otherwise, one community's economic problem tends to be another community's economic gain, and Maine, as Stephen Mulkey mentioned in last night's lecture, is a refugia of sorts for many climate related concerns, but particularly rain-fed agriculture.
There will be more extreme weather. And we can't easily predict where it will hit. Too much of this kind of impact will, however, predictably contribute to another recession or depression, or will affect our ability to pull out of the current recession. It's also possible, as happened in the 14th Century in Europe (detailed in a book by Barbara Tuchman titled "A Distant Mirror: The Calamitous 14th Century" (1978)), for climate change effects to create a breeding ground for war and revolution. It seems that high food prices exacerbated by climate change did contribute to something like this in this year's "Arab Spring."
When will Americans change their minds and demand political action on climate?
"When they realize how bad things can get," seems to be the best answer I can give and indeed the one I gave in my PhD dissertation conclusion. In other words, after things get worse, and, given the increasing power of climate denialism, possibly much worse.
Right now the combined impacts are bad but not bad enough, and as mentioned the Lean and Rind study shows only relatively slow change. This slow change is enough to create huge problems, but we could adapt to the new climate reality, perhaps without even recognizing it as climate change.
Most likely the change will be large enough that most ordinary people will realize climate change is occurring, which is itself a blessing of sorts. It will help us get something done before feedbacks kick in.
If we are lucky, that is.
But with the various fast feedbacks possible in the global climate system, they may easily get bad enough soon enough, certainly in my remaining lifetime. It's eminently possible that some threshold will be crossed in the next few years.
Remember, the extreme weather events we are currently experiencing result from only roughly one degree Celsius of average global warming since measurements began around 1850. L & R's model predicts between one and two before 2050, but extrapolation of a regression model this far out is statistically unreasonable, meaning L & R is best used for the next two or at most three decades, after which we must return to GCMs to work out scenarios.
There are at least two and possibly eight more degrees in the pipeline this century, if we don't slow the burning of oil and stop burning coal, according to the IPCC FAR, based on multiple GCM outputs.
Two degrees over the course of the century, we can probably deal with. More than three or four is a lot, and will be very difficult to deal with.
Here I tend to look at other great American changes-of-mind such as the fight over slavery that ended in the Civil War, or the Civil Rights Movement, or importantly for me as a Briton, the period of isolationism leading up to World War II.
Americans, it seems, change their minds only slowly, but generally do so in the end. A practical people, concerned mostly for their own well-being and that of their families and communities, Americans require a good deal of very obvious evidence before they are willing to change their ideas and mental models of how the world and society work. Hurricane Katrina, and even the numerous weather disasters of 2010-2011 were not that sufficient a Pearl Harbor.
But as Churchill said, perhaps somewhat in exasperation as German bombs were literally falling around British heads,
"Americans can always be counted on to do the right thing...after they have exhausted all other possibilities."
