The physical impacts of the global warming forecast can be bracketed with some degree of statistical confidence. Biological effects are more difficult to gauge, except in special cases such as the likely demise of polar bears that would result from the demise of Arctic sea ice. The societal effects, however, are nearly uncharted territory, at least to me. Perhaps the topic of global warming suffers from the same sort of cultural divide as university faculties, between the techies and the touchies; that is the sciences and the humanities. A new report (pdf) called The Age of Consequences, just released by the Center for Strategic and International Studies and the Center for a New American Security, tries to bring the social sciences, in particular history, geography, and political science, into the forecast of climate change in the coming century. It makes for fascinating if frightening reading.
The report was based on discussions of a group of senior luminaries with a wide range of expertise. I already knew or knew of and respect the climate scientists Mike MacCracken and Bob Correll, and Ralph Cicerone, head of the National Academy of Sciences. The group also included Nobel laureate Thomas Schelling, former CIA Director James Woolsey, former Chief of Staff to the President John Podesta, and former National Security Advisor to the Vice President Leon Fuerth. (Apparently not all group members, listed in the executive summary on page 8, got writing assignments, so not all of them are listed as authors.)
Images of the future can be constructed based on the lessons of history. The history chapter (beginning on page 26) begins with Table 1, which I will reprint here:
It is sobering to note that the potential horsemen of climate change, floods, droughts, and epidemics, are all at the big end of this list. There is no historical precedent for the type of global multidimensional challenge that changing climate may bring, but there are common elements in societal responses to natural disasters, and many of the impacts of climate change will be regional in scope rather than global, like natural disasters.
The report considers the historical societal impacts of disasters ranging from bubonic plagues in the middle ages to Katrina. History teaches that people tend to return to religion in times of trouble, and to turn against people outside their social group. Governments are destabilized by hard times. Natural disasters tend to impact most strongly in less affluent parts of the world.
History also teaches that people have a tendency to develop ways of coping with environmental fragility, by choices of individual living strategies such as the ability to migrate, or by decisions made at the societal level, such as engineered flood control measures or mobilizing assistance from outside. The report offers the idea that it takes a population a few generations to learn how to operate within the limits of its natural world. For example, the report attributes the dust bowl drought in some measure to environmental inexperience of a population who had only recently migrated from more humid regions. With our recent increased mobility, and with climate change itself, we find ourselves losing this buffer of experience and understanding.
The group imagined three potential scenarios, labeled expected, severe, and catastrophic. These are not forecasts exactly, since forecasting society is even harder than forecasting climate, which is itself pretty dicey on a regional spatial scale, but rather a fleshing out of plausible possibilities, a story-telling, visualization-type exercise.
The “expected” scenario calls for 1.3 °C of warming globally above 1990 levels, by the year 2040. Changes in precipitation and sea level prompt migration at a scale sufficient to challenge the cohesion of nations. The potential responses to this scenario are broken down into specific regions with their particular historical and political settings. Just to pick a region at random, Nigeria in West Africa will suffer accelerated desertification with climate change, prompting intensified migration into the megacity of Lagos, which is itself threatened by sea level rise. Compounding Nigeria’s misfortune, there is oil in the Niger Delta, and as global oil supplies dwindle, the strife and corruption that oil brings a weak nation will only intensify.
In the “severe” scenario, the globe warms by 2.6 °C by 2040 and sea level rises about a half a meter. Scientists in 2040 conclude that the eventual collapse of Greenland and the West Antarctic ice sheets has become inevitable in the centuries that follow. Agricultural production declines in the arid subtropics and in increasingly flooded river deltas. Again to pick a random example from the report: the river systems in the American Southwest collapse, leading to impoverishment of Northern Mexico and increased migration pressure in the U.S. Resource stress in Latin American leads to a tendency toward populist, Chavez-type governments, and more extensive regions of de facto anarchy such as found today in parts of Colombia.
The “catastrophic” scenario assumes positive feedbacks in the carbon cycle to warm the planet by 5.6 °C by the year 2100, and sea level has risen by 2 meters. I feel compelled to note that if this is supposed to be a worst-case scenario, I personally can imagine worse in terms of sea level rise. In the social realm the crystal ball gets murkier as the report progresses from expected to severe to catastrophic, but one important ingredient in the prognosis for the catastrophic scenario is the migration of millions of people, a scale unprecedented in human history, potentially enough to undermine the stability of civilized governance. One participant recommended that we check out the movie Mad Max, only imagine it hotter.
There is far too much in this report for any sort of summary really to cover, and anyway I’m a techie rather than a touchie so my retread wouldn’t do the original report justice, but you get the idea. Results from the IPCC are summarized clearly, including regional climate projections, but the point is also made and discussed that climate forecasts tend to be in general conservative. In the arenas in which I have some competence to assess, the judgments the authors have made seem measured and fair to me. The report is authoritative and very meaty, bringing an astonishing array of perspectives and insights to the table. One could read this report and nothing else, and come away with a considerable expertise on the potential impacts of climate change. I highly recommend it to the readership of realclimate, and I look forward to reading your comments.
Thanks to Hank Roberts for digging this up.