Published in October 2003, this study looked at the national security implications for the USA of abrupt climate change (note that most of the report is equally valid for any country).

The authors’ opening statement provides a succinct summary of their position:

We have created a climate change scenario that although not the most likely, is plausible, and would challenge United States national security in ways that should be considered immediately.

I believe that the events discussed in this paper warrant further research for the following reasons:

1. Research in paleoclimatology shows that abrupt climate change has happened at least 8 times in the climate record.

2. On each occasion the precipitating factors have been different, but the common denominator appears to be an abrupt decrease (if not a complete shutdown) of the North Atlantic part of the thermohaline circulation.

3. Evidence is accumulating that the thermohaline circulation has already slowed: While opinion is divided, some scientists think that there could be a complete (even irreversible) shutdown within the next century.

4. Current events unfolding in Greenland in particular could lead to a rapid freshening of the North Atlantic, with potentially dire consequences for our climate. The update section of the Inconvenient Truth DVD addresses this issue in detail: Essentially accelerated melting of the Greenland ice-cap (due to global warming) allows the melt-water to penetrate deeply beneath the surface. When it reaches bedrock it effectively lubricates the junction between the ice and rock, reduces friction, and allows movement of large chunks of ice (perhaps massive chunks of the ice-cap?). No-one knows for sure yet.

5. While there is considerable uncertainty at many levels, I believe that the possible implications and impacts are so severe that such a scenario should be seriously considered, even if it is of low probability.

Now back to the report. I have kept most of the original headings, and edited the text of the report to provide an extended summary of its contents. 

Introduction
The conventional wisdom is that modern civilization will either adapt to whatever weather conditions we face and that the pace of climate change will not overwhelm the adaptive capacity of society, or that our efforts such as those embodied in the Kyoto protocol will be sufficient to mitigate the impacts.

This view of climate change may be a dangerous act of self-deception, as increasingly we are facing weather related disasters - more hurricanes, monsoons, floods, and dry-spells - in regions around the world. Rather than decades or even centuries of gradual warming, recent evidence suggests the possibility that abrupt climate change may actually be unfolding.

With over 400 million people living in drier, subtropical, often over-populated and economically poor regions today, climate change and its follow-on effects pose a severe risk to political, economic, and social stability.For some countries, climate change could become such a challenge that mass emigration results as the desperate peoples seek better lives in regions that have the resources to adaptation.

The Cooling Event of 8,200 Years Ago
The climate change scenario outlined in this report is modelled on a century-long climate event that records from an ice core in Greenland indicate occurred 8,200 years ago.

Immediately following an extended period of warming, much like the phase we appear to be in today, there was a sudden cooling . Average annual temperatures in Greenland dropped by roughly 5 degrees Fahrenheit, and temperature decreases nearly this large are likely to have occurred throughout the North Atlantic region.During the 8,200 event (or 8.2k event as some call it) severe winters in Europe and some other areas caused glaciers to advance, rivers to freeze, and agricultural lands to be less productive.

Scientific evidence suggests that this event was associated with, and perhaps caused by, a collapse of the ocean’s conveyor following a period of gradual warming.Longer ice core and oceanic records suggest that there may have been as many as eight rapid cooling episodes in the past 730,000 years, and sharp reductions in the ocean conveyor - a phenomenon that may well be on the horizon - are a likely suspect in causing such shifts in climate.



A climate change scenario for the future
The past examples of abrupt climate change suggest that it is prudent to consider an abrupt climate change scenario for the future as plausible, especially because some recent scientific findings suggest that we could be on the cusp of such an event. Rather than predicting how climate change will happen, our intent is to dramatize the impact that such an event could have on society if we are unprepared for it (which is essentially in the same vein as the Hirsch Report).

There appears to be general agreement in the scientific community that an extreme case like the one depicted (in this report) is not implausible.

Warming Feedback Loops
As global temperatures increase, potent positive feedback loops kick-in, accelerating the pace of warming and crossing tipping points. As the surface warms, the hydrologic cycle (evaporation, precipitation, and runoff) accelerates, causing temperatures to rise even higher: Water vapor, the most powerful natural greenhouse gas, traps additional heat and brings average surface air temperatures up.

As evaporation increases, higher surface air temperatures cause drying in forests and grasslands, where animals graze and farmers grow grain.

As trees die and burn, forests absorb less carbon dioxide, again leading to higher surface air temperatures as well as fierce and uncontrollable forest fires.

Warmer temperatures melt snow cover in mountains, open fields, high-latitude tundra areas, and permafrost throughout forests in cold-weather areas. With the ground absorbing more heat and reflecting less of the sun’s rays, temperatures increase even higher.

Thermohaline circulation collapse
This is the authors’ dramatisation of what could happen in the Northern Hemisphere were the Atlantic Conveyor to slow considerably or shut-down completely:

After roughly 60 years of slow freshening, the thermohaline collapse begins in 2010, disrupting the temperate climate of Europe, which is made possible by the warm flows of the Gulf Stream (the North Atlantic arm of the global thermohaline conveyor).Ocean circulation patterns change, bringing less warm water north and causing an immediate shift in the weather in Northern Europe and eastern North America. The North Atlantic Ocean continues to be affected by fresh water coming from melting glaciers, Greenland’s ice sheet, and perhaps most importantly increased rainfall and runoff.

Decades of high-latitude warming cause increased precipitation and bring additional fresh water to the salty, dense water in the North, which is normally affected mainly by warmer and saltier water from the Gulf Stream. That massive current of warm water no longer reaches far into the North Atlantic. The immediate climatic effect is cooler temperatures in Europe and throughout much of the Northern Hemisphere and a dramatic drop in rainfall in many key agricultural and populated areas. However, the effects of the collapse will be felt in fits and starts, as the traditional weather patterns re-emerge only to be disrupted again—for a full decade.

The Weather Report: 2010-2020

• Drought persists for the entire decade in critical agricultural regions and in the areas around major population centers in Europe and eastern North America.
• Average annual temperatures drop by up to 5 degrees Fahrenheit over Asia and North America and up to 6 degrees Fahrenheit in Europe.
• Temperatures increase by up to 4 degrees Fahrenheit in key areas throughout Australia, South America, and southern Africa.
• Winter storms and winds intensify, amplifying the impact of the changes. Western Europe and the North Pacific face enhanced westerly winds.

Impact on Natural Resources
Crop yields, affected by temperature and water stress as well as length of growing season fall by 10-25% and are less predictable as key regions shift from a warming to a cooling trend. As some agricultural pests die due to temperature changes, other species spread more readily due to the dryness and windiness – requiring alternative pesticides or treatment regiments. Commercial fishermen that typically have rights to fish in specific areas will be ill equipped for the massive migration of their prey.

The changing weather patterns and ocean temperatures will affect agriculture, fish and wildlife, water and energy.

With only five or six key grain-growing regions in the world (US, Australia, Argentina, Russia, China, and India), there is insufficient surplus in global food supplies to offset severe weather conditions in a few regions at the same time – let alone four or five. The world’s economic interdependence make the United States increasingly vulnerable to the economic disruption created by local weather shifts in key agricultural and high population areas around the world. Catastrophic shortages of water and energy supply – both which are stressed around the globe today – cannot be quickly overcome.

Impact on national security
Violence and disruption stemming from the stresses created by abrupt changes in the climate pose a different type of threat to national security than we are accustomed to today. Military confrontation may be triggered by a desperate need for natural resources such as energy, food and water rather than by conflicts over ideology, religion, or national honor. The shifting motivation for confrontation would alter which countries are most vulnerable and the existing warning signs for security threats.

Modern civilization has never experienced weather conditions as persistently disruptive as the ones outlined in this scenario.

There is a long-standing academic debate over the extent to which resource constraints and environmental challenges lead to inter-state conflict. While some believe they alone can lead nations to attack one another, others argue that their primary effect is to act as a trigger of conflict among countries that face pre-existing social, economic, and political tension. Regardless, it seems undeniable that severe environmental problems are likely to escalate the degree of global conflict.

In the event of abrupt climate change, it’s likely that food, water, and energy resource constraints will first be managed through economic, political, and diplomatic means such as treaties and trade embargoes. Over time though, conflicts over land and water use are likely to become more severe – and more violent.

As states become increasingly desperate, the pressure for action will grow.

Decreased carrying capacity
Many point to technological innovation and adaptive behaviour as a means for managing the global ecosystem. Indeed it has been technological progress that has increased carrying capacity over time. Over centuries we have learned how to produce more food, energy and access more water. But will the potential of new technologies be sufficient when a crisis like the one outlined in this scenario hits? Abrupt climate change is likely to stretch carrying capacity well beyond its already precarious limits. And there’s a natural tendency or need for carrying capacity to become realigned. As abrupt climate change lowers the world’s carrying capacity, aggressive wars are likely to be fought over food, water, and energy. Deaths from war as well as starvation and disease will decrease population size, which will eventually re-balance carrying capacity overshoot.

 

The link between carrying capacity and warfare
Peace occurs when carrying capacity goes up (as with the invention of agriculture, newly effective bureaucracy, remote trade, technological breakthrough, or a large scale die-off such as from plague). Such peaceful periods are short-lived because population quickly rises to once again push against carrying capacity, and warfare resumes. Indeed, over the millennia most societies define themselves according to their ability to conduct war, and warrior culture becomes deeply ingrained. The most combative societies are the ones that survive.

With over 200 river basins touching multiple nations, we can expect conflict over access to water for drinking, irrigation, and transportation. The Danube touches twelve nations, the Nile runs though nine, and the Amazon runs through seven.

Our current, relatively peaceful world could collapse if carrying capacities everywhere were suddenly lowered drastically by abrupt climate change. Humanity would revert to its norm of constant battles for diminishing resources, which the battles themselves would further reduce even beyond the climatic effects. Once again warfare would define human life. As famine, disease, and weather-related disasters strike, many countries’ needs will exceed their carrying capacity. This will create a sense of desperation, which is likely to lead to offensive aggression in order to reclaim balance.

Conclusion
New evidence over the past decade suggests that the plausibility of severe and rapid climate change is higher than most of the scientific community (and perhaps all of the political community) is prepared for. If it occurs, this phenomenon will disrupt current gradual global warming trends, adding to climate complexity and unpredictability. And paleoclimatic evidence suggests that such an abrupt climate change could begin in the near future. With at least eight abrupt climate change events documented in the geological record, it seems that the questions we must ask are: When will this happen? What will the impacts be? And, how can we best prepare for it? Rather than: Will this really happen?

POM Comment
While this is understandably US-centric, much of the report is generalisable to other locations. It highlights one of the same issues as peak oil: If the evidence is accumulating, and if the consequences might be severe, why don’t we do something?

If you wanted to read just one book to extend your knowledge about the issues raised by this report, I would suggest Catton’s Overshoot. Even though it was published in the early eighties, it is still (sadly) just as relevant today.

This is probably old news, but this fascinating video from the BBC Horizons program (featured on a peak oil blog) is a must see.

In essence: Particulates from the burning of fossil fuels have been reflecting a reasonable percentage of incoming sunlight back into space, thereby partially protecting us from global warming.

The program contends that, as air pollution is decreased by more stringent emission legislation, global warming will accelerate (if we do not also reduce carbon dioxide release).

Although peak oil is not mentioned, the basic hypothesis still applies: A fairly rapid reduction in oil-fuelled transport (especially air travel, as jet contrails seem particularly important dimming agents) could accelerate the great warming (although perhaps increased coal use may partially offset it).

Watch the video here: http://simplereduce.blogspot.com/2006/12/global-dimming.html.