Our 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. The
future scenario that we have constructed is based on the 8,200 years before present
event, which was much warmer and far briefer than the Younger Dryas, but more
severe than the Little Ice Age. This scenario makes plausible assumptions about
which parts of the globe are likely to be colder, drier, and windier. Although
intensified research could help to refine the assumptions, there is no way to confirm
the assumptions on the basis of present models.
Rather than predicting how climate change will happen, our intent is to dramatize
the impact climate change could have on society if we are unprepared for it. Where
we describe concrete weather conditions and implications, our aim is to further the
strategic conversation rather than to accurately forecast what is likely to happen with
a high degree of certainty. Even the most sophisticated models cannot predict the
details of how the climate change will unfold, which regions will be impacted in
which ways, and how governments and society might respond. However, there
appears to be general agreement in the scientific community that an extreme case like
the one depicted below is not implausible. Many scientists would regard this
scenario as extreme both in how soon it develops, how large, rapid and ubiquitous
the climate changes are. But history tells us that sometimes the extreme cases do occur, there is evidence that it might be and it is DOD’s job to consider such scenarios.
Keep in mind that the duration of this event could be decades, centuries, or millennia
and it could begin this year or many years in the future. In the climate change
disruption scenario proposed here, we consider a period of gradual warming leading
to 2010 and then outline the following ten years, when like in the 8,200 event, an
abrupt change toward cooling in the pattern of weather conditions change is
assumed to occur.

Warming Up to 2010

Following the most rapid century of warming experienced by modern civilization,
the first ten years of the 21st century see an acceleration of atmospheric warming, as
average temperatures worldwide rise by .5 degrees Fahrenheit per decade and by as
much as 2 degrees Fahrenheit per decade in the harder hit regions. Such temperature
changes would vary both by region and by season over the globe, with these finer
scale variations being larger or smaller than the average change. What would be very
clear is that the planet is continuing the warming trend of the late 20th century.
Most of North America, Europe, and parts of South America experience 30% more
days with peak temperatures over 90 degrees Fahrenheit than they did a century ago,
with far fewer days below freezing. In addition to the warming, there are erratic
weather patterns: more floods, particularly in mountainous regions, and prolonged
droughts in grain-producing and coastal-agricultural areas. In general, the climate
shift is an economic nuisance, generally affecting local areas as storms, droughts, and
hot spells impact agriculture and other climate-dependent activities. (More French
doctors remain on duty in August, for example.) The weather pattern, though, is not
yet severe enough or widespread enough to threaten the interconnected global
society or United States national security.

Warming Feedback Loops

As temperatures rise throughout the 20th century and into the early 2000s potent
positive feedback loops kick-in, accelerating the warming from .2 degrees Fahrenheit,
to .4 and eventually .5 degrees Fahrenheit per year in some locations. 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 Further, 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 and
reflecting less of the sun’s rays, temperatures increase even higher.
By 2005 the climatic impact of the shift is felt more intensely in certain regions
around the world. More severe storms and typhoons bring about higher storm
surges and floods in low-lying islands such as Tarawa and Tuvalu (near New
Zealand). In 2007, a particularly severe storm causes the ocean to break through
levees in the Netherlands making a few key coastal cities such as The Hague
unlivable. Failures of the delta island levees in the Sacramento River region in the
Central Valley of California creates an inland sea and disrupts the aqueduct system
transporting water from northern to southern California because salt water can no
longer be kept out of the area during the dry season. Melting along the Himalayan
glaciers accelerates, causing some Tibetan people to relocate. Floating ice in the
northern polar seas, which had already lost 40% of its mass from 1970 to 2003, is
mostly gone during summer by 2010. As glacial ice melts, sea levels rise and as
wintertime sea extent decreases, ocean waves increase in intensity, damaging coastal
cities. Additionally millions of people are put at risk of flooding around the globe
(roughly 4 times 2003 levels), and fisheries are disrupted as water temperature
changes cause fish to migrate to new locations and habitats, increasing tensions over
fishing rights.
Each of these local disasters caused by severe weather impacts surrounding areas
whose natural, human, and economic resources are tapped to aid in recovery. The
positive feedback loops and acceleration of the warming pattern begin to trigger
responses that weren’t previously imagined, as natural disasters and stormy weather
occur in both developed and lesser-developed nations. Their impacts are greatest in
less-resilient developing nations, which do not have the capacity built into their
social, economic, and agricultural systems to absorb change.
As melting of the Greenland ice sheet exceeds the annual snowfall, and there is
increasing freshwater runoff from high latitude precipitation, the freshening of
waters in the North Atlantic Ocean and the seas between Greenland and Europe
increases. The lower densities of these freshened waters in turn pave the way for a
sharp slowing of the thermohaline circulation system...

>> later : period 2010 > 2020