The Last 1,000 Years
Summary
The Medieval Warm Period
The Little Ice Age
Year Without a Summer
Volcanoes and Climate
Attribution of Climate Change
Exam 2 on Wednesday!
Geography and Planning teaches you concepts, theories
and methods that provide a unique set of skills applicable
to a wide range of questions asked in many occupations, in
both the public and private sectors.
With a degree in Geography or
Planning you could become a…
GIS Specialist
 Urban or City
Planner
 Climatologist
 Transportation
manager
 Cartographer

Remote-Sensing
Analyst
 Transportation
Planner
 Researcher
 National Park
Service Ranger
 Demographer

But will I be able to get
a good Job?

The potential for practicing geography has grown
considerably in recent years with the use of Geographic
Information Systems.

The Bureau of Labor Statistics predicts a
Geography jobs from 2010-2020:
35% increase in
Percent change in employment, projected 2010-20
Geographers
35%
Social
Scientists
All
Occupations
18%
14%
• In their May 2012 report, the median yearly income for Urban and
Regional Planners was $65,230 and $74,760 for
Geographers.
More Information
http://www.aag.org/cs/what_geographers
_do
http://geo.appstate.edu/academics/underg
raduate-programs
Locations of Proxy Records
Instrumental: Red Triangles
Tree Ring: Brown Triangles
Borehole: Black Circles
Ice Core: Blue Stars
Other: Purple Squares
How might the locations
of proxy records influence
the climate reconstructions?
Medieval Warm Period
Also known as the Medieval Climate
Anomaly (MCA)
~1000 to 1200 AD
Most pronounced in the North Atlantic
region?
Debate persists as to how significant this
was globally.
Quite evident in tropical South America,
however.
Figure 7. Reconstructed tropical South American temperature anomalies (normalized to the
1961–1990AD average) for the last ∼1600 years (red curve, smoothed with a 39‐year Gaussian
filter). The shaded region envelops the ±2s uncertainty as derived from the validation period.
Poor core quality precluded any chemical analysis for the time interval between 1580 and 1640
AD.
Kellerhals et al. 2010
Viking Settlement of the North Atlantic
Little Ice Age
~1500 to 1850 AD
Widespread global cooling, particularly in
the North Atlantic region (Europe and
eastern North America).
Glacier advance in most of the world, best
chronicled in Europe.
Discussion Question
What are believed to be the two most
important climate forcings during the
period 1000 to 1850 AD?
Tambora in 1815, together with an eruption
from an unknown volcano in 1809, produced
the “Year Without a Summer” (1816)
Alan Robock
Department of Environmental Sciences
Tambora -- 1815




Largest volcanic eruption of
modern times
Located on Sumbawa Island
along the east Sunda Arc
Heard up to 1400 km away!
Ash remained in
atmosphere for several
years, leading to
pronounced cooling and the
“Year without a summer” in
the northeastern U.S. in
1816
Year without a Summer
http://www.dandantheweatherman.com/
Tambora in 1815, together with an eruption
from an unknown volcano in 1809, produced
the “Year Without a Summer” (1816)
Global Surface Temperature Reconstruction
0.3
Anomaly (°C)
0.2
0.1
0
-0.1
-0.2
-0.3
Year
Alan Robock
Department of Environmental Sciences
Mann et al. (2000)
1980
1960
1940
1920
1900
1880
1860
1840
1820
1800
1780
1760
1740
1720
1700
-0.4
Tambora, 1815, produced the
“Year Without a Summer” (1816)
Percy Bysshe Shelley
Alan Robock
Department of Environmental Sciences
Mary Shelley
George Gordon,
Lord Byron
Tambora, 1815, produced the
“Year Without a Summer” (1816)
“Darkness”
by Byron
I had a dream, which was not all a dream.
The bright sun was extinguish'd, and the stars
Did wander darkling in the eternal space,
Rayless, and pathless, and the icy earth
Swung blind and blackening in the moonless air;
Morn came and went—and came, and brought no day,
And men forgot their passions in the dread
Of this their desolation; and all hearts
Were chill'd into a selfish prayer for light:
And they did live by watchfires—and the thrones,
The palaces of crowned kings—the huts,
The habitations of all things which dwell,
Were burnt for beacons; cities were consumed,
And men were gather'd round their blazing homes
To look once more into each other's face; . . .
Alan Robock
Department of Environmental Sciences
Discussion Question
How do volcanoes influence climate? What are
the physical processes?
Volcanoes and Climate
Large volcanic eruptions inject sulphate aerosols
into the troposphere and stratosphere, reducing
the amount of solar radiation reaching the
surface and therefore resulting in a negative
radiative forcing.
More Reflected
Solar Flux
Stratospheric aerosols
(Lifetime  1-3 years)
Less
Upward
IR Flux
backscatter
absorption
(near IR)
H2S  H SO
2
4
SO2
CO2
H2O
Solar Heating
IR
Heating
Heterogeneous Less
O3 depletion Solar Heating
emission
IR Cooling
absorption (IR) emission
forward scatter
Ash
Reduced
Direct
Flux
Enhanced
Diffuse
Flux
Tropospheric aerosols
(Lifetime  1-3 weeks)
SO2  H2SO4
Indirect Effects
on Clouds
Alan Robock
Department of Environmental Sciences
Effects
on cirrus
clouds
Less Total
Solar Flux
More
Downward
IR Flux
Krakatau, 1883
The Loudest Explosion Ever Heard
Alan Robock
Department of Environmental Sciences
Projected Cooling following a “Mega-Colossal” Eruption
http://www.springerlink.com/content/f40022142221l168/fulltext.html
Solar Forcing
Historical records, paleo-archives, and model
simulations suggest that the Medieval Warm
Period was associated with positive solar
irradiance forcing (relative to 1500 to 1899 mean
values) while much of the Little Ice Age was
associated with negative solar irradiance forcing.
Sunspots and Climate
There is some evidence that sunspot activity
positively correlates to surface temperature (e.g.,
greater sunspot activity is associated with higher
temperatures).
The Maunder Minimum of sunspot activity
occurred at the heart of the Little Ice Age.
Discussion Question
How/why does sunspot activity appear to be an
important climate forcing?
Sunspots and Solar Irradiance
During periods of low sunspot activity, total solar
irradiance decreases. During years when sunspots are
abundant, the amount of radiation emitted in solar flares
is a maximum.
Mechanisms operating within the sun simultaneously
regulate both sunspots and net solar emissions.
Recent observations from space suggests that the
decrease in ultraviolet (UV) irradiance during low sunspot
activity may be considerably greater than previously
thought.
Sunspot Cycle 24
The current data for Sunspot Cycle 24 gives a
smoothed sunspot number maximum of about
101. We are currently over six years into Cycle 24.
The current predicted size makes this the
smallest sunspot cycle in about 100 years.
http://solarscience.msfc.nasa.gov/predict.shtml
Solar Forcing in the News
http://www.nature.com/news/2010/10100
6/full/news.2010.519.html
http://www.nature.com/nature/journal/v4
67/n7316/pdf/nature09426.pdf
http://science.nasa.gov/sciencenews/science-atnasa/2013/08jan_sunclimate/