1. Global Warming

3. Specifically, people seem to want to be able to compare land-based temperature trends with global, probably in an attempt to identify unadjusted urban heat contamination of the data. These from NCDC:

4. Artic Sea Ice Increases at Record Rate

7. CO2, Ice Ages, Temperatures

9. Little Ice Age

10. Little Ice Age

11. Little Ice Age ↓

13. Due to an increase in drift ice along Greenland's east coast, the sailing route had to be changed. Ivar Bardsson, a Norwegian priest who lived in Greenland from 1341 to 1364, wrote: "From Snefelsness in Iceland, to Greenland, the shortest way: two days and three nights. Sailing due west. In…the sea there are reefs called Gunbiernershier. That was the old route, but now the ice is come from the north, so close to the reefs that none can sail by the old route without risking his life." (Ladurie, 1971.) In 1492, the Pope complained that no bishop had been able to visit Greenland for 80 years on account of the ice (Calder, 1974.)
The graves and ruins in Greenland show that the people did make an attempt at civilized living until the end but the cold and lack of proper nourishment took a heavy toll (Bryson, 1977.) The early Greenland Vikings stood 5'7" or taller but by about 1400, Lamb (1966) states that the average Greenlander was probably less than five feet tall. After World War I, Denmark sent a commission to Greenland which found the remains of the early settlements.

15. Figure 17: Price of rye in Germany vs. time expressed as an index
Figure 17: Price of rye in Germany vs. time expressed as an index. (Source: Lamb, 1995)
Each of the peaks in prices corresponds to a particularly poor harvest, mostly due to unfavorable climates with the most notable peak in the year "the year without a summer." One of the worst famines in the seventeenth century occurred in France due to the failed harvest of Millions of people in France and surrounding countries were killed.
The effect of the LIA on Swiss farms was also severe. Due to the cooler climate, snow covered the ground deep into spring. A parasite, known as Fusarium nivale, which thrives under snow cover, devastated crops. Additionally, due to the increased number of days of snow cover, the stocks of hay for the animals ran out so livestock were fed on straw and pine branches. Many cows had to be slaughtered.

16. These paintings covered the period from 1400 to 1967
These paintings covered the period from 1400 to He categorized the blueness of the sky into a three-step scale consisting of pale blue, medium blue, and deep blue. Cloudiness was estimated according to the U.S. airways code: clear (less than 10 percent coverage), scattered (10 to 50 percent), broken (60 to 90 percent), and overcast (more than 90 percent cloud coverage.) In addition, the types of clouds were observed according to four families: high, middle, low, and convective (vertically-developed) clouds. Neuberger separated his data into three epochs. According to the data in Fig. 19 below, during the second epoch when the LIA was at its peak, cloudiness and darkness prevailed.

17. During the LIA, there was a high frequency of storms
During the LIA, there was a high frequency of storms. As the cooler air began to move southward, the polar jet stream strengthened and followed, which directed a higher number of storms into the region. At least four sea floods of the Dutch and German coasts in the thirteenth century were reported to have caused the loss of around 100,000 lives. Sea level was likely increased by the long-term ice melt during the MWP which compounded the flooding. Storms that caused greater than 100,000 deaths were also reported in 1421, 1446, and Additionally, large hailstorms that wiped out farmland and killed great numbers of livestock occurred over much of Europe due to the very cold air aloft during the warmer months. Due to severe erosion of coastline and high winds, great sand storms developed which destroyed farmlands and reshaped coastal land regions.

18. Olafur Einarsson ( ), a pastor in eastern Iceland, wrote the following poem (Bryson, 1977) which illustrates the troubles Icelanders faced:
Formerly the earth produced all sorts of fruit, plants and roots. But now almost nothing grows....
Then the floods, the lakes and the blue waves Brought abundant fish. But now hardly one can be seen. The misery increases more. The same applies to other goods....
Frost and cold torment people The good years are rare. If everything should be put in a verse Only a few take care of the miserables....

20. Possible Cause for Climate Change
Sunspot Variation

21. Volcanic Eruptions
Ash and other small particulate matter injected into the stratosphere can effectively reduce incoming solar radiation received at the earth's surface. Sulfur compounds from eruptions condense into very tiny sulfuric acid droplets that form clouds which may stay suspended in the stratosphere for years, further reducing incoming sunlight (Pollock et al., 1976.) Fig. 9 illustrates the process.
Figure 9: Influence of volcanic plume on planetary albedo. (Source: Garrett, 1997)

22. Large-Scale Ocean Current Conveyor Belt
Figure 11: Large-scale ocean current conveyor belt. (Source: Miller, 2000)
Warm waters in the upper 1500 meters flow northward to the vicinity of Iceland. Winter cooling increases the density of the water permitting it to sink to great depths. Once at depth, the water flows the length of the Atlantic and becomes mixed into the deep southern hemisphere current. Because the ocean and atmosphere are a coupled system any changes in this large-scale ocean circulation could cause large-scale atmospheric changes on the order of hundreds of years (Miller, 2000.) The ocean is both a heat source for the atmosphere by releasing carbon dioxide, a greenhouse gas, and a heat sink by conducting heat away from the air that rests upon it. Surface water that comes into contact with air is referred to as ventilated water. Broecker et al. (1999) have demonstrated that very high rates of deep water ventilation occurred during the LIA, which means the oceans were removing heat from the atmosphere at a greater rate than normal during that period. That could explain the dramatic cooling observed during the LIA.

23. Earth Albedo
Albedo is a measure of the reflectivity of a surface. Snow and ice have a high albedo because their properties allow them to reflect up to 90% of incoming sunlight. After a global cooling event has begun, it can become self-perpetuating. With increased snow cover and glaciation, the planet's surface will have a higher albedo, which in turn will cause more incoming sunlight to be reflected. With less sunlight being absorbed at the earth's surface there will be a subsequent cooling effect. This cooling effect may cause even more snow cover and glaciation that would increase the planet's albedo even more. As the climate cooled during the LIA, earth's albedo increased due to more snow and greater glaciation. The process can last for many years however, it eventually does subside because cooler oceans experience less evaporation which leads to a decrease in cloud cover. Reduced cloud cover allows more sunlight to reach the surface which results in higher global air temperatures.