CAUSAS DE LA PEQUEÑA ERA DEL HIELO
1.- Actividad Solar
2. Causes For The Little Ice Age:
1. Solar Activity:
- The sun experienced an extended quiet period in which its intensity fell by as
much as 1/4 of a percent. This leads to less radiant heat emitted from the sun to
neighboring bodies, therefore a cooling occurs.
- Decrease in observable sunspots were noted. Amount of sunspots is correlated
to the activeness of the sun-more sunspots means more emission of radiant heat
from the sun. During this declined period of sunspots, people have connected it
to Maunder Minimum, who proposed this idea of sunspot and solar activity
correlation.
2. Volcanic Activity:
- During the Little Ice Age, records show that this was a period of numerous
volcanic eruptions.
- As volcanoes erupt they spit particles and gases into the air, an event leading to
the aerosol effect.
- Aerosol effect reduces the amount of incoming solar heat by relecting it back
into space. This increases the earth's albedo. A higher albedo coincides with lower
temperatures-a cooling if you will.
- An example of this idea can be seen in the eruption of Tambora. This eruption
produced so much gases and particles that it lowered earth's temperature enough
that it robbed Europe of a summer the following year (The year without a
summer).
The variation caused by the sunspot cycle to solar output is relatively small, on
the order of 0.1% of the solar constant (a peak-to-trough range of
1.3 W.m−2 compared to 1366 W.m−2 for the average solar constant).[5][6] Sunspots
were rarely observed during the Maunder Minimum in the second part of the
17th century (approximately from 1645 to 1715). This coincides with the middle
(and coldest) part of a period of cooling known as the Little Ice Age.
Recently, total solar irradiance (TSI) has been reconstructed from a composite of
several 10Be records measured in polar ice for the past 9300 years (Steinhilber et
al., 2008, 2009). The composite is mainly based on the 10Be record from the
GRIP ice core, Greenland. As system effects mostly influence the signal on short
time-scales, 40-year averages have been built from the 10Be records.
The climatic variations during the ‘Little Ice Age’ caused worldwide growth of
glaciers, but the evidence from Scandinavia and the European Alps is best
documented (Grove, 1988; Lowell,
2000).
Estimates of Northern Hemisphere mean annual temperature for
the last millennium (Mann et al., 1999; Crowley and Lowery,
2000) do not show a marked LIA cooling, but rather a gradual
temperature decline during the first half of the last millennium.
It is also evident that there was significant regional temperature
variations during the LIA. Several temperature data sets obtained
from different archives (tree rings, corals, varved sediments, ice
cores, glaciers, historical records, etc.) show that some regions
were warm while others were cold, and vice versa. Most of the
reconstructed climatic changes have been linked to external forcing
factors (e.g., solar activity, volcanic eruptions) in combination
with internal ocean-atmosphere interactions (Crowley and Kim,
1996; Mann et al., 1998). Since these forcing factors, together
with ‘greenhouse’ gases, are suggested by the Third Assessment
IPCC Report, published in 2001, to play a role in future climatic
variations, it is important to obtain better records of climatic
change in the recent past and a better understanding of the relative
contribution of these forcing factors.
Until recently, and mainly based on evidence from western Europe
and the North Atlantic region, the conventional view of the climate development
during the last millennium has been that it
followed the simple sequence of a warm Mediaeval period, then
a cool ‘Little Ice Age’, followed by global warming. However,
climate reconstructions obtained recently have challenged this
rather simple sequence of climate development. The centralEngland temperature record going back to the late 1650s indicates
that the rapid glacier advance which is historically documented in
the early eighteenth century in western Norway may be explained
mainly by increased winter precipitation (mild and humid) due to
prevailing ‘positive NAO weather mode’ in the Ž rst half of the
eighteenth century. Lower summer temperatures alone cannot
explain such a signiŽ cant glacier advance over a few decades.
Figure 1: A) Zoom-in of the 9300-year long total solar irradiance (TSI) reconstruction
(Steinhilber et al., 2009) for the past 1200 years. The gray band is the 1σ
uncertainty. Inset shows the group sunspot number. MCA: Medieval climate
anomaly; LIA: Little Ice Age. Capital letters mark grand solar minima: O=Oort,
W=Wolf, S=Spörer, M=Maunder, D=Dalton. B) Total global stratospheric volcanic
sulfate aerosol injection in teragram (Tg) (Gao et al., 2008).