The Little Ice Age “”new Reasearch”

The origin of this abrupt and long term temperature reduction has always been a mystery wrapped in speculation, but now an international team led by researchers at the University of Colorado Boulder in the U.S., Cree have the answer to the riddle. The intense cold was caused, as published this week in the journal Geophysical Research Letters, by a huge volcanic eruptions in the tropics that initiated a chain of effects on climate.

According to new research, the Little Ice Age began suddenly between 1275 and 1300 AD succession after four massive volcanic eruptions in the tropics, some episodes that lasted fifty years. The persistence of cold summers after the eruptions can be explained by the subsequent expansion of sea ice and a weakening of the Atlantic currents related, according to computer simulations performed for the study, also analyzed patterns of dead vegetation and data from ice and sediment .

Scientists have theorized that the Little Ice Age was caused by reduced solar radiation in summer, by erupting volcanoes that cooled the planet by emitting sulphates and other aerosol particles that reflect sunlight back into space, or a combination of both. “This is the first time someone has clearly identified the specific initiation of cold weather that marked the Little Ice Age,” says Gifford Miller, a researcher at the University of Colorado at Boulder and author of the study. “We also explained how this cold period could continue for so long. If the climate system is beaten again and again by the cold during a relatively short period in this case, volcanic eruptions, seems to be a cumulative cooling effect “

“Our simulations showed that volcanic eruptions may have had a profound cooling effect,” says Bette Otto-Bliesner, a scientist at the National Center for Atmospheric Research (NCAR) and coauthor of the study. “The eruptions may have caused a chain reaction, affecting the ice and ocean currents in a way that reduced temperatures for centuries.”

Advancing glaciers

Scientists estimate that the beginnings of the Little Ice Age occurred thirteenth to the sixteenth century, but there is little consensus. While cooling temperatures could affect as far away as South America and China, was particularly evident in northern Europe. The advance of glaciers in the mountain valleys and alpine villages destroyed period paintings show people ice skating on the river Thames in London and the canals of the Netherlands, places that were free of ice before and after .

“The dominant form in which scientists have defined the Little Ice Age is due to the expansion of glaciers in the Alps and Norway”, says Miller. “But the time when the European glaciers progressed enough to demolish entire villages came long after the beginning of the period of cold.”

Miller and colleagues radiocarbon dated to about 150 samples of dead plant material with intact roots, collected in Baffin Island in the Canadian Arctic. Found a large number of samples between 1275 and 1300, indicating that the plants had been frozen and enveloped by the ice for a relatively sudden event. They found one second rise in frozen plant samples for 1450, indicating a cooling segund0.

Thicker layers of ice

To extend the study, researchers analyzed sediment samples from glacial lakes associated with the ice of 367 square kilometers in the Langjökull, in the central highlands of Iceland, which reaches almost a kilometer high. The annual layers in the cores suddenly became thicker in the late thirteenth century and again in the fifteenth century due to increased erosion caused by the expansion of the ice that cools the climate.

The scientists used a model that simulates water conditions from 1150 to 1700 AD, which revealed the existence of large eruptions that could have cooled the Northern Hemisphere enough to trigger the expansion of Arctic sea ice.

For scientists, one of the questions to reflect on the Little Ice Age is unusual is the current warming of the Earth. Previous research conducted by Miller in 2008 on Baffin Island indicated that current temperatures are the warmest in the last 2,000 years.