INDIANAPOLIS — Although she doesn’t have a crystal ball, historical climatologist Evelyn Browning-Garriss was able to share some insight about this year’s possible weather conditions with attendees at the Indiana Livestock, Forage and Grain Forum.

In her profession, she looks at what factors are shaping the upcoming weather and then takes that information and pours over historical documents, such as coral reefs, tree rings, glacier cores and other manmade records, she explained.

Browning-Garriss said last year’s unusual weather was formed by three factors — volcanoes, warm waters such as the Atlantic, Indian and Pacific oceans and winds that have been carrying heat into the breadbasket areas of the northern hemisphere.

When there is a large enough volcano, she noted, the debris and smoke will cause the sunlight to be blocked, which can cause a change in temperature.

“If it goes high enough into the stratosphere, debris can stay there for years, blocking sunlight, changing temperature, affecting moisture and rainfall patterns,” she said.

In the stratosphere, she added, moisture and ash gather and can form clouds the size of Montana.

Browning-Garriss said there were two large volcanoes in 2011 that went off in the Arctic, and although most didn’t hear about it because the polar bears and the seals “had enough problems,” there was one in Russia and another in Iceland.

She added there was so much debris in the Arctic that it caused a change in the wind patterns, and the last time this happened was in 1783 and 1784, which is one reason why the weather that Hoosiers and much of the Midwest experienced last year had not been seen in two centuries.

Browning-Garriss explained that because of the debris being trapped in the stratosphere and forming huge clouds, the strong, cold air also was trapped, which is why there was a warmer winter in the southern U.S.

However, she said, it is beginning to drop lower, so some of the cold air is escaping, which is why there already has been a colder winter this year compared to last year.

Another factor that will be important in trying to grasp how this year’s weather will be, Browning-Garriss said, is whether the Gulf Stream is flowing fast or slow. If it’s flowing fast, it carries a lot of heat, she noted.

“Back in 1995, it flowed fast and heated up, which changed the temperatures in North America,” she noted.

The weather expert noted that Scandinavians love fish, especially herring, which love warm water, and they have kept yearly records from when the water warmed up and the fish arrived for more than 500 years.

Looking through the records, it shows that they have 40 years of warm weather and then 30 years of cold weather, she said.

“In 1995, the Atlantic and the Gulf Stream started flowing fast and will do so for 40 years,” she said.

Last year, she added a fishing fleet reported that the herring arrived six weeks earlier than normal, and the ocean was as hot by May as it typically is during July.

Browning-Garriss said she believes that least year was the peak of the 40-year warm period, and there will be 20 more years before it makes its next transition.