California has been experiencing the worst drought in 1,200 years. According to a team of researchers from UCLA, the state has drought patterns caused by warming events and some of these lasted for thousands of years. The current warming is caused by greenhouse gasses.

The team, led by professor Glen MacDonald, tested some sediment cores from Kirman Lake in the Sierra Nevada mountains. It is said that the lake is sensitive to climate and the sediments found have recorded California's climatic history for 12,000 years.

Their study lasted for years before reaching the final analysis that showed the state's climate history to date. It has been linked to the Pacific Ocean's history that was taken from marine sediments cores and other sources, as reported by ZME Science.

The study showed that during the Holocene period (between 6,000 and 1,000 B.C.E.), the state experienced a drought that lasted 5,000 years. The marine sediment record shows that during that time, the Pacific Ocean was in a La Niña-like state that extremely reduced the rain in California and made the state warm and dry.

Meanwhile, the researchers said that it is still uncertain whether the climate change caused by the greenhouse gasses today will affect the ocean dynamics just like what happened in the past. MacDonald said that they do not know how the Pacific Ocean is going to respond, LA Times reported.

MacDonald added that the climate models that they are using are not good enough. While some study suggested that the Northern California could receive more rain, a 2014 study co-authored by UCLA climate scientist Alex Hall said that the state may experience the same climate for decades.

On the other hand, California is the country's top agricultural producer. Despite of the drought, the state is still able to sustain the huge agricultural production through man-made irrigation works.