The years 2013-2014 marked the warmest period in California’s recorded history. They also market the fourth consecutive year of drought in the state. According to new research from a team at Stanford University that year could become the norm for California as the impact of climate change begin to set in.

The research, led by Stanford professor Noah Diffenbaugh, was published in the March 2 edition of the journal of the Proceedings of the National Academy of Sciences. It examines the role that temperature has played in California’s drought cycle over the last 120 years.

The researchers also looked at human emissions of greenhouse gasses and attempted to model its implications in terms of California’s normal cycles.

The team found that droughts were most likely during warm and dry years and that climate change is increasing the number of both.

“Of course low precipitation is a prerequisite for drought, but less rain and snowfall alone don’t ensure a drought will happen. It really matters if the lack of precipitation happens during a warm or cool year. We’ve seen the effects of record heat on snow and soil moisture this year in California, and we know from this new research that climate change is increasing the probability of those warm and dry conditions occurring together,” said Diffenbaugh in a statement.

The team analyzed both historical records and climate change simulations, including a recently released data set of monthly precipitation, temperature, and drought data stretching back to 1895.

The analysis shows that years that were both warm and dry were twice as likely to be severe drought years compared to cool dry years. The team also found that during the early and mid 20th century temperature and moisture seemed to fluctuate independent of one another.

“Imagine having two coins-one controls temperature, and the other precipitation. In the past, when you flipped the coins, they each came up tails half the time, meaning that a quarter of the time both coins came up tails, representing a warm and dry year,” said Diffenbaugh.

However, nearly every year for the last two decades has been warm or hot in the state.

“Now the temperature coin is coming up tails most years. So, even though the precipitation coin is still coming up tails only half the time, it means that over the past two decades we have gotten two tails-warm and dry-in half the years, compared with only a quarter of years in the preceding century,” he added.

“When we look at the historical record, not only do we see a doubling of the odds of a warm-dry year, but we also see a doubling of the frequency of drought years. Warm conditions reduce snowfall, increase snowmelt, and increase water loss from soils and plants,” said Danielle Touma, a graduate student in Diffenbaugh’s Climate and Earth System Dynamics research group and a coauthor on the study.

Using climate modeling, the team examined temperature and precipitation over the 20th century with and without high levels of greenhouse gasses. The team found that, while global warming hasn’t substantially impacted precipitation yet it has resulted in more warm years, making the dry years worse.

Their modeling shows that given the current levels of Co2 and other greenhouse gasses, hot, dry, drought years are likely to become more frequent going forward.

The researchers hope that their work will help state officials plan for California’s future.