Climate Change and Rising Temperatures Have Contributed to Making the Current California Drought the Worst in 1,200 Years

By Katherine Podoll

In the years 800 to 1200, the Earth was an extremely warm place. Ocean levels were higher than ever before, and with little snow far up north, exploration and colonization by the Norse people was at its peak. While this made it easier to travel for people globally, it also contributed to record droughts, and the period became known as the Medieval Warming Period.

Now, nearly 1,200 years later, California faces its fourth year in another serious drought. While it has made only small impacts on most people’s day-to-day lives, it is proving to be extremely detrimental to the environment. Over the past few years California residents have been asked to incrementally reduce their water usage.   But there remains a disconnect for most Californians and scientists were not aware of the severity, either, until they began to experiment on a vital species of the natural local environment: Blue Oak trees.

Centuries-old discoveries about the nature of the environment, particularly in relation to precipitation and drought severity, are made today as a product of dendrochronology, or tree ring data. Daniel Griffin, a dendrochronologist at the University of Minnesota, studied soil moisture and temperature in Blue Oak tree rings to determine how exceptional the current drought is in relation to others in the past 1,200 years. In his Blue Oak Study published in a partnership between the University of Minnesota and the Woods Hole Oceanographic Institution, Griffin described how, “We’re looking at the combined influence of precipitation and temperature on soil moisture, through this method known as the Palmer Drought Severity Index [PDSI], which is an index of available soil moisture. And when we look at PDSI, and we compare that to tree ring reconstructions of PDSI that go back in time for the last 1,200 years, that’s where this short term drought episode that began in 2012 stands out as exceptional.”

The current California drought’s severity is due in large part to temperature and precipitation change, which at its core is climate change. Climate change causes weather patterns to alter, creating uneven precipitation, and average global temperatures to increase due to growing greenhouse gas emissions into the atmosphere. Griffin relates this back to the California drought: “These record high temperatures may be contributing about 20% of the magnitude of this drought. So there’s no doubt that this drought in California is predominantly the result of precipitation deficit, but it is being exacerbated by record high temperatures.”

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So, if this drought is the result of climate change, what can we predict to see in the environment in the near future? “We’re moving into levels of carbon dioxide concentration in the atmosphere that have not been experienced any time during human history, and probably for the last 3.5 million years or more,” says Griffin. He adds that “this type of hot drought, where you’ve got low precipitation magnified by record high temperatures, is a pretty good prototype for the type of drought that we expect to see in the twenty first century as temperatures continue to rise in direct response to human emissions of greenhouse gases into the atmosphere.”

Looking into the future, we will need to create better systems for managing water usage in a drought. The last civilization to experience a drought similar in degree to the current one was the Mayans in Central and South America. But when did that great civilization disappear? 1,200 years ago, exactly the time of the last drought.

As dire as the outlook for the future is with droughts such as our current one becoming a regularity, there is hope that these droughts will not be sustained as ongoing, decade-long events, such as the drought during the Medieval Warming Period, but rather short, punctual dry periods intermixed with wet years. This coming winter of the 2015-2016 season, we hope to end, or at least put on hold, this current dry spell with a possible “El Nino” rainy season. But despite what happens this winter, despite what happens in a year from now, it is our duty as residents of California in this critical time to do everything in our power to preserve our environment and keep California alive and flourishing: taking shorter showers, removing non-native grass lawns, and spreading awareness are all easy ways to help the land, and therefore the people. We must learn from the wisdom of the trees. We don’t want to end up like the Maya.