Trees Warning For California: Worst Drought In Centuries
By Gracy Buckholtz, EarthScope Reporter

Dendrochronology, a big word with a fascinating meaning, Daniel Griffin, a dendrochronologist at the University of Minnesota, gives the definition as “study of annual growth increments in trees as a metric for understand environmental history” Griffin can look at tree rings and recreate the environment centuries ago. He began looking at the California drought through his tree rings and gathering facts about how past droughts might relate to our current one. What could Blue Oaks tell him about the severity of the drought and where it was headed?

Every school kid learns that you can tell the age of a tree by the number of rings it has. By looking at the width of the rings, Griffin can tell a lot about what the environment was like hundreds of years ago. Years with more rainfall result in wider rings while years that are dryer have very thin rings. By looking at the ring width of past years, Griffin can identify which years had high growth periods and compare them today.

Keep in mind that a drought isn’t just years of low rainfall. Droughts mean high temperatures combined with low rainfall. Even when rainfall is consistent, high temperatures can dry out the soil meaning trees don’t have the water they need to grow. “Some of our colleagues have released other studies...and one of the more recent suggest that these record high temperatures may be contributing to about 20% of this extreme drought”. Taking into the account not only the rainfall but also the temperature helps Griffin determine the soil moisture. This tells him about the growing condition the trees had to face.

Trees are our most accurate weather tools to date. Modern day technology only tells us about data to about 125 years but trees can tell us about weather in 800 AD. Their rings tell us more about climate than any other instrument. 

The last drought that was even close to the severity we see today was in the warming period in the middle ages. This warm period was probably due to more natural environmental effects, not the man made kind that we see today. With a rise of greenhouse gases directly contributing to high temperatures, it’s looking like this drought might last long than the one in the warming period. 

Sadly trees can’t predict the future but they can give us a great look into what’s ahead. Using tree ring data we can help improve climate models of the past which in turn help create more accurate models of the future. Hopefully from there we can determine ways to combat the rising temperatures that we are seeing. Its pretty incredibly how much trees can tell us.

To learn more about Blue Oaks and Daniel Griffins Study: http://onlinelibrary.wiley.com/doi/10.1002/2014GL062433/full