Instrument based temperature and precipitation records in the American Southwest have just over a hundred years of data and then, source locations were few. These records are critical for water resource planners, wildfire scientists, and climate based science. Traditionally, to plan for the future, one reviewed the past to identify wet, average, and dry year water years and cold and hot years. But as expected, inadequate data generates incomplete conclusions. Enter the field of dendroclimatology.
Dendro (tree) based science is the study of tree rings and they show a very clear picture of hot, cold, dry and wet years in the tree rings of ancient trees. Trees like the Bennett Juniper in the Sierras live 2,200 years. Others live longer. The Gran Abuelo, a Patagonian cypress can live 3,600 years and Great Basin Bristlecone Pines can live an astonishing 4,850 years. That’s the time early civilizations were developing in Mesopotamia and about the time the construction of the Great Pyramid of Giza commenced.
Wider tree rings show wetter and warmer years, while colder and dryer years yield less growth. Scientists from the UCLA published findings in the journal Nature Climate in 2022 that the 22-year period 2000-2021 was the hottest and driest period in the American Southwest since 800 AD. (A. Park Williams). Similarly, scientists from the University of Arizona’s Laboratory of Tree Ring Research and Colorado State University’s Rocky Mountain Tree-Ring Research Center and Biogeography Lab confirm, the West’s “mega-drought” may signal uncharted territory in that critical dry years are now occurring in hotter years (the years 2000-2025 are the hottest years of record). That perfect storm of temperature rise and drought forecasts sustained uncertainty.
What does this mean to the average person. Rising utility costs, rising food costs, and increased wildfire risk (think increased insurance costs) to name a few impacts. An example of the impact of incomplete data: The Colorado River that serves as the source of agricultural and municipal water for over 40 million people across seven western states and Mexico, was divided up by a contract, ultimately approved by Congress, in 1922. The Colorado River Compact’s assumption was the river flowed 16.5 million acre feet/year on average. The Upper Basin States (Wyoming, Colorado, Utah, New Mexico, and a sliver of Arizona were allocated 7.5 million acre feet. The Lower Basin States, Arizona, Nevada, and California were allocated another 7.5 maf/year. A later treaty guaranteed Mexico 1.5 maf/year. It all looked good on paper. The framers used empirical climate records for the 22 year period 1900-1921. Tree ring studies now demonstrate those 22 years were among the wettest in 1100 years. Turns out the basin yields closer to 13.2 maf/year not 16.5 maf/year. Ooops. Good science matters.
This week, the world heard climate change called a con-job. A comprehensive effort is being made to cancel the inconvenient scientific evidence of a changing climate, with websites, studies, raw data, and words literally being censored and removed from public view. A cancel culture of scientific evidence will not solve problems, any more than defunding the National Weather Service will make hurricanes and extreme weather events go away. For those of us that rely on good scientific data to help make opinions, means, and methods to ensure that industry, municipalities, and economic prosperity is not impaired by a lack of water supply, it’s dangerous.