November 28, 2021 | David F. Coppedge

California Had Long Droughts Before Recent Climate Change

Those who attribute droughts to recent human-
caused climate change should read this paper.

 

Reporters like to point to extreme weather events as evidence of man-caused global warming. One often-cited connection is the drought in California that has been going on for recent decades (e.g., PhysOrg 11/22/2021). Researchers examined a cave stalagmite, expecting to see a record of recent drought. Instead, they deduced that long droughts have always plagued California, long before fossil fuels were being used by humans. Kathleen Johnson comments on the findings in Geophysical Research Records, a journal of the American Geophysical Union. The “plain language summary” says,

Precipitation in California exhibits substantial variability, with frequent large swings between dry and wet conditions. Human-caused climate change is expected to increase the frequency and intensity of these extremes, likely leading to more severe and damaging droughts and floods than those we have experienced in recent centuries. Paleoclimate records are needed to provide baseline information about precipitation variability in California, which can help distinguish the impact of anthropogenic climate change from natural variability. Quantitative hydroclimate records are rare, however, especially beyond the tree ring record.

So here is a hydroclimate record that did not find what was expected.

A recent article by de Wet et al. (2021) provides the first semi-quantitative record of precipitation variability in central California, based on calcium isotope variations in a uranium-series dated stalagmite. They use this recently-developed method to study precipitation changes during the 8.2 kyr event, an abrupt climate event that impacted climate patterns globally. They find that precipitation variability before and during this event may have reached or exceeded the magnitude of that experienced in recent decades, highlighting that large amplitude precipitation shifts are a persistent feature of California climate. Even without the intensification of climate extremes caused by human activities, California needs to prepare for greater precipitation variations than those experienced in recent centuries.

If the record shows precipitation variability that “reached or exceeded” what Californians experience now, how can anyone know for sure that human activities will make them worse?

See another example of past climate uncertainty reported by the Columbia Climate School: “Why Did Glacial Cycles Intensify a Million Years Ago?” Quote: “It was one of the most substantial climate transitions and we don’t fully understand it.”

Death Valley (DFC)

It’s more a political statement than a geophysical statement to blame humans. Long before SUVs and diesel trucks existed, the stalagmite proxy record shows that “large amplitude precipitation shifts” have always been “a persistent feature” of California climate. That’s assuming their own belief that records of stalagmite delta-44 calcium levels preserve a reliable record of climate conditions according to their preferred timescale as reckoned by questionable radiogenic dating methods. If their own records cannot confirm it, they should state to the media that a record of anthropogenic climate change does not exist in this particular stalagmite. How many think that the media will accurately report this paper? Or will they protect the consensus against all contrary evidence?

(Visited 368 times, 1 visits today)

Leave a Reply