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New Study: ‘Climate change’ made California drought ‘less likely’ – Published in Journal of Climate

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Journal of Climate 2015

How Has Human-induced Climate Change Affected California Drought Risk?

Linyin Cheng,1,2,* Martin Hoerling,3 Amir AghaKouchak,4 Ben Livneh,2 Xiao-Wei Quan,2 and Jon Eischeid2

1 University of Colorado, Boulder, CO 80305, USA.

2 Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80305, USA.

3 National Oceanic and Atmospheric Administration, Earth System Research Laboratory/PSD, Boulder, CO 80305, USA.

4 University of California Irvine, Irvine, CA 92697, USA.

Abstract

The current California drought has cast a heavy burden on statewide agriculture and water resources, further exacerbated by concurrent extreme high temperatures. Furthermore, industrial-era global radiative forcing brings into question the role of long-term climate change on CA drought.

How has human-induced climate change affected California drought risk? Here, observations and model experimentation are applied to characterize this drought employing metrics that synthesize drought duration, cumulative precipitation deficit, and soil moisture depletion. The model simulations show that increases in radiative forcing since the late 19th Century induces both increased annual precipitation and increased surface temperature over California, consistent with prior model studies and with observed long-term change. As a result, there is no material difference in the frequency of droughts defined using bivariate indicators of precipitation and near-surface (10-cm) soil moisture, because shallow soil moisture responds most sensitively to increased evaporation driven by warming, which compensates the increase in the precipitation. However, when using soil moisture within a deep root zone layer (1-m) as co-variate, droughts become less frequent because deep soil moisture responds most sensitively to increased precipitation. The results illustrate the different land surface responses to anthropogenic forcing that are relevant for near-surface moisture exchange and for root zone moisture availability. The latter is especially relevant for agricultural impacts as the deep layer dictates moisture availability for plants, trees, and many crops. The results thus indicate the net effect of climate change has made agricultural drought less likely, and that the current severe impacts of drought on California’s agriculture has not been substantially caused by long-term climate changes.

* Corresponding author. Address: 216 UCB, University of Colorado Boulder campus, Boulder, CO 80309. E-mail:
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Related Links: 
New studies & data reveal ‘global warming’ NOT behind California drought – Not ‘unprecedented’ – 1970’s droughts blamed on ‘global cooling’

E&E News on 2012 U.S. drought: ‘For the scientists who take the long view of history, it’s merely a climatological blip’ — 1930s ‘Dust Bowl & 1988 both eclipse 2012 drought, scientists say’ 

AMS Journal study finds California drought is ‘not unprecedented’ over past 440 years: 9 other droughts as bad or worse

1 COMMENT

  1. Warmer air carries more water. We are in a cooling trend and California gets all aerial water from the North Pacific. If we could have CO2 caused global warming it would bring us more water from the seas.

    CO2 is a “trace gas” in air, insignificant by definition. It absorbs 1/7th as much IR, heat energy, from sunlight as water vapor which has 188 times as many molecules capturing 1200 times as much heat making 99.8% of all “global warming.” CO2 does only 0.2% of it. For this we should destroy our economy?

    There is no “greenhouse effect” in an atmosphere. A greenhouse has a solid, clear cover that traps heat. The atmosphere does not trap heat as gas molecules cannot form surfaces to work as greenhouses. Molecules must be in contact, as in liquids and solids to form surfaces.

    The Medieval Warming from 800 AD to 1300 AD Micheal Mann erased for his “hockey stick” was several Fahrenheit degrees warmer than anything “global warmers” fear. It was 500 years of world peace
    and abundance, the longest in history.

    Vostock Ice Core data analysis show CO2 increases follow temperature by 800 years 19 times in 450,000 years. Thus temperature change is cause and CO2 change is effect. This alone refutes the anthropogenic global warming hypothesis.

    Methane is called “a greenhouse gas 20 to 500 times more potent than CO2,” by Heidi Cullen and Jim Hansen, but it is not per the energy absorption chart at the American Meteorological Society. It has an absorption profile very similar to nitrogen which is classified “transparent” to IR, heat waves and is
    only present to 18 ppm. “Green vegans” blame methane in cow flatulence for global warming in their war against eating meat.

    Carbon combustion generates 80% of our energy. Control and taxing of carbon would give the elected ruling class more power and money than anything since the Magna Carta of 1215 AD.

    Most scientists and science educators work for tax supported institutions. They are eager to help government raise more money for them and they love being seen as “saving the planet.”

    Google “Two Minute Conservative” for clarity.

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