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This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Tuesday, August 25, 2015

Drought and Extremes of Heat Reduce Farm Yields and Worsen Wildfires

[Updated September 16, 2015]       

Man-made global warming worsens the extreme drought in the American West because of its excessive heating.  Farms in California receive inadequate water supplies, leading to crop losses.  Wildfires are burning record areas of forest in the West as well as in Alaska.  In order to minimize future damaging effects such as these, Americans should join forces with other nations of the world to reduce use of fossil fuels so that greenhouse gas emissions are lowered.

The drought in California.   Barry Baker, an almond farmer in California’s Central Valley, couldn’t provide enough water for the 5,000 acres (about 2,000 hectares) of almond trees he grows, the Vancouver, WA Columbian reported in February 2014  So he tore up about one-fifth of his trees, an irreversible decision (see the image below), and had them reduced to wood chips to fuel a local power plant. 

Alan Thompson of G&F Agri Service oversees the removal of almond trees at Baker Farming Company in Firebaugh, CA, on Feb. 3, 2014. (Scott Smith/AP)

The prolonged drought in California, now in its fourth year, has cut supplies of water used to be available to irrigate crops. In July 2015 the state ordered farmers to stop pumping the water.  A year earlier, farmers’ bids for water drawing rights were rumored to be as high as US$3,000 an acre-foot (a measure of water volume), instead of normal rates of about US$60. The wells on California’s farms have been pumping more water out of the region’s aquifer than is replenished by rainfall, so that the land of the Central Valley is actually sinking.  The resulting damage to the aquifer is permanent, reducing its capacity to hold water if and when rainfall returns.

Economic effects.  A 2015 study by the University of California, Davis of the economic effects of the drought on agriculture in California projects that a) lack of surface water for irrigation is only partly offset by pumping groundwater from deeper wells at higher cost; b) as many as 21,000 agriculture and related jobs will be lost; c) 542,000 acres (about 217,000 hectares) of agricultural land would lie fallow, more than 25% higher than in 2014; and d) US$2.7 billion of economic activity would be lost.  Thus the drought has serious negative consequences on the state’s economy.

Wildfires in the Western U.S.  In the U. S., forest and grassland wildfires have become significant problems in recent years.  So far in 2015, up to August 23, there have been almost 42,000 wildfires which have burned about 7,500,000 acres (about 2,800,000 hectares).  Over the last ten years, information for the year-to-this-date includes some years with higher numbers of fires, but none with a higher acreage burned.  The ten year average for the year-to-this-date was 5,350,800 acres (about 2,140,000 hectares) burned.

An example of the damage that wildfires cause is in the image below.

House threatened by wildfire in California, about Aug. 2, 2015.

One firefighter, David Ruhl, 38, died in California on about Aug. 2, 2015 as he was caught in the blaze in the region shown in the photo above.  Three firefighters, Tom Zbyszewski, 20, Andrew Zajac, 26, and Richard Wheeler, 31, died battling a blaze in Washington state.
The map below shows the locations of most of the 70 large wildfires active on Aug. 23, 2015.
A portion of the U. S. Department of Agriculture, Forest Service map showing large (greater than 100 acres (40 hectares)) wildfire incidents present on August 23, 2015.  70 locations are mapped; red, blue, and gray show level 1, level 2 and other incidents, respectively.  In addition to those shown, the total includes five other incidents in Texas, Oklahoma, Louisiana and South Dakota (not shown in this map portion).  The web page stated that in addition there were 99 new fires on this date.
Source: U. S. Department of Agriculture, Forest Service Active Fire Mapping Program; (accessed August 23, 2015).
The Forest Service states that on this date there were 72 uncontained large fires and 2 contained fires.  Their locations reflect the severe wildfire hazard presented by severe drought conditions in California and the inland regions of the Pacific Northwest.  The U.S. Drought Monitor showed that as of June 30, 2015 most of California, as well as portions of Nevada and Oregon, experienced extreme or exceptional drought, and other regions of Washington state, Oregon, Idaho and Montana experienced severe drought.  In general regions of drought correlate with incidence of wildfires.
Wildfires in Alaska.  More than a month earlier, the U. S. National Oceanic and Atmospheric Administration (NOAA) reported that Alaska has had more than 600 fires, burning millions of acres of forest, the worst on record.  More than 350 structures have been damaged or destroyed.  Alaska had extreme high temperatures in interior regions during spring 2015 with temperatures 30ºF (16.7ºC) higher than typical, and were drier than usual as well. 
Extreme heat in the West and Alaska. NOAA reports that extreme heat has been prevalent over California and much of the West for the last three years.  This has worsened the effects of drought conditions in the region, which have lasted as long as six years.  In addition to lack of rainfall, low snowpacks in the mountains have led to reduced streamflow in the region, worsening the dryness of the soil.  The high temperatures paired with moderate to exceptional dryness in the American West and Alaska readily set the stage for ignition and spreading of forest wildfires.
Expenses of wildfire management.  The total costs of fire management have risen dramatically, by 60% over the last ten years, to US$2.5 billion.  As of Aug. 20, 2015, direct firefighting expenses have reached US$830 million; in all of 2014 the cost was US$1.2 billion.  Because of funding constraints, the U. S. Forest Service has reduced the proportion of administrative personnel and redirected staffing into firefighting in the field.
The role of global warming.  When confronted with climate extremes such as those described here, we may wonder whether global warming plays any role.  Generally drought refers to low rainfall; excess heat from global warming worsens its effects.  A. P. Williams and coworkers conducted detailed analyses of climate-related variables for California from 1901 to 2014; (Geophys. Res. Let. 2015; DOI: 10.1002/2015GL064924).  They found the drought was record-breaking in 2014 and a near-record for the three years 2012-2014.  From rigorous statistical analysis the authors estimate that global warming was responsible for 8-27% of the observed excess drought conditions for 2012-2014, and for 5-18% for 2014 alone.  These findings indicate that although drought conditions may originate from various climatic factors operating cyclically over many years, its full extreme extent is worsened by global warming, producing the record conditions identified by the authors.
Robeson analyzed periods of drought in central and southern California as far back as 1200 years ago (Geophys. Res. Let. 2015; DOI: 10.1002/2015GL064593.  The drought experienced in 2014, viewed against the earlier droughts, had a probability of happening of once in 140-180 years.  The three-year drought period 2012-2014 was very severe, having a probability of 1 in 10,000.  The four-year drought over 2012-2015 was unprecedented in the 1200 years examined, and is so severe its probability is beyond estimation using the analysis in the report. 
The U. S. Environmental Protection Agency reports, in a post current as of July 15, 2015, that Alaska’s long-term average air temperature has increased 3.4ºF (1.9ºC) over the last 50 years, and that winter temperatures have increased by almost twice as much.  The rate of warming in Alaska is twice as fast as it is for the rest of the U. S.  These trends are due to global warming.  The higher temperatures, coupled with the drought in Alaska’s interior, provide the conditions suitable for starting and spreading forest wildfires.
Images such as the photos shown here speak to us directly, as if we ourselves are experiencing the losses shown.  They are immediate and compelling.
California farms provide a significant fraction of the vegetable and fruit crops that Americans consume.  Yet in recent years California has experienced record combined heat-and-drought conditions, which have led to destruction of fruit (here, almond) trees, and to land deliberately being withdrawn from cultivation instead of producing crops.  This ultimately can affect us all by leading to scarcity and/or higher prices for the foods we consume.
The increasing extent of forest wildfires in U. S. destroys public and private forest lands, and increasingly threatens homes built in the backcountry.  Protecting those homes from fire is the highest priority of wildfire fighters, leading to loss of life and requiring more expenses paid from our taxes. 

[Update] Valerie Trouet and colleagues published a detailed analysis of precipitation in the Sierra Nevada mountains of eastern California online in Nature Climate Change in September 2015.   They focused on the annual mountain snowfall that on melting provides much of the water resources for the state, going back to 1500 C.E.  They found that the water originating as snowfall in the winter of 2015 was the least for the entire 515 year period examined.  The likelihood of such a low snowpack having occurred in the past is estimated at once in every 3,100 years, which points out the extreme nature of this year’s minimum.  In view of projected worsening of man-made warming in the Sierra Nevada, the authors fear “major future impacts” on the region’s water storage ability.
Man-made global warming is a significant factor contributing to the harms and damages exemplified in this post.  In order to minimize the effects of further warming, which will only make droughts, food shortages and forest wildfires worse, we Americans have to join with the people of all nations to reduce the use of fossil fuels so that the further accumulation of carbon dioxide is minimized.  Our policymakers are infused with the same humanity common to  all Americans, and with all inhabitants of our planet.  We must come together to implement meaningful measures to combat the warming of our home, the Earth.
© 2015 Henry Auer

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