US Drought Conditions Intensify Over Central US; Hold Mainly Steady Elsewhere

The US drought got progressively worse in the past week over most of the middle of the US.  For the remainder of the country, some places witnessed worsening drought conditions while other areas saw some small amount of relief.

According to the US Drought Monitor’s weekly update, “The August 7 Drought Monitor map shows 52.27 percent of the United States and Puerto Rico in moderate drought or worse, compared to 52.65 percent last week; 38.48 percent in severe drought or worse, compared to 38.12 percent a week earlier; 20.18 percent in extreme drought or worse, up from 18.62 the previous week; and 3.51 percent in exceptional drought, up from 2.52 percent last week.”

So extreme and exceptional drought areas expanded slightly compared to the previous week.  But the overall area affected by moderate drought or worse was essentially unchanged.

Figure 1 – Drought conditions across the US as of 7 August 2012.  Exceptional drought areas in Missouri, Arkansas, Oklahoma, Kansas, Nebraska, and Illinois grew in the past week.  Some relief of drought conditions occurred in South Dakota, Wyoming, and Arizona.

This drought is not expected to be significantly relieved before October.  Hopefully, weather conditions in the next two months prove that prediction wrong or the effects of this drought will be further reaching and longer lasting than what people currently think.  This is a good time to examine current drought-related policies and determine whether or nor they are equipped to deal with early 21st century drought conditions.  If they aren’t, it seems reasonable to conclude they won’t be able to handle late 21st century drought conditions either.  For example, Georgia farmers have begun irrigating crops.  That practice reduces above ground streamflow, depriving aquifers the chance to recharge.  Millions of people in the southeast depend on aquifer water for drinking.  Which interest will win if the drought continues another 10 years?  Do people get drinking water or do farmers get irrigation water?  And that’s just one potential impact.  The time to think and plan for this is now, before the problems grow in magnitude and complexity.

2012 U.S. Drought: Impacts & Historical Context

The National Climate Data Center, in its summary of drought conditions as of the end of June 2012, reported that 55% of the contiguous U.S. was experiencing moderate to extreme drought, as the graphic below shows.  This is the largest percentage since December 1956 when 58% of the U.S. experienced similar conditions.  The Palmer Drought Index, whose data base goes back 112 years, is relied upon for drought comparisons before 2000.

Figure 1. Drought conditions across the United States as of early July 2012 from the Drought Monitor.

In my last post on drought, I stated, “There’s no widespread crisis to speak of yet, but inhabitants as well as policymakers should monitor conditions as the year progresses.”  Well, the NCDC established the case for a widespread crisis with their latest summary, which was not issued until after my post.  Crops and livestock are now being negatively affected.  The following two charts show corn and soybean prices.  The recent peaks are due to worsening conditions across the breadbasket and the USDA’s recent crop downgrade.

Figure 2. Corn (top) and soy (bottom) prices and volume charts for the past 12 months.

[h/t Bonddad]

1988 was also a very bad year for corn in the U.S.  Here is a chart from the USDA comparing 1988 and 2012 corn ratings:

Figure 3.  Comparison of corn ratings (good + excellent) as determined by the USDA as of early July 2012.

You can see that conditions in 1988 worsened earlier in the year (solid blue line @30% ~3 weeks before the solid yellow line).  It remains to be seen how bad conditions eventually get in 202.

So conditions are the worst since Dec. 1956.  How else do today’s conditions compare to earlier droughts?  The following graphic from USA Today helps put them in context:

Figure 4. Comparison of extensive drought in U.S. history.

The percentage of the country in moderate to severe drought in June 2012 is the sixth highest since 1900.  The 1930s are well known as Dust Bowl years.  Conditions aren’t expected to get that bad, even if drought were to dominate the area for the next few years, primarily because of changes in farming practices.  Topsoil was easily scoured from the earth in the 1930s and was moved around by winds, sometimes for dozens or hundreds of miles, hence the name ‘Dust Bowl’.  The droughts of the mid-1950s were also quite extensive.  The U.S. is fortunate that the return period of these conditions was ~55 years.

I’ve also written in my drought posts that the current drought, extensive and intense as it is, is not without historical precedent and that a clear climate change linkage is not available at this time.  With generally warmer temperatures and more variable precipitation patterns, one might conclude that drought would be more likely to occur in recent years than in the 1900s.  As the USA Today chart shows, that clearly hasn’t happened.  The conditions in 2012 are more closely related to the double-dip La Niña that just ended:

Figure 5. Time series of temperature anomalies in the NINO3.4 region.  Positive values for 5 consecutive 3-month periods correspond to El Niño events while similar periods with negative values correspond to La Niña events.

This drought is very serious and everybody should treat it as such  Part of that statement is acknowledging the lack of a clear anthropogenic climate change signal at this point in time.  Conditions aren’t expected to significantly improve in the next couple of weeks.  The extent and intensity of drought can expand and worsen within that time.  We can also expect higher prices for food starting next year and into 2014 – additional economic headwinds that the U.S. can ill-afford at this time.

US Drought Conditions early-July 2012: 77% in West, 68% in Southeast

The record warmth of the past seven months in the US was more than just a set of numbers or a temporary interesting headline.  Along with the heat, precipitation for most of the southern half of the country has been below average during the same time period.  The result is that drought conditions exists today across most of the Western US, with almost all of the Southwest (CO, NM, AZ, NV, UT, CA) experiencing Severe drought:

Figure 1. Drought conditions over the West US for the week ending 3 July 2012.

As you can probably tell from Figure 1, the Pacific Northwest had below average temperatures and above average precipitation during the same time period, thus the relative lack of drought in OR, WA, ID & MT.  Drought has increased into Wyoming and recently to a lesser extent into Montana.

Interestingly, the areas experiencing the most severe level of drought are also those with the largest wildfires: New Mexico, Colorado, Wyoming, and Montana have all had very large wildfires in the past month.  The effects of the drought so far in this region is extensive: early snowpack runoff, failing crops, reduced river levels, and livestock stress.

The seasonal monsoon kicked off some widespread and at times heavy precipitation across the southwest in the days since the Drought Monitor created this map.  In the same way that a tropical system affected site-specific drought conditions over Florida last month, some short-term drought conditions might be alleviated in the West, which the Monitor should reflect in the next issued analysis.

The Southeast finally got some relief last month due to Tropical Storm Debby, which left behind record rainfall (and flooding) throughout Florida.  Meanwhile, extremely warm and dry conditions spread north.  The result is clear in the table below: the percent area experiencing some level of drought dropped significantly through last week, from over 75% three months ago to 56% last week, before rebounding back to 68%.  Unfortunately, the areas with the worst drought conditions didn’t get their long-term drought busted, especially Georgia.  This area typically receives some relief from drought during the Atlantic tropical storm season.  Aside from Debby in Florida, the Atlantic basin hasn’t produced much in the way of help so far this year.  The Southeast will have to wait a bit longer for additional relief.

Figure 2. Drought conditions over the Southwest US for the week ending 3 July 2012.

Drought has been present across GA for over one year now.  The area affected by drought expanded to neighboring states during the end of the winter and beginning of spring, then shifted in the last month both north and west.

There’s no widespread crisis to speak of yet, but inhabitants as well as policymakers should monitor conditions as the year progresses.  These conditions are not a result of climate change in any direct way.  They are simply a result of a chain of events, some of which (e.g. Arctic ice loss in recent years) are more directly related to climate change than others.  Drought is a complex phenomenon that has widespread effects, as people across the US are experiencing again this summer.