Weatherdem's Weblog

Bridging climate science, citizens, and policy


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48.2% of US in Moderate or Worse Drought – 17 Sep 2013 (Thank You, Monsoon!)

According to the Drought Monitor, drought conditions worsened slightly across the entire US compared to three weeks ago. As of September 17, 2013, 48.2% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  This value is about 11 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought decreased from 14.8% last month to 6.9% last week!  This is more than 10% lower than it was six months ago. The eastern third of the US was wetter than normal during August, which helped keep drought at bay.  The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012, assisted by a persistent upper level blocking pattern.  Instead of Exceptional drought in the West like there was earlier this summer, record rains and flash flooding was the story in September.  While this record-breaking series of events broke the drought in some areas of the West, long-term drought continues to exert its hold over the region.  Compared to earlier this summer, drought increased in area and intensity across the Midwest.

 photo USDrought20130917_zps29a0436a.gif

Figure 1US Drought Monitor map of drought conditions as of September 17th.

If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories.  Compared to mid-August and early September, and despite recent rain events, drought expanded or worsened in the Midwest (Iowa, Missouri, Illinois, Minnesota, and the Dakotas) as well as Louisiana, Arkansas, and Mississippi.  On the other hand, alleviation is evident in small places in the West, as the following map shows.

 photo west_drought_monitor_20130917_zpsd2784c0e.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of September 17th.

After worsening during late winter into spring 2013, drought conditions steadied in late summer.  The differences between this map and early September’s is the reduction in area and severity of drought, especially in the southern half of the West.  The area experiencing Exceptional drought decreased significantly over the West and the percent area with no drought increased.  Figure 2 also shows that the percent area with no drought is still lower since the start of the calendar year (24% to 18%).

Here are the current conditions for Colorado:

 photo co_drought_monitor_20130917_zps9d17a4ef.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of September 17th.

There is evidence of substantial improvement in Colorado since just a few weeks ago and certainly compared to earlier this year, when drought conditions were their worst.  Compared to the start of the calendar year or even three months ago, the percent area of every drought category decreased significantly.  Only 1.5% of the state currently has Exceptional drought.  Only 84% of the state is even experiencing any drought condition today, a far cry from the 100% that lasted for well over one year.  The links in the first paragraph dealing with last week’s rains combine with this graphic to demonstrate that places that receive one year’s worth of precipitation in one week’s time bust their drought!  Many communities would trade those record rains for a little bit of drought, given the extensive damage to infrastructure and the eight people who, as of this morning, perished in the severe weather event.

Let’s compare Figure 3 to similar Colorado maps from earlier in the year.  First, this is what conditions looked like just two weeks ago:

 photo CO_drought_monitor_201309033_zps07464c14.png

Figure 4 – US Drought Monitor map of drought conditions in Colorado as of September 3rd.

The over-active monsoon season helped reduce drought severity from Denver northwest toward the Wyoming border.  I said at the time I hoped that trend continued, but I could never imagine what would happen in the interim.

Here is a look at some of the worst drought conditions Colorado experienced in the past year, from late April 2013:

 photo CO_drought_monitor_20130425_zpsbf9ccb2d.png

Figure 5 – US Drought Monitor map of drought conditions in Colorado as of April 25th.

Conditions were horrible earlier this year.  Reservoir levels declined and crops failed as a result of the higher than normal temperatures and much lower than normal precipitation.  I certainly don’t want to see additional flooding, but I would like to see normal precipitation return to the state and the region.

 photo midwest_drought_monitor_20130917_zpsf91b6be4.png

Figure 6 – US Drought Monitor map of drought conditions in the Midwest as of September 17th.

Drought expanded in the Midwest in the past two weeks: the percent area with no drought decreased significantly from 48% to 43%.  Three months ago, the value was 93%.  This region collected rainfall this month, but the amounts continued to track below average.

 photo south_drought_monitor_20130917_zps76d5a2cf.png

Figure 7 – US Drought Monitor map of drought conditions in the South as of September 17th.

Compared to early summer, drought as a whole expanded across the South in 2013.  Instead of 44% area with no drought three months ago, there is only 16% today.

Policy Context

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.  Without comprehensive planning, dwindling fresh water supplies will threaten millions of people.  That very circumstance is already occurring in western Texas where town wells are going dry.  An important factor in those cases is energy companies’ use of well water for natural gas drilling.  This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water?  In the 21st century, we will not have both options available at the same time as happened in the 20th century.  This presents a radical departure from the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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50.1% of the Contiguous United States in Moderate or Worse Drought – 3 Sep 2013

According to the Drought Monitor, drought conditions worsened slightly across the entire US compared to three weeks ago. As of September 3, 2013, 50.1% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  This value is about 9 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought decreased from 14.8% three weeks ago to 9.9% last week; this is approximately 10% lower than it was six months ago. The eastern third of the US was wetter than normal during August, which helped keep drought at bay.  The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012.  Instead of Exceptional drought in Georgia and Extreme drought in Florida two years ago, there is flash flooding and rare dam water releases in the southeast.  Four eastern states experienced their top-four wettest Julys on record.  The West presents a different story.  Long-term drought continues to exert its hold over the region, as it remained warmer than normal but six southwestern states received top-20 July precipitation this year.  Meanwhile, Oregon recorded its driest July on record.  Compared to three weeks ago, drought area increased in the Midwest.

 photo USDrought20130903_zpsf4845451.gif

Figure 1US Drought Monitor map of drought conditions as of September 3rd.

If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories.  Compared to early July and mid-August, and despite recent rain events, drought expanded or worsened in the Midwest (Iowa, Missouri, Illinois, Minnesota, and the Dakotas) as well as Louisiana, Arkansas, and Mississippi.

 photo west_drought_monitor_20130903_zps6a3a6205.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of September 3rd.

After worsening during late winter into spring 2013, drought conditions steadied during the past month.  The differences between this map and mid-August’s is the spatial shift of conditions; the total percent area values are about the same.  The area experiencing Exceptional drought decreased slightly over the West and the percent area with no drought increased slightly, but remains at low levels.  Figure 2 also shows that the percent area with no drought decreased since the start of the year (24% to 14%).

Here are the current conditions for Colorado:

 photo CO_drought_monitor_201309033_zps07464c14.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of September 3rd.

There is clear evidence of relief evident over the past three months here.  Severe drought area dropped from 72% to 60% (this was 100% about last year!).  Extreme drought area dropped from 27% to 22% (also down from 50%+ six months ago).  Exceptional drought decreased significantly from three and six months ago.  Instead of 16% of Colorado (and as much as 17% earlier this year), Exceptional drought now covers only 3% of the state.  The good news for southeastern Colorado was the recent delivery of substantial precipitation.  I didn’t think it would be enough to completely alleviate the worst conditions, but they received enough precipitation that drought conditions improved from Exceptional to Extreme.  Their drought is not over yet, but they are finally trending in a good direction.  And for the first time in over one year, some small percentage (2%; up from 1% three weeks ago) of Colorado does not currently have any drought.  This is great news – hopefully this area expands throughout the rest of the year.

 photo midwest_drought_monitor_20130903_zpseafbaad1.png

Figure 4 – US Drought Monitor map of drought conditions in the Midwest as of September 3rd.

Drought expanded and worsened slightly in the Midwest in the past few months: the percent area with no drought decreased significantly from 91% to 52%.  The percent area with Moderate drought increased significantly from 3% to 29% this week.  Severe drought now impacts most of Iowa and small portions of Missouri, Wisconsin and Minnesota.

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.  Without comprehensive planning, dwindling fresh water supplies will threaten millions of people.  That very circumstance is already occurring in western Texas where town wells are going dry.  An important factor in those cases is energy companies’ use of well water for natural gas drilling.  This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water?  In the 21st century, we will not have both options available at the same time as happened in the 20th century.  This presents a radical departure from the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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45.3% of the Contiguous United States in Moderate or Worse Drought – 15 Aug 2013

According to the Drought Monitor, drought conditions improved recently across some of the US. As of Aug 15, 2013, 45.3% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  This value is about 10 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought increased from 14.6% to 14.8%; this is approximately 4% lower than it was six months ago. The eastern third of the US was wetter than normal during July into August, which helped keep drought at bay.  The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012.  Instead of Exceptional drought in Georgia and Extreme drought in Florida two years ago, there is flash flooding and rare dam water releases in the southeast.  Four eastern states experienced their top-four wettest Julys on record.  The West presents a different story.  Long-term drought continues to exert its hold over the region, as it remained warmer than normal but six southwestern states received top-20 July precipitation this year.  Meanwhile, Oregon recorded its driest July on record.

 photo USDrought20130815_zpse8a61c7f.gif

Figure 1US Drought Monitor map of drought conditions as of August 13th.

If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories.  Compared to early July, and despite recent rain events, drought expanded in the Midwest (into Iowa, Missouri, Illinois, and Minnesota) as well as Louisiana, Arkansas, and Mississippi.

Here is the Western US drought map this week:

 photo west_drought_monitor_20130815_zpsb980edee.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of August 15th.

After worsening during late winter into spring 2013, drought conditions steadied during the past month.  The differences between this map and early July’s is the spatial shift of conditions; the total percent area values are about the same.

Temporary drought relief occurred over parts of Arizona and Colorado as the summer monsoon brought moisture northward and interacted with cooler air masses than normal from Canada.

Here are the current conditions for Colorado:

 photo CO_drought_monitor_20130815_zps0644308d.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of July 9th.

There is clear evidence of relief evident over the past three months here.  Severe drought area dropped from 72% to 69% (this was 100% about six months ago!).  Extreme drought area dropped slightly from 27% to 26% (also down from 50%+ six months ago).  Exceptional drought is down significantly from three and six months ago.  Instead of 17% of Colorado, Exceptional drought now covers only 3% of the state.  The good news for southeastern Colorado was the recent delivery of substantial precipitation.  I didn’t think it would be enough to alleviate the worst conditions, but they received enough precipitation that drought conditions improved from Exceptional to Extreme.  Their drought is not over yet, but they are finally trending in a good direction.  And for the first time in over one year, some small percentage (1%) of Colorado does not currently have any drought condition.  This is great news – hopefully this area expands throughout the rest of the year.

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.  Without comprehensive planning, millions of people dwindling fresh water supplies will threaten millions of people.  That very circumstance is already occurring in western Texas where town wells are going dry.  An important factor in those cases is energy companies’ use of well water for natural gas drilling.  This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water?  In the 21st century, both options will not be available at the same time as they were in the 20th century.  This presents a radical departure from the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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44.9% of the Contiguous United States in Moderate or Worse Drought – 9 Jul 2013

According to the Drought Monitor, drought conditions improved recently across some of the US. As of Jul. 9, 2013, 47.3% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  That is the lowest percentage in a number of months. The percentage area experiencing extreme to exceptional drought increased from 14.6% to 14.8%, but this is ~4% lower than it was six months ago. The eastern third of the US was wetter than normal during June, which helped keep drought at bay.  The east coast in particular was  much wetter than normal.  Instead of Exceptional drought in Georgia and Extreme drought in Florida two years ago, there is flash flooding and rare dam water releases in the southeast.  Eight eastern states experienced their top-three wettest Junes on record.  The West is quite a different story.  Long-term drought continues to exert its hold over the region, as it remains warmer and drier than normal month after month.

 photo USDrought20130709_zpsc09f25c7.gif

Figure 1US Drought Monitor map of drought conditions as of July 9th.

If we focus in on the West, we can see recent shifts in drought categories:

 photo west_drought_monitor_20130709_zpse8877571.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of July 9th.

Early year snowmelt relief was short-lived, as drought conditions expanded as worsened in the past three months.  More than three-fourths of the West is in Moderate drought.  More than half of the West is now is Severe drought.  And one-fifth of the West is in Extreme drought.

Temporary drought relief might occur in New Mexico and southern Colorado due to the recent heavy rains brought by a retrograding low pressure system that also brought cooler than normal temperatures to Oklahoma and Texas.

Here are the conditions for Colorado:

 photo CO_drought_monitor_20130709_zps9faef3f3.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of July 9th.

There is some evidence of relief evident over the past six months here.  Severe drought area dropped from 95-100% to 83%.  Extreme drought area dropped significantly from 53% to 39%.  Exceptional drought shifted in space from central Colorado to southeastern Colorado, which left the percentage area near 17%.  The good news for southeastern Colorado is the recent delivery of substantial precipitation.  It isn’t likely to alleviate the long-term drought, but will hopefully dent short-term drought.

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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Ideology and Misperception in Energy and Climate

I could write a dissertation on this topic and spend the rest of my life researching and publishing on it.  I will have to settle for a short blog post for now, because my own research is in need of my attention.

People posted a number of tweets and articles on how “Political ideology affects energy-efficiency attitudes and choices“, which is the title of a new PNAS article.  The upshot: ideology trumps the free market.  This isn’t a surprise to me anymore – I’ve studied plenty of cases in the past two years that demonstrate this phenomenon.  In this case, peoples’ purchases of energy-efficient light bulbs were most influenced by what the bulb’s labeling stated.  The study made two stickers available: “Protect the Environment” or blank.  In both cases, the researchers made the same bulb benefits (energy use & cost) available to each potential purchaser.  The only difference was the presence of a blank or pro-environment sticker on the packaging.  With the pro-environmental sticker, conservatives were less likely to purchase the CFL bulb.  Without it, conservatives and liberals were equally likely to purchase the CFL bulb.  That’s not rational, which is a significant assumption of modern economic theory.  The result shows, unsurprisingly, that peoples’ behavior depends on their personal ideology and value system.  This has obvious implications for climate change activists: you have to operate in the value system of your targeted audience if you want them to receive your proposals well.  Beating the same drums harder won’t make conservatives care about climate change.

Climate groups are willfully failing elsewhere.  A new Yale Project on Climate Change Communication and George Mason University Center for Climate Change Communication poll demonstrates that increasing numbers of Americans are drawing incorrect conclusions from recent weather events to climate change.  The warmest year on record in the US (2012) was made more severe due to global warming, according to 50% of respondents.  A similar number believe the ongoing US drought is worse due to global warming.  The results go on and on.

Here is the rub: these beliefs have no basis in scientific fact.  2012 US temperatures were largely influenced by natural interannual variability.  It was warmer than 1998 by more than 1°F, which is significant.  But identifying a global warming signal in one year’s temperature data for the US is beyond the current capabilities of science.  We can say more robustly that the 2000s were significantly warmer than the 1990s, which were warmer than the 1980s, etc.  2012’s temperatures were extreme and it had implications that are still being felt by human and ecological systems.  The important point there is this: are existing systems capable of handling today’s weather extremes?  If not, we should do something.

The belief in climate change enhanced drought is also unsupported, as I wrote about a couple of weeks ago.  Initial findings from a NOAA-led team were unable to detect a global warming-related signal in either the onset, magnitude, or extent of the extraordinary 2012 drought.  This isn’t particularly surprising when you consider the last two droughts of similar extent and severity occurred in the 1950s and 1930s – prior to much anthropogenic forcing.  Specifically, they found that “The interpretation is of an event resulting largely from internal atmospheric variability having limited long lead predictability.”  Again, this drought is producing effects, but it isn’t directly attributable to climate change.  The question remains: are existing systems capable of handling these types of extreme events?  If they aren’t, we should do something about them, not draw unscientific causal linkages in an effort to build support for change.

The IPCC’s SREX report (Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation), issued just last year, reinforces this message.  There is a detectable global warming signal in a few measurable parameters such as temperature, water vapor, and sea level change.  But the climate system retains a great deal of natural variability which scientists do not fully understand.  Climate conditions will change in the next 90 years, but the likelihood of those changes varies.  Weather conditions may or may not change.  Their inherent transience makes it difficult to ascribe causal factors behind any changes.  Note further that climate projections of the 2090s are not climate conditions of the 2090s or 2010s.  Identifying likely future changes does not translate to detecting those changes today.

Yale and George Mason should digest their poll results along with the latest guidance from scientific peer-reviewed literature to help guide their communication efforts moving forward.  Given the results of this latest poll, they have their work cut out for them.  Framing, whether it is related to selling CFLs to a diverse public or differentiating between weather and climate, is critically important in climate communication.


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47.3% of the Contiguous United States in Moderate or Worse Drought – 25 Apr 2013

According to the Drought Monitor, drought conditions improved recently across some of the US. As of Mar. 12, 2013, 47.3% of the contiguous US is experiencing moderate or worse drought (D1-D4) as the 2011-2012 drought extended well into 2013.  That is the lowest percentage in a number of months. The percentage area experiencing extreme to exceptional drought increased from 14.6% to 14.7%, but this is ~3% lower than it was three months ago. Percentage areas experiencing drought across the West decreased in the past month as a series of late season cyclones impacted the region.  Drought across the Southwest worsened slightly while rain from storms maintained the low-level of drought conditions in the Southeast.

My previous post preceded the series of major winter storm that affected much of the US.  In some places in the High Plains and Midwest, 12″ or more of snow fell.  With relatively high liquid water equivalency, each storm dropped almost ~1″ of water precipitation, of which the area was in sore need.  Unfortunately, these same areas required 2-4″ of rain to break their long-term drought.  In other words, while welcome, recent snows have reduced the magnitude of the drought in many areas, but have not completely alleviated them.  Ironically, a very different problem arose from these storms: flooding.

 photo USDrought20130425_zps91e60b7e.gif

Figure 1US Drought Monitor map of drought conditions as of April 25th.

If we focus in on the West, we can see recent shifts in drought categories:

 photo west_drought_monitor_20130425_zpsf7678347.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of April 25th.

Some relief is evident in the past month (see table on left), including some changes in the mountains as storms recently dumped snow across the region.  Mountainous areas and river basins will have to wait until spring for snowmelt to significantly alleviate drought conditions.  As you can probably tell, this is a large area experiencing abnormally dry conditions for about one year now.

Here are conditions for Colorado:

 photo CO_drought_monitor_20130425_zpsbf9ccb2d.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of April 25th.

There is some evidence of relief evident over the past three months here.  Instead of 100% of the state in Severe drought, only 78% is today.  The central & northern mountains, as well as the northern Front Range (Denver north to the border) enjoyed the most relief since February.  The percentage area in Extreme drought also dropped significantly from 59% to 38%.  Exceptional drought shifted in space from northeastern Colorado to central Colorado while southeastern Colorado remained very dry.

Drought conditions improved somewhat across the southwestern portion of the state in the past couple of weeks.  The percentage area that is experiencing less than Severe drought conditions continues to track downward, which is a good sign.  Unfortunately, Exceptional drought conditions continued their hold over the eastern plains.

Here are conditions for the High Plains states:

 photo high_plains_drought_monitor_20130425_zps845616a5.png

Figure 4 – US Drought Monitor map of drought conditions in the High Plains as of April 25th.

The large storms that moved over this area in the past month reduced the worst drought conditions across Nebraska, South Dakota, and Wyoming.  The percentage area with Exceptional drought dropped from 27% to 7%; Extreme drought dropped from 61% to 28%; and Severe drought dropped from 87% to 70%.

With rather significant areas still experiencing moderate or worse drought across much of the US west of the Mississippi River, drought remains a serious concern in 2013.  I previously hypothesized that much of the 2012 drought was partly a result of natural climate variability and underlying long-term warming.  I wrote about NOAA’s examination into the causes of the 2012 drought a couple of weeks ago in which the authors suggested it was not heavily influenced by long-term warming.

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows when they turn their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as we will find this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


3 Comments

No Significant Climate Change Signal In 2012 US Drought

A team of atmospheric scientists, led by the National Oceanic and Atmospheric Association, issued a report this week that presented initial results of an examination into the extreme 2012 US drought.  Its core finding was the drought likely resulted mostly from natural variability.  Any climate change signal is relatively small but likely made conditions across the Midwest US a little dryer and a little warmer than they otherwise would have been absent climate change.

The 2012 drought did not grow out of the 2010-2011 Southern drought that impacted Texas and Oklahoma, as many, including myself, theorized as the drought developed.  Instead, a stubborn ridge of high pressure took hold over the Plains, which cut off the vital Gulf of Mexico water supply upon which the region depends for agriculture.

This sentence, in the Executive Summary, is key: “The interpretation is of an event resulting largely from internal atmospheric variability having limited long lead predictability.”  Many people think severe weather events should be easy to forecast, but the opposite is true.  The rarer the event, the more difficult it is to accurately forecast with any kind of time difference.  Additionally, the connection to low-frequency climate oscillations (i.e., La Niña: “the 2012 drought occurred in concert with an appreciably warmer ocean in most basins than was the case for any prior historical drought”) were minimal in the 2012 drought, contrary to what I have theorized.  That’s the beauty of science, of course.  You can be incorrect about something and demonstrate as such when data are analyzed.

Recently, some folks have characterized this event as a “flash drought”, owing to the sudden onset of such an event, as the first graphic below shows.  The term obviously borrows from the better known “flash flood” concept.  Unlike a flood however, droughts have longer-term impacts on human and ecosystems.  Costs are still only estimated at this time (because the drought is ongoing) at $12 billion.  While significant, the 1980 drought event that caused 56 billion (2012$) and the 1988 drought that caused 78 billion (2012$) of damages eclipsed the 2012 event (so far).  The $12 billion figure is likely to grow as the drought impacts water supply reductions and livestock.  The 2012 crop yield deficit was the greatest since 1866.

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Figure 1 – U.S. Drought Monitor maps showing the evolution of the 2012 “flash drought” across the US Great Plains.  Little evidence existed in November 2011 or even May 2012 that the drought would achieve the extent and intensity that it did.

The drought was the worst on record for WY, CO, NE, KS, MO, and IA, as the following graphic shows.  The region experienced a 53% rainfall deficit (39.3mm vs. 73.5mm) in 2012.  1934 held the previous record of -28.4mm deficit.  The 2012 deficit corresponds to a 2.7 standardized deficit, which approaches a 1-in-100 event.  This relates well to the precipitation time series in the graph below.

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Figure 2 – Precipitation and temperature departures from normal for the six states impacted by the 2012 drought.  Note the extreme minimum in precipitation on the right side of the top graph.  2012 temperatures as a whole were not as extreme as those recorded twice during the 1930s, but July 2012 still ranks as the warmest month on record for the six states as well as the entire US.

The analysis also suggests that we should not expect similar 2013 precipitation anomalies on the basis of 2012 anomalies alone (based on the report’s Figures 10 and 11).  Put another way, just because 2012 was drier than normal, 2013 shouldn’t automatically be drier also.  Dry epochs occurred in this region before: in the 1930s and 1950s.  Subsequent dry years occurred then due to longer-term changes in natural variability as well as land use practices.  The currently is no indication that the 2010s will similarly be a dry epoch.  As with the 2012 drought, such a prediction remains beyond current skill.

The diagnosed linkage to low-frequency forcing is interesting.  Warm tropical sea-surface temperatures (SSTs) in the Indo-West Pacific Oceans and cold east Pacific conditions tend to dry the mid-latitudes in the winter/spring season and not the summer season.  As the first graphic demonstrates, the 2012 drought flashed in the summer and not the winter.  So despite primed conditions for drying in winter 2011-12, the Great Plains drought occurred for different reasons.

Of further interest to the future is the following graphs.  The researchers generated a 20-member NCAR CAM-4 ensemble with monthly varying SSTs, sea ice, and specified external radiative forcings consisting of greenhouse gases (e.g. CO2, CH4, NO2, O3, CFCs), aerosols, solar, and volcanic aerosols via observations through 2005 and then an emission scenario thereafter (RCP6.0, a moderate emissions scenario pathway developed for the upcoming IPCC’s AR5).

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Figure 3 – Model results of the 1996-2012 precipitation minus the 1979-1995 precipitation.

The NCAR CAM4 model might be representing the actual climate well for this time period.  Left unsaid in the report is any analysis of the model’s future projections.  Other model studies suggest that the central US could experience 2012-type temperature and precipitation conditions more regularly by the end of the 21st century.

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Figure 4 – Model probability density functions of precipitation deficits for the six study states.

This figure suggests that the latter half of the time period (1996-2012) modeled had a higher probability of being drier than did the former half (1979-1995).  The report did not present a potential cause for this shift in probability.  If this probability does not revert back to the 1979-1995 distribution, dry conditions could become a more regular feature of future years.

 photo 2012Drought5-NOAAReport_zps4f4b62c1.png

Figure 5 – Model probability density functions of precipitation surpluses for the six study states.

This figure is not the logical companion to the previous figure.  The probability of being wetter and drier could increase if the overall probability density function existed in a certain way.    This is not the case however.  Instead, the probability of the six states experiencing wetter conditions in the second half of the period studied decreased with respect to the first half.

This report is useful in diagnosing what happened prior to and during the 2012 US drought and in trying to ascertain how predictable such an event might have been.  There is considerable interest in accurately predicting this type of event well in advance so as to prepare those who might be affected.  This capability remains beyond us for now since this event was primarily driven by natural variability enhanced slightly by underlying change.  With climate model projection studies indicating a much warmer and somewhat drier future for this region, stakeholders will likely have to adapt farming and ranching practices.  Similarly, municipalities will have to prepare for extremely dry years in their infrastructure planning and practices.  Of course, future change could be reduced as a result of our efforts to mitigate anthropogenic forcing.  The scale of that endeavor is much larger than most people are aware and thus not likely to take place any time soon.  Climate and energy policies need significant revamping at all levels.

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