Weatherdem's Weblog

Bridging climate science, citizens, and policy


Leave a comment

California’s Ongoing Drought & Related Climate News

California’s drought is severe and lengthy.  2013 was a record dry year for areas in the state with extensive data records: Los Angeles’s 3.60″ (14.93″ normal) and San Francisco’s 5.59″ (23.65″ normal) among others.  Recent research characterized California as drier than at any time in the past 500 years (an important point that I’ll return to below).  California experienced three consecutive very dry years (2011-2013), and 2014 provided little difference so far.  This dryness and the ensuing drought conditions are part of a longer term decadal-plus drought affecting the southwest US since 2000.

Additional metrics include:

Seventeen rural communities in California are in danger of running out of water within 60 to 120 days, according to a list compiled by state officials. As the drought goes on, more communities are likely to be added to the list.

With only about seven inches of rain in California in 2013 — far below the average of 22 inches — wells are running dry and many reservoirs are about 30 percent full (including Folsom Lake, shown above).

The Sierra snowpack, where California gets about a third of its water, was 88 percent below average as of Jan. 30.

Soon, people will face a lack of fresh water to their homes.  With reservoirs at record low levels, farmers will not be able to plant the crops they want which will reduce our food availability and increase food prices later this year.  This means the impacts will be local and national.  Moving forward, legal fights over very limited water will likely occur.  Folks are about to find out they water they’ve taken for granted is legally obligated to other users.  No one knows what the results will be, but many people have feared this very set of circumstances for a long time.

It would take between 8″ and 16″ of liquid water across most of California to break the drought.  That is unlikely to happen any time soon.  California’s drought is directly related to the snowy winter the eastern half of the nation experienced due to the persistent high-amplitude anomalous jet stream.  High pressure pushed the jet stream to the north over the western US while low pressure allowed the jet stream to dive south over the eastern US.  Usually such a pattern breaks down after a short time.  This winter’s jet stream has been essentially stuck for months now.

In related news, Arctic albedo decreased more than previously thought due to melting Arctic sea ice.  This phenomenon warms the Arctic, including the Arctic Ocean, which affects other parts of the globe, including the US.

And now back to the interesting point I wrote about above: CA is drier than at any point in the past 500 years.  Not forever, 500 years.  That means CA has been this dry in the past (the relatively recent past, in geologic time scales).  Moreover, we should all recall that CO2 concentrations were much lower 500 years ago than they are today.  That means that CA’s dryness is to some extent caused by natural variability.  The scientific question then becomes: “How much?”  Climate attribution studies remain at the forefront of climate research, which is another way of saying we don’t know how much natural variability plays a role in today’s dryness.

A NY Times article captured this recently:

While a trend of increasing drought that may be linked to global warming has been documented in some regions, including parts of the Mediterranean and in the Southwestern United States, there is no scientific consensus yet that it is a worldwide phenomenon. Nor is there definitive evidence that it is causing California’s problems.

The article notes that there are significant similarities between this drought and a similar drought in 1976-77.  What we do know is that temperatures are higher during this drought than they were in 1976-77, which exacerbates the drought’s effects.  What precipitation fell in 2013 evaporated more quickly than before because of warmer temperatures.  So we can say that a similar drought is occurring in a warmer environment, which is something relatively new and noteworthy.

An important point is that this drought is occurring in a world with higher CO2 concentrations than in 1976 or in the 1500s.  But this drought is similar to previous droughts.  Today’s higher CO2 concentrations aren’t the dominant cause of this drought.  Droughts later this century will likely have a more noticeable human fingerprint, but this drought could have (and did) occur in contemporary history.  There is nothing about today’s state of the climate (or 1970′s or 1930′s state of the climate) that precludes this drought.  Quite the opposite is true: this drought belongs to the state of the climate today, not tomorrow.

It is true that the southwest has been in some level of drought condition for 15 years or so.  Those conditions also exist in today’s climate.  They might also exist in the end of the century’s climate, but they will exhibit characteristics that we can’t foresee with any accuracy today.  That said, there are people today in the southwest US that this drought impacts.  That is the reality regardless of the anthropogenic or natural influence on the climate system.  The demand on annual available water now exceeds the supply.  That reality will increasingly shape the southwest in the near future, not the distant future.  Increasingly restrictive water usage policies are more likely than not.


Leave a comment

Denver’s September 2013 Climate Summary

Temperature

During the month of September 2013, Denver, CO’s (link updated monthly) temperatures were 2.8°F above normal (66.4°F vs. 63.6°F).  The National Weather Service recorded the maximum temperature of 97°F on the 5th and 6th; they recorded the minimum temperature of 38°F on the 28th.  Here is the Denver temperature September 2013 time series:

 photo Denver_Temps_201309_zps687d6b03.png

Figure 1. Time series of temperature at Denver, CO during September 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off with a heat wave, as a result of an anomalous high pressure ridge over the western US.  It’s not obvious on this chart, but the week of September 8th ushered in a big change from the early month heat wave, which I discuss in the precipitation section below.

Denver’s temperature was above normal for the past five consecutive months.  May 2013 ended a short streak of four months with below normal temperatures.  Looking back a little further in time, October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September, 2013, there were 57 90°F+ days in 2013, which means 2013 gained sole 4th place status of most 90°F days in one year.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).  After last year’s record hot summer, summer 2013 felt comparatively cool, which just goes to show how truly monumental last year’s records were.

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post.

Precipitation

Instead of amazing temperature records (although 97°F in September is very hot!), September saw precipitation records.  Total precipitation was much greater than normal during September 2013: 5.61″ precipitation fell at Denver during the month instead of the normal 0.92″!  Most of this fell at DIA on the 14th and 12th of the month (2.01″ and 1.11″).  As I wrote about after the event, Denver and other communities with similar rain totals paled in comparison to southern Aurora and Boulder, which received over 18″ of rain in one week, and more for the month!  Given that the normal annual total precipitation for these places is 15″, Denver and other places received over 1/3 of their yearly annual precipitation total in one month – a month that is normally relatively dry.

During the week of the 8th, the confluence of a slow-moving upper-level low, a surface stationary front, and tropical moisture from both the Pacific Ocean and Gulf of Mexico generated record rainfall over the northern Front Range of Colorado, including Denver.  This rainfall led to devastating flooding, from which communities are just beginning to recover.  About the only good news from this natural disaster is it busted the area’s long-term drought.

Interannual Variability

I have written literally hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


2 Comments

Epic Rain Event in Boulder, CO

A local emergency quickly became national news today: record-setting rainfall caused overnight flash flooding at multiple locations in and around Boulder, CO todaySome homes were swept away and reports list three people killed so far.  6.8 inches of rain fell in 24 hours by early morning today after rain fell for more than two previous days along the Front Range.  The previous rains saturated the ground, which set the stage for today’s life-threatening emergency.

From Monday through 11:30A today, eight to nine inches of rain fell over Boulder County.  This shattered the previous September record of 4.8″ of rain set in 1919!  These values are simply stunning in magnitude.  The rain continued to fall through the day today.  Additional rain is forecasted for tonight through Sunday, which means this disaster may not be over for days yet.

The flash floods and ongoing rainfall hampered rescue efforts since roads were washed out by creeks and helicopters were grounded.  Previous years’ wildfires left mountainsides outside of Boulder devoid of plant life, which allowed the majority of water that fell to flow directly into streams that are not equipped for these rainfall rates.  The cities of Lyons and Longmont are currently cut off from surrounding areas by flooding waters.  The effects spread this afternoon into north and east Denver suburbs.

These conditions were in stark contrast to different record-setting weather just last week.  Three daily high temperatures were set or tied at DIA: 97 on the 5th and 6th, 95 on the 7th.  Two record high low temperatures (nighttime) were also set: 68F on the 3rd and 69F on the 4th.  Daily average temperatures were 12 and 13 degrees warmer than normal during this late-season heat spell.  These were caused by a ridge of high pressure that previously slid west over the Front Range.

The same ridge of high pressure moved back to the east earlier in the week.  This allowed a cool front from Canada to slide south over the Denver metro area Monday.  It also allowed subtropical monsoon moisture flowing north to move over the Front Range.  The cool front brought moist low-level air in from the east and forced it up against the mountains.  The combination of low-level and high-level moisture with decent instability generated rains that started on Monday and haven’t really stopped very long since then.  The only good news is these rains will lessen the severity of the ongoing drought over the region.

This event harkens back to the Big Thompson River Flood of 1976.  More than 100 people died in that event, but it also occurred overnight.


1 Comment

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.


Leave a comment

Denver’s August 2013 Climate Summary

Temperature

During the month of August 2013, Denver, CO’s (link updated monthly) temperatures were 2.1°F above normal (74.6°F vs. 72.5°F).  The National Weather Service recorded the maximum temperature of 99°F on the 20th and they recorded the minimum temperature of 52°F on the 9th.  Here is the time series of Denver temperatures in August 2013:

 photo Denver_Temps_201308_zps974cdaa4.png

Figure 1. Time series of temperature at Denver, CO during August 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off cooler than normal as this year’s very active monsoon continued well into August 2013.  High pressure began to dominate the region again in the middle of the month.  Note the large number of days with daily mean temperatures equal to or greater than 78°F.  This was mainly due to the excessive nighttime heat (note the blue line above the climatological normal lows), but also the daily high temperatures in the mid to upper-90s.

Denver’s temperature was above normal for the past four months in a row.  May 2013 ended a short streak of four months with below normal temperatures.  October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September 4th, 2013, there were 50 90°F+ days in 2013, which ties three other years (1960, 1964, 2011) for 10th most 90°F days.  As of September 5th, the NWS forecast calls for an additional four days with maximum temperatures equal to or greater than 90°F, which would push the yearly total to 54, good for a tie for sixth place.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post..

Precipitation

Precipitation was greater than normal during August 2013: 2.78″ precipitation fell at Denver during the month instead of the normal 1.69″.  Most of this fell at DIA on the 22nd of the month (1.94″).  This wasn’t the case for every location in the Denver metro area however since precipitation is such a variable phenomenon.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013 (the exception being along the Front Range in northern Colorado, which received almost daily monsoon rainfall in August).  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.  The good news is this area shrank in the last month or so.  Colorado still needs the jet stream to substantially shift position this fall and next spring in order to receive the amount of precipitation required to break the long-term drought.  The last NWS 3-month projection didn’t indicate that this was likely to happen.  Hopefully, for the state’s sake, I hope the NWS is wrong.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


Leave a comment

Denver’s July 2013 Climate Summary

Temperature

During the month of July 2013, Denver, CO’s (link updated monthly) temperatures were 0.1°F above normal (74.3°F vs. 74.2°F).  The National Weather Service recorded the maximum temperature of 100°F on the 11th and they recorded the minimum temperature of 55°F on the 2nd.  Here is the time series of Denver temperatures in July 2013:

 photo Denver_Temps_201307_zps3eecd5f9.png

Figure 1. Time series of temperature at Denver, CO during July 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Compared to spring 2013, June and July brought less extreme weather to the Denver area.   After a very warm start to the month’s temperature due to high pressure that covered the area since mid-June, cooler temperatures were the rule for the 2nd half of the month.  This change was due to an active monsoon season.  Clouds formed nearly every day and the NWS measured rain 9 out of the last 18 days of the month – a big change from last year.

Denver’s temperature was above normal for the past three months (May- June-July).  May 2013 ended a short streak of four months with below normal temperatures.  Seven of the past twelve months were warmer than normal.  October finally broke last year’s extreme summer heat, which included the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Precipitation

Precipitation was lighter than normal during July 2013: only 1.98″ precipitation fell at Denver during the month instead of the normal 2.16″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received rainfall on days that the official Denver recording site did not, which is the usual case for convective-type precipitation.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however and the area with D4 conditions slowly expanded during the past few months.  Absent a significant shift in the upper-level jet stream’s position, the NWS expects dry conditions to persist over CO during the next one to three months, which will likely worsen drought conditions.


6 Comments

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.


2 Comments

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.


Leave a comment

Denver’s June 2013 Climate Summary

Temperature

During the month of June 2013, Denver, CO’s (link updated monthly) temperatures were 3.7°F above normal (71.1°F vs. 67.4°F).  The National Weather Service recorded the maximum temperature of 100°F on the 11th and they recorded the minimum temperature of 39°F on the 2nd.  Here is the time series of Denver temperatures in June 2013:

 photo Denver_Temps_201306_zpsee96454c.png

Figure 1. Time series of temperature at Denver, CO during June 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

In comparison to April 2013, June 2013 brought less extreme weather to the Denver area.   After a moderate start to the month’s temperature, high pressure began to dominate the area by the 11th through the end of the month.  This high pressure brought warmer than average temperatures, which offset the early month cool snap.  This same pattern brought warmer than average temperatures to much of the southwestern United States, culminating in extremely dangerous heat at the end of the month from Idaho to Arizona.

Denver’s temperature was above normal for the past two months in a row.  May 2013 ended a short streak of four months with below normal temperatures.  Seven of the past twelve months were warmer than normal.  October broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Precipitation

Precipitation was lighter than normal during June 2013: only 0.75″ precipitation fell at Denver during the month instead of the normal 1.98″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received rainfall on days that the official Denver recording site did not, which is the usual case for convective-type precipitation.

Precipitation a couple of months ago alleviated some of the worst drought conditions in northern Colorado.  The link goes to a late April 2013 post; further relief occurred in May with regular rain events.  With below average precipitation in June for most areas, drought conditions unfortunately worsened during the month.  All of Colorado continues under at least some measure of drought in early July 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however and the area with D4 conditions slowly expanded during the past few months.  Absent a significant shift in the upper-level jet stream’s position, the NWS expects dry conditions to persist over CO during the next one to three months, which will likely worsen drought conditions.  I will write an updated drought post within the week.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


Leave a comment

Denver’s May 2013 Climate Summary

Temperature

During the month of May 2013, Denver, CO’s (link updated monthly) temperatures were 0.8°F above normal (57.9°F vs. 57.1°F).  The maximum temperature of 88°F was recorded on the 17th while the minimum temperature of 19°F was recorded on the 2nd.  Here is the time series of Denver temperatures in May 2013:

 photo Denver_Temps_201305_zpsacd74199.png

Figure 1. Time series of temperature at Denver, CO during May 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

In comparison to March and April 2013, May 2013 brought much less extreme weather to the Denver area.   After a cold start to the month, there was a general regime change that allowed high pressure to dominate in the middle and at the end of the month.  This high pressure brought warmer than average temperatures, which offset the early month cold snap.

Precipitation

Precipitation was lighter than normal during May 2013: only 0.82″ precipitation fell at Denver during the month instead of the normal 2.12″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received higher than normal precipitation during the same time period.

Precipitation in the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a late April 2013 post; further relief occurred in May with regular rain events.  All of Colorado continues under at least some measure of drought in early June 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.

Follow

Get every new post delivered to your Inbox.

Join 248 other followers