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Bridging climate science, citizens, and policy


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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.


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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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4th Daily April Record Low in Denver & Record Snow in Boulder

I spent a lot of time on record temperatures in Colorado in 2012 – they were all record highs.  Due to annual weather variability, there are a couple of different records in April 2013: record lows.  There have been four record lows set or tied in Denver, CO this April:

9F on April 9th

6F on April 10th

22F on April 16th (tie)

21F on April 22nd

Needless to say, with record low temperatures due to vigorous synoptic cyclones that brought Arctic air masses down into the middle of the country, April’s average temperature is among the lowest on record.  I will have more to say about that next week after the month ends.  Denver may not record a bottom-10 moth because much more seasonable weather is on tap for the next week.  In contrast, two record highs were set in April 2012: 84F on the 1st and 88F on the 24th.

In other news, Boulder, CO set a monthly record for snowfall: 47.4″ through the 23rd!  The old record of 44″ was set in 1957.  The official snowfall measurement site for Denver (Denver Int’l Airport) recorded “only” 20.4″ of snow for the month-to-date.  With 60F+ temperatures forecasted from today through next Tuesday, DIA won’t challenge the top-10 snowiest Aprils (#10 recorded 21.0″ of snow).

Remember that one month’s, season’s or year’s temperatures, precipitation, or even drought are not indicative by themselves of climate change.  They are too heavily influenced by individual weather systems.  When I discuss climate change, I write about long-term trends (decadal to multi-decadal).  Natural variability influences individual weather events that overlie the long-term climate signal.  I’ve written before that climate change means we are more likely to see record high temperatures than record low temperatures.  The weather will continue to set both, but will set the former at a higher rate moving forward than the latter.  Of course, I for one am very glad there was more precipitation than normal for April.  Last year’s drought and record hot summer was not enjoyable to live through.  Denver-Boulder and the surrounding region will unfortunately need months in a row of above average precipitation to break the long-term drought.  This spring’s precipitation pattern slightly reduced the intensity and areal coverage of drought.  I will update my last drought post in the next couple of days.


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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.

 photo 2012Drought-NOAAReport_zpsde8de4b2.png

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.

 photo 2012Drought2-NOAAReport_zpsa23b4e6a.png

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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Extreme Weather, Climate Change, and Public Reporting

If you have had any exposure to this subject, you probably already have your mind made up about my title. As I’ve gained exposure, via multiple disciplines, I’ve changed my mind. And that allows me to look at climate reporting in new ways.  Take this article and interview for instance. It’s meta-related, masked by the climate’s relationship to extreme weather. There are thousands of examples of conservatives ignoring science when it suits them. Doing so actually has more to do with conservatives operating from their value system. Are there similar examples of others ignoring science when it similarly suits them? I think it would be foolhardy to assume otherwise. Here is what I think about this article.

First, the mask: climate-extreme weather. There is no documented causal relationship between the two. In fact, the number of identified causal relationships between climate change and anything is still relatively small. There is a strong temperature signal. There is a growing ocean acidification signal. The sea level change signal is small but present and growing. How about precipitation? Nothing definitive. How about snowstorms? Nothing definitive.

But those signals are small against much stronger climate signals. Would something like drought or hurricanes or floods or tornadoes exhibit a stronger signal. In a word, no. There simply is not a detectable climate and extreme weather link today. That is not to say a future signal will not exist – there very well might be. But as of today, there is not. What science backs up that claim? The 2008 U.S. Climate Change Science Program’s Synthesis Report for starters (p.42; 2.2.2.1):

When averaged across the entire United States (Figure 2.6), there is no clear tendency for a trend based on the PDSI. Similarly, long-term trends (1925-2003) of hydrologic droughts based on model derived soil moisture and runoff show that droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the U. S. over the last century (Andreadis and Lettenmaier, 2006).

So as of the early 21st century, U.S. droughts have become less severe, not more. The IPCC’s global analysis on extreme events concurred (p.171):

There is not enough evidence at present to suggest high confidence in observed trends in dryness due to lack of direct observations, some geographical inconsistencies in the trends, and some dependencies of inferred trends on the index choice. There is medium confidence that since the 1950s some regions of the world have experienced more intense and longer droughts (e.g., southern Europe, west Africa) but also opposite trends exist in other regions (e.g., central North America, northwestern Australia).

One big impediment to our extreme event trend ascertainment is our basic inability to monitor events in the first place. But based on the observations made, there is, in the IPCC’s own language, only medium confidence that droughts in some areas of the world are increasing in severity while decreasing in other places. Is climate change increasing extreme events? Not droughts – not yet.

What about storms like Sandy or Katrina (note: the former was a tropical system that changed to an extratropical system at landfall while the latter was a full-fledged hurricane at landfall)? There is at this time no global trend in hurricane frequency or intensity that demonstrates a clear causal relationship to climate change. There are indexes that a few scientists have developed to examine the data in different ways with differing results, but they require fairly complex methodologies to calculate. If I created my own index that demonstrated a relationship between the type of food I ate and climate change, does one cause the other? Certainly not directly. The hurricane-climate change relationship should exhibit a detectable signal in 50 more years or so. Until then, scientists cannot confidently say the data supports such a relationship. Extratropical storms increased in strength a little over the past century, although the locations of increase are limited. Their frequency has not increased.

Quickly, the same thing holds for floods and tornadoes. Datasets are simply too limited in space and time to currently identify a robust relationship.

As I wrote above, there are clear signals that we have already detected. The effects of those signals are mostly well-known, although some surprises are certainly in store for the planet. Extreme weather is not one of those signals. At least, not yet. If people are concerned about the level of inaction taken on climate change to date, it is folly to chase down or exaggerate signals that do not yet exist. If arguments based on signals detected are not enough to propel action, then we need to address their sets of values and how we communicate them. Fear-mongering and purposeful ignorance of science are not adequate substitutes.

Finally, I question the following from the article:

“I quote the climate skeptics or deniers — whatever term you prefer — when they’re relevant. So when I’m doing a piece about the science itself and what the latest scientific findings are, especially if that’s a short piece, I don’t necessarily feel obliged to quote the climate skeptics the same way that if you were doing a story about evolution, a New York Times reporter wouldn’t feel obliged to call up a creationist and ask them what they think. On the other hand, the climate skeptics are politically relevant at this point in American history [in a way that] the creationists are not, for example. So we have a fair chunk of the Congress … that sees political traction right now in questioning climate science or purporting not to believe it, so in a political story or in a longer story, I usually do give some amount of space to the climate skeptics.”

This quote comes from Justin Gillis, who writes about climate change for The New York Times. Does any of the above evidence make it into his interview with NPR? Here is my question: is Mr. Gillis a climate change writer or a politics writer? Scientific climate change writers should focus on the science. If Mr. Gillis wants to be a political climate change writer, he and the NYT owe it to their readers to make that distinction clear. Especially when double standards are applied to a different type of science writing. I would argue that creationists have a considerable amount of political traction right now also. I do not agree with their viewpoint, but if Mr. Gillis and the NYT want to write comparison pieces and not news pieces, I do not see why that effort should stop at climate change.


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Agricultural and Economic Effects of US Drought

In the wake of the hottest year on record for the contiguous US:

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Figure 1 – NOAA Graph showing year-to-date average US temperatures from 1895-2012.

Plus extensive moderate and worse drought conditions across the US agricultural region heading into early 2013:

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Figure 2 – US Drought Monitor map of drought conditions as of the 8th of January.

The US Department of Agriculture released estimates for 2013 crops.  The larger picture isn’t pretty, as the link explains.  Due to climatological as well as global market pressures, crop prices have risen leading up to 2013.  We can expect those prices to rise further in 2013, especially if there is limited or nonexistent drought relief.  Consider the following:

Corn prices are 3x what the average price from 1988-2006.

Soybean prices are more than 2X their average price from 1988-2006.

Wheat prices are more than 2X their average price from 1988-2006.

If nothing else, we will likely see a great deal of price volatility in crop prices in 2013.  But any further price increases will pinch most of our bank accounts more so than they already are.  This is another downstream effect of climate change and the lack of a national climate policy.  Moreover, how are farmers supposed to stay afloat if they never take climate change effects (record high temperatures and widespread drought) into account?  As elected officials in D.C. continue to think there is not enough political capital in return for climate change action, crop prices double and triple, impacting every person in the country.  We need to remove the politicization surrounding the issue.


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2012: Hottest Year On Record For United States

It’s official: 2012 was indeed the hottest year in 100+ years of record keeping for the contiguous U.S. (lower 48 states).  The record-breaking heat in March certainly set the table for the record and the heat just kept coming through the summer.  The previous record holder is very noteworthy.  2012 broke 1998′s record by more than 1°F!  Does that sound small?  Let’s put in perspective: that’s the average temperature for thousands of weather stations across a country over 3,000,000 sq. mi. in area for an entire year.  Previously to 2012, temperature records were broken by tenths of a degree or so.  Additionally, 1998 was the year that a high magnitude El Niño occurred.  This El Niño event caused global temperatures to spike to then-record values.  The latest La Niña event, by contrast, wrapped up during 2012.  La Niñas typically keep global temperatures cooler than they otherwise would be.  So this new record is truly astounding!

The official national annual mean temperature: 55.3°F, which was 3.3°F above the 20th century mean value of 52°F.

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Figure 1 – NOAA Graph showing year-to-date average US temperatures from 1895-2012.

This first graph shows that January and February started out warmer than usual (top-5), but it was March that separated 2012 from any other year on record.  The heat of July also caused the year-to-date average temperature to further separate 2012 from other years.  Note the separation between 2012 and the previous five-warmest years on record from March through December.  Note further that four of the six warmest years on record occurred since 1999.  Only 1921 and 1934 made the top-five before 2012 and now 1921 will drop off that list.

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Figure 2 – Contiguous US map showing state-based ranks of 2012 average temperature.

Nineteen states set all-time annual average temperature records.  This makes sense since dozens of individual stations set all-time monthly and annual temperature records.  Another nine states witnessed their 2nd warmest year on record.  Nine more states had top-five warmest years.  Only one state (Washington) wasn’t classified as “Much Above Normal” for the entire year.  The 2012 heat wave was extensive in space and severe in magnitude.

Usually, dryness tends to accompany La Niña events for the western and central US.  This condition was present again in 2012, as the next figure shows.

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Figure 3 – Contiguous US map showing state-based ranks of 2012 average precipitation.

As usual, precipitation patterns were more complex than were temperature patterns.  Record dryness occurred in Nebraska and Wyoming.  Colorado and New Mexico saw bottom-five precipitation years.  Severely dry conditions spread across the Midwest all the way to the mid-Atlantic and Georgia continued to experience dryness.  Washington and Oregon were wetter than normal as a result of the northerly position of the mean jet stream in 2012.  Louisiana and Mississippi saw wetter than normal conditions, largely as a result of Hurricane Isaac.

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Figure 4 – Contiguous US map showing state-based average actual precipitation.

I always find it useful to know the magnitude of measurements as well as how they stack up comparatively.  Figure 4 provides the former while Figure 3 provides the latter.  “Normal” precipitation varies widely across the country and even between neighboring states.  How much precipitation fell to allow NE and WY to record driest years on record?  13.04 and 8.03″, respectively.  Another useful map would be state-based difference from “normal”.

So the brutal heat that most Americans experienced was one for the record books.  As the jet stream remained in a more northerly than usual position, heat across the country dominated.  More heat and fewer storm systems in 2012 meant widespread and severe drought expanded across the country.  That drought tended to reinforce both the temperatures recorded (drying soils meant incoming solar radiation was more easily converted directly to sensible heat) and the lack of precipitation (dry soils required extra moisture to return to normal conditions).

Thankfully, record-setting temperatures didn’t occur all over the globe in 2012 (although Australia is having their own problems now in 2013).  I therefore don’t expect 2012 will be the warmest year on record globally, but a top-10 finish certainly is not out of the question.  Again, this is significant because of the extended La Niña event that ended in mid-2012.  Without the influence of anthropogenic (man-made) climate change, 2012 probably would have been cooler than will be recorded.  The background climate is warming and so La Niñas today are warmer than El Niños of yesterday.

These warming and drying conditions have massive implications for our society.  The drought that afflicted the Midwest in 2012 helped push up commodity prices as crops failed.  If that trend continues into 2013, prices will rise further, which will pinch all of our finances.  Drought in the Southwest and Midwest impacted flows in rivers (Colorado & Mississippi, among others).  The former could mean imposed restrictions in 2013 while the latter could mean reduced river transportation, which puts further pressure on goods sold in the US.  Conditions aren’t the worst recorded yet, but it is imperative that we examine resource management policies.  Are policies robust enough to handle the variability of today’s climate?  If not, they probably aren’t equipped to address future variability or change either.  What systems are critical to today’s society?  If the Southwest remains dry, does agriculture (largest user of CO river water) reduce its use or do urban users?  What sets of values guide these and other decision-making processes?


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Drought Continues To Affect Middle U.S.

The extensive and high magnitude drought that has afflicted various parts of the U.S. continues late into the 2012 calendar year.  These conditions will only be alleviated if significant changes in precipitation patterns occur in 2013.  I wanted to do a quick post on this topic as a significant winter storm is making its way across the country so I can do a before/after look next week.  This storm will largely impact the inter-mountain west as some places receive 1 to 3 feet of snow.  Some slight relief will also be felt across the High and northern Great Plains as a blizzard impacts the region today and tomorrow.  Here are drought conditions in the West as of last week:

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The percent area values haven’t changed too much since early July, but the specific areas impacted have moved around somewhat in response to weather systems in the intervening time period.  The mountains in this region are experiencing their own drought, just as the inter-mountain plateaus are.

Look at the High Plains, which saw drought conditions expand and worsen quickly this summer and fall:

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Only a tiny stretch of North Dakota is not currently experiencing any level of drought.  A majority of the High Plains is actually in Extreme drought (red or dark brown).  These conditions developed rapidly north of 40 degrees latitude (northern border of Kansas) this year.  These locations will benefit somewhat from winter snow, but need spring and summer rain to really get rid of this drought.

Denver Area

So far in the month of December, the average temperature for Denver, CO is 37.3°F, which is 7.1°F above normal.  The next week or so will include near and below average temperatures, which will reduce this anomaly.  With only 12 days left in the month however, December will likely be another month in 2012 that higher than normal temperatures were the rule.  Denver’s average November temperature was 43.5°F, 5.2°F above normal.  October bucked the 2012 trend with a -1.9°F anomaly (49.0°F average).  September was 2.9°F above normal (66.3°F average).

In November, there was a -0.34″ precipitation deficit from normal.  October was slightly more wet than normal: +0.20″ (1.22″ total), as was September: +1.99″ (2.95″ total).  This is largely why drought severity in the Denver area is only moderate and not severe or extreme.  Note that most of the positive precipitation anomaly in September was the result of one storm which rained overnight on the 25th into the 26th (1.95″).  Without this storm, local drought conditions would likely be worse.

Precipitation for 2012 remain anomalously low.  The NWS recorded 9.89″ of precipitation so far this year, compared to a normal of 14.17″ (-4.28″ or 30% deficit).  In contrast, 2011 was a wet year with 17.31″ through Dec. 31st.  We all hope 2013 returns to normal or above average conditions so that this drought ends.

Data from Denver-Boulder NWS Office.


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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.

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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.

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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:

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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:

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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:

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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.

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