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:

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.

Denver’s April 2013 Climate Summary With A Bonus

During the month of April 2013, Denver, CO (link updated monthly) recorded a 74°F difference between maximum and minimum temperatures.  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 5.7°F below normal (41.7°F vs. 46.4°F).  The maximum temperature of 80°F was recorded on the 29th while the minimum temperature of 6°F was recorded on the 10th.  Here is the time series of Denver temperatures in April 2013:

Figure 1. Time series of temperature at Denver, CO during April 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]

There is a big disparity between 2013 temperatures and normal temperatures, especially daily maxima.  Three outbreaks of Arctic air impacted Denver during the month, which set record low temperatures on four different days.  This graph also shows something else that is eye-opening: five daily maximum temperatures were equal to or lower than the climatological daily minimum temperature!  As someone who was ready for spring to spring, April was a disappointing weather month.

But it also got me to thinking about the difference between spring 2013 and spring 2012.  As many of us remember, temperatures in the US in 2012 were very warm compared to climatological norms.  So how different were temperatures in Denver in February-March-April 2013 versus 2012?  I decided to take a look.  Let’s start with extending the dates in Figure 1 back to the beginning of February 2013:

Figure 2. Time series of temperature at Denver, CO during February-April 2013.  Daily high temperatures are in red, daily low temperatures are in blue, climatological normal (1981-2010) high temperatures are the top dark gray line, and normal low temperatures are the bottom dark gray line. [Source: NWS]

This graphic simply demonstrates the same story that I wrote above as well as in my March and February Denver Climate Summary posts.  February was obviously colder than normal due to extended cold air masses over the area.  March and April were also colder than normal, but this was due to vigorous mid-latitude cyclones that brought Arctic air masses south over the area.  This is evident by the significant dips in both maximum and minimum daily temperatures: there was one in the beginning of March, another in the end of March, and three in April.

With this chart in mind, let’s look at the difference between 2012 and 2013.  First, daily maximum temperatures:

Figure 3. Time series of maximum temperature at Denver, CO during February-April 2012 and 2013.  2013 temperatures are in brick-red, 2012 temperatures are in red, and climatological normal (1981-2010) high temperatures are the dark gray line with green crosses. [Source: NWS]

My memory of 2012′s maximum temperatures was close to reality.  February 2012 was colder than I remember, but this was likely affected by the warmth of April 2012 and the record-setting daily highs in the summer of 2012.  Figure 3 shows a very large difference between daily maximum temperatures in 2012 and 2013, especially after the 22nd of March.  I didn’t remember the cold snap on April 3, 2012.  This graphic shows, by proxy, the lack of spring synoptic storms in 2012.  Daily maximum temperatures rarely fell below the normal for the date.  Instead, April temperatures were as much as 20°F warmer than normal on some dates, but regularly 10°F warmer than normal.  In contrast, 2013 temperatures were often 25-30°F colder than normal.  The difference between two years’ temperatures is a measure of interannual weather variability.  I have more on that below.

Figure 4. Time series of minimum temperature at Denver, CO during February-April 2012 and 2013.  2013 temperatures are in blue, 2012 temperatures are in green, and climatological normal (1981-2010) high temperatures are the dark gray line with brown pluses. [Source: NWS]

Again, February 2012′s temperatures were similar to February 2013′s.  The specific dates of temperature swings obviously varies between the two years.  March 2012 and March 2013 also look similar, up until the 22nd of March (see maximum temperatures above also).  Thereafter, the time series diverge with much colder air in place over Denver four different times through the end of April.  2012 had warmer than normal minimum temperatures through most of April.  The combination of warmer than normal nights and days, combined with a relative lack of precipitation in 2012 set the stage for the record-setting warmth in the summer as well as the rapid decline in drought conditions, which are still largely present now.

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.

Precipitation

Precipitation was above normal again during April 2013, extending this new trend to three months.  During the month, 1.87″ of liquid water equivalent precipitation fell, compared to 1.71″ normally.  The wettest April on record was in 1983 when 4.56″ of precipitation fell.  There were three notable weather events during April: a 6″+ snowstorm on the 9th, a 7″+ snowstorm on the 15th, and a 5″+ snowstorm on the 22nd.  In total, the NWS recorded 20.4″ of snow.

The recent precipitation surplus reduced northeast CO drought severity in the last three m months, but did not break it yet.  Above-average precipitation will have to fall for longer than three months for that to happen.  The NWS expects continued drought conditions across most of Colorado through the next three months.  Additional improvement in eastern Colorado might occur, but NOAA and the CPC expects western Colorado drought  to remain the same or worsen.

Ideology and Misperception in Energy and Climate

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Here are conditions for Colorado:

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

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

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

Here are conditions for the High Plains states:

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

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

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

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

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

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

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.

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.

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).

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.

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.

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.

Denver’s March 2013 Climate Summary

During the month of March 2013, Denver, CO (link updated monthly) recorded a 74°F difference between maximum and minimum temperatures.  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 2.7°F below normal (37.7°F vs. 40.4°F).  The maximum temperature of 76°F was recorded on the 15th while the minimum temperature of 2°F was recorded on the 25th.

Figure 1. Time series of temperature at Denver, CO during March 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]

Precipitation was above normal again during March 2013, making a two-month trend.  During the month, 1.47″ of liquid water equivalent precipitation fell, compared to 0.92″ normally.  The wettest March on record was in 1983 when 4.56″ of precipitation fell.  There were two notable weather events during March: a 6″+ snowstorm on the 9th and the 23rd.  In total, the NWS recorded 23.5″ of snow, 13.5″ more than the normal of 10.0″ for the month.

While more precipitation fell than normal during the month, the drought impacting the region was still not broken.  Above-average precipitation will have to fall for longer than one month for that to happen.  The NWS expects continued drought conditions across most of Colorado through the next three months.  Some improvement in northeast Colorado might occur.  In contrast to February and March, the NWS projects warmer and drier than normal conditions over Colorado during the next three months.

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.

51.4% of the Contiguous United States in Moderate or Worse Drought – 12 Mar 2013

According to the Drought Monitor, drought conditions improved recently across some of the US. As of Mar. 12, 2013, 51.4% of the contiguous US is experiencing moderate or worse drought (D1-D4).  That is the lowest percentage in a number of months. The percentage area experiencing extreme to exceptional drought increased from 17.7% to 16.5% in the last month. Percentage areas experiencing drought across the West stayed mostly the same while snowpack generally increased. Drought across the Southwest decreased slightly and rain from storms improved drought conditions in the Southeast.

My previous post preceded a major winter storm that affected much of the US.  In some places in the High Plains and Midwest, 12″ or more of snow fell.  With relatively high liquid water equivalency, this snow represented ~1″ of water precipitation.  Unfortunately, these same areas required 2-4″ of rain to break their long-term drought.  In other words, while welcome, recent snows have not substantially reduced drought severity affecting the middle of the nation, as the following map shows.

Figure 1 – US Drought Monitor map of drought conditions as of the 12th of March.

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

Figure 2 – US Drought Monitor map of drought conditions in Western US as of the 12th of March.

Some small relief is evident in the past couple of weeks, including some changes in the mountains as storms recently dumped snow across the region.  Mountainous areas and river basins will have to wait until spring for snowmelt to significantly alleviate drought conditions.  As you can probably tell, this is a large area experiencing abnormally dry conditions for almost a year now.

Here are conditions for Colorado:

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of the 12th of March.

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

Here are conditions for the High Plains states:

Figure 4 – US Drought Monitor map of drought conditions in the High Plains as of the 12th of March.

Again, even with large snowfalls in the past month, little drought relief is evident across this region.  What these states need are frequent soaking rains in the spring and summer to alleviate their long-term drought.  Agriculture certainly could use that relief this year.

And finally the area that experienced the most relief in the past month, the Southeast:

Figure 5 – US Drought Monitor map of drought conditions in the Southeast as of the 12th of March.

The shifts in the numbers in the table tell a good story.  Frequent storms tracked over this region recently, which helped bust the worst conditions (Severe and worse).  Look at the ‘None’ category now versus three months ago: the percent area doubled!  Now the rains need to continue through the rest of the year.

US drought conditions are related to Pacific and Atlantic sea surface temperature conditions.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Nino-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, their policy responses vary.  A growing number of water utilities recognize the need to be proactive with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows when they turn their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation.  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.  Warmer conditions include warmer water today than what existed 30 years ago.  Warmer water into a plant either mean warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  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.

55.7% of the Contiguous United States in Moderate or Worse Drought – 12 Feb 2013

According to the Drought Monitor, drought conditions are relatively unchanged in the past two weeks. As of Feb. 12, 2013, 55.7% of the contiguous US is experiencing moderate or worse drought (D1-D4). The percentage area experiencing extreme to exceptional drought increased from 19.4% to 17.7% in the last two weeks. Percentage areas experiencing drought across the West stayed mostly the same while snowpack increased. Drought across the Southwest decreased slightly. Meanwhile, storms improved drought conditions in the Southeast.

This post precedes a significant snow event across the High and Great Plains.  The NWS expects up to a foot of snow in some areas of the Plains over the next couple of days, which will provide about 1″ of liquid water equivalent.  Since these areas currently suffer from a 2-4″ liquid water deficit, this storm will not break the short-term drought.  Moreover, long-term drought will only be broken by substantial spring and summer rainfall.  After one or two more Drought Monitor updates, we should see some welcome differences in these maps.

Figure 1 – US Drought Monitor map of drought conditions as of the 12th of February.

Figure 2 – US Drought Monitor map of drought conditions in Western US as of the 12th of February.  Some small relief is evident in the past week, including some changes in the mountains as storms recently dumped snow across the region.  Mountainous areas and river basins will have to wait until spring for snowmelt to significantly alleviate drought conditions.

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of the 12th of February.  Drought conditions held mostly steady across the state in the past week.  For the first time in over a month, less than 100% of CO is experiencing Severe drought conditions.  This improvement occurred over the southwestern portion of the state due to mid-season snow storms.  Unfortunately, Exceptional drought conditions expanded over the northeastern plains.

Figure 4 – US Drought Monitor map of drought conditions in Southeast US as of the 12th of February.  As mentioned above, drought conditions contracted a little and grew less severe in the past couple of weeks.  The worst hit area, in central Georgia, has experienced the longest duration drought conditions on this map.

Cooler than normal sea-surface temperatures (SSTs) are present in the eastern Pacific, according to current MJO and ENSO data.  Additionally, eastern Pacific SSTs are cooler than the climatic average due to the current negative phase of the IPO.  This in turn is due in part to global warming, which is causing warmer western Pacific and Indian Ocean SSTs than usual.  The cool SSTs in the eastern Pacific initiate and reinforce air circulations that generally keep precipitation away from the Southwest and Midwest US.  This doesn’t mean that drought will be ever-present; only that we are potentially forcing the climate system toward more frequent drought conditions in these regions.  Some years will still be wet or normal; other years (increasing in number) will be dry.  This counters skeptics who claim that more CO2 and warmer temperatures are better for plants.  If there is no precipitation, plants cannot take advantage of longer growing seasons.  Moreover, we will experience years with increased food pressure.  These conditions’ extent in the future is up to us and our climate policy (or lack thereof).

While MJO, ENSO, and IPO are all in phases that tend to deflect storm systems from the Southwest, this week’s storm demonstrates that the conditions are not ever-present.  Weather variability still occurs with the dryer regime.  Put another way, weather is not climate.

57.7% of Contiguous US in Moderate or Worse Drought – 29 Jan 2013

According to the Drought Monitor, drought conditions are relatively unchanged in the past two weeks. As of Jan. 29, 2013, 57.7% of the contiguous US is experiencing moderate or worse drought (D0-D4). The percentage area experiencing extreme to exceptional drought increased from 19.3% to 19.4%. Percentage areas experiencing drought across the West stayed mostly the same at the end of January as they were at in the middle. Drought across the Southwest decreased slightly. Meanwhile, drought across the Southeast grew due to relative lack of precipitation.

Figure 1 – US Drought Monitor map of drought conditions as of the 29th of January.

Figure 2 – US Drought Monitor map of drought conditions in Western US as of the 29th of January.  Some small relief is evident in the past week, but note the lack of change of drought conditions across the regions, despite recent snows throughout the mountains.  Mountainous areas and river basins will have to wait until spring for snowmelt to help start to alleviate drought conditions.

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of the 29th of January.  Drought conditions held steady across the state in the past week.  100% of Colorado experienced Severe or worse drought conditions for the past three weeks.

Figure 4 – US Drought Monitor map of drought conditions in Southeast US as of the 29th of January.  As mentioned above, drought conditions expanded and worsened in the past couple of weeks.  The worst hit area, in central Georgia, has experienced the longest duration drought conditions on this map.  Drought has expanded and contracted around this area during that time.

The latest seasonal (three-month) outlook from the National Weather Service predicts enhanced chances for above-average temperature and below-average precipitation for the central US.  This means that drought conditions are likely to continue for at least another three months and probably longer if prevailing conditions do not change.  One of the major weather stories of 2012 was drought; 2013 is shaping up to have the same story.

What is causing this?  A combination of factors: the Arctic Oscillation (AO), the Madden-Julian Oscillation (MJO), the El-Nino and Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO), and background climate warming.

As I discussed in my last drought post:

The lack of sea ice in the Arctic back in September is part of what caused the negative phase of the AO.  The Arctic Ocean absorbed solar radiation instead of reflecting it back to space.  The ocean then slowly released that heat to the atmosphere before new ice could form.  That extra heat in the atmosphere changed how and where the polar jet stream established this winter.  Instead of a tight loop near the Arctic Circle, the jet stream has grown in North-South amplitude, allowing cold air to pour to latitudes more southerly than usual and warm air to move over northern latitudes.  The large amplitude jet has kept the normal type of storms from moving over locations that used to see them regularly during the winter.

An active MJO is keeping trade winds stronger than they otherwise would be, which piles up warm ocean water in the western tropical Pacific Ocean.  This causes cool, deep ocean water to rise in the eastern Pacific, as seen in Figure 5.

Figure 5 – Madden-Julian Oscillation conditions as of 2 Feb 2013 from NOAA-CPC.

Figure 6 – ENSO conditions as of 2 Feb 2013 from NOAA-CPC.

Cooler than normal sea-surface temperatures (SSTs) are present in the eastern Pacific due to the current MJO and ENSO data.  Additionally, eastern Pacific SSTs are cooler than the climatic average due to the current negative phase of the IPO.  This in turn is due in part to global warming, which is causing western Pacific and Indian Ocean SSTs warmer than usual.  The cool SSTs in the eastern Pacific initiate and reinforce air circulations that generally keep precipitation away from the Southwest and Midwest US.  This doesn’t mean that drought will be ever-present; only that we are potentially forcing the climate system toward more frequent drought conditions in these regions.  Some years will still be wet or normal; other years (increasing in number) will be dry.  This is a counter to skeptics who claim that more CO2 and warmer temperatures are necessarily better for plants.  If there is no precipitation, plants cannot take advantage of longer growing seasons.  Moreover, we will experience years with food pressure.  These conditions’ extent in the future is up to us and our climate policy (or lack thereof).