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.

Record Low Temperatures for Denver, CO Today

An arctic air mass plunged down the east side of the Rocky Mountains in the past day.  This air mass will cause record low temperatures for the Denver, CO area.  According to the NWS, the record low maximum temperature for April 9th is 27F, which was set in 1973.  The record low minimum temperature for April 9th is 12F, which was set in 1959.  The temperature at DIA at midnight this morning was 24F.  The maximum temperature during the day today will not be higher than 20F, which means the calendar day’s maximum temperature has likely already been set.  It’s 15F right now, which is quite frigid for April in Denver.

The storm system that brought this cold air to the area was also supposed to bring considerable snow.  Yesterday’s forecast predicted up to 12″.  Because of the chaotic nature of the atmosphere, Denver will not receive 12″ of snow.  The upper level low split into two smaller pieces as it tried to traverse the intermountain west.  This development is not unusual, but numerical models have a hard time handling this behavior due to their limited resolution.  When upper level lows split, the energy associated with the storm also splits.  So instead of 12″ over the Denver area, lower amounts will be spread over a larger area.  The timing of vertical lift and the passage of a series of cold fronts through Denver also affected the beginning of precipitation.  Rain was supposed to fall starting around 6P last night, then switch to snow between 9P and midnight.  Instead, light snow started to fall around 10P.

This storm system is part of a different pattern than what occurred last year.  During early April 2012, record maximum temperatures were set.  Most of the change is due to simple interannual weather and climate variability, including low-frequency climate oscillations like the El Nino-Southern Oscillation and the Interdecadal Pacific Oscillation.  We can attribute part of the change to the underlying warming climate, which impacts those climate oscillations.

Climate change skeptics will likely point to this storm and the record lows that the NWS will record as “proof” that a warming climate is not occurring.  To the contrary, there is a climate-related reason why this storm system is impacting the western US today and bringing record warm temperatures to the eastern US.  The following plot shows today’s jet stream configuration:

The strength of the jet stream is characterized by the speed of the winds.  As the figure shows, there are very fast winds on the west side of the trough over the western US (red-filled contour where winds are in excess of 125 knots).  There are very slow winds south of Louisiana and east of northern Florida.  I have included an arrow on this figure to highlight the climate-related impact.  As the Arctic warmed more than the equatorial region, the temperature gradient weakened.  Temperature gradients cause pressure and density gradients (Ideal Gas Law).  As the average annual equator-pole temperature gradient weakens, the average pressure gradient similarly weakens.  This reduced pressure gradient causes the west-to-east movement of storm systems to slow down.  The arrow above highlights the amplitude of the current wave traversing North America.  This wave’s amplitude is characterized as high due to its large latitudinal extent (it stretches from Mexico to northern Canada, which is a very large distance).  This high amplitude simultaneously causes cold air to move from the Arctic to more southerly locations, such as Denver, CO, and warm air to move from the sub-tropics to more northerly locations, such as the eastern US.

Absent long-term anthropogenic climate change, this storm system would be much less likely to move slowly and bring record low temperatures to the middle of the US.  Instead, the storm would move quickly across the country.  Denver would receive cooler than average temperatures, but not record cold temperatures.  The cold air would remain further north and impact Canada and the northern US.

To summarize, climate change will not banish record low temperatures.  They will become more rare, however.  Winter will still occur in the mid- and high-latitudes.  But those winters will, on average, become warmer in the future.  Precipitation that would have fallen as snow in the 20th century will be likelier to fall as rain as the 21st century progresses.  More precipitation will likely fall during each event, but there will be longer time periods between precipitation events.  Overall, aridity will increase and flash flooding could become a more common problem for communities.

Thankfully, the NWS predicts temperatures to return to normal by this weekend.  I’m sure happy to receive the precipitation, but I wish it came as rain and left the Arctic air up in the Arctic.

Research: New Land Surface Warming Paper & Post

A quick word and some questions on a SkepticalScience post that discusses yet another warming analysis that comes up with the same answer than other studies have.   The post itself is good if you want a paper summary.  Where I think it needs attention is the “so what” part.  I’ll start with the concluding paragraph because it is what triggered a desire to actually write something about the post instead of walking away from it.

How much more evidence do we need?  The accuracy of the instrumental global surface temperature record is essentially settled science at this point.  The Earth is warming, it’s warming very fast, and continuing to deny this fact is a waste of time.

Many researchers and activists won’t like my answer: we don’t need much more scientific evidence.  Indeed, I would argue that the science largely weighed in years ago and additional information has only provided small-scale refocusing on parts of the issue.  Scientists haven’t discovered anything truly transformative in many years.  Are fields advancing as a result of new observations, methodologies, and expertise.  Yes, but that doesn’t answer Dana’s question.  What climate field advancement will be the one that magically triggers a switch in skeptics’ minds?  What new data set or analysis technique will do the trick?  I argue that no such advancement will ever occur.  Do we really believe that nobody has yet been smart enough to develop the one advancement that unlocks universal understanding of a complex topic?  That’s clearly an absurd assumption, but it seems to permeate this and other similar posts.  The spectrum of people who care about this topic have made up their minds (whether through tribalism or critical thought).  I will not convince any large number of skeptics to accept my argument any more than Hansen, Gore, or McKibben.  And here is where things get raw: strategies that those activists and most others have employed will not convince those people who don’t care about this topic.  As voices get more shrill and combative, more people tune the arguers out.

So if the evidence isn’t the problem, what is?  I believe the problem is the use of climate science as a proxy for a values fight.  Most people are unwilling to identify and fight about their values; it is much easier to throw climate science in the middle of the ring to fight for them.  Skeptics challenge the “facts” because of their beliefs and value system.  Advocates challenge the skeptics because of their beliefs and value system, not because of the “facts”.  Both groups try to bludgeon each other with “facts” and in so doing talk past each other, not to each other.  What concerns do skeptics have regarding climate change; how can advocates listen and address those concerns and vice versa.  Bypassing others’ concerns is the thing that wastes time.  So why do advocates and skeptics do it so much?

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.

Denver’s February 2013 Climate Summary

During the month of February 2013, Denver, CO recorded a 58°F difference between maximum and minimum temperatures (20°F less than January!).  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 2.4°F below normal (30.1°F vs. 32.5°F).  The maximum temperature of 63°F was recorded on the 17th while the minimum temperature of 5°F was recorded on the 22nd.

Figure 1. Time series of temperature at Denver, CO during February 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 finally above normal again during February 2013.  During the month, 0.77″ of liquid water equivalent precipitation fell, compared to 0.37″ normally.  For the first time in my life, rain fell across the Denver metro area in February!  On the 6th, it rained very lightly, just enough to make the streets and plants wet.  To add to the oddity and rarity of the situation, the ground was still wet with liquid on the morning of the 7th – it wasn’t cold enough to freeze the rain overnight. A similar event occurred in late January.  Conditions returned to normal in the second half of the month.  Measurable snow finally fell on the 20th and 21st of the month.  Then a significant winter storm hit the area on the 24th, dropping ~9″ of snow across the metro area.  In total, the NWS recorded 14.1″ of snow, 8.2″ more than the normal of 5.9″ for the month.

While more precipitation fell than normal during the month, the drought impacting the region was not broken.  Above-average precipitation will have to fall for longer than one month for that to happen.

Not Breaking: Obama Misjudges Republican Willingness To Negotiate

In the sordid mess leading up to this week’s sequester, the NY Times editorial board diagnoses part of the problem:

The White House strategy on the sequester was built around a familiar miscalculation about Republicans. It assumed that, in the end, they would be reasonable and negotiate a realistic alternative to indiscriminate cuts. Because the reductions hurt defense programs long held sacrosanct by Republicans, the White House thought it had leverage that would reduce the damage to the domestic programs favored by Democrats.

Obama chose excellent election staffs throughout his political career.

He did not choose competent political strategists.  He himself is not a competent political strategist.  His team spent 18 months on health insurance legislation, during which he gave away concession after concession without getting anything of value in return.  Why?  Because he wanted a Grand Bargain as part of his political legacy.  One result of this shortsightedness was the Republican wave election of 2010, when state legislatures and governorships flipped from Democratic to Republican control.  The Democratic base didn’t think Obama had done much for them for 2 years, so they didn’t show up to vote.  The biggest problem with this: your average Republican wasn’t elected; the far right-wing fringe of the Republican Party was: enter the Teabaggers to the US Congress, governorships, and state legislatures.

Obama’s team made multiple deals on financial items: the debt ceiling (Republicans don’t want to pay for the bills they charged up), the Bush tax cuts (expired after 1 extension), and the 2011 deal to initiate blind spending cuts because the Republican-led House of Representatives can’t execute their Constitutional duty to pass an annual budget on time.  Hence the leading NYT paragraph.

Time after time after time, the Teabagging Republicans have refused to negotiate or work with President Obama or Democrats.  How many times will it take before Democrats take the Teabaggers at their word: despite the trillions of debt run up by their party in the 2000s, they won’t allow Obama to run up any more debt, regardless of the cost to the US economy or its citizens.  Well, it will take at least one more time, apparently.

No more Grand Bargains, Mr. President.

El Niño and La Niña Redefined

This is the week to publish lots of interesting events and articles apparently.  I have a number of things I would love to post about, but only so much time.  Here is one that relates directly to something I posted on earlier: warmest La Niña years.  Just a few short weeks after NOAA operations wrote that 2012′s La Niña was the warmest on records, NOAA researchers announced they recalculated historical La Niñas because of warming global temperatures.  NOAA confirmed something that occurred to me while I was writing that post: eventually, historical El Niños will be cooler than future La Niñas.  How then will we compare events across time as the climate evolves?  The answer is simple: redefine El Niño and La Niña.  Instead of one climate period of record, compare historical ENSO events to their contemporary climate.  In other words, “each five-year period in the historical record now has its own 30-year average centered on the first year in the period”: compare 1950-1955 to the 1936-1965 average climate; compare 1956-1960 to the 1941-1970 average.  This is different from the previous practice in which NOAA compared 1950-1955 to 1981-2010 and compared 2013 to 1981-2010.  The 1950-1955 period existed in a different enough climate that it cannot be equitably compared to the most recent climatological period.

Figure 1. “The average monthly temperatures in the central tropical Pacific have been increasing. This graph shows the new 30-year averages that NOAA is using to calculate the relative strength of historic El Niño and La Niña events.”

I want to point out something on this graph.  Is long-term warming evident in this graph?  Yes, there is.  But note they plot the breakdown by month.  The difference between 1936-1965 and 1981-2010 in October is >1°F.  Meanwhile, the same difference in May is ~0.5°F.

Here is the effect of NOAA’s change:

Figure 2.  3-month temperature anomalies in the Nino-3.4 region.   (Top) Characterization of ENSO using 1971-2000 data.  (Bottom) Same as top, but using 1981-2010 data.

NOAA’s updated methodology resulted in the identification of two new La Niñas: 2005-06 and 2008-09.  The reason is warmer temperatures in the most recent decade than the 1970s (it sounds obvious when you say it like that).  That warming masked La Niñas with the old methodology.  It also means that the 2012 La Niña is no longer the warmest La Niña, as I related from the National Climatic Data Center last month:

Figure 3. Anomalies of annual global temperature as measured by NOAA.  Blue bars represent La Niña years, red bars represent El Niño years, and gray bars represent ENSO-neutral years.

That record will now go down as a tie between 2006 and 2009, with 2012 coming in a close third.  This situation is analogous to the different methodologies that NOAA and NASA use to compute global temperatures and where they rank individual years.  Records might differ because of methodological differences, but the larger picture remains intact: the globe warmed in the 20th and so far in the 21st centuries.  That signal is apparent in many datasets.  Within the week, I’m sure we’ll hear from GW skeptics that La Niña years have been getting cooler since 2006.  Here is what is most important: 2000s La Niñas were warmer than 1990 Niñas, which were warmer than 1980 Niñas, etc.

Denver’s January 2013 Climate Summary

During the month of January 2013, Denver, CO recorded a 78°F difference between maximum and minimum temperatures.  Does that tell you anything about whether it was warmer or colder than normal?  No, it does not.  For the entire month, Denver was 0.4°F below normal (30.3°F vs. 30.7°F).  But the maximum temperature of 66°F was recorded on the 24th while the minimum temperature of -12°F was recorded on the 12th.

Figure 1. Time series of temperature at Denver, CO during January 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 below normal again during January 2013.  0.31″ of liquid water equivalent precipitation fell during the month, compared to 0.41″ normally.  For the first time in my life, rain fell across the Denver metro area in January!  Two days after hitting the high for the month, the National Weather Service recorded 0.01″ of rain on the 26th.  I haven’t read anything regarding historical rain in Denver in January, but I think such an event is very rare indeed.  4.6″ of snow fell, which was 2.4″ below the normal of 7.0″.

You Get What You Vote For

Bill McKibben of 350.org has a snarky post over at the Daily Beast that ends with the following:

That’s why it would be so scary if it wasn’t a hoax. But it must be, because if it was a real crisis, responsible authorities would be taking action. The president wouldn’t be approving new oil drilling in the Arctic on the very same week. The Interior Secretary wouldn’t be auctioning off a vast new store of coal. The Republican presidential nominee wouldn’t be promising to approve the Keystone pipeline to the vast tarsands of Canada as his very first order of business.

Let’s all be very, very honest here: that president is a Democrat.  So is that Interior Secretary.  The obfuscation and obstruction isn’t the sole province of Republicans: both major political parties have done their fair share of ignoring the climate and energy arenas in the last few decades.  There were elections to win and financial supporters to pay back with political favors.  Boring stuff like energy policy can always wait until the next Congress or President is in office.

On this topic, there isn’t much difference between the major party candidates for President, as evidenced by the overall lack of action in the past 3.5 years by the “Hope and Change” candidate.  True, Obama hasn’t campaigned against action the way the $1 Billion candidate has, but that’s a pretty shoddy comparison that we’re forced to make.  You get what you vote for.

Chief Justice Roberts Concerned About Supreme Court’s Integrity

And he should be concerned, considering the history of the institution in the past 200+ years.  There has been a recent resurgence of bench activism, with Bush v. Gore and Citizens United providing two highly memorable examples.

Chief Justice Roberts took something to heart that is critically important, IMO.  If the populace loses faith in the Court’s decisions, the populace will grow to resent those decisions and actively work to undermine the Court’s authority.  What would happen in Americans refused to acknowledge the Court’s legitimacy?  9 hollow shells whose actions mattered not a whit does not bode well for a functioning democracy.

I think Roberts tried to walk the Court back from the step or two with the Obamacare ruling.  The other right-wing extremists would have taken the Court even closer to the edge, if not a little bit over it.

Congress might want to learn a little bit of the same lesson for its own good.  Both parties seem primarily interested in getting elected and re-elected, not governing.  The Democrats have done a slightly better job of governing, but not much – and what kind of bar am I comparing them to?  Some of the most extreme bunch of folks to ever control any kind of power in US government.  Thus, my statement should not be taken as a ringing endorsement of the Democratic Party or its so-called “accomplishments”.

To the contrary, the Democratic establishment continues to try to play the Democratic base for fools with their fear-mongering of the Republican Teahadists.  I want to see real progress made on every critical issue of our time.  What I’ve come to realize is the Democratic establishment doesn’t want that any more than the Republican establishment does.  Doing actual work would distract us from the scary “others” out there that need to be constantly fought.  No, what I and millions of other Americans want are effective political movements – the kind which were squashed in the 1960s with all of the assassinations of the previous movements’ leaders and high-profile supporters.  We have seen what the lack of those movements has meant for America: stagnation on multiple different fronts.  Sure, I can buy lots of crazy cool crap, but is my life really significantly better than the average Americans’ life at the end of the 2nd third of the 20th century.  I don’t think so.

So Roberts took a small step back – good for him.  The question is: will it be enough?  How many more decisions have to be made; how many more elections have to be held until most Americans not only realize the establishment isn’t working for them, but are willing to actually do something about it?