USA

North Carolina climate compared to the USA and globe

April 27, 2013 by Brian Magi
Categories: Earth System Observer

The first months of 2013 here in Charlotte have seemed unusually cool, but rather than relying on our gut feeling, let’s look at the numbers. Start by going to the NCDC website and mine out the data to find that in Charlotte, January was the 27th warmest in 118 years, February was the 40th coolest, and March was the 4th coldest in 118 years. Now a fair second question is how does Charlotte fit into the big picture? Namely, is Charlotte’s temperature ranking similar to that of the whole state of North Carolina, the USA, and even the world? With only a little bit of work, we can figure this out. The data below shows temperature anomaly compared to the 20th Century average as a +/- number, and the parenthetical numbers are the ranking in the overall temperature record (1 is hottest). USA has 119-120 years of data, while the global time series begins in 1880. 

                  Charlotte*    North Carolina   USA**        Global Land   Global***
    April 2012    +1.7 (31)     +1.1 (39)        +3.7 (3)     +1.1 (6)      +0.6 (7) 
      May 2012    +2.9 (13)     +2.9 (11)        +3.3 (2)     ? (7)         +0.5 (10) 
     June 2012    -1.5 (93)     -1.5 (98)        +2.0 (12)    +0.9 (4)      +0.6 (7) 
     July 2012    +2.4 (8)      +3.2 (2)         +3.3 (1)     +0.8 (5)      +0.6 (7) 
   August 2012    -1.3 (97)     -0.4 (69)        +1.7 (13)    +0.8 (2)      +0.6 (8) 
September 2012    -1.6 (83)     -0.9 (72)        +1.4 (23)    +0.9 (4)      +0.5 (8) 
  October 2012    -1.5 (81)     -0.6 (65)        -0.3 (73)    +1.1 (2)      +0.6 (8) 
 November 2012    -3.6 (109)    -3.6 (108)       +2.0 (20)    +1.1 (6)      +0.7 (5) 
 December 2012    +5.1 (8)      +5.5 (8)         +3.3 (10)    +0.2 (49)     +0.4 (18)
  January 2013    +2.8 (27)     +3.5 (24)        +1.5 (42)    +0.9 (13)     +0.5 (9)
 February 2013    -2.0 (80)     -0.8 (70)        +0.9 (49)    +1.0 (11)     +0.6 (9)
    March 2013    -6.7 (116)    -5.9 (114)       -0.8 (77)    +1.1 (11)     +1.0 (10)

What’s remarkable is that at first glance, it seems like the rankings of Charlotte and NC are essentially on the opposite end of the spectrum of rankings compared to the global rankings in the last 12 months. There’s an easy way to quantitatively evaluate the relationship between sets of numbers and that is by using the statistical correlation coefficient, usually represented by the variable r. A positive r value means the numbers go up and down together, while a negative r means one set of numbers go up while the other goes down. When r is +1 or -1, that means the two sets of numbers are perfectly correlated and perfectly anti-correlated, respectively. Perfect correlation or anti-correlation never happens with data, unless you calculate the correlation of a dataset against itself which isn’t very interesting. That being said, r near +1 or -1 usually indicates that the two datasets being compared are statistically related. To quantify “usually” from the previous sentence and to contextualize the r value, a corresponding statistic that accompanies r is the p value. The p value is a way to quantify the statistical significance of the r value and depends. A p value less than 0.05 means there’s a 95% chance that a random set of numbers is not better related than the numbers you are testing. Thus when p is less than 0.05, you can be confident there is “statistically significant” relationship – remembering that correlation does not imply causation. This kind of analysis is done all the time in all fields of science, which speaks to the idea that math is the universal language. In the table below, r is the +/- number, p is the parenthetical number.

                NC              USA           Global Land    Global
    Charlotte   +0.97 (<0.05)   +0.52 (0.08)  -0.43 (0.16)   -0.43  (0.16)
           NC   -               +0.48 (0.11)  -0.39 (0.21)   -0.44  (0.16)
          USA   -               -             -0.10 (0.77)   +0.002 (0.99)
  Global Land   -               -             -              +0.92  (<0.05)

Now we’re getting somewhere. Over the last 12 months, Charlotte and NC temperatures are, as expected, significantly correlated (r = +0.97, p < 0.05). If Charlotte sets a cold or warm record, so does NC. Global land and ocean ("global" in the table) and global land are significantly correlated (+0.92, p < 0.05) as well. Not that shocking. What I didn't expect until I started comparing the trend in the rankings is that NC and Charlotte rankings are not significantly related to the USA or global temperature rankings. This is evident by the high p values in parenthesis in the 1st and 2nd rows. Surprisingly, NC and Charlotte are nearly significantly anti-correlated (negative r values, see above) with global rankings, something that might be worth looking into with more data. What’s perhaps even more surprising to me is that USA temperature rankings are essentially unrelated to the either of the global temperature rankings. This means that any given month in the USA tells you absolutely nothing about the global ranking for the same month – you might as well just guess. More data will tell the a more complete story here (and provide better stats), but over the last 12 months, there are some interesting possible relationships (Charlotte and NC similar to the USA, but opposite of the globe), and then occasions where the two datasets have no idea the other exists (USA and the globe). No wonder people get mixed up when looking at the news about global warming and then try to relate it to what’s going on in their backyard.

* NC Climate Division 5
** Contiguous USA
*** Combined land and ocean since 1880, as opposed to “global land” which is only land surfaces. Note May 2012 T anomaly wasn’t listed on NCDC site, but the ranking was. My stats analysis was based on the ranking, so the “missing” data point is not relevant.
Tags: climatedata analysisglobal warmingNCDCnorth carolinastatisticsUSA

USA in December remains much warmer than average

December 17, 2012 by Brian Magi
Categories: Earth System Observer

A blowout in sports – whether it’s baseball, football, basketball, or soccer – is usually boring to watch. By blowout, I mean a game when one team obliterates the other. You know, 14-2 in baseball, 40-7 in football, etc. But in climate, the month-to-month ups and downs in temperature departures, are one example when a blowout is actually more fascinating to watch than another month of the “climate normal“.

As I mentioned earlier, December 2012 is setting the year 2012 to be a blowout in terms of the “competition” between years to be the warmest on the 118 year record. Here’s the updated evolution of December 2012 temperature departures from figures I got from the HPRCC map maker and laced together for an animated look at the month.

The most obvious feature is the continuing large and positive temperature departures for most of the country. You have to be a little careful because the figures have shifting colorbars on the bottom. Dark red doesn’t mean the same thing on every figure, but the message is clear as day. December is much much warmer than usual. The last week or so has continued the trend, although you do see the effect of the cold frontal passage around December 11-12 in the animation. Stay tuned, but based on a quick look at long-term weather model forecasts, I wouldn’t expect a dramatic change in the weather regime until at least December 25.

Tags: 2012global warmingNCDCRecord warmthUSA

Shattering the temperature record?

December 11, 2012 by Brian Magi
Categories: Earth System Observer

Glancing through the temperature anomalies of the last year, it’s clear we’re heading – barrelling really – towards a record hot year. Temperature data is collected and archived very quickly through various climate centers. The High Plains Regional Climate Center (HPRCC) has a particularly fluid interface for quickly assessing the state of the climate over different time and space (or spatiotemporal) scales. The USA as a whole experienced a record hot March and July in 2012, as listed in the table here. Records weren’t broken in every single state of course, but the records were broken when all the temperatures were averaged together. Here’s the story though. December 2012 is set to be the final nail in the plaque on the wall that says “HOTTEST YEAR ON RECORD: 1998 2012” and at this point (9 days into the month), December 2012 will not only be the nail, but will help 2012 shatter the temperature record. Look at these anomalies figures produced using the HPRCC tool for March, July, and so far for December:



Without even reading a number, you know that the deep red color for the anomaly from December 1-9 implies that it’s much hotter than the average temperature for December 1-9**. There’s hardly a speck of any the green or yellow that represents near normal temperature! But let’s not overreact. Whether this early trend will continue depends on the weather. All things being equal, weather over the entire month will probably moderate the unusual warmth seen so far in December. However, human activities have fundamentally changed how the concept of “all things being equal” applies to weather, so better to look at what weather models are saying rather than just assuming… Near-term weather forecasts suggests that the first half of the month will be more of the same. Long-term weather forecasts for the month (for example, clicking on the options for 100 hr+ forecast times) suggest a nor’easter may develop around Dec 16 and subsequently affect the mid-Atlantic Dec 17-18, but even that weather system seems to bring rain rather than snow (use the same forecast tool and “precip type” option to see that). Regardless, there is no chance of widespread snowmen to cool things down before at least December 15. Odds are in favor of a shattered temperature record on New Years Day.

*on record is the 118 year temperature record
**1981-2010 is the period that any month on the 118 year record is compared to. HPRCC call it the Climate Normal. NOAA NCDC call it the base period. Both use the same range of 30 years, which is a typical length of a climate-relevant – as opposed to weather – temperature dataset

Tags: 2012global warmingRecord warmthUSA

2012 Temperatures in North Carolina and USA

December 08, 2012 by Brian Magi
Categories: Earth System Observer

The big news, if you’re paying attention the inexorable increase in temperatures, is that the biggest contributor to fossil fuel carbon (the USA) is experiencing the hottest year in 118 years. We have one month remaining this year, but the record will be set unless the USA suddenly experiences the coldest December in 118 years (it won’t – we’re well on our way to a warmer than average December and there’s a weak-moderate El Nino in place right now too which tends to result in more mild winters for at least part of the USA). Certainly many locations in the contiguous USA will be cold, but it’s not the cold that matters though. It’s the comparison of the current temperature to an average of past temperatures that really highlights relative warmth or cold. Mining what has quickly become my favorite climate data source, at least for the USA, i went to the NCDC website and pulled down the data to look at how temperatures of our home state compare to those of our home country. Here’s what I got:

             North Carolina   NC Climate Division 5*  Contiguous USA
  January    +2.9 (92)        +3.1 (94)               +5.8 (115)
 February    +2.7 (88)        +2.3 (83)               +3.9 (104)
    March    +8.7 (117)       +9.8 (117)              +8.8 (118)
    April    +1.1 (80)        +1.7 (88)               +3.7 (116)
      May    +2.9 (108)       +2.9 (106)              +3.3 (117)
     June    -1.5 (21)        -1.5 (26)               +2.1 (107)
     July    +3.2 (117)       +2.4 (111)              +3.3 (118)
   August    -0.4 (50)        -1.3 (22)               +1.7 (106)
September    -0.9 (47)        -1.6 (36)               +1.4 (96)
  October    -0.6 (54)        -1.5 (38)               -0.3 (46)
 November    -3.6 (11)        -3.6 (10)               +2.0 (99)
 December    TBD (TBD)        TBD (TBD)               TBD (TBD)

*includes Charlotte and Mecklenburg County

The numbers with the + and – are the anomaly (departure) of that month’s temperature from the 20th Century average for that month. The numbers in parentheses are how the particular month for the particular region ranks (118 is hottest, 1 is coldest following NCDC protocol). The regions are NC, a smaller part of NC that includes CharMeck, and the USA minus Hawaii and Alaska. So, if you’re from North Carolina and can’t wait to have the dinnertime conversation with your friend/relative about how global warming is a joke/hoax/conspiracy, here is what you do. Pull up that table and you can heartily agree that, yes, North Carolina has been cooler than average, particularly since August. CharMeck (middle column essentially) has pretty much been the same, maybe even cooler. But then there’s the USA. The USA had below average temperatures in October, but the warmth has otherwise been shockingly constant. March and July 2012 were both the hottest in the 118 year record. On January 1, it’ll be clear that the USA has been warmer than it has been in over a century. North Carolina has finished cooler than average, but as I pointed out before, it was the warmth in the beginning of the calendar year that set the stage. And GLOBAL warming has never been about the warming or cooling of a particular US State – it is the response of an entire planet to the energy imbalance imposed on it by human activities. The data is mounting up though and the temperature trends of regions like the USA are slowly creeping out of the noise of the day-to-day variability.

Tags: 2012global warmingNCDCnorth carolinaRecord warmthUSA

Remembering the warmth with temporal averaging

October 15, 2012 by Brian Magi
Categories: Earth System Observer

It’s been cool in North Carolina and in Charlotte in August and September 2012, as I talked about on one of my posts. In that post, I said that if you really want to know whether the temperatures you are experiencing are representative of the bigger picture, you can “zoom out” from the city level (or Climate Division) to the state level and even to the country level. This is easy with the NCDC website which archives USA climate data. Another way to think about the temperatures in a particular month (like September 2012) is to zoom out in time. In other words, take a longer time average to see whether the temperature averaged over the last few months or even the whole year are at all like the temperature you are experiencing in the here and now. (we’re still talking about monthly temperature, not the weather).

Using figures that you can get at NCDC, I made the animation above. The figure shows the temperature averaged over progressively fewer months (starting with 12 months up to Sep 2012 and going down to just Sep 2012). I think the data in the figure shows that the temperatures departures over the last year (Oct 2011 to Sep 2012) in North Carolina were dominated by unusually large warm anomalies back in the winter months, from about Oct 2011 to Mar 2012. Starting in May 2012, the temperature anomalies in NC were below average, but these below-average temperatures we’ve been experiencing are swamped by the above-average temperatures from the what we did experience (but may have forgotten). When you look at the trend in the country as a whole, and focus on the Oct 2011 to Sep 2012 image when it pops up, you can see that most of the country is very warm compared to average.

Tags: global warmingNCDCRecord warmthspatiotemporal analysisUSA

Cool in North Carolina, but not the USA

October 10, 2012 by Brian Magi
Categories: Earth System Observer

Between all the various climate excitement in the news – like record-low Arctic sea ice – temperature measurements continue to be collected. A really great webpage to actually examine the temperature data is at the NOAA National Climatic Data Center. The NCDC data shows that in 2012

           North Carolina   NC Climate Division 5*  Contiguous USA
     July  80.5 (+3.2)      81.1 (+2.4)             77.2 (+3.3)
   August  75.7 (-0.4)      76.1 (-1.3)             74.6 (+1.7)
September  69.8 (-0.9)      70.3 (-1.6)**           67.0 (+1.4)

*includes Charlotte and Mecklenburg County
**corrected after an NCDC website glitch which originally had values of 74.1 (-1.5)

where the bigger number under each header is the avereage temperature for the particular month in degrees Fahrenheit, while the number in the parentheses is the departure (or anomaly) of the month to the average temperature for that month for the 20th century (1900-1999). North Carolina, like most of the USA, had a really warm July 2012 and the country experienced the warmest July in the 118 years of records. On the other hand, August and September temperatures in North Carolina this year were about a half degree to nearly a full degree less than the 20th century average temperatures. These much cooler-than-average temperatures were even more pronounced in southern North Carolina, which I show above as NC Climate Division 5. This climate division includes Charlotte and Mecklenburg County.

This is a great example of how even when the local temperature for a particular month is below or above average, this may not be true when you examine other parts of the country, or in the case of Charlotte, other parts of the state. This same analogy is true when comparing regional (like USA) to global temperature trends. The summary is that even though NC had a cooler than average Aug-Sep, the USA on the whole still experienced a warmer than average August and September to pile on to the warmest July on record.

Tags: 2012global warmingnorth carolinaRecord warmthspatiotemporal analysisUSA