By Paul Homewood
https://www2.ucar.edu/atmosnews/news/1036/record-high-temperatures-far-outpace-record-lows-across-us
Every so often, the hoary old chestnut of record daily temperatures is wheeled out, as evidence of global warming. The above chart is from the NCAR study by Gerard Meehl in 2009, and the NCAR Press Release stated:
Record high temperatures far outpace record lows across U.S.
November 12, 2009
BOULDER—Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows. The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.
“Climate change is making itself felt in terms of day-to-day weather in the United States,” says Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR). “The ways these records are being broken show how our climate is already shifting.”
This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole.
The study, by authors at NCAR, Climate Central, The Weather Channel, and the National Oceanic and Atmospheric Administration (NOAA), has been accepted for publication in Geophysical Research Letters. It was funded by the National Science Foundation, NCAR’s sponsor, the Department of Energy, and Climate Central.
If temperatures were not warming, the number of record daily highs and lows being set each year would be approximately even. Instead, for the period from January 1, 2000, to September 30, 2009, the continental United States set 291,237 record highs and 142,420 record lows, as the country experienced unusually mild winter weather and intense summer heat waves.
A record daily high means that temperatures were warmer on a given day than on that same date throughout a weather station’s history. The authors used a quality control process to ensure the reliability of data from thousands of weather stations across the country, while looking at data over the past six decades to capture longer-term trends.
This decade’s warming was more pronounced in the western United States, where the ratio was more than two to one, than in the eastern United States, where the ratio was about one-and-a-half to one.
The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs. This indicates that much of the nation’s warming is occurring at night, when temperatures are dipping less often to record lows. This finding is consistent with years of climate model research showing that higher overnight lows should be expected with climate change.
Remember that last paragraph,as we move on later. But first, a quick recap of the huge flaw in Meehl’s exercise.
The data starts in 1950, and consequently picks up all of the daily low records set during the much colder 1960’s and 70’s, but fails to pick up the daily highs during the 1930’s and 40’s. This flaw was so significant, and obvious, that I am amazed the paper ever made its way past review.
http://www.ncdc.noaa.gov/cag/time-series/us
Nevertheless, we can now move on. WUWT mentioned the other day that CDIAC, The Carbon Dioxide Information Analysis Center of the Department Energy, have introduced a new tool, which crucially uses data right the way back to 1911. It also only uses USHCN stations, regarded as high quality, and excludes any that don’t have complete, or nearly so, records back to 1911.
The data only goes up to 2010, so there will no doubt be a batch of record highs in 2012, and record lows last year, not included.
Interestingly, CDIAC introduce their new interface thus:
Like politics, you might say that all climate is local. As researchers seek to help the public better understand climate and climate change, a sensible approach would include helping people know more about changes in their own backyards. High and low temperatures are something that all of us pay attention to each day; when they are extreme (flirting with or setting records) they generate tremendous interest, largely because of the potential for significant impacts on human health, the environment, and built infrastructure.
In other words, they want to “educate” the public, who remain stubbornly sceptical! However, it appears they may have shot themselves in the foot
.
Southeast Region
Greg Kent, in his essay on WUWT, put together some graphs for the CONUS, which did not look as scary as the original NCAR study, but I wanted to delve a little deeper, so decided to take a closer look at the thing region by region, starting with the Southeast (encompassing VA,NC,SC,GA,FL & AL). Altogether, there are nine regions in the CONUS.
Within the region, CDIAC list 37 stations, out of the national total of 424. The interface offers these screens for each.
So, using the record highs and lows, I have built up a database for the whole region. (The 1910’s start in 1911, and so on).
Figure 1
Figure 2
As far as daily highs go, there are 17730 records/ties, an average of 479 per station (i.e suggesting 113 ties). The total number of records set between 2001 & 2010 was 1222, much lower than the average of 1773. Daily lows were also below average in the last decade, with 1094, against an average of 1604.
We can also look at the ratio of highs and lows, in Figure 3, showing that they have been pretty much in balance since 1991. The imbalance during the warm 1920’s to 50’s, and cold 1960’s to 80’s, is also evident.
Figure 3
I don’t want to make too big an issue of these figures, because the Southeast is generally accepted to have shown the least warming of any regions during the last century. We can only get the full picture when I have worked my way through the other regions.
But, here things started to get a bit interesting.
Urban Heat Island Effect
As I was transferring the data, I noticed that some stations had much higher ratios of highs to lows. I only really cottoned on when I noticed it for Charleston, SC, which you may have realised is a rather large city!
So, I backtracked, and entered the population data, using the GISS database. GISS either show <10,000, or the actual population, so I have split the Southeast database into two, one for “rural”, or less than 10,000, and the other half for urban, or more. The numbers split almost equally, with 18 rural, and 19 urban.
The difference between the two sets in Figures 4 & 5 is startling.
Rural stations now show more lows than highs, with a ratio of 0.86 highs to lows during the last decade. In contrast, urban stations show a ratio of 1.61.
Figure 4
Figure 5
It is clear from analysing the numbers that it is record lows, and not highs, which are making the urban and rural ratios so different, as the Table below shows.
| 2001-10 | Decadal
Average 1911 to 2010 |
% of average | |
| Record Highs | |||
| Urban | 593 | 911 | 65 |
| Rural | 629 | 862 | 73 |
| Total | 1222 | 1773 | 69 |
| Record Lows | |||
| Urban | 367 | 813 | 45 |
| Rural | 727 | 791 | 92 |
| Total | 1094 | 1604 | 68 |
Rural stations are actually showing a slightly higher number of record highs than urban ones, relative to the average. But, with daily lows, rural sites have posted double the number compared with urban.
It is hard to find clearer evidence, that night time temperatures have been biased upwards by the Urban Heat Island effect in recent years.
OK, these are just daily records for one region. What does any of this tell us about annual trends for the country as a whole?
The second part of the question will be answered in due course, once I have run through the other eight regions. But the following comment in the NCAR press release, introducing Meehl’s work is significant:
The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs. This indicates that much of the nation’s warming is occurring at night, when temperatures are dipping less often to record lows. This finding is consistent with years of climate model research showing that higher overnight lows should be expected with climate change.
So NCAR admit that much of the warming has occurred at night, and believe that this is caused by “climate change”. The evidence from the Southeast suggests that this is not the case, and that night time warming is largely the result of UHI.
It is also worth bearing in mind, that many of the stations, which I have labelled as rural, could still be small towns with their own UHI effect, given that GISS lump all sites with populations of less than 10,000 together. Lexington, VA is a good example of this. It has a population of 7000, and a ratio of highs to lows during the last decade of 2.82.
Clearly, a lot more work needs doing, but this exercise suggests a lot of serious questions need to be asked about the true impact of the Urban Heat Island effect.
References
The CDIAC interface is here. Go play!
http://cdiac.ornl.gov/climate/temp/us_recordtemps/dayrec.html
I have believed for some time that UHI is the huge “elephant in the room” in regard to temp studies, patterns and interpretations. I believe it biases scientific perspectives, especially amongst warmists and I’m quite certain it’s a variable not at all understood by the general public. I would argue that the (vast) majority of climate change researchers grew up entirely in urban environments in which UHI has been a common and constant factor. Their “bodily” experience since infancy has been shaped by life in a UHI bubble. As cities expand, and adjacent green space declines, we can expect to see a popular sense that things are hotter (or are getting hotter). There is a also a local change in weather consistent with increased UHI (anecdotally, in my historical view).
I grew up in a city of about 60K people in the ’50s and ’60s, about 30mi from Toronto, then about several 100K population. Toronto was surrounded by rural farmland between the municipalities within that 30mile radius (today, it is almost entirely built up). Regularly, in the summer, we would make a party pilgrimage into downtown TO to savour the “big city” night life. Back home, a summer’s day that was 85 in the peak of the day would cool to as low as 70 in the evenings. Downtown Toronto would peak out at 87-90 that same day, but the nights would only drop to about 80, maybe 75 by dawn. It was always a topic of conversation how hot and stuffy Toronto downtown was at night (well ok, hot, TO is stuffy all the time). Over the intervening years, that gradient has flattened, as much or more, IMO, due to expansion of the urban environment. This heat retention has had local effect, I believe , both locally in terms of weather, and in human perceptions of the climate environment. People, literally, don’t experience the real “global average” because most never live in the “average” environment.
Hi Paul,
We’ve recently finished a series of three articles investigating urbanization bias, which we’ve submitted for open peer review in a new forum we’ve set up called Open Peer Review Journal. For our studies, we were mostly looking at monthly averaged temperature records instead of the daily records you discuss here. But, you might find our results relevant. We’ve summarised our findings on our blog here.
Steve Mosher is correct about the GISS population metadata being quite crude, although it’s actually just a copy of NOAA’s GHCN metadata. But, we found it to be still useful if we combine it with the GHCN night brightness metadata. In our analysis, we divided the weather stations into “fully rural” (GHCN population 100,000; night brightness = bright “C”) and “intermediate” (everything else).
By combining two metrics, we managed to find some quite strong rural-urban differences, because if both metrics indicate “urban” or both metrics indicate “rural”, we can have a bit of confidence about how urbanized the stations are.
P.S. We borrowed the Viz cartoon in Figure 14 on our blog post summary from your blog – I hope you don’t mind! 😉
“In our analysis, we divided the weather stations into “fully rural” (GHCN population 100,000; night brightness = bright “C”) and “intermediate” (everything else).” was cut for some reason! I think it was because I was using the “less than” and “greater than” symbols.
That should read,
In our analysis, we divided the weather stations into “fully rural” (GHCN population less than 10,000; night brightness = dark “A”); “fully urban” (GHCN population greater than 100,000; night brightness = bright “C”) and “intermediate” (everything else).
Resourceguy says:
March 14, 2014 at 1:45 pm
Thank goodness there is this double standard in science that holds medical research to a much higher standard for peer review and product or procedure review.
HAHAHAHAHAHAHAHAHAHAHA!
HAHAHAHAHA!
HAHAHAHAHAHAHAHAHAHAHAHAHAHA!
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3700330/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3702092/
And thousands more…
I keep saying *nobody* is automatically more trustworthy than anyone else because of their professions. Auto mechanics, lawyers, politicians, scientists, doctors, ad nauseam.
If you place a profession above suspicion (even as a social conceit), frauds will flock to it.
Jimbo says:
March 14, 2014 at 2:30 pm
“The 1930s was a bad decade for warm weather.
30 May 1934
“SULTRY” IN ANTARCTIC. 25 Degrees Above Zero!”
Warming fanatics are busy trying to make such major climate periods more localized. Only Europe experienced the LIA and MWP… that sort of thing.
Range of snow cover in the northern hemisphere on 14/03/2014.
http://oi58.tinypic.com/b5jp1c.jpg
One big gripe I have is that looking at record highs and lows is rather silly, since you are throwing away a lot of data contained in the temp record. If you want to see what what the temps are doing, then LOOK AT THE TEMP AVERAGE, not at something like record highs/lows.
The oft told meme is that global warming leads to more temperature extremes. Where’s Waldo? Most of the “average” temperature increase is at the low end, not the high end. That fits nicely into UHI.
People in Christchurch NZ have swallowed AGW though.
Earthquakes and flooding all results of CO2! Save our souls!
http://www.ccc.govt.nz/thecouncil/newsmedia/mediareleases/2014/201403144.aspx
Cheers
Roger
http://www.thedemiseofchristchurch.com
Every CAGW paper wanting to find an increase in weather “extremes” starts in the 1950’s, or as the Warmists know it, the beginning of time.