Guest Post by Willis Eschenbach
[See Addendum at the bottom.] [See Second Addendum at the bottom]
I got to thinking about the distribution of the so-called “global” warming. I’d heard that a good chunk of it was due to increasing nighttime minimum temperatures. So I grabbed the Berkeley Earth land-only temperature dataset. It has its problems, and I suspect the overall warming trend is exaggerated, but at least it is internally complete and consistent. I wanted to know both where and when the warming is strongest, and where and when it is weakest. I used the post-1900 data because prior to that the error bars get pretty wide, but the choice of starting point doesn’t make much difference.
For my first subdivision in time and space, I looked at the daytime maximum and the nighttime minimum temperatures by hemisphere. Figure 1 shows the result:
Figure 1. Maximum daytime temperatures (orange/red) and minimum nighttime temperatures (dark/light blue) by hemisphere. Data goes from 1900 through 2014.
This shows that as a hemispheric average, the nighttime minimum temperatures are rising faster than the daytime maximums, and that the northern hemisphere nights are warming the fastest of the four groups.
(I note in passing that while both the northern and southern hemisphere daytime temperatures dropped strongly from about 1945 to 1975, the corresponding drop in the nighttime temperatures is nowhere near as large. No idea why … always more questions than answers, gotta love that, but I digress …)
However, that wasn’t quite what I was looking for. I wanted to know more details about exactly where and when the warming was going on. So I made a couple of movies. Since the fastest warming is in the night-time, here are the century-plus nighttime minimum temperature trends, on a 1°x1° gridcell basis:
Figure 2. Berkeley Earth month-by-month average minimum nighttime temperature trends, in degrees C per decade.
This is what I was looking for, the details of the location and timing of the warming. The Northern Hemisphere nighttime temperatures are increasing the most during the winter in Siberia and Canada. And similarly, in the Southern Hemisphere the nighttime warming is greatest in the winter, although it is more evenly distributed spatially. Meanwhile, there is little trend change month-over-month in the tropics.
Now, call me crazy, but I don’t recall anyone ever saying “Boy, I sure wish that the February nights in the Yukon were colder” …
What about the daytime maximum temperatures? Figure 3 below shows the days:
Figure 3. Berkeley Earth month-by-month average maximum daytime temperature trends, in degrees C per decade.
Curiously, or perhaps not curiously, this daytime view shows the same pattern as the nighttime temperatures. The warming is concentrated in the extratropics in the winter.
Conclusions? Well, the most obvious conclusion is that the “global” warming is not global at all. Instead, it is strongest at night in the winter in Siberia and Canada. I’m pretty sure the poor people in Murmansk are not complaining about that …
In addition, there are large regions of the earth where for one or more months of the year, over more than a century the temperatures have actually cooled … the entire southeastern US, for example, is now colder in January than it was a century ago, both during the day and at night. If nothing else, this highlights the complex nature of the climate.
That’s what I see so far, but there’s much more to learn in the movies …
Clear weather today. I’m off to build an outdoor viewing tower so our cat can survey its domain … got to take my shirt off and saw up some wood in the sunshine, we melanin-deficient folks need to get our Vitamin D.
Best wishes to you all, whether you are in sunshine or rain,
w.
Addendum: I was accused in the comments of suffering from hypo-Europhilia, as evidenced by my Pacific-centered movies. Hey, I’m a tropical South Pacific boy, guilty as charged, so here’s the new movie:
Second Addendum: A commenter asked how well the climate models do at reproducing the patterns shown above. Here are a comparison of four different months (Feb, May, Aug, Nov) of one single GISS-E2-R model run from the KNMI dataset:
I don’t find the agreement particularly compelling, but YMMV.
Data: I got the Berkeley Earth temperature data from the marvelous KNMI site. Click the link entitled e.g. “1833-now: Berkeley 1°” and look down at the bottom of the resulting page for the gridded NetCDF dataset.
PS: I am reliably informed that it is no longer politically correct to refer to so-called “white” people as being “melanin-deficient”, as it implies that something is wrong with them. The new politically approved term is “melanin-challenged”.
My Usual Request: If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of my words.
My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.
The weatherman always attributed the much larger differences between day/night to cloud cover, as the clouds tended to “hold in” the heat much like a blanket would for bedtime. If CO2 acts as a kind of invisible (transparent) blanket then it would seem that if someone were to prove that day/night temps were less different then it may follow that CO2 is a possible culprit. This could be run on individual stations in many locations. The averages, in my opinion, are less valuable than many individual locations.
For example, the day/night temps of Venus don’t differ much (percentage wise) due to the makeup of the atmosphere.
WARNING: I am only an interested observer to these fascinating discussions. I am only an expert in….ah…well, I can’t think of anything just now…I’ll get back.
Thanks, brad. Off the top of my head I can think of a few possible reasons for extratropical winter nights having the highest rate of warming:
1. UHI. The urban heat island effect is stronger at night, and is stronger in the winter, in many locations.
2. Increased winter clouds. Wintertime clouds indeed warm the surface, particularly at night.
3. Increased summer clouds. Summertime clouds cool the surface. Since we are looking at relative warming rates, this would leave wintertime rates higher.
4. Increased extratropical daytime windspeeds. This would cool the day time rates and leave the night time rates untouched.
I’m sure there are more … oh, yeah, increased CO2 would increase nighttime rates more than daytime … but I’m not sure why that would hit the extratropics hardest. Could be, though.
My point is that we can’t really tell either which or which combination of these is affecting the trends …
Regards,
w.
Willis,
You wrote, “Increased CO2 would increase nighttime rates more than daytime … but I’m not sure why that would hit the extratropics hardest. Could be, though.?
CO2 could have more effect in extra-tropical winters because there would be less water vapor masking CO2’s greenhouse effect. This might also explain why a lot of the warming seems to occur in the middle of continents, away from humid coastal regions.
Wind speeds:
http://www.nature.com/ngeo/journal/v3/n11/images_article/ngeo979-f4.jpg
Good work, Willis.
This is something I wanted to look into but have not had time.
It the reason that Karl et al 2015 is bunk. The night time temperature record is not representative of the full 24h record, so using NMAT to “correct” SST is just adding bias to the data , not correcting it.
To prove the point, a similar exercise needs to be done using marine air temperatures MAT and NMAT to see a similar comparison.
ICOADS MAT, and hadNMAT are available from KNMI.
In part it was the problems with the ocean that led me to use the Berkeley Earth dataset.
w.
As always an interesting essay by Willis.
How does this look against the OCO-2 published here bu Erik Swenson?
http://wattsupwiththat.com/2015/10/04/finally-visualized-oco2-satellite-data-showing-global-carbon-dioxide-concentrations/
During the Soviet era, it was common practice throughout Russia to report lower than actual temperatures in order to “game the system” and obtain a greater quota of heating coal. Some one else mentioned that many airports were added in northern areas. The significance was that they were the primary source of temperature data and with time subject to ever greater urban warming effects.
Your maps are great, but for many of us could probably be even better. We Europeans seem to be a bit in the shade, as it were! Would it not be possible to arrange for the edge of the plots to run roughly through the mid Atlantic? Or possibly the Pacific?
The reasoning is that there is virtually no data for these regions, whereas Europe, currently almost invisible, and presumably a region of general interest, would then become somewhere that could be studied. It would also keep the Americas in full view, so there’s little to be lost.
Just a thought. Robin
We’re nothing if not a full-service website … I’ve added the minimum temperature movie to the end of the head post in a more Europhilic projection.
w.
I’ve not looked yet, Willis, but have total confidence that you will have done a great job. Thanks!
In my layman (have no idea what I am talking about) opinion, it looks like heat is being transported from the tropics to the poles. We are doing a better job of observing that heat when it is over land and causing a significant variance (Canada, Siberia). I suspect the air temp over the northern oceans would have a similar pattern. The SH doesn’t have much for land stations to observe this movement and the graphs show this lack of stations rather than a lack of heat (potentially). I don’t think stations on Antarctica tell us too much about anything besides Antarctica. It seems to have it’s own climate cut-off from the rest of the planet. But, I would guess that warming in the SH would be concentrated over the southern oceans.
So the variance between the SH and NH could just be lack of data availability in key areas. Trying to measure such small changes over such a large area with such shabby data (not a jab at BEST) seems quit the daunting task.
Oceans tend to convert heat to water vapour pretty effectively so if this heating actually exists- big if in my opinion, it may not show up as a temperature change. It would perhaps show up as greater snowfall in Antarctica, which whaaaat? There’s seems to be strong evidence of!
Now I wonder if there is any indication of increased snowfall in the Arctic. If northern ocean temps are higher and water is more open, shouldn’t there be more snow?
This is a very interesting finding, Willis. Do current climate models explain, predict or attempt to pretend that they foresee this specific development? I personally feel that these findings are very suspect, however, they do somewhat jive with what we see taking place in the Arctic.
@ur momisugly Kristian February 23, 2016 at 10:34 pm
Actually, Willis’ Figure 1 seems to show …
1900 to 1940: Diurnal minimum temperature anomalies increased slightly faster than diurnal maximums.
1940 to about 1980: Diurnal maximum anomalies fell but minimums held steady.
After about 1980: Min and max anomalies rose at about the same rate.
Clouds tend to cool the days and warm the nights so increased cloudiness could be a cause of the 1940 to 1980 period.
Thomas: I think Willis, Bob and you agree.
Personally, I think there are huge regional discrepancies but I am not capable of analyzing the data like they do so I will defer to my own biases.
I don’t know if Bob Tisdale will object to quoting him here from his book, if so, the mods can remove this:
(With apologies to Bob if you wouldn’t like this referenced)
@BC, February 23, 2016 at 4:17 pm:
I don’t know what ‘persistent’ contrails are, but I often thought that contrails may have some impact.
Say, 5% of the sky are covered with contrails. At day, they reflect some light back to space and thus cool the
surface somewhat down. At night, the opposite happens, they keep some warmth from escaping to space.
Plus the jets propably warm up the air a bit, plus they leave a host of exhausts, say CO, CO2, NOx, SO2 and some particles in this layer of the atmosphere
Of course this all has some impact. But is it measurable? Is the effect bigger than the Hongkong butterfly flapping it’s wings?
But I think the contrail ‘density’ does not correlate to regions in Willis’ animations that show warming or cooling.
Regards, Lorenz
Or some of the (hidden) properties of the Berkeley Earth dataset used?
What would we expect to see if the CO2 theory were right? Uniform warming in all regions??
What would we expect to see if Willis Eschenbach’s theory were right? No warming in the tropics??
Willis,
John Christy has long emphasized the point that daytime maximum temperatures are much more meaningful than nighttime minimum temperatures, at least over land. The reason is that a temperature inversion often forms at night, so the surface T is only representative of the lowest 50 to 100 meters. The daytime T is usually representative of the entire boundary layer (allowing, of course, for the lapse rate), with a thickness of several hundred meters up to 2 or 3 km. I think that you have provided more evidence in support of using just daytime max T.
Do you happen to know how much difference that would make in the temperature trend?
Mike M.
I think the surface temperatures reported by most groups are the daily average. So, considering Figure 1. it looks like using only daily maximum temperature would cool the trend by a significant 0.3°C, which is about one third of the warming shown in, for example, the GISS temperature series since 1940.
Nightly minimums are also much more susceptible to localized, artificial, heating because man-made structures can slow nighttime surface winds, which reduces mixing, which decreases temperature.
Someone asked above how well the models compare with this result. I’ve posted a comparison of the GISS-E2-R model results at the bottom of the head post.
w.
Willis,
I studied your first images again and there’s something I don’t understand:
The first image shows a temperature anomaly from -0.1 (1900) to around 1.0 (2015)
But the following animations only show temperature anomalies from -0.1 to 0.4. How does this sum up?
Regards, Lorenz
With the data set starting around a cold AMO and ending on a warm AMO, there would be faster warming trends for the northern high latitudes.
Not a chance in hell that NH and SH are so in synch with each other. To see a 60 year period in the data but not the SH and NH out of sync like the Arctic and Antarctic sea-ice extent is a bit unbelievable,