I have previously addressed the NASA study that concluded the AIRS satellite temperatures “verified global warming trends“. The AIRS is an infrared temperature sounding instrument on the NASA Aqua satellite, providing data since late 2002 (over 16 years). All results in that study, and presented here, are based upon infrared measurements alone, with no microwave temperature sounder data being used in these products.
That reported study addressed only the surface “skin” temperature measurements, but the AIRS is also used to retrieve temperature profiles throughout the troposphere and stratosphere — that’s 99.9% of the total mass of the atmosphere.
Since AIRS data are also used to retrieve a 2 meter temperature (the traditional surface air temperature measurement height), I was curious why that wasn’t used instead of the surface skin temperature. Also, AIRS allows me to compare to our UAH tropospheric deep-layer temperature products.
So, I downloaded the entire archive of monthly average AIRS temperature retrievals on a 1 deg. lat/lon grid (85 GB of data). I’ve been analyzing those data over various regions (global, tropical, land, ocean). While there are a lot of interesting results I could show, today I’m going to focus just on the United States.
AIRS temperature trend profiles averaged over the contiguous United States, Sept. 2002 through March 2019. Gray represents an average of day and night. Trends are based upon monthly departures from the average seasonal cycle during 2003-2018. The UAH LT temperature trend (and it’s approximate vertical extent) is in violet, and NOAA surface air temperature trends (Tmax, Tmin, Tavg) are indicated by triangles. The open circles are the T2m retrievals, which appear to be less trustworthy than the Tskin retrievals.
Because the Aqua satellite observes at nominal local times of 1:30 a.m. and 1:30 p.m., this allows separation of data into “day” and “night”. It is well known that recent warming of surface air temperatures (both in the U.S. and globally) has been stronger at night than during the day, but the AIRS data shows just how dramatic the day-night difference is… keeping in mind this is only the most recent 16.6 years (since September 2002):
The AIRS surface skin temperature trend at night (1:30 a.m.) is a whopping +0.57 C/decade, while the daytime (1:30 p.m.) trend is only +0.15 C/decade. This is a bigger diurnal difference than indicated by the NOAA Tmax and Tmin trends (triangles in the above plot). Admittedly, 1:30 a.m. and 1:30 pm are not when the lowest and highest temperatures of the day occur, but I wouldn’t expect as large a difference in trends as is seen here, at least at night.
Furthermore, these day-night differences extend up through the lower troposphere, to higher than 850 mb (about 5,000 ft altitude), even showing up at 700 mb (about 12,000 ft. altitude).
This behavior also shows up in globally-averaged land areas, and reverses over the ocean (but with a much weaker day-night difference). I will report on this at some point in the future.
If real, these large day-night differences in temperature trends is fascinating behavior. My first suspicion is that it has something to do with a change in moist convection and cloud activity during warming. For instance more clouds would reduce daytime warming but increase nighttime warming. But I looked at the seasonal variations in these signatures and (unexpectedly) the day-night difference is greatest in winter (DJF) when there is the least convective activity and weakest in summer (JJA) when there is the most convective activity.
One possibility is that there is a problem with the AIRS temperature retrievals (now at Version 6). But it seems unlikely that this problem would extend through such a large depth of the lower troposphere. I can’t think of any reason why there would be such a large bias between day and night retrievals when it can be seen in the above figure that there is essentially no difference from the 500 mb level upward.
It should be kept in mind that the lower tropospheric and surface temperatures can only be measured by AIRS in the absence of clouds (or in between clouds). I have no idea how much of an effect this sampling bias would have on the results.
Finally, note how well the AIRS low- to mid-troposphere temperature trends match the bulk trend in our UAH LT product. I will be examining this further for larger areas as well.
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It’s UHI right???? Isn’t that obvious or am I being ignorant here?
Exactly. This phenomenon does not occur at rural stations.
Disagree. It’s water vapor that’s keeping the nights warmer.
The article claims that this phenomena reverses over the oceans. If it was just water vapor, you should see the strongest signal over the oceans, not a reversed one.
Never mind. Over the oceans, the amount of water in the air would be pretty much constant so there would be no change. I withdraw my objection.
It is the dew point in fact!
John
3% of land surface is urban. It is only a problem with thermometer readings in those areas.
That’s a good point Bruce. I wonder if the datapoints can be separated out to see where the delta between day and night is most evident. When all data is mashed together, could the effect of the urban heat islands be so strong that it affects the overall results?
Do you realise that this post is about satellite measurements?
So are you suggesting that satellite measurements are unable to differentiate between UHI in cities and the lower rural temperatures?
A breakdown between geographic urban and rural temperatures as measured by satellite would be very helpful. Intriguingly, as stated, the greatest night time warming is in winter, but without comment that is the season when houses and offices are heated massively with attendant heat loss to atmosphere.
On what had been presented, with no urban / rural differentiation I suspect that UHI is a very significant component ov the revorded “warmjng”.
Do you realise it is data measured from the surface upwards?
I live in the rural mountains of Northern California, 100 miles from the Pacific. The night time temps have also been warmer for years, although that has changed in recent years with night temps returning to average temps at times. Also, I spent many hundreds of hours looking at evening temps at other locations around the globe using weather sites who have historical data, and have noted a similar change where the above average night temps have returned closer to average, or even below average at times in some regions. There has been a definite change underway over the last 4 years.
Not uhi.
Urban area is less than 5%.
I am uncertain why the greater warming at night is at all a surprise. It is a prediction of both global warming caused by CO2, and the Urban Heat Island Effect.
The warming at an altitude at night would have to be due to either CO2 or additional water in the atmosphere (possibly as clouds) – can’t blame a nighttime rise of temperature on the Sun. People sometimes forget it isn’t one or the other – its both. Some temperature rise do to CO2 and some to UHIE which would explain nicely the sudden increase near the surface.
To separate UHIE and CO2, just look at a large rural area and see if the curve changes.
Or look at northern Canada…if its CO2 then nighttime temperatures in northern Canada have had to go up even more dramatically.
If its clouds, then coasts where cloud formation is likely would show the greatest changes. southern Texas would be a good location to look for that (Gulf warm air).
Try looking at the Sahara desert …. ain’t no water vapor, and probably not a whole lotta clouds either. ….. if it’s a CO2 signal, that would be where I would expect to see it.
Maybe it is mostly the CO2 signal, demonstrating the benign nature of CO2 induced warming. The main impact of such warming would be longer growing seasons, wider growing regions and less chance of killing frosts and freezes during growing seasons.
If we weren’t adding CO2 to the air accidentally, we would have to do it on purpose! The benefits are extraordinary!
My guess is some form of UHI related to more luxury – more 24hr heating.
Both day and night are warmed but night would be affected by UHI to a greater degree.
the massive shift to reverse cycle aircons pumping out hot air? instead of more confined older radiant or indoor fan heaters?
It’s a satellites view. Less than 5 percent of what is viewed is urban
cloud cover at night holds the heat in. Water Vapor is the culprit…if natural or artificial (chemtrails)… Greenhouse effect as cause of global warming is a nighttime phenomenon…the heat of the day is held in and is not going out into space. I am very concerned about the geoengineering that is going on, the weaponization of weather, chemtrails, and the “Global Dimming Project” being funded by Bill Gates.
Looks like the new approach is to take a lead from sceptics and plant a conspirator in the oppositions ranks to make them look dumb like we did with AOC.
That’s funny, right there 🙂
“… I am very concerned about…the weaponization of weather, chemtrails…”
Stick to InfoWars and tinfoil hat functions.
even if it isnt chemtrails but just the massive increase in airflights heating the upper areas from engines and the vapourtrails as well.
Dr Spencer, is there any indication cloudiness has increased? That clouds are forming at higher temperatures? If so that might explain the night time bias at least.
My understanding is that all the temperature data was collected when there was no cloud. Cloudless nights got warmer faster than cloudless days and the effect was more pronounced on the coldest nights.
Could it be said that the data intentionally then filters out much of the effect of clouds?
Seem to recall that the sensors can’t measure temperature through cloud.
Eric, where I live the dew point is what sets the nighttime low temps. When RH is 85% of saturation, there won’t be much cooling, clouds or clear (or shall we say hazy summer nights). The colder the air mass is, the more any moisture in it retards further cooling. That’s why the Arctic can’t get as cold in the winter, because at -60 F, a few molecules of water per cubic foot raise the temperature considerably.
In China it is the change from the 40w light bulb to the more common 100w bulb as the country gentrifies. At night time this must translate into greater temperatures Dr Spencer has indicated. The sheer volume of ‘new’ power being added in China and India is huge. It is no surprise that it is going up at night.
Increasing UHI effect across much of the US will also slow night time cooling to a greater extent than pushing up daytime warming. UHI can be thought of as more thermal mass (ever higher amounts of concrete, steel, asphalt) with more automobiles spewing heated exhaust and AC moving warmth to the “outside” air.
The vast open ocean areas and vast deserts with no urban growth is where AGW would be seen as a signature of GHE warming, separate from increasing UHIE.
Along with CO2, cars also emit considerable water vapor. While it has a short resident time, it is being replenished continuously.
Nope.
Mosher
Thank you for your informative, authoritative response that so succinctly demolishes Joel’s opinion.
Do you really think that anyone here so highly values your opinion that a single word is an adequate response to what wasn’t a solicitation of your opinion?
UHI mainly affects night time temperatures by buffering cooling as heat is released out of the heated surroundings…
This has been told many, many times. Global warming is not global. It is mainly over land and not over sea. It is mainly in the Northern Hemisphere and not in the Southern Hemisphere. It is mainly during winter and not during summer. And it affects mainly minimal (night) temperature and not maximal (day) temperature.
It does not fit the theory on how global warming should work, and since it affects mainly winter-night temperature it is not dangerous in the least. Quite the contrary.
Excellent summary. Why are the facts ignored by the MSM and Democrat politicians who constantly spew of gross exaggerations? Also even in the Northern Hemisphere the warming is greater in the ARCTIC and northern climes.
That makes sense if you go buy killing freezes in the Gulf of Mexico as we have not had one since 1989. This is when there is ice on the bays, shallow water especially in lower salinity. Fish die in significant numbers, shallow water oysters the same. Effect, often blamed on other things, is obvious in populations for a few years. They vary some in intensity and location falling a little more to the east or west. Last bunch 1940, 1947 1951, 1962, 1983, 1989. 1977 more towards Florida. 1962 and 1899 were real bad. Fed the Taylor army in 1845-46 with fish and turtles. Minor freezes since 1989 have had relatively small effects. Interesting to study however, as sea levels fall from very high pressure. Before modern regulations, people could gather them for food. Nice and fresh, well refrigerated.
Read Willis’ post . Yesterday .
Increased clouds/water vapor .
Looks like he’s ahead of the curve again ….. 😉
If I remember correctly the late John L Daly suggested in the 1980’s that one way of assessing CO2 impact on global temperature was to set up a large number of maximum/minimum thermometers worldwide at carefully selected sites away from UHI effects. A narrowing of the gap between Max. and Min. would indicate the effect of increasing CO2
Yes indeed Peter, a great citizen scientist . . .
For those who don’t know his work, check out:
https://www.john-daly.com
Yup. We see that
I know. Let’s spend $5 trillion on more roads, parking lots, and dense urban housing project incentives.
CO2 is a lady of the evening don’t you know?
Fifty years of riding a motorcycle have taught me that UHI effect is growing here in the US of A and much more noticeable at night.
And 30 years of me driving a convertible have shown me the same. It’s abundantly obvious that there are a good several up to and over 10 degrees F difference in night time temperatures near man made thermal masses. Highway overpasses come to mind.
48 years of riding motorcycles has taught me to get and use an electrically heated vest
Not uhi.
This is a satellite view of the entire surface
When I look at a satellite picture of the world at night (not that I can understand how they manage to film so that it is night at all points) I am struck by how much of the Northern Hemisphere and other populated areas is glowing. Is this light produced without hear?
That brightness is mostly produced by overexposure. From those satellite photos, one can calculate approximately what percentage of the Earth is the same temperature as the surface of the Sun. Incorrect of course.
Yes, light is silent.
…. but deadly
Sorry, I couldn’t resist.
Deadly if you are a vampire.
I share Dr. Spencer’s suapicion:
“If real, these large day-night differences in temperature trends is fascinating behavior. My first suspicion is that it has something to do with a change in moist convection and cloud activity during warming. For instance more clouds would reduce daytime warming but increase nighttime warming. But I looked at the seasonal variations in these signatures and (unexpectedly) the day-night difference is greatest in winter (DJF) when there is the least convective activity and weakest in summer (JJA) when there is the most convective activity.”
Not UHI which only effects thermometer readings in urban areas.
My guess would be drought followed by heavy rains and snow at the end of the trend period. An independent researcher found a good correlation of maximum temperatures with rainfall in Australia. The more humid air keeps maximum temps down. Contra to that is that cold fronts bring in rain but most of the rain comes from huge downpours. There was no correlation with minimum temperatures even though you would expect more humidity to keep temperatures up. I’m guessing that is unique to Australia where half the country gets most of its rain in monsoonal downpours in warmer months when it doesn’t get close to the dew point at night. The US might be significantly different but if its possible, it would be good to look at different zones and rainfall.
What I have always thought about this phenomenon is that the oceans are the reason for the night time warming. Surface winds carry the warmed air over land in the form of water vapor. In the daytime that leads to a slight cooling, while at night it means warmer temps. I think the current offshore surface winds are an example of how this works.
Note how there are no clouds offshore until way down by Los Angeles area. The surface winds then turn eastward and clouds immediately form, and then move east across the US. I have been watching this for the last 5 days. Prior to that the surface winds flowed south to around Monterey approximately, before turning to the west. Clouds then formed and were driven back up the middle of the Pacific towards Alaska and the Aleutian islands. Thus the warmer Alaska which alarmists like to make a big deal over. That has also meant warmer air flowing in to the west side of the Arctic which has led to reduced sea ice extent mainly in the Bering Sea. Thus the alarmists crowing over sea ice loss. I would like to hear their explanation how CO2 can drive surface winds. … https://earth.nullschool.net/#current/wind/surface/level/overlay=total_cloud_water/orthographic=-112.95,37.03,1107/loc=-122.748,34.888
We are talking about a warming trend. Given that the data shows a warming (nighttime) trend, that implies (not proves) something is changing that is causing that. One thing that we know is changing (increasing) is urban development. This factor cannot be ignored… and one would think that 3% of the landmass where there is a potential multiple degree warming trend would contribute to the overall trend.
And so my comment that warmer oceans is what leads to warmer temps at night for rural areas such as where I live. There is no UHI up here. I agree that UHI around urban areas is a strong effect. An example of what warmer night means for the mountain area where I live is that back in the 1960s/70s it was hard to grow tomatoes in Trinity County because the temps at night were much cooler than in recent decades. Night time temps have been running at least 6 degrees F above average from prior to the 1990s.
Over the last 9 years where I have lived up here it has been easy to grow nice tomatoes with the exception of last year where there was a definite change, and almost no spring time warmth. Many of the locals struggled with their tomato plants last year. This spring was a bit warmer earlier on, but cool spells keep intruding. Temps dropped 6 F to 38F in the last 2 nights.
Tonight is forecast to drop to 36 F and 35F tomorrow night. Then evening temps are slated to rise 10 F back into the mid 40s on Thursday. Typically, a gardener never set their plants out before mid to late May in this county. I will have to cover my tomatoes for the next several nights.
Goldminor: I did miss that you have no U affect in your area. Your information is terrific! Wow… there seems to be a real trend that you have felt because you are tuned to it. Farmers really need to know their conditions especially with organic sensors such as tomatoes. Thank you!
goldminor.
Thanks for explaining the lack of ice extent in the Bering Sea. I recently noticed those high billowing clouds between Paso Robles and Monterey. Beautiful but unusual here on the Central Coast.
It would be very interesting to see the difference between Arid and Tropical sites as this would help identify if the culprit is actually water ?
Anecdotally, I would whole heartedly agree with that assessment for my area in central Indiana. I can’t remember so may consecutive warm nights as we had during last summer. Usually on a Friday or Saturday night on a weekend you’ll find me and my neighbor and some family or friends out around one of the fire pits solving the problems of the world and on clear nights , checking out the night skies with my telescope. Last summer it was just too darn warm to enjoy a fire almost every evening.
The nighttime warming effect is much more noticeable in built-up areas and is likely due to the Urban Heat Island Effect. Increasing clouds and water vapour would add to the effect. All this leaves a very little role for the dreaded CO2.
We have balloon data that give humidity over this same period. What does it say about humidity in the atmosphere over the U. S. of A.?
Would be UHI except there isn’t nearly enough U.
Would be WVP except humidity lowers at night as air cools.
So, the science IS NOT settled.
Isn’t 3% of a big number, significant when we’re talking about fractions of a degree change? I do not think it is necessarily true that there is not enough U.
Mario. Especially when there is a clustering of thermometers in Urban areas. Also suburban is less heated, but more than rural. IIRC, Roy did a study that showed the effect present in communities of less than 100,000. I’d give the UHI effect maybe double 3% or more.
The data in this study isn’t from thermometers, in urban areas or anywhere else. This is looking at the IR spectrum from the AIRS satellite.
Yes, that is correct. Is their any position granularity that can be gleaned from the AIRS data? That may help dispel the UHI issue.
Randy, no, but the its the source of the heat! detected by AIRS.
“except humidity lowers at night as air cools.”
…
This is not true. For example, if the air has 30% relative humidity at 50F, when the temperature drops to 40F, the relative humidity increases. This continues until the air temperature drops low enough, reaching the dew point, then, and only then does the water vapor condense out of the air. When the dew point is reached the relative humidity is at 100%.
All true about RH vs AH (relative humidity vs absolute humidity)… Another thing that most non science people miss is that while AH decreases normally reduces as it cools… RH may increase when it cools. During this period, heat of condensation is released, thus resisting said cooling. Conclusion, AH does in fact store heat and resist cooling.
Rud
How does RH or AH lower as the air cools without precipitation? I would expect the RH to increase and the AH to stay constant. What am I missing?
One negative feedback to any kind of surface warming is convective cooling. This occurs predominately at the warmest times of the day. The atmosphere is always trying to cool things off using buoyancy and latent heat.
At night it really isn’t warm enough to have much convective cooling going on. Since, winters are cooler to begin with and have more night time hours you should see less convective cooling during those periods as well. So, I believe Roy’s first thoughts were mostly correct but didn’t take in account the longer nights that allow them to warm more.
This is more evidence of negative water vapor feedback to whatever is causing the warming. Note in this case a lot of the warming “trend” was created by the recent super El Nino. The planet’s hydrology didn’t care, it still tried to cool us off.