I continue to get blog comments and e-mails from well-intentioned folks who still don’t understand what determines temperature.

More specifically, I’m talking about those who claim that the atmosphere cannot influence the temperature of the surface because the atmosphere is (usually) colder than the surface. You know who you are. 😉

Their argument goes like this…since net heat flow must be from warmer to colder temperatures (the 2nd Law of Thermodynamics), the presence of the cold atmosphere cannot cause “heating” of the surface. I understand the source of this confusion, and it’s partly a matter of semantics: rather than saying that the “atmosphere heats the surface”, it would be less confusing to say that the “atmosphere reduces the ability of the surface to cool”.

To examine the issue, I’m going to keep the discussion as simple as I possibly can without sacrificing accuracy. Let’s return to one of my favorite examples, an open pot of warm water on the stove. Let’s assume the stove is set on low, and the water has reached a rather warm temperature.

Now, we all know from personal experience that if you put a lid on the pot, you can cause the water’s temperature to rise.

But how can that be, if the lid is colder than the water?

It’s because temperature is determined by both the rates of energy gain AND energy loss, and the lid reduces the water’s ability to cool to its surroundings. It doesn’t matter what the specific mechanism of energy loss is: conductive, convective, evaporative, or radiative.

When we put a lid on the pot, we reduce the rate of evaporative and convective heat loss, as well as radiative loss from the water surface, and the water’s temperature rises until the pot once again reaches a state of energy equilibrium. Convective and radiative energy losses increase with the water’s increasing temperature compared to its surroundings. In a sense, the lid further insulates the warm water from its cooler surroundings, where “insulates” means reducing heat flow in a general sense.

The same is true of the atmosphere. Greenhouse gases in the atmosphere represent a sort of “radiative lid”, reducing the rate at which the Earth’s surface cools to outer space.

One of the major points I am making is that you cannot determine equilibrium temperature based upon the rate of energy input alone: it’s a function of rates of energy gain AND energy loss.

An extreme example is the Sun. At the core of the Sun, “weak nuclear force” reactions produce energy (so I am told) at a rate even less what the human body produces…yet temperatures in the core reach an estimated 15,000,000 deg. C. The reason why the temperature reaches such extreme values is that energy LOSS outward from the Sun’s core is so inefficient.

The everyday examples of the presence of cooler objects keeping things warmer than they would otherwise be are everywhere. For example, coffee in a cold Styrofoam cup. Stack a second cup with the first, and the temperature of the coffee will stay warmer than it would otherwise be.

In fact, everything I can think of that has a heated warm core has its equilibrium temperature controlled by cooler materials surrounding that core. A blanket over your body, etc.

No doubt my detractors will claim I am making absurd comparisons, between a pot of water and the climate system. No, the basic principles of heat flow are the same. If you pump energy into an object, no matter what it is, its temperature will increase until it’s mechanisms of energy LOSS increase to the point where they equal the rate of energy gain. The temperature will then stabilize.

But those mechanisms of energy loss routinely involve materials with cooler temperatures than the warm object itself, materials which reduce the rate of energy loss.

I’ve purposely stayed away from arguments over the specific ways in which infrared radiation courses through the atmosphere so that I can make the more general point.

This issue is so basic I cannot fathom how seemingly intelligent people refuse to accept it, and are so militant in their attempts to refute it. I sometimes wonder whether they are funded by global warming alarmists to waste my time. 😉

More on Trenberth’s Missing Heat

While I don’t necessarily buy Trenberth’s latest evidence for a lack of recent surface warming, I feel I need to first explain why Trenberth is correct that it is possible for the deep ocean to warm while surface warming is seemingly by-passed in the process.

Then I will follow up with observations which run counter to his (and his co-authors’) claim that an increase in ocean surface wind-driven mixing has caused the recent lack of global warming.

Can Deep Ocean Warming Bypass the Surface?

It depends on what one means by “warming”. A temperature change is the net result of multiple processes adding and subtracting heat. Warming of the deep ocean originally caused by radiative forcing of the climate system cannot literally bypass the surface without some effect on temperature. But that effect might be to keep some cooling process from causing an even steeper dive in temperature.

It’s like adding a pint of warm water, and a gallon of cold water, to a sink full of room temperature water. Did adding the pint of warm water cause the temperature in the sink to rise?

To appreciate this, we first need to understand the basic processes which maintain the vertical temperature distribution in the global oceans. The following cartoon shows a North-South cross section of measured ocean temperatures in the Atlantic.

The average temperature distribution represents a balance between 3 major processes:

(1) surface heating by the sun (mitigated by surface evaporation and infrared radiative loss) which warms the relatively shallow ocean mixed layer;

(2) cold deepwater formation at high latitudes, which slowly sinks and fills up the oceans on time scales of centuries to millennia, and

(3) vertical mixing from wind-driven waves, the thermohaline circulation, and turbulence generated by flow over ocean bottom topography (the latter being partly driven by tidal forces).

The key thing to understand is that while processes (1) and (2) continuously act to INCREASE the temperature difference between the warm mixed layer and the cold deep ocean, the vertical mixing processes in (3) continuously act to DECREASE the temperature difference, that is, make the ocean more vertically uniform in temperature.

The average temperature distribution we see is the net result of these different, competing processes. And so, a change in ANY of these processes can cause surface warming or cooling, without any radiative forcing of the climate system whatsoever.

So, let’s look at a few ocean mixing scenarios in response to radiative forcing of the climate system (e.g. from increasing CO2, increasing sunlight, etc.), all theoretical:

Scenario 1) Warming with NO change in ocean mixing: It this case, surface warming is gradually mixed downward in the ocean, leading to warming trends that are a maximum at the ocean surface, but which decrease exponentially with depth.

Scenario 2) Warming with a SMALL increase in ocean mixing. This case will result in weaker surface warming, and slightly stronger warming of the deep ocean, both compared to Scenario 1. The warming still might decrease exponentially with depth.

Scenario 3) Warming with a LARGER increase in ocean mixing. This case could lead to an actual surface temperature decrease, but warming of the deep ocean, similar to what I believe Trenberth is claiming.

Yes, the surface waters “warmed” before the deep ocean in Scenario 3, but it was in the form of a weaker temperature drop than would have otherwise occurred.

Because of the immense heat capacity of the deep ocean, the magnitude of deep warming in Scenario 3 might only be thousandths of a degree. Whether we can measure such tiny levels of warming on the time scales of decades or longer is very questionable, and the new study co-authored by Trenberth is not entirely based upon observations, anyway.

I only bring this issue up because I think there are enough legitimate problems with global warming theory to not get distracted by arguing over issues which are reasonably well understood. It takes the removal of only one card to cause a house of cards to fall.

But it also points out how global warming or cooling can occur naturally, at least theoretically, from natural chaotic variations in the ocean circulation on long time scales. Maybe Trenberth believes the speedup in the ocean circulation is due to our driving SUVs and flipping on light switches. He has already stated that more frequent El Ninos are caused by anthropogenic global warming. (Except now they are less frequent — go figure).

In some sense, natural global warming and cooling events are made possible by the fact that we live within an exceedingly thin warm surface “skin” of a climate system in which most of the mass (the deep ocean) is exceedingly cold. Any variations in the heat exchange between those two temperature worlds (such as during El Nino with decreased mixing, or La Nina with increased mixing) can cause large changes in our thin-skinned world. It than sense, Trenberth is helping to point out a reason why climate can change naturally.

Have Ocean Winds Increased Recently?

Trenberth and co-authors claim that their modeling study suggests an increase in ocean surface winds since 2004 has led to greater mixing of heat down into the ocean, limiting surface warming.

Fortunately, we can examine this claim with satellite observations. We have daily global measurements of ocean surface roughness and foam generation, calibrated in terms of an equivalent 10 meter height wind speed, from AMSR-E:

I don’t know about you, but I don’t see an increase in surface winds since 2004 in the above plot. This plot, which is based upon wind retrievals that have been compared to (as I recall) close to 1 million buoy observations, really needs to be extended back in time with SSM/I and SSMIS data, which would take it back to mid-1987. That’s on my to-do list.

So far, I would say that the so-called missing heat problem is not yet solved. I have argued before that I don’t think it actually exists, since the “missing heat” argument assumes that feedbacks in the climate system are positive and that radiative energy is accumulating in the system faster than surface warming would seem to support.

For the reasons outlined above, Trenberth’s view of deep ocean storage of the missing heat is still theoretically possible since increased vertical ocean mixing doesn’t have to be wind-driven. But I remain unconvinced by arguments that depend upon global deep ocean temperature changes being measured to an accuracy of hundredths or even thousandths of a degree.

Finally, as I have mentioned before, even if increased rate of mixing of heat downward is to blame for a recent lack of surface warming, the total energy involved in the warming of the deep oceans is smaller than that expected for a “sensitive” climate system. Plots of changes in ocean heat content since the 1950’s might look dramatic with an accumulation of gazillions of Joules, but the energy involved is only 1 part in 1,000 of the average energy flows in and out of the climate system. To believe this tiny energy imbalance is entirely manmade, and has never happened before, requires too much faith for even me to muster.

Here’s a Youtube video of the Stossel segment on which Gavin Schmidt and I appeared on March 28.

The satellite-based microwave global average sea surface temperature (SST) update for March 2013 is -0.01 deg. C, relative to the 2003-2006 average (click for large version):

The anomalies are computed relative to only 2003-2006 because those years were relatively free of El Nino and La Nina activity, which if included would cause temperature anomaly artifacts in other years. Thus, these anomalies cannot be directly compared to, say, the Reynolds anomalies which extend back to the early 1980s. Nevertheless, they should be useful for monitoring signs of recent ocean surface warming, which appears to have stalled since at least the early 2000’s. (For those who also track our lower tropospheric temperature [“LT”] anomalies, these SST anomalies average about 0.20 deg. C cooler since mid-2002).

The SST retrievals come from Remote Sensing Systems (RSS), and are based upon passive microwave observations of the ocean surface from AMSR-E on NASA’s Aqua satellite, the TRMM satellite Microwave Imager (TMI), and WindSat. While TMI has operated continuously through the time period (but only over the tropics and subtropics), AMSR-E stopped nominal operation in October 2011, after which Remote Sensing Systems patched in SST data from WindSat. The various satellite datasets have been carefully intercalibrated by RSS.

Despite the relatively short period of record, I consider this dataset to be the most accurate depiction of SST variability over the last 10+ years due to these instruments’ relative insensitivity to contamination by clouds and aerosols at 6.9 GHz and 10.7 GHz.

Our Version 5.5 global average lower tropospheric temperature (LT) anomaly for March, 2013 is +0.18 deg. C, essentially unchanged from February (click for large version):

Later I will post the microwave sea surface temperature update, but it is also unchanged from February.

The global, hemispheric, and tropical LT anomalies from the 30-year (1981-2010) average for the last 15 months are:

YR MON GLOBAL NH SH TROPICS
2012 1 -0.134 -0.065 -0.203 -0.256
2012 2 -0.135 +0.018 -0.289 -0.320
2012 3 +0.051 +0.119 -0.017 -0.238
2012 4 +0.232 +0.351 +0.114 -0.242
2012 5 +0.179 +0.337 +0.021 -0.098
2012 6 +0.235 +0.370 +0.101 -0.019
2012 7 +0.130 +0.256 +0.003 +0.142
2012 8 +0.208 +0.214 +0.202 +0.062
2012 9 +0.339 +0.350 +0.327 +0.153
2012 10 +0.333 +0.306 +0.361 +0.109
2012 11 +0.282 +0.299 +0.265 +0.172
2012 12 +0.206 +0.148 +0.264 +0.138
2013 1 +0.504 +0.555 +0.453 +0.371
2013 2 +0.175 +0.368 -0.018 +0.168
2013 3 +0.184 +0.332 +0.036 +0.221

Whenever I see reference to the regional nature of climate feedbacks, I cringe.

I will admit that what happens on a regional basis determines net global climate feedbacks, but feedbacks cannot be evaluated regionally. Feedbacks only make sense in the global average.

First, a summary of what climate feedbacks are, by definition: In response to a surface temperature change, other changes in the climate system (clouds, etc.) can either magnify (positive feedback) or reduce (negative feedback) the original temperature change. The single largest feedback is negative: the increase in infrared energy lost to space as temperature increases. This so-called “Planck effect” is what stabilizes the climate system against runaway change.

Cloud feedbacks are generally considered to be the most uncertain, and could be positive or negative (I believe they are negative). The contribution to water vapor feedback by the atmospheric boundary layer is almost certainly positive, but the free-tropospheric contribution to water vapor feedback is much more uncertain, since it depends upon microphysical processes within precipitation systems which are the source of free tropospheric air.

(And for those who object to the use of “feedback” in a climate context, sorry. Until a better term comes along which better reflects the recursive nature of the forcing-response process, we are stuck with it.)

So, why can’t feedbacks be evaluated regionally? Because a change in one region will, in general, affect other regions, through changes in atmospheric vertical circulation systems.

For example, if the Pacific warm pool was to warm, we might expect increases in clouds and precipitation there. But those changes are the result of increased rising air over the warm pool, and that extra rising air must — through mass continuity — be exactly matched by increased sinking air away from the warm pool…possibly thousands of miles away.

In fact, since in the tropics the areal extent of (weakly) sinking air is so much greater than that of the (strongly) rising air, the feedback response to a warming of the warm pool can be dominated by what happens thousands of miles away from the warm pool. This is why the original “thermostat hypothesis” of Ramanathan and Collins (1991) was widely criticized as too simplistic.

Feedbacks can only be evaluated over entire vertical circulation systems, and since these systems are interconnected around the world without clear boundaries, feedbacks really only make sense in the global average.

Now, it might well be that the feedback response is different for different kinds of forcing, or it might be that the net feedback varies over time as the climate system evolves in response to a forcing. My only point is that it doesn’t really make sense to talk about “regional feedbacks”, unless you know that the regional change has not affected vertical circulation systems that extend outside the region of interest. Sure, you can compute a number for the change in the regional radiative budget in response to a temperature change, but it would be incorrect to call that number the “feedback response” to the temperature change.

John Stossel interviewed me and Gavin Schmidt yesterday at the FoxNews studios in Manhattan, and I’m told he will interview Matt Ridley today, for tomorrow nights Stossel Show (9 p.m. EDT Thursday, March 28, Fox Business Channel) entitled “Green Tyranny”. As is often the case, the show might air on FoxNews Channel once or twice this weekend.

Looking for a global warming debate, Stossel said they asked 10 natural climate change deniers (sorry, my term, I couldn’t help myself), and only Gavin took them up on it. Scott Denning was also willing, but unavailable.

At least Gavin knows what he’s talking about…I’ve debated people who so badly mangled the explanation of anthropogenic climate change that I had to fix it for them so the audience wouldn’t be misled.

I thought we both held our own, although I wish I would have answered his CO2 “fingerprint” claims better. There is no CO2 fingerprint of warming; warming due to any cause (say, a slight decrease in oceanic cloudiness) will look basically the same: stronger over land than ocean (a land-vs-ocean heat capacity issue); warming *should* increase with height in the troposphere (a moist convective adjustment issue).

What could cause a natural change in clouds (as I am sometimes asked by the other side)? Well, what causes chaos?

I agreed with Gavin that stratospheric cooling might well be a fingerprint of increasing CO2, but the stratosphere involves MUCH simpler physics than the troposphere/land/ocean system, with basically just radiation operating, no clouds, and a vanishingly small heat capacity. The coupled ocean/atmosphere climate system is a nonlinear dynamical system, thus chaotic, capable of causing changes all by itself. The past evidence for natural climate change on multidecadal, centennial, and millennial time scales is abundant.

The average energy imbalance associated with ocean warming since the 1950s — so widely attributed to our CO2 emissions — is only 1 part in 1,000 (around 0.25 Watts/m2 versus average flows closer to 250 W/m2)…do we really believe the climate system is incapable of causing such imbalances all by itself? Just based upon global warming theory, I believe part of the warming *is* anthropogenic, but as I said during taping, I don’t think we have a clue how much of it.

Talking with Stossel afterward, he said he thought Gavin did a good job of articulating his position. I hope Gavin is willing to return, although I could tell he was somewhat annoyed by the conservative/libertarian vibe he was surrounded by. It will also be interesting to see what Matt Ridley has to say.

Many people have noted on the satellite temperatures webpage the plunge in temperatures as recorded by AMSU channel 5 on the Aqua satellite. Since it looked pretty suspicious, I decided to investigate.

The following plot shows 3 satellites’ global AMSU5 measurements (Aqua, NOAA-15, and NOAA-18) that I computed this morning from the raw orbit files. The dates run from Feb. 1 through yesterday, March 24:

Clearly, Aqua AMSU ch 5 is now “out to lunch”. The reason why the plunge in Aqua temperatures in the above plot is so much stronger than what is displayed on the daily update website is that the latter shows running 3-day averages, and is only updated through March 23.

We knew that this channel has been slowly failing for a long time, which is why we have not been using it in our monthly updates. We will discuss the possibility of switching to the NOAA satellites on the website, although since the site is NASA-funded, they are reluctant to spend resources on NOAA satellite data. But, given the popularity of the page, we will work something out even if we have to make our own web page.

I ran across an old pamphlet with photos of the tornado which struck Omaha 100 years ago today, and thought I would post a few. The tornado killed 140, injured 350, and demolished 550 houses (click on the photos for the full-size versions).

Here’s the 1st page description:
Nut-Shell Story of the Deadly Tornado
This most destructive windstorm hit Omaha about six o’clock in the evening, Easter Sunday, March 23, 1913. To the eye it had the distinctive funnel-shaped twisting character of the typical tornado, sweeping along at a furious rate of speed.

The damage done and the desolation left in its wake are clearly portrayed by the photographs taken the next day, and by those taken a second day after a light snowfall.

The description suggests an isolated supercell thunderstorm merging with a squall line, which was followed by a cold air mass. Clearly, had they known about the science of tornadoes back then, the event would have been blamed on the methane emissions from their horses. /sarc

Check out the cool skull-tornado artwork:

Note the board driven through the side of this upright piano:

If the tornado had hit this area today, there would be much more damage simply because there are more structures. It is hard to say what the loss of life would be, though, with a higher population density but better warnings.

There is a new location for the daily global satellite temperature page:

http://ghrc.nsstc.nasa.gov/amsutemps/

Choose “ch. 5” to get the channel closest to our (UAH) lower tropospheric (LT) product that we update once a month. Use “ch. 9” if you are interested in the lower stratosphere.

As a reminder…this page shows data from the AMSU instrument flying on the Aqua satellite, which we don’t use anymore because it is drifting warm relative to other satellites. For ch. 5, it is currently running about 0.2 deg. C too warm, so keep that in mind when estimating how the current month is shaping up compared to the same calendar month in previous years.