As the result of complaints I’m getting regarding certain commenters here who can’t make a point without insulting others, I’ve been forced to read through hundreds of comments. I will probably be implementing one or more changes regarding commenting. More on that later…

I’m also seeing some recurring science talking points that are “incorrect” (as incorrect as can be in the realm of science). I’ve gotten where I’ll let bad science be expressed here if it’s done respectfully, and then let others attempt to correct it. But since not everyone can remember what I’ve blogged on in years past (even I can’t remember some of it), I thought it might be good to review some highlights. It might reduce confusion from some of our newer visitors about what *I* understand and promote from the science, rather than letting my allowing of opinions being expressed here being interpreted as some sort of endorsement of others’ ideas.

Yes, the Greenhouse Effect is like a Real Greenhouse

Most objections to using the greenhouse analogy is that the atmosphere does not have a “roof” preventing convective heat loss like a greenhouse does. But those who claim this don’t realize that the greenhouse effect (GHE) is defined with no convective heat transport. The GHE is like a real greenhouse with a perfect roof. The original paper on this is Manabe & Strickler (1964), where they calculated the average surface temperature in pure radiative equilibrium (the surface and each atmospheric layer achieving a temperature where rates of absorbed and emitted radiation are equal– no convection) was about 70 deg. C warmer than what is actually observed. The weaker “33 deg. C” effect you often see attributed to the GHE is actually the sum of [GHE warming + convective cooling]. It is NOT the extra warming from the GHE alone. So, yes, Virginia, Earth’s greenhouse effect is like a real greenhouse (even more so, because its “roof” is perfect, whereas a real greenhouse roof does lose some heat through conduction of heat through the roof and then convective air currents cooling the roof).

No, the Saturation Effect of Increasing CO2 on Global Temperatures is Not Being Ignored in Global Warming Projections

As CO2 increases in the atmosphere, the effect it has on the loss of IR energy to outer space becomes progressively less, producing a saturation effect. But this is true in all climate models as well, including the ones that produce unrealistic (5 deg. C or more) of warming from a doubling of atmospheric CO2. Thus, invoking the “saturation effect” as a magical talisman to refute CO2-induced warming will not work.

In fact, it is not possible for a planetary atmosphere to become totally opaque to IR radiation, because it would have to be fully, 100% saturated across all pressure-broadening affected wavelengths and through the entire depth of the atmosphere. Even Venus, with ~200,000 times as much CO2 as Earth’s atmosphere, is not “saturated” regarding the absorption of IR radiation.

The saturation talking point seems to have ramped up since publication of the recent theoretical line-by-line computations by my friend Will Happer & his co-author last year. But their calculations result in the same amount of radiative forcing from 2XCO2 as others have computed, and (again) are already included in even the most strongly warming climate models out there. Happer’s calculations might be the most complete and accurate to date (I don’t know), but their results do not change what is already in climate models in any significant way.

Yes, the Cold Atmosphere can Keep the Surface Warmer than if the GHE Did Not Exist

Just like adding insulation to the walls in your house in winter can increase the temperature inside (for the same amount of energy input from a furnace), the “cold” atmosphere helps keep the Earth’s surface warmer than if the radiative insulation it provides did not exist. As I’ve stated before, just take a $50 handheld IR thermometer and point it upward in a clear sky, and see how the indicated temperature warms as you point the thermometer obliquely, away from the zenith. That is the GHE acting on the thermopile within the thermometer, raising its temperature because more IR radiation from the sky occurs from the oblique angle than from pointing it straight up…. even though the atmosphere up there is colder than the interior of the thermometer.

A recent experiment posted at Watts Up With That shows how a cooler object can make a warm object even warmer. Over 10 years ago I used a different experimental setup to demonstrate the same thing.

Now, regarding commenting here… To begin with, I think I will spend a couple of hours computing how many of the frequent commenters’ comments here include insults. Would everyone like to see those statistics? Should we consider an award for the person who has the highest percentage of insults?

As you can tell, Dr. Roy is grumpy this morning.

Now, get off my lawn.

UPDATE: I’m going to start limiting comments to 10 per person per day. Also, at least 50% of some commenters’ comments are just insults or other negative noise with no useful input. Start policing your own behavior because in a week or so I might start posting Insult Scores and banning folks. Others visiting this blog don’t want to wade through all of your negativity to find useful insights. Grumble, grumble…

The Version 6 global average lower tropospheric temperature (LT) anomaly for July, 2024 was +0.85 deg. C departure from the 1991-2020 mean, up from the June, 2024 anomaly of +0.80 deg. C.

The linear warming trend since January, 1979 now stands at +0.15 C/decade (+0.13 C/decade over the global-averaged oceans, and +0.21 C/decade over global-averaged land).

The following table lists various regional LT departures from the 30-year (1991-2020) average for the last 19 months (record highs are in red):

The full UAH Global Temperature Report, along with the LT global gridpoint anomaly image for July, 2024, and a more detailed analysis by John Christy, should be available within the next several days here.

The monthly anomalies for various regions for the four deep layers we monitor from satellites will be available in the next several days:

Lower Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt

Mid-Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tmt/uahncdc_mt_6.0.txt

Tropopause:

http://vortex.nsstc.uah.edu/data/msu/v6.0/ttp/uahncdc_tp_6.0.txt

Lower Stratosphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tls/uahncdc_ls_6.0.txt

That title might trigger some people, so let me explain. Yes, in a warming world due to increasing CO2 there will be a statistical increase in “unusually warm” years. But assuming the warming is entirely due to steadily increasing CO2 causing a slight (currently ~1%) energy imbalance in the climate system, then the warming that results is about ~0.02 deg. C per year.

Anything different from that small 0.02 deg. C per year warming is due to natural climate variability.

This can be easily demonstrated with a simple 1D energy balance model. Anything different is due to natural weather and climate variability.

If we take our UAH global lower tropospheric temperature product as an example, 2023 was a whopping +0.51 deg. C above the 1991-2020 average. Using our trend of +0.14 deg. C per decade as a warming rate baseline, then 2023 should have been +0.25 deg. C above the baseline, but instead it was twice as warm as that. So, about half that warmth was natural (AGAIN… assuming the background warming trend is 100% due to humans).

So, when we get a really warm year (like 2023, and probably 2024) then something other than CO2 is mostly to blame. All of the media and environmentalist hype is just noise. Really warm years will be offset by cooler years (which no one reports on because it’s not newsworthy) so that the long term temperature trends remains ~0.02 deg C per year of warming (+0.014 deg C per year in our satellite data).

Again, this assumes CO2 is 100% to blame for the long-term warming trend, and the 0.02 value assumes a climate sensitivity on the low end of IPCC projections, which is consistent with observations-based diagnoses of climate sensitivity; change it to 0.03 if you want, my point still stands.

It’s really that simple.

The Version 6 global average lower tropospheric temperature (LT) anomaly for June, 2024 was +0.80 deg. C departure from the 1991-2020 mean, down from the May, 2024 anomaly of +0.90 deg. C.

The linear warming trend since January, 1979 remains at +0.15 C/decade (+0.13 C/decade over the global-averaged oceans, and +0.20 C/decade over global-averaged land).

The following table lists various regional LT departures from the 30-year (1991-2020) average for the last 18 months (record highs are in red):

The full UAH Global Temperature Report, along with the LT global gridpoint anomaly image for June, 2024, and a more detailed analysis by John Christy, should be available within the next several days here.

The monthly anomalies for various regions for the four deep layers we monitor from satellites will be available in the next several days:

Lower Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt

Mid-Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tmt/uahncdc_mt_6.0.txt

Tropopause:

http://vortex.nsstc.uah.edu/data/msu/v6.0/ttp/uahncdc_tp_6.0.txt

Lower Stratosphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tls/uahncdc_ls_6.0.txt

One of the main complaints rational people have had about global warming projections is that the “baseline” scenarios assumed for future CO2 emissions are well above what is realistic. As Roger Pielke, Jr, has been pointing out for years, the U.N. IPCC continues to make these exaggerated scenarios a high priority, and it looks like the next IPCC Assessment Report (AR7) will continue that tradition.

While Roger doesn’t believe there are nefarious motives in this strategy, I do: The IPCC knows very well that as long as climate models are run that produce extreme amounts of climate change, few people will question the assumptions that went into those model projections. Peoples’ careers now depend upon the continuing fear of a “climate crisis” (which has yet to materialize).

But I haven’t been able to find a good, recent graph showing how actual global CO2 emissions compare to those scenarios. So I made one. In the following plot I show estimates of global CO2 emissions from fossil fuel use through 2023, and EIA projections every 5 years from 2025 through 2050 (green). Also shown are the latest (AR6) SSP scenarios that come closest to the AR5 RCP scenarios. (In order to get the SSP scenarios to line up pretty well with the actual emissions in the early years I had to subtract the SSP land use CO2 emissions from the SSP total CO2 emissions values).

While an emissions scenario like SSP5-8.5 has been widely used to scare humanity with climate model projections of extreme warming, this plot shows the last several years of global emissions (through 2023) suggest the future will look nothing like that scenario.

(And, it should come as no surprise that “Net Zero” emissions by 2050 is a delusion.)

I encourage everyone to subscribe to Pielke’s The Honest Broker substack, where he discusses this and related issues in great detail.

The recent record-setting UAH satellite-based temperatures of the lower troposphere can be compared to a different combination of satellite MSU/AMSU channels which help to corroborate the temperature trends from our “lower tropospheric” (LT) combination of channels.

The three channels we use for LT are MSU channels 2 (“MT”), 3 (“TP”), and 4 (“LS”), (AMSU channels 5, 7, and 9). The primary channel used comes from “MT” (MSU channel 2 or AMSU channel 5), which has the largest weight:

LT = 1.538*MT – 0.548*TP + 0.01*LS

Here is a figure from our 2017 paper on Version 6 of our dataset, showing the three main temperature sounding channels and how they are combined for the LT product:

But we have also experimented with a weighted average of MSU channels 3 (“TP”) and 4 (“LS”), (AMSU channels 7 and 9), which produces an averaging kernel in the upper troposphere (nearly insensitive to stratospheric cooling in the tropics, but somewhat sensitive to stratospheric cooling in the extra-tropics where the tropopause [the boundary between troposphere and stratosphere] is lower). This provides an independent check on our LT synthesized channel, keeping in mind one is centered in the lower troposphere and the other is centered in the upper troposphere.

We noticed that last month (May, 2024) produced a record warm global average temperature in the tropopause channel (AMSU channel 7), so I decided to investigate. Combining channel 7 and 9 for an Upper Troposphere (UT) synthesized channel,

UT = 1.35*TP – 0.35*LS

The resulting vertical profile of weight in the atmosphere is the purple curve, below:

That UT synthesized channel produces the following temperature anomalies:

Note that for the global average, the synthesized UT channel reached record warm values in February, then March, then April, and then May, 2024.

In the tropics, March and then May produced records, but not by much… the 1997/98 El Nino produced upper tropospheric warmth nearly as strong as our recent El Nino.

If we look at just the extra-tropics (next chart) we see the northern latitudes had record warmth in March. But the southern latitudes May came in only 3rd warmest, behind September 2019, and November, 1988.

Note also that the global UT trend is the same as the lower tropospheric (LT) trend, +0.13 C/decade. Since the global UT has some small contamination from lower stratospheric cooling, the “true” UT value (if the stratospheric influence could be removed) would be somewhat warmer. By how much? I’m not sure… maybe +0.15 rather than +0.13 C/decade as an educated guess.

Taken together, I believe this shows that our traditional LT (lower tropospheric) temperature trends are basically corroborated by the other channels of MSU/AMSU.

Keep in mind that when John Christy and I compare these various trends to climate models, it is always apples-to-apples: the climate models’ atmospheric pressure level data are combined and weighted to approximate the same weighting functions as the satellite senses.

The Version 6 global average lower tropospheric temperature (LT) anomaly for May, 2024 was +0.90 deg. C departure from the 1991-2020 mean, down from the record-high April, 2024 anomaly of +1.05 deg. C.

The linear warming trend since January, 1979 remains at +0.15 C/decade (+0.13 C/decade over the global-averaged oceans, and +0.20 C/decade over global-averaged land).

The following table lists various regional LT departures from the 30-year (1991-2020) average for the last 17 months (record highs are in red):

The full UAH Global Temperature Report, along with the LT global gridpoint anomaly image for May, 2024, and a more detailed analysis by John Christy, should be available within the next several days here.

The monthly anomalies for various regions for the four deep layers we monitor from satellites will be available in the next several days:

Lower Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt

Mid-Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tmt/uahncdc_mt_6.0.txt

Tropopause:

http://vortex.nsstc.uah.edu/data/msu/v6.0/ttp/uahncdc_tp_6.0.txt

Lower Stratosphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tls/uahncdc_ls_6.0.txt

The Version 6 global average lower tropospheric temperature (LT) anomaly for April, 2024 was +1.05 deg. C departure from the 1991-2020 mean, up from the March, 2024 anomaly of +0.95 deg. C, and setting a new high monthly anomaly record for the 1979-2024 satellite period.

The linear warming trend since January, 1979 remains at +0.15 C/decade (+0.13 C/decade over the global-averaged oceans, and +0.20 C/decade over global-averaged land).

It should be noted that the CDAS surface temperature anomaly has been falling in recent months (+0.71, +0.60, +0.53, +0.52 deg. C over the last four months), while the satellite deep-layer atmospheric temperature has been rising. This is usually an indication of extra heat being lost by the surface to the deep-troposphere through convection, and is what is expected due to the waning El Nino event. I suspect next month’s tropospheric temperature will fall as a result.

The following table lists various regional LT departures from the 30-year (1991-2020) average for the last 16 months (record highs are in red):

The full UAH Global Temperature Report, along with the LT global gridpoint anomaly image for April, 2024, and a more detailed analysis by John Christy, should be available within the next several days here.

The monthly anomalies for various regions for the four deep layers we monitor from satellites will be available in the next several days:

Lower Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt

Mid-Troposphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tmt/uahncdc_mt_6.0.txt

Tropopause:

http://vortex.nsstc.uah.edu/data/msu/v6.0/ttp/uahncdc_tp_6.0.txt

Lower Stratosphere:

http://vortex.nsstc.uah.edu/data/msu/v6.0/tls/uahncdc_ls_6.0.txt

Some commenters on my previous blog post, Net Zero CO2 Emissions: A Damaging and Totally Unnecessary Goal, were dubious of my claim that nature will continue to remove CO2 from the atmosphere at about the same rate even if anthropogenic emissions decrease…or even if they were suddenly eliminated.

Rather than appeal to the simple CO2 budget model I created for that blog post, let’s look at the published data from the 123 (!) authors the IPCC relies upon to provide their best estimate of CO2 flows in and out of the atmosphere, the Global Carbon Project team. I created the following chart from their data spreadsheet available here. Updated yearly, the 2023 report shows that their best estimate of the net removal of CO2 from the atmosphere by land and ocean processes has increased along with the rise in atmospheric CO2. This plot is from their yearly estimates, 1850-2022.

The two regression line fits to the data are important, because they imply what will happen in the future as CO2 in the atmosphere continues to rise. In the case of the nonlinear fit, which has a slightly better fit to the data (R2 = 89.3% vs. 88.8%) the carbon cycle is becoming somewhat less able to remove excess CO2 from the atmosphere. This is what carbon cycle modelers expect to happen, and there is some weak evidence that is beginning to occur. So, let’s conservatively assume that nonlinear rate of removal (a gradual decrease in nature’s ability to sequester excess atmospheric CO2) will exist in the coming decades as a function of atmospheric CO2 content.

A Modest CO2 Reduction Scenario

Now, let’s assume a 1% per year cut in emissions (both fossil fuel burning and deforestation) in each year starting in 2024. That 1% per year cut is nowhere near the Net Zero goal of eliminating CO2 emissions by 2050 or 2060, which at this point seems delusional since humanity remains so dependent upon fossil fuels. The resulting future trajectory of atmospheric CO2 looks like this:

This shows that rather modest cuts in global CO2 emissions (33% by 2063) would cause CO2 concentrations to stabilize in about 40 years, with a peak CO2 value of 460 ppm. This is only 2/3 of the way to “2XCO2” (a doubling of estimated pre-Industrial CO2 levels).

How Much Global Warming Would be Caused Under This Scenario?

Assuming all of the atmospheric CO2 rise is due to human activities, and further assuming all climate warming is due to that CO2 rise, the resulting eventual equilibrium warming (delayed by the time it takes for mixing to warm the deep oceans) would be about 1.2 deg.C assuming the observations-based Effective Climate Sensitivity (EffCS) value of 1.9 deg. C we published last year (Spencer & Christy, 2023). Using the Lewis and Curry (2018) value around 1.6-1.7 deg. C would result in even less future warming.

And that’s if no further cuts in emissions are made beyond the 33% cuts vs. 2023 emissions. If the 1% per year cuts continue past the 2060s, as is shown in the 2nd graph above, the CO2 content of the atmosphere would then decline, and future warming would not be in response to 460 ppm, which was reached only briefly in the early 2060s. It would be a still lower value than 1.2 deg. C. Note these are below the 1.5 deg. C maximum warming target of the 2015 Paris Agreement, which is the basis for Net Zero policies.

Net Zero is Based Upon a Faulty View of Nature

Net Zero assumes that human CO2 emissions must stop to halt the rise in atmospheric CO2. This is false. The first plot above shows that nature removes atmospheric CO2 at a rate based upon the CO2 content of the atmosphere, and as long as that remains elevated, nature continues to remove CO2 at a rapid rate. Satellite-observed “global greening” is evidence of that over land. Over the ocean, sea water absorbs CO2 from the atmosphere in proportion to the difference in CO2 partial pressures between the atmosphere and ocean, that is, the higher the atmospheric CO2 content is, the faster the ocean absorbs CO2.

Neither land nor ocean “knows” how much CO2 we emit in any given year. They only “know” how much CO2 is in the atmosphere.

All that is needed to stop the rise of atmospheric CO2 is for yearly anthropogenic emissions to be reduced to the point where they match the yearly removal rate by nature. The Global Carbon Project data suggest that reduction is about 33% below 2023 emissions. And that is based upon the conservative assumption that future CO2 removal will follow the nonlinear curve in the first plot, above, rather than the linear relationship.

Finally, the 1.5 deg. C maximum warming goal of the 2015 Paris Agreement would be easily met under the scenario proposed here, a 1% per year cut in global net emissions (fossil fuel burning plus land use changes), with a total 33% reduction in emissions vs. 2023 by the early 2060s.

I continue to be perplexed why Net Zero is a goal, because it is not based upon the science. I can only assume that the scientific community’s silence on the subject is because politically driven energy policy goals are driving the science, rather than vice versa.

The goal of reaching “Net Zero” global anthropogenic emissions of carbon dioxide sounds overwhelmingly difficult. While humanity continues producing CO2 at increasing rates (with a temporary pause during COVID), how can we ever reach the point where these emissions start to fall, let alone reach zero by 2050 or 2060?

What isn’t being discussed (as far as I can tell) is the fact that atmospheric CO2 levels (which we will assume for the sake of discussion causes global warming) will start to fall even while humanity is producing lots of CO2.

Let me repeat that, in case you missed the point:

Atmospheric CO2 levels will start to fall even with modest reductions in anthropogenic CO2 emissions.

Why is that? The reason is due to something called the CO2 “sink rate”. It has been observed that the more CO2 there is in the atmosphere, the more quickly nature removes the excess. The NASA studies showing “global greening” in satellite imagery since the 1980s is evidence of that.

Last year I published a paper showing that the record of atmospheric CO2 at Mauna Loa, HI suggests that each year nature removes an average of 2% of the atmospheric excess above 295 ppm (parts per million). The purpose of the paper was to not only show how well a simple CO2 budget model fits the Mauna Loa CO2 measurements, but also to demonstrate that the common assumption that nature is becoming less able to remove “excess” CO2 from the atmosphere appears to be an artifact of El Nino and La Nina activity since monitoring began in 1959. As a result, that 2% sink rate has remained remarkably constant over the last 60+ years. (By the way, the previously popular CO2 “airborne fraction” has huge problems as a meaningful statistic, and I wish it had never been invented. If you doubt this, just assume CO2 emissions are cut in half and see what the computed airborne fraction does. It’s meaningless.)

Here’s my latest model fit to the Mauna Loa record through 2023, where I have added a stratospheric aerosol term to account for the fact that major volcanic eruptions actually *reduce* atmospheric CO2 due to increased photosynthesis from diffuse sunlight penetrating deeper into vegetation canopies:

What Would a “Modest” 1% per Year Reduction in Global CO2 Emissions Do?

The U.N. claims that CO2 emissions will need to decline rapidly to achieve Net Zero by mid-Century. Specifically, they say 45% reductions below 2010 levels will need to be made by 2030, and Net Zero will need to be achieved by 2050, in order to limit future global warming to the (rather arbitrary) goal of 1.5 deg. C.

But let’s look at what a much more modest reduction in CO2 emissions (1% per year) would do to future atmospheric CO2 concentrations. Here’s a plot of the history of global CO2 emissions, and how that trajectory would change with 1% per year reductions from 2023 onward. (Even this seems optimistic, but we can all agree the U.N.’s goal is delusional),

When we run the CO2 model with these assumed emissions, here’s how the atmospheric CO2 concentration responds:

Even though the CO2 emissions continue, atmospheric CO2 levels start to fall around 2060. Also shown for reference are the four CMIP5 scenarios of future CO2 emissions, with RCP8.5 often being the one used to scare people regarding future climate change, despite it being extremely unlikely.

The message here is that CO2 emissions don’t have to be cut very much for atmospheric CO2 levels to reverse their climb, and start to fall. The reason is that nature removes CO2 in proportion to how much excess CO2 resides in the atmosphere, and that rate of removal can actually exceed our CO2 emissions with modest cuts in emissions.

I don’t understand why this issue is not being discussed. All of the Net Zero rhetoric I see seems to imply that warming will continue if we don’t cut our CO2 emissions to essentially zero. But that’s not true, because that’s not how nature works.