Climate: In Case You Were Wondering

Reblogged from Watts Up With That:

Guest opinion by David Archibald

The global warming hysteria was reaching a crescendo in the lead up to the climate confab in Copenhagen in 2009 when a civic-minded person released the Climategate emails, deflating the whole thing. Those emails demonstrated that the science behind global warming was more like science fiction, concocted from the fevered imaginations of the scientists involved.

Nigh on 10 years have passed since then and we are currently experiencing another peak in the hysteria that seems to be coordinated worldwide. But why? Why now? The global warming scientists have plenty of time on their hands and plenty of money. Idle curiosity would have got some to have a stab at figuring out what is going to happen to climate. Do they see an imminent cooling and they have to get legislation in place before that is apparent?

The passage of those ten years has given us another lot of data points on the global warming. There are now 40 years of satellite measurements of atmospheric temperature and this is how that plots up for the Lower 48 States:

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What the graph shows is the departure from the average for the 30 years from 1981 to 2010. The last data point is February 2019 with a result of -0.03 degrees C. So we have had 40 years of global warming and the temperature has remained flat. In fact it is slightly cooler than the long term average. Is it possible to believe in global warming when the atmosphere has cooled? No, not rationally. Is it possible for global warming to be real if the atmosphere has cooled? Again no.

Now let’s look at carbon dioxide which is supposed to be driving the global warming, if it was happening. A lab high up on Mauna Loa in Hawaii has been measuring the atmospheric concentration since 1958. As it is the annual change in concentration that is supposed to be driving global warming let’s see how that plots up:

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What it shows is that the driving effect has been in a wide band from 1979 when the satellites to measure temperature went up but the trend is flat. Think about that – 40 years of forcing and no result in the actual atmospheric temperature. If it was ever going to happen it would have happened by now.

The opposite of global warming is global cooling. What are the chances of that? Pretty good in fact. Only one graph is need to show the potential for that – the aa Index which is a measure of the Sun’s magnetic field strength. Records of that have been kept since 1868:

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The second half of the 20th century had a solar magnetic field strength that was 50% higher than that of the last 60 years of the Little Ice Age. That ended in 2006. We are now back to the solar activity levels of the 19th century and that may bring the sort of climate our forbears had then.

And so it has come to pass. January-February had record cold over North America. Seemingly the polar vortex was everywhere because Japan also had record cold.

Waiting for global warming to happen is like Waiting for Godot. It is never going to happen and the wait is getting beyond tedious.

In the meantime there is no evidence for global warming and the opposite is happening, as shown by the record cold we have just experienced. It is time to stop giving global warmers the benefit of doubt – they are loons. That includes Rick Perry.


David Archibald has lectured on climate science in both Senate and House hearing rooms.

Satellite Evidence Affirms Solar Activity Drove ‘A Significant Percentage’ Of Recent Warming

Reblogged from the NoTricksZone:

In a new paper, two astrophysicists shred the IPCC-preferred and model-based PMOD solar data set and affirm the ACRIM, which is rooted in observation and shows an increase in total solar irradiance (TSI) during the 1980-2000 period. They suggest a “significant percentage” of recent climate change has been solar-driven.

Scafetta and Willson, 2019

I. The PMOD is based on proxy modeled predictions, “questionable” modifications, and degraded, “misinterpreted” and “erroneously corrected” results 

• “The PMOD rationale for using models to alter the Nimbus7/ERB data was to compensate for the sparsity of the ERBS/ERBE data and conform their gap results more closely to the proxy predictions of solar emission line models of TSI behavior.”
• “PMOD’s modifications of the published ACRIM and ERB TSI records are questionable because they are based on conforming satellite observational data to proxy model predictions.”
• “The PMOD trend during 1986 to 1996 is biased downward by scaling ERB results to the rapidly degrading ERBE results during the ACRIM-Gap using the questionable justification of agreement with some TSI proxy predictions first proposed by Lee III et al.(1995).”
• PMOD misinterpreted and erroneously corrected ERB results for an instrument power down event.”
• “PMOD used overlapping comparisons of ACRIM1 and ACRIM2 with ERBE observations and proxy models to construct their first composite. Other PMOD composites [17, 18] used different models of the ERBE-ACRIM-Gap degradation. The result of these various modifications during the ACRIM-Gap was that PMOD introduced a downward trend in the Nimbus7/ERB TSI data that decreased results by 0.8 to 0.9 W/m2 (cf. [18, 20]).”

II. The PMOD TSI composite “flawed” results were an “unwarranted manipulation” of data intended to support AGW, but are  “contraindicated”

• “The dangers of utilizing ex-post-facto corrections by those who did not participate in the original science teams of satellite experiments are that erroneous interpretations of the data can occur because of a lack of detailed knowledge of the experiment and unwarranted manipulation of the data can be made based on a desire to support a particular solar model or some other nonempirical bias. We contend that the PMOD TSI composite construction is compromised in both these ways.”
 “[O]ur scientific knowledge could be improved by excluding the more flawed record from the composite. This was the logic applied by the ACRIM team. In point of fact PMOD failed to do this, instead selecting the ERBE results that were known to be degraded and sparse, because that made the solar cycle 21–22 trend agrees with TSI proxy models and the CAGW explanation of CO2 as the driver of the global warming trend of the late 20th century.”
• “The use of unverified modified data has fundamentally flawed the PMOD TSI satellite composite construction.”
• “The consistent downward trending of the PMOD TSI composite is negatively correlated with the global mean temperature anomaly during 1980–2000. This has been viewed with favor by those supporting the COanthropogenic global warming (CAGW) hypothesis since it would minimize TSI variation as a competitive climate change driver to CO2, the featured driver of the hypothesis during the period (cf.: [IPCC, 2013, Lockwood and Fröhlich, 2008]).”
• “Our summary conclusion is that the objective evidence produced by all of the independent TSI composites [3,5, 6, 9] agrees better with the cycle-by-cycle trending of the original ACRIM science team’s composite TSI that shows an increasing trend from 1980 to 2000 and a decreasing trend thereafter. The continuously downward trending of the PMOD composite and TSI proxy models is contraindicated.”

III. The ACRIM TSI supports the conclusion that “a significant percentage” of climate change in recent decades was driven by TSI variation

Graph Source: Soon et al., 2015
• ACRIM shows a 0.46 W/m2 increase between 1986 and 1996 followed by a decrease of 0.30 W/m2 between 1996 and 2009. PMOD shows a continuous, increasing downward trend with a 1986 to 1996 decrease of 0.05 W/m2 followed by a decrease of 0.14 W/m2 between 1996 and 2009. The RMIB composite agrees qualitatively with the ACRIM trend by increasing between the 1986 and 1996 minima and decreasing slightly between 1996 and 2009.”
• “ACRIM composite trending is well correlated with the record of global mean temperature anomaly over the entire range of satellite observations (1980–2018) [Scafetta. 2009]. The climate warming hiatus observed since 2000 is inconsistent with CO2 anthropogenic global warming (CAGW) climate models [Scafetta, 2013, Scafetta, 2017]. This points to a significant percentage of the observed 1980–2000 warming being driven by TSI variation [Scafetta, 2009, Willson, 2014, Scafetta. 2009]. A number of other studies have pointed out that climate change and TSI variability are strongly correlated throughout the Holocene including the recent decades (e.g., Scafetta, 2009,  Scafetta and Willson, 2014, Scafetta, 2013Kerr, 2001, Bond et al., 2001, Kirkby, 2007, Shaviv, 2008, Shapiro et al., 2011, Soon and Legates, 2013, Steinhilber et al., 2012, Soon et al., 2014).”
• “The global surface temperature of the Earth increased from 1970 to 2000 and remained nearly stable from 2000 and 2018. This pattern is not reproduced by CO2 AGW climate models but correlates with a TSI evolution with the trending characteristics of the ACRIM TSI composite as explained in Scafetta [6,12, 27] and Willson [7].”

IV. The Correlation:

Graph Source: Soon et al., 2015
Image Source: Smith, 2017

V. The Mechanism: Higher solar activity on decadal-scales limits the seeding of clouds, which means more solar radiation is absorbed by the surface, warming the Earth 

Image Source: Fleming, 2018

Image Source: Sciencedaily.com

VI. The radiative forcing from the increase in surface solar radiation: +4.25 Wm-2/decade between 1984-2000

Image Source: Goode and Palle, 2007

Image Source(s): Hofer et al., 2017 and Kay et al., 2008

Experts reveal that clouds have moderated warming triggered by climate change

Reblogged from Watts Up With That:

A new study has revealed how clouds are modifying the warming created by human-caused climate change in some parts of the world

Swansea University

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Trees are removed from cold lake beds in Scandinavia. Credit: Professor Mary Gagen, Swansea University

A new study has revealed how clouds are modifying the warming created by human-caused climate change in some parts of the world.

Led by Swansea University’s Tree Ring Research Group, researchers from Sweden, Finland and Norway analysed information contained in the rings of ancient pine trees from northern Scandinavia to reveal how clouds have reduced the impact of natural phases of warmth in the past and are doing so again now to moderate the warming caused by anthropogenic climate change.

Even though northern Scandinavia should be strongly affected by global warming, the area has experienced little summer warming over recent decades – in stark contrast to the hemispheric trend of warming temperatures, which is strongly linked to rising greenhouse gas emissions. According to the study, temperature changes have been accompanied by an increase in cloudiness over northern Scandinavia, which in turn has reduced the impact of warming.

Mary Gagen, Professor of Geography at Swansea University, said: “The surface warming caused by rising greenhouse gases is modified by many complicated feedbacks – one thing changing in response to another – meaning that there are large geographical variations in the temperature of a particular place at a particular time, as the global average temperature rises. One of the most important, and most poorly understood, climate feedbacks is the relationship between temperature and clouds. We might think that, simply, when it is cool it is cloudy, and when it is warm it is sunny, but that is not always the case.”

The research team analysed tree ring records to find out what summer temperatures were like in the past, and how cloudy it was. Using their collected data, the team produced a new reconstruction of summer cloud cover for northern Scandinavia and compared it to existing temperature reconstructions to establish the relationship between temperature and cloud cover.

Professor Mary Gagen said: “Most people know that the width of a tree ring can tell us what the temperature was like in the summer that ring grew, but we can also measure other things in tree rings such as the isotopes of carbon and water that the wood is made from. Isotopes are just different types of an element, the amount of the different isotopes of carbon in the wood tells us how cloudy it was in the summer the tree ring grew. By combining the tree ring width and tree ring carbon measurements we built a record of both past summer temperatures and past summer cloud cover. Summer temperatures in Scandinavia have increased by less than the global average in recent decades because it also got cloudier at the same time, and that modified and reduced the warming. That turns out to also be the case back through time.”

Author Professor Danny McCarroll explained: “We found that over short timescales, increased cloud cover lead to cooler temperatures and vice versa in the past. However, over longer timescales -decades to centuries-we found that in warmer times, such as the medieval, there was increased cloud cover in this part of the world, which reduced local temperatures. The opposite being true in cool periods, such as the Little Ice Age.

“These finding are important as they help to explain the feedback relationship between cloud cover and temperature, which is one of the major uncertainties in modelling future climate. Understanding the past relationship between temperature and cloud cover in this part of the world means we can now predict that, as the global temperature continues to rise, that warming will be moderated in northern Scandinavia by increasing cloud cover. The next step is to find out whether the same is true for other parts of the world.”

Professor Mary Gagen added: “One of the main sources of uncertainty about future climate change is the way that clouds are going to respond to warming, cloud cover has a really big influence on temperature at the surface of the Earth.

“Clouds are going to be critical in modify warming of the climate. In some places, like Scandinavia, it turns out that the summer climate gets cloudier as the planet warms, in other places though it is likely that warming will be enhanced by a reduction in cloudiness which will make the surface of the Earth even warmer. What is really worrying is that climate models have shown that, if greenhouse gas emissions are allowed to continue until there is double or even triple the pre industrial amount of carbon dioxide in the atmosphere, then some of the most important clouds for cooling our planet, the big banks of oceanic clouds that reflect a lot of sunlight back to space, could stop forming altogether and this would really accelerate warming.”

###

The study, Cloud Cover Feedback Moderates Fennoscandian Summer Temperature Changes Over the Past 1,000 Years, is published in Geophysical Research Letters.

From EurekAlert!

Public Release: 25-Mar-2019

The Greenhouse Effect Refresher

Sierra Foothill Commentary

Atmospheric Gases: When discussing atmospheric gases, it is useful to refresh one’s memory of the relative concentrations of various gases. To be more useful these will be put in the same units, that is ppmv: parts per million by volume. In the idealized dry atmosphere:

Nitrogen is about 78% of the atmosphere or 780,840 ppmv;

Oxygen is 20.9% or 209,460 ppmv;

Argon is 0.93% of the atmosphere or 9,340 ppmv;

Carbon dioxide is about 0.04% of the atmosphere or 400 ppmv [carbon dioxide varies seasonally and is increasing]. The next greenhouse gas, significantly lower, is

Methane, with about 0.00018% of the atmosphere or 1.79 ppmv;

Nitrous oxide is about 0.0000325% or 0.325 ppmv; and

Ozone is about 0 to 0.000007% or 0 to 0.07 ppmv.

The greenhouse influence of ozone is predominantly in the upper the atmosphere, the stratosphere, where it is created naturally by chemical reactions involving solar ultraviolet…

View original post 405 more words

California Drought History

Sierra Foothill Commentary

During the last drought, I made about 85 posts on the issue, pointing out the drought history of the region was chaotic, with dry periods and wet periods, with some very long dry periods. In those posts, I supported the need for more dams to catch and store the feeble about of moisture collected during the dry periods, including the Centennial Dam Project.

This drought timeline tells the story of drought in the region;

california_drought_timeline

California is relatively drought-free right now, but if history is an indicator of the future we will have more drought.

california-drought-comparision

H/T to Watts Up With That for links to the Graphics.  

If you are interested in learning more about drought and flooding in the region, I recommend The West Without Water and books by Anthropologist David L. Stuart on the struggle of the Pueblo Peoples to survive in the South West. Our relatively wet period could…

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Hurricanes & climate change: 21st century projections

Climate Etc.

by Judith Curry

Final installment in my series on hurricanes and climate change.

View original post 4,485 more words

FORCE MAJEURE–The Sun’s Role in Climate Change

From the GWPF:

Henrik Svensmark, 11 Mar 2019

Executive Summary

Over the last twenty years there has been good progress in understanding the solar influence on climate. In particular, many scientific studies have shown that changes in solar activity have impacted climate over the whole Holocene period (approximately the last 10,000 years). A well-known example is the existence of high solar activity during the Medieval Warm Period, around the year 1000 AD, and the subsequent low levels of solar activity during the cold period, now called The Little Ice Age (1300–1850 AD).

An important scientific task has been to quantify the solar impact on climate, and it has been found that over the eleven-year solar cycle the energy that enters the Earth’s system is of the order of 1.0–1.5 W/m2. This is nearly an order of magnitude larger than what would be expected from solar irradiance alone, and suggests that solar activity is getting amplified by some atmospheric process.

Three main theories have been put forward to explain the solar–climate link, which are:

  • solar ultraviolet changes
  • the atmospheric-electric-field effect on cloud cover
  • cloud changes produced by solar-modulated galactic cosmic rays (energetic particles originating from inter stellar space and ending in our atmosphere).

Significant effort has gone into understanding possible mechanisms, and at the moment cosmic ray modulation of Earth’s cloud cover seems rather promising in explaining the size of solar impact.

This theory suggests that solar activity has had a significant impact on climate during the Holocene period. This understanding is in contrast to the official consensus from the Intergovernmental Panel on Climate Change, where it is estimated that the change in solar radiative forcing between 1750 and 2011 was around 0.05 W/m2, a value which is entirely negligible relative to the effect of greenhouse gases, estimated at around 2.3 W/m2. However, the existence of an atmospheric solar-amplification mechanism would have implications for the estimated climate sensitivity to carbon dioxide, suggesting that it is much lower than currently thought.

In summary, the impact of solar activity on climate is much larger than the official consensus suggests. This is therefore an important scientific question that needs to be addressed by the scientific community.

The PDF report is available here: GWPF

Solar input to high latitudes and the global ice volume

Climate Etc.

by Donald Rapp, Ralf Ellis and Clive Best

A review of the relationship between the solar input to high latitudes and the global ice volume over the past 2.7 million years.

View original post 4,522 more words

Is Satellite Altimeter-based Sea Level Rise Acceleration from a Biased Water Vapor Correction?

Reblogged from Dr. Roy Spencer:

March 7th, 2019 by Roy W. Spencer, Ph. D.

SUMMARY: Evidence is presented that an over-correction of satellite altimeter data for increasing water vapor might be at least partly responsible for the claimed “acceleration” of recent sea level rise.

I have been thinking about an issue for years that might have an impact on what many consider to be a standing disagreement between satellite altimeter estimates of sea level versus tide gauges.

Since 1993 when satellite altimeter data began to be included in sea level measurements, there has been some evidence that the satellites are measuring a more rapid rise than the in situ tide gauges are. This has led to the widespread belief that global-average sea level rise — which has existed since before humans could be blamed — is accelerating.

I have been the U.S. Science Team Leader for the Advanced Microwave Scanning Radiometer (AMSR-E) flying on NASA’s Aqua satellite. The water vapor retrievals from that instrument use algorithms similar to those used by the altimeter people.

I have a good understanding of the water vapor retrievals and the assumptions that go into them. But I have only a cursory understanding of how the altimeter measurements are affected by water vapor. I think it goes like this: as tropospheric water vapor increases, it increases the apparent path distance to the ocean surface as measured by the altimeter, which would cause a low bias in sea level if not corrected for.

What this potentially means is that *if* the oceanic water vapor trends since 1993 have been overestimated, too large of a correction would have been applied to the altimeter data, artificially exaggerating sea level trends during the satellite era.

What follows probably raises more questions that it answers. I am not an expert in satellite altimeters, I don’t know all of the altimeter publications, and this issue might have already been examined and found to be not an issue. I am merely raising a question that I still haven’t seen addressed in a few of the altimeter papers I’ve looked at.

Why Would Satellite Water Vapor Measurements be Biased?

The retrieval of total precipitable water vapor (TPW) over the oceans is generally considered to be one of the most accurate retrievals from satellite passive microwave radiometers.

Water vapor over the ocean presents a large radiometric signal at certain microwave frequencies. Basically, against a partially reflective ocean background (which is then radiometrically cold), water vapor produces brightness temperature (Tb) warming near the 22.235 GHz water vapor absorption line. When differenced with the brightness temperatures at a nearby frequency (say, 18 GHz), ocean surface roughness and cloud water effects on both frequencies roughly cancel out, leaving a pretty good signal of the total water vapor in the atmosphere.

What isn’t generally discussed, though, is that the accuracy of the water vapor retrieval depends upon the temperature, and thus vertical distribution, of the water vapor. Because the Tb measurements represent thermal emission by the water vapor, and the temperature of the water vapor can vary several tens of degrees C from the warm atmospheric boundary layer (where most vapor resides) to the cold upper troposphere (where little vapor resides), this means you could have two slightly different vertical profiles of water vapor producing different water vapor retrievals, even when the TPW in both cases was exactly the same.

The vapor retrievals, either explicitly or implicitly, assume a vertical profile of water vapor by using radiosonde (weather balloon) data from various geographic regions to provide climatological average estimates for that vertical distribution. The result is that the satellite retrievals, at least in the climatological mean over some period of time, produce very accurate water vapor estimates for warm tropical air masses and cold, high latitude air masses.

But what happens when both the tropics and the high latitudes warm? How do the vertical profiles of humidity change? To my knowledge, this is largely unknown. The retrievals used in the altimeter sea level estimates, as far as I know, assume a constant profile shape of water vapor content as the oceans have slowly warmed over recent decades.

Evidence of Spurious Trends in Satellite TPW and Sea Level Retrievals

For many years I have been concerned that the trends in TPW over the oceans have been rising faster than sea surface temperatures suggest they should be based upon an assumption of constant relative humidity (RH). I emailed my friend Frank Wentz and Remote Sensing Systems (RSS) a couple years ago asking about this, but he never responded (to be fair, sometimes I don’t respond to emails, either.)

For example, note the markedly different trends implied by the RSS water vapor retrievals versus the ERA Reanalysis in a paper published in 2018:

Ho-et-al-TPW-RSS-vs-ERA-interim-550x309

The upward trend in the satellite water vapor retrieval (RSS) is considerably larger than in the ERA reanalysis of all global meteorological data. If there is a spurious component of the RSS upward trend, it suggests there will also be a spurious component to the sea level rise from altimeters due to over-correction for water vapor.

Now look at the geographical distribution of sea level trends from the satellite altimeters from 1993 through 2015 (published in 2018) compared to the retrieved water vapor amounts for exactly the same period I computed from RSS Version 7 TPW data:

MSL-vs-vapor-trends-1993-2015-550x733The geographic pattern of 23-years of sea level rise from satellite altimeter data looks similar to the pattern of water vapor increase (percent per decade), suggesting cross-talk between the water vapor correction and sea level retrieval.

There is considerably similarity to the patterns, which is evidence (though not conclusive) for remaining cross-talk between water vapor and the retrieval of sea level. (I would expect such a pattern if the upper plot was sea surface temperature, but not for the total, deep-layer warming of the oceans, which is what primarily drives the steric component of sea level rise).

Further evidence that something might be amiss in the altimeter retrievals of sea level is the fact that global-average sea level goes down during La Nina (when vapor amounts also go down) and rise during El Nino (when water vapor also rises). While some portion of this could be real, it seems unrealistic to me that as much as ~15 mm of globally-averaged sea level rise could occur in only 2 years going from La Nina to El Nino conditions (figure adapted from here) :

Sea-Level-from-altimeters-versus-ENSO-events-550x413

Especially since we know that increased atmospheric water vapor occurs during El Nino, and that extra water must come mostly from the ocean…yet the satellite altimeters suggest the oceans rise rather than fall during El Nino?

The altimeter-diagnosed rise during El Nino can’t be steric, either. As I recall (e.g. Fig. 3b here), the vertically integrated deep-ocean average temperature remains essentially unchanged during El Nino (warming in the top 100 m is matched by cooling in the next 200 m layer, globally-averaged), so the effect can’t be driven by thermal expansion.

Finally, I’d like to point out that the change in the shape of the vertical profile of water vapor that would cause this to happen is consistent with our finding of little to no tropical “hot-spot” in the tropical mid-troposphere: most of the increase in water vapor would be near the surface (and thus at a higher temperature), but less of an increase in vapor as you progress upward through the troposphere. (The hotspot in climate models is known to be correlated with more water vapor increase in the free-troposphere).

Again, I want to emphasize this is just something I’ve been mulling over for a few years. I don’t have the time to dig into it. But I hope someone else will look into the issue more fully and determine whether spurious trends in satellite water vapor retrievals might be causing spurious trends in altimeter-based sea level retrievals.

No, Increasing CO2 isn’t going to trigger a hot world without clouds

From DrRoySpencer.com:

March 1st, 2019 by Roy W. Spencer, Ph. D.

I’ve received many more requests about the new disappearing-clouds study than the “gold standard proof of anthropogenic warming” study I addressed here, both of which appeared in Nature journals over the last several days.

The widespread interest is partly because of the way the study is dramatized in the media. For example, check out this headline, “A World Without Clouds“, and the study’s forecast of 12 deg. C of global warming.

The disappearing clouds study is based upon the modelling of marine stratocumulus clouds, whose existence substantially cools the Earth. These extensive but shallow cloud decks cover the subtropical ocean regions over the eastern ocean basins where upwelling cold water creates a strong boundary layer inversion.

Marine-stratocumulus-Oregon_AMO_2006272
Marine stratocumulus clouds off the U.S. West Coast, which form in a water-chilled shallow layer of boundary layer air capped by warmer air aloft (NASA/GSFC).

In other words, the cold water causes a thin marine boundary layer of chilled air up to a kilometer deep, than is capped by warmer air aloft. The resulting inversion layer (the boundary between cool air below and warm air aloft) inhibits convective mixing, and so water evaporated from the ocean accumulates in the boundary layer and clouds then develop at the base of the inversion. There are complex infrared radiative processes which also help maintain the cloud layer.

The new modeling study describes how these cloud layers could dissipate if atmospheric CO2 concentrations get too high, thus causing a positive feedback loop on warming and greatly increasing future global temperatures, even beyond what the IPCC has predicted from global climate models. The marine stratocumulus cloud response to warming is not a new issue, as modelers have been debating for decades whether these clouds would increase or decrease with warming, thus either reducing or amplifying the small amount of direct radiative warming from increasing CO2.

The new study uses a very high resolution model that “grows” the marine stratocumulus clouds. The IPCC’s climate models, in contrast, have much lower resolution and must parameterize the existence of the clouds based upon larger-scale model variables. These high resolution models have been around for many years, but this study tries to specifically address how increasing CO2 in the whole atmosphere changes this thin, but important, cloud layer.

The high resolution simulations are stunning in their realism, covering a domain of 4.8 x 4.8 km: https://d2r55xnwy6nx47.cloudfront.net/uploads/2019/02/CloudGraph_Vimeo.mp4

CloudGraph_Vimeo

The main conclusion of the study is that when model CO2 concentrations reach 1200 ppm or so (which would take as little as another 100 years or so assuming worst-case energy use and population growth projections like RCP8.5), a substantial dissipation of these clouds occurs causing substantial additional global warming, with up to 12 deg. C of total global warming.

Shortcomings in the Study: The Large-Scale Ocean and Atmospheric Environment

All studies like this require assumptions. In my view, the problem is not with the high-resolution model of the clouds itself. Instead, it’s the assumed state of the large-scale environment in which the clouds are assumed to be embedded.

Most importantly, it should be remembered that these clouds exist where cold water is upwelling from the deep ocean, where it has resided for centuries to millennia after initially being chilled to near-freezing in polar regions, and flowing in from higher latitudes. This cold water is continually feeding the stratocumulus zones, helping to maintain the strong temperature inversion at the top of the chilled marine boundary layer. Instead, their model has 1 meter thick slab ocean that rapidly responds to only whats going on with atmospheric greenhouse gases within the tiny (5 km) model domain. Such a shallow ocean layer would be ok (as they claim) IF the ocean portion of the model was a closed system… the shallow ocean only increases how rapidly the model responds… not its final equilibrium state. But given the continuous influx of cold water into these stratocumulus regions from below and from high latitudes in nature, it is far from a closed system.

Second, the atmospheric environment in which the high-res cloud model is embedded is assumed to have similar characteristics to what climate models produce. This includes substantial increases in free-tropospheric water vapor, keeping constant relative humidity throughout the troposphere. In climate models, the enhanced infrared effects of this absolute increase in water vapor leads to a tropical “hot spot”, which observations, so far, fail to show. This is a second reason the study’s results are exaggerated. Part of the disappearing cloud effect in their model is from increased downwelling radiation from the free troposphere as CO2 increases and positive water vapor feedback in the global climate models increases downwelling IR even more. This reduces the rate of infrared cooling by the cloud tops, which is one process that normally maintains them. The model clouds then disappear, causing more sunlight to flood in and warm the isolated shallow slab ocean. But if the free troposphere above the cloud does not produce nearly as large an effect from increasing water vapor, the clouds will not show such a dramatic effect.

The bottom line is that marine stratocumulus clouds exist because of the strong temperature inversion maintained by cold water from upwelling and transport from high latitudes. That chilled boundary layer air bumps up against warm free-tropospheric air (warmed, in turn, by subsidence forced by moist air ascent in precipitation systems possibly thousands of miles away). That inversion will likely be well-maintained in a warming world, thus maintaining the cloud deck, and not causing catastrophic global warming.


[Hifast Note:  Excellent comment thread here:  DrRoySpencer.com]