Archives par mot-clé : Clouds

climate-debate

Cooling The Niño

by W. Eschenbach, July 14, 2024 in WUWT

This is a two-part post. The first part is to correct an oversight in my recent post entitled Rainergy.

The second part is to use that new information to analyze the effect of clouds on the El Nino region.

So, to the first part. In my post Rainergy, I noted that it takes ~ 80 watts per square meter (W/m2) over a year to evaporate a cubic meter of seawater. Thus, the evaporation that creates the ~1 meter of annual rain cools the surface by – 80 W/m2.

Then the other day I thought “Dang! I forgot virga!”

Virga is rain that falls from a cloud but evaporates completely before it hits the ground.

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better to know...?, climate-debate

More on Cloud Reduction. CO2 is innocent but Clouds are guilty.

by C. Blaisdell, 15 Apr 2023, in WUWT

Abstract

This is a continuation of previous papers (1) and (2) on Cloud Reduction.  Further analysis of cloud data has revealed four new observations:

  1.  Mount Pinatubo ash in the atmosphere and Amazonia deforestation may be seen in the cloud data.
  2. A correlation of measured “Temperature – Dew point Temperature”, T-Td, to Cloud Cover was found.
  3. The Temperature – Dew point Temperature variable suggests Cloud Reduction has been going on before 1975.
  4. A simple model shows that Clouds either by reduced Cloud Fraction, decreased Cloud Albedo (lower reflectivity), or both can account for most of the observed Radiation and the associated Global Warming, GW.

CO2 is innocent but Clouds are guilty.

Introduction

Climate change leaves a multi variable data finger print in the Atmosphere that is useful in drawing conclusions and testing theories.  The first of these finger prints is shown in Figure 1 where Cloud Cover, Temperature, Specific Humidity, and Relative Humidity (ground and 850mb) are shown on the same time scale.  None of Figure 1 graphs is a flat line any theory on GW should account for all these observations.  Figure 1 is NOAA data from “NOAA Physical Science Laboratory”, (3) average Northern and Southern Hemisphere.  In Figure 1 note that relative humidity at 1000mb is much less sensitive than the relative humidity at 850mb(where cumulus cloud are).  Cloud Data is from Climate Explorer, (11)

Another data finger-print data set is shown in Figure 2 from “Met Office Climate Dashboard” (“HadISDH” data), (4)  (station and buoy data).  Note that the Met Data has a much better relative humidity correlation.  The relative humidity is significant variable in the Dew Point temperature calculation, Figure 2 (e).

climate-debate

Think We Can Model the Climate? Clouds Get in the Way

by R. Barmby, 9 Apt 2023 in CO2Coalition

I’ve looked at climate change from both sides now, and I have found common ground between proponents and skeptics of the belief that climate change is largely caused by humans. When it comes to forecasting global temperatures, distinguished experts in both camps agree a dominant variable cannot be simulated in computer models because clouds get in the way.

Among the proponents is Dr. Bjorn Stevens, a contributing author to the Intergovernmental Panel on Climate Change (IPCC) Assessment Report 5 (2014). Dr. Stevens is also director at the Max Planck Institute for Meteorology, Hamburg, Germany, and a cloud expert. In a recent interview he acknowledged the contribution of clouds to global warming is overestimated in the IPCC’s “Climate Change 2021: The Physical Science Basis.”

“Clouds are tricksters,” he said, referring to their complexity. However, he said, many scientists use oversimplified representations of clouds in modeling “as a guide because they are easier to simulate. This makes the climate models less accurate.”

On the skeptic side is Dr. Richard S. Lindzen, a former lead author for IPCC Assessment Report 3 and now a vocal critic of the IPCC. In a recent podcast the interviewer noted that Lindzen had published sufficient research papers to earn 80 PhDs. (Lindzen humbly declined the praise.)

Lindzen, professor emeritus of Atmospheric Sciences at the Massachusetts Institute of Technology,  points out that IPCC models rely on the assumption that water vapor and clouds amplify the greenhouse gas effects of CO2 in order to achieve forecasts of catastrophic global warming. The IPCC theory is that a warmer atmosphere will have a higher content of water vapor – itself is a greenhouse gas – that adds to the warming caused by CO2. Without this amplifying “positive feedback” effect, the models are still wrong for many reasons, but they no longer project “catastrophic” warming.

Dr. Stevens, who is on record stating that global warming is a “huge problem,” agrees that increased clouds do not amplify global warming: “Water-rich low clouds over the tropical ocean have the greatest cooling effect and low-water ice clouds at high altitudes have the strongest warming effect. Overall, the cooling effect is greater.” That’s called “negative feedback.”

Dr. Lindzen argues that global average temperature is controlled by the polar regions. The temperature at the tropics remains relatively constant over long periods of time while the polar regions have significant variations. In other words, a small change in global average temperature is the result of a big change in polar temperatures. The stability of tropical temperatures indicates that increased clouds provide negative feedback in times of global warming. Rather than exacerbating the global warming effect of CO2, clouds reduce it.

Lindzen proposes the mechanism by which greater negative feedback is produced: High altitude cirrus clouds (Dr. Stevens’ low-water high altitude ice clouds that cause warming) control heat emissions to space. As the air below these clouds warms, the cirrus clouds dissipate and allow more energy to radiate into space. He calls this the Iris Effect.

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better to know...?, climate-debate

A Misunderstanding Of Clouds Is Driving Global Warming Fervor

by R. Barmby, Apr 10, 2023 in ClimateChangeDispatch

I’ve looked at climate change from both sides now, and I have found common ground between proponents and skeptics of the belief that climate change is largely caused by humans.

When it comes to forecasting global temperatures, distinguished experts in both camps agree a dominant variable cannot be simulated in computer models because clouds get in the way.

Among the proponents is Dr. Bjorn Stevens, a contributing author to the Intergovernmental Panel on Climate Change (IPCC) Assessment Report 5 (2014). Dr. Stevens is also the director at the Max Planck Institute for Meteorology, Hamburg, Germany, and a cloud expert. [emphasis, links added]

In a recent interview, he acknowledged the contribution of clouds to global warming is overestimatedin the IPCC’s “Climate Change 2021: The Physical Science Basis.”

“Clouds are tricksters,” he said, referring to their complexity. However, he said, many scientists use oversimplified representations of clouds in modeling “as a guide because they are easier to simulate. This makes the climate models less accurate.”

On the skeptic side is Dr. Richard S. Lindzen, a former lead author for IPCC Assessment Report 3 and now a vocal critic of the IPCC.

In a recent podcast, the interviewer noted that Lindzen had published sufficient research papers to earn 80 PhDs. (Lindzen humbly declined the praise.)

Lindzen, professor emeritus of Atmospheric Sciences at the Massachusetts Institute of Technology, points out that IPCC models rely on the assumption that water vapor and clouds amplify the greenhouse gas effects of CO2 in order to achieve forecasts of catastrophic global warming.

The IPCC theory is that a warmer atmosphere will have a higher content of water vapor – itself a greenhouse gas – that adds to the warming caused by CO2.

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climate-debate

Earth’s Greenhouse Effect Has Not Been Enhanced, But Instead Its Impact Has Declined Since 1983

by K. Richard, April 10, 2023 in NoTricksZone

In the satellite era scientists have continued to observe the Earth’s total greenhouse effect (which includes effects from greenhouse gases and clouds) exerting an overall negative impact (cooling) on surface temperatures since the 1980s. This rules out both CO2 and an enhanced greenhouse effect as drivers of global warming.

Earth’s total greenhouse effect impact on climate is realized by the sum of all contributors to it: water vapor, clouds, and the “anthropogenic” greenhouse gases CO2 and CH4.

Given the modern assumption that humans are responsible for global warming due especially to our CO2 and CH4 emissions, it stands to reason that Earth’s downwelling longwave (LWdn) should be increasing and thus the Earth’s greenhouse effect should be enhanced due to the rising greenhouse gases emissions.

But, as Cess and Udelhofen (2003) reported 20 years ago, Earth’s greenhouse effect has not been enhanced in recent decades. Instead, it has been in a state of decline since the 1980s.

“[T]he negative trend in G [greenhouse effect] indicates that the atmospheric greenhouse effect is temporarily [1985-1999] decreasing despite the fact that greenhouse gasses are increasing.”

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climate-debate

Scientists: Only 10% Of The 1984-2017 Greenhouse Gas (Longwave) Forcing Was From CO2

by K. Richard, Aug 25, 2022 in NoTricksZone

A late 2021 study finds water vapor and temperature changes accounted for 90% of the changes in clear-sky downwelling longwave or greenhouse effect forcing since the mid-1980s. CO2 forcing assumed a mere bit-player role.

The seminal Feldman et al. (2015) study concluded it takes 10 years and a 22 ppm increase in CO2 to account for just one-tenth of the total longwave or greenhouse effect forcing in recent (2000-2010) climate change trends. The remaining longwave forcing contribution is from water vapor and clouds.

 

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better to know...?

Scientists: The Global Warming Since 1985 Cannot Be Attributed To CO2 Forcing

by K. Richard, Aug 8, 2022 in NoTricksZone

Cloud modulation of shortwave radiation and greenhouse effect forcing has largely been the determining factor in the global warming of the last 45 years. Not CO2.

CO2 forcing and its effect on surface temperatures is detailed in analyses of changes in clear-sky radiation only because all-sky radiation effects that include clouds (and the real-world atmosphere has clouds) overshadow the CO2 impact (Feldman et al., 2015, Harries et al., 2001).

Late 20th Century Climate Forcing

Per satellite observations, from 1985 to 1998 the “background clear-sky OLR [outgoing longwave radiation] was essentially unchanged” (Wang et al., 2002). In other words, any variations in OLR attributed to changes in greenhouse gas concentrations were not detectable.

In contrast, cloud vertical distributions explained 40% of increased tropical outgoing longwave radiation (OLR) and 60% could be explained by the emissivity of clouds, which means OLR changes were “most likely due entirely to changes in tropical cloud characteristics” and “cannot be attributed to increases in greenhouse gas concentrations.”

Furthermore, there was a decrease in reflected shortwave radiation (RSR) of -2.4 W/m² per decade observed from 1985 to 1999, which means there was a +3.6 W/m² increase in solar radiation absorbed by the Earth system during these 14 years. This can easily explain the warming during this period.

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unclassified

Evidence that Clouds Actively Regulate the Temperature

by W. Eschenbach, Oct 6, 2013 in WUWT

I have put forth the idea for some time now that one of the main climate thermoregulatory mechanisms is a temperature-controlled sharp increase in albedo in the tropical regions. I have explained that this occurs in a stepwise fashion when cumulus clouds first emerge, and that the albedo is further increased when some of the cumulus clouds evolve into thunderstorms.

I’ve demonstrated this with actual observations in a couple of ways. I first showed it by means of average photographs of the “view from the sun” here. I’ve also shown this occurring on a daily basis in the TAO data. So I thought, I should look in the CERES data for evidence of this putative phenomenon that I claim occurs, whereby the albedo is actively controlling the thermal input to the climate system.

Mostly, this thermoregulation appears to be happening over the ocean. And I generally dislike averages, I avoid them when I can.  So … I had the idea of making a scatterplot of the total amount of reflected solar energy, versus the sea surface temperature, on a gridcell-by-gridcell basis. No averaging required. I thought well, if I’m correct, I should see the increased reflection of solar energy required by my hypothesis in the scatterplots. Figure 1 shows those results for four individual months in one meteorological year. (The year-to-year variations are surprisingly small, so these months are quite representative.)

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climate-debate

Clouds From Both Sides Now

by W. Eschenbach, March 15, 2021 in WUWT

Clouds are said to be the largest uncertainty in climate models, and I can believe that. Their representation in the models is highly parameterized, each model uses different parameters as well as different values for the same parameters, and so of course, different models give very different results. Or to quote from the IPCC, the Intergovernmental Panel on Climate Change:

In many climate models, details in the representation of clouds can substantially affect the model estimates of cloud feedback and climate sensitivity. Moreover, the spread of climate sensitivity estimates among current models arises primarily from inter-model differences in cloud feedbacks. Therefore, cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates.

The question of importance is this—if the earth heats up, will clouds exacerbate the warming or will they act to reduce the warming? The general claim from mainstream climate scientists and the IPCC is that the clouds will increase the warming, viz:

All global models continue to produce a near-zero to moderately strong positive net cloud feedback.

My own theory is that clouds and other emergent climate phenomena generally act to oppose any increases in surface temperature. So me, I’d expect the opposite of what the models show. I figured that there should be a negative cloud feedback that opposes the warming.

So I thought I’d take a look at answering the question using the CERES satellite dataset. As a prologue, here’s a short exposition about measuring the effect of clouds.

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climate-debate

The natural ‘Himalayan aerosol factory’ can affect climate

by University of Helsinki, Dec 10, 2020 in WUWT

Large amounts of new particles can form in the valleys of the Himalayas from naturally emitted gases and can be transported to high altitudes by the mountain winds and injected into the upper atmosphere.

The emitted particles may eventually affect climate by acting as nuclei for cloud condensation. These new findings about particles formation and sources will contribute to a better understanding of past and future climate.

“To understand how the climate has changed over the last century we need to know as reliably as possible the natural atmospheric conditions before the industrialization,” says Associate Professor Federico Bianchi from the University of Helsinki’s Institute for Atmospheric and Earth System Research (INAR).

In order to do that scientists are looking for pristine locations around the world where human influence is minimal. An international group of researchers has now completed a comprehensive study at the Nepal Climate Observatory at Pyramid station, located in the proximity of the Everest base camp at 5050 m above sea level. There, they were able to investigate the formation of atmospheric particles far from human activities. The results were published today in the prestigious journal Nature Geoscience.

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better to know...?, climate-debate

Climate Scientists Admit Clouds are Still a Big Unknown

by E. Worrall, Sep 12, 2020 in WUWT

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The authors assert that if we had a better understanding clouds, the spread of model predictions could be reduced. But there is some controversy about how badly cloud errors affect model predictions, and that controversy is not just limited to climate alarmists.

Pat Frank, who produced the diagram at the top of the page in his paper “Propagation of Error and the Reliability of Global Air Temperature Projections“, argues that climate models are unphysical and utterly unreliable, because they contain known model cloud physics errors so large the impact of the errors dwarfs the effect of rising CO2. My understanding is Pat believes large climate model physics errors have been hidden away via a dubious tuning process, which adds even more errors to coerce climate models into matching past temperature observations, without fixing the original errors.

Climate skeptic Dr. Roy Spencer disagrees with Pat Frank; Dr. Spencer suggests the cloud error biases hilighted by Pat Frank are cancelled out by other biases, resulting in a stable top of atmosphere radiative balance. Dr. Spencer makes it clear that he also does not trust climate model projections, though for different reasons to Pat Frank.

Other climate scientists like the authors of the study above, Paulo Ceppi and Ric Williams, pop up from time to time and suggest that clouds are a significant problem, though Paulo and Ric’s estimate of the scale of the problem appears to be well short of Pat Frank’s estimate.

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Whoever is right, I think what is abundantly clear is the science is far from settled.

better to know...?, climate-debate

California’s Creek Fire Creates Its Own Pyrocumulonimbus Cloud

by NASA, September 9, 2020 in WUWT

On Friday September 4, 2020 at about 6:44 PM PDT the Creek Fire began in the Big Creek drainage area between Shaver Lake, Big Creek and Huntington Lake, Calif. NASA’s Suomi NPP satellite captured these images of the fire on Sep. 05 through Sep. 07, 2020. From the series of images the spread of the fire can be seen in the outward movement of the red hot spots, although the huge cloud on the 6th obscures all readings due to its size.

The huge, dense cloud created on Sep. 05 and seen in the Suomi NPP image was a pyrocumulonimbus cloud (pyroCb) and the resulting smoke plume that grew upward was spotted and confirmed on Sep. 06, 2020. A pyrocumulonimbus cloud is also called a cumulonimbus flammagenitus. The origins of the latter word are from the Latin meaning “flame” and “created from.” This perfectly describes a cloud that is caused by a natural source of heat such as a wildfire or volcano. Rising warm air from the fire can carry water vapor up into the atmosphere causing clouds. Any type of convective cloud can be created. In this case, the cumulonimbus, or thunderhead cloud, was created. Precipitation and lightning can also occur with these types of clouds creating a risk that the fire will expand due to increased wind from precipitation downdraft or by creating new fires due to lightning strikes. These are all things that fire managers must keep in mind while continuing to try to fight the fire.

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climate-debate

Scientists: It’s ‘Impossible’ To Measure Critical Cloud Processes…Observations 1/50th As Accurate As They Must Be

by K. Richard, August 20, 2020 in NoTricksZone

Clouds dominate as the driver of changes in the Earth’s radiation budget and climate. A comprehensive new analysis suggests we’re so uncertain about cloud processes and how they affect climate we can’t even quantify our uncertainty. 

According to scientists (Song et al., 2016), the total net forcing for Earth’s oceanic atmospheric greenhouse effect (Gaa) during 1992-2014 amounted to -0.04 W/m² per year. In other words, the trend in total longwave forcing had a net negative (cooling) influence during those 22 years despite a 42 ppm increase in CO2. This was primarily due to the downward trend in cloud cover that overwhelmed or “offset” the longwave influence from CO2.

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Cloud impacts on climate are profound – but so are uncertainties

The influence of clouds profoundly affects Earth’s radiation budget, easily overwhelming CO2’s impact within the greeenhouse effect. This has been acknowledged by scientists for decades.

Despite the magnitude of clouds’ radiative impact on climate, scientists have also pointed out that our limited capacity to observe or measure cloud effects necessarily results in massive uncertainties.

For example, Stephens et al. (2012) estimated the uncertainty in Earth’s annual longwave surface fluxes is ±9 W/m² (~18 W/m²) primarily due to the uncertainties associated with cloud longwave radiation impacts.

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unclassified

Settled Science? New Climate Study Shifts the Goalposts to 2.6-3.9C

by Eric Worall, July 24, 2020 in WUWT

A new climate study has dismissed utterly implausible high end climate models. But the new study also seeks to raise the low end of the range of estimated climate sensitivity into the discomfort zone.

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The treatment of cloud feedback is interesting. The study acknowledges large cloud feedback uncertainties, mentions the Lindzen et al. (2001) “iris effect”, and admits GCMs cannot be trusted to reproduce observed cloud response, yet still appears to attempt to derive a cloud feedback factor based on satellite observations, and mix this observational cloud factor with model predictions.

The treatment of clouds may turn out to be one of the most controversial assumptions in the study – as Pat Frank has pointed out on a number of occasions, the magnitude of model cloud response error is significantly greater than the CO2 driven warming which models attempt to project, which calls into question whether climate models have any predictive skill whatsoever.

To the author’s credit they have described their method in great detail, so I’m looking forward to detailed responses to this study.

better to know...?, climate-debate

SCIENTIFIC PAPER “PROVES” CLOUDS CONTROL THE CLIMATE, NOT MAN

by Cap Allon, June28, 2020 in Electroverse

A June, 2019 research paper concludes that human activity can account for no more than a 0.01C rise in global temperatures, and goes so far as to “prove” low-level clouds “practically control the global temperature”.

The paper, entitled “No Experimental Evidence for the Significant Anthropogenic Climate Change“ and published in Nature, is the work of a group Finnish scientists. It explains how the IPCC’s analysis of global temperatures suffers from at least one glaring error — namely, the failure to account for “influences of low cloud cover” on global temperatures.

ABSTRACT

In this paper we will prove that GCM-models used in IPCC report AR5 fail to calculate the influences of the low cloud cover changes on the global temperature. That is why those models give a very small natural temperature change leaving a very large change for the contribution of the green house gases in the observed temperature. This is the reason why IPCC has to use a very large sensitivity to compensate a too small natural component. Further they have to leave out the strong negative feedback due to the clouds in order to magnify the sensitivity. In addition, this paper proves that the changes in the low cloud cover fraction practically control the global temperature.

For the full paper, click here.

 

climate-debate

New Studies Show Cloud Cover Changes Have Driven Greenland Warming And Ice Melt Trends Since The 1990s

by K. Richard, April 20, 2020 in NoTricksZone

Scientists now acknowledge cloud cover changes “control the Earth’s hydrological cycle”, “regulate the Earth’s climate”, and “dominate the melt signal” for the Greenland ice sheet via modulation of absorbed shortwave radiation.  CO2 goes unmentioned as a contributing factor.

 

 

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better to know...?, climate-debate, pollution-contamination

Ships’ emissions create measurable regional change in clouds

by  University of Washington, March 24, 2020 in ScienceDaily

A container ship leaves a trail of white clouds in its wake that can linger in the air for hours. This puffy line is not just exhaust from the engine, but a change in the clouds that’s caused by small airborne particles of pollution.

New research led by the University of Washington is the first to measure this phenomenon’s effect over years and at a regional scale. Satellite data over a shipping lane in the south Atlantic show that the ships modify clouds to block an additional 2 Watts of solar energy, on average, from reaching each square meter of ocean surface near the shipping lane.

The result implies that globally, cloud changes caused by particles from all forms of industrial pollution block 1 Watt of solar energy per square meter of Earth’s surface, masking almost a third of the present-day warming from greenhouse gases. The open-access study was published March 24 in AGU Advances, a journal of the American Geophysical Union.

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better to know...?, climate-debate

New Study Asserts Cloud Cover Changes Drove The Post-1980s Solar Radiation Increase Important To Recent Warming

by K. Richard, March 2, 2020 in NoTricksZone

Using NASA’s MERRA-2 radiation data, scientists find shortwave radiation (SW) has been rising since the 1980s. The SW increase has been larger and faster than longwave radiation (LW) changes during this same timespan. Cloud variability has been the “main driver” of these trends.

In a new Nature journal paper (Delgado-Bonal et al, 2020) published in Scientific Reports, scientists use radiation records from NASA to conclude shortwave (SW) changes are “mainly determined” by cloud modulation.

Clouds are “showing a declining trend” from 1984-2014. Fewer clouds means less SW radiation is reflected to space and more is absorbed by the Earth’s surface.

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climate-debate

Finally! The missing link between exploding stars, clouds and climate on Earth

by Shaviv, December  19, 2017 in ScieneBits/fromNature

Blog topic:
astronomy, cosmic rays, global warming, personal research, weather & climate

By Henrik Svensmark and Nir shaviv

Our new results published today in nature communications provide the last piece of a long studied puzzle. We finally found the actual physical mechanism linking between atmospheric ionization and the formation of cloud condensation nuclei. Thus, we now understand the complete physical picture linking solar activity and our galactic environment (which govern the flux of cosmic rays ionizing the atmosphere) to climate here on Earth though changes in the cloud characteristics. In short, as small aerosols grow to become cloud condensation nuclei, they grow faster under higher background ionization rates. Consequently, they have a higher chance of surviving the growth without being eaten by larger aerosols. This effect was calculated theoretically and measured in a specially designed experiment conducted at the Danish Space Research Institute at the Danish Technical University, together with our colleagues Martin Andreas Bødker Enghoff and Jacob Svensmark.

Background:

It has long been known that solar variations appear to have a large effect on climate. This was already suggested by William Herschel over 200 years ago. Over the past several decades, more empirical evidence have unequivocally demonstrated the existence of such a link, as exemplified in the examples in the box below.

climate-debate, to keep an eye on...

NASA: We Can’t Model Clouds, So Climate Model Projections Are 100x Less Accurate

by K. Richard, August 30, 2019 in ClimateChangeDispatch

NASA has conceded that climate models lack the precision required to make climate projections due to the inability to accurately model clouds.

Clouds have the capacity to dramatically influence climate changes in both radiative longwave (the “greenhouse effect”) and shortwave.

Cloud cover domination in longwave radiation

In the longwave, clouds thoroughly dwarf the CO2 climate influence. According to Wong and Minnett (2018):

  • The signal in incoming longwave is 200 W/m² for clouds over the course of hours. The signal amounts to 3.7 W/m² for doubled CO2 (560 ppm) after hundreds of years.

  • At the ocean surface, clouds generate a radiative signal 8 times greater than tripled CO2 (1120 ppm).

  • The absorbed surface radiation for clouds is ~9 W/m². It’s only 0.5 W/m² for tripled CO2 (1120 ppm).

  • CO2 can only have an effect on the first 0.01 mm of the ocean. Cloud longwave forcing penetrates 9 times deeper, about 0.09 mm.

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climate-debate

Greenland ice loss projections are clouded by clouds

by Brooks Hays, June 24, 2019 in UPI

June 24 (UPI) — Predicting where, how and how quickly Greenland’s ice will melt is difficult. Projections by the best models are cloudy, and new research suggests clouds are doing the clouding.

Currently, models of Greenland’s melting ice sheet put the greatest emphasis on the impacts of greenhouse gas emissions. But new research, published this week in the journal Nature Climate Change, suggests the microphysics of clouds are equally important.

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Under high emission scenarios, the uncertainties of Greenland ice sheet models are caused almost entirely by the uncertainties of cloud dynamics.

Cloud cover dictates the ice sheet’s longwave radiation exposure. When clouds over Greenland are thicker, they operate like an insulating blanket, encouraging longwave radiation and surface-level melting.

climate-debate

Scientists: The CO2 Greenhouse Effect Was Cancelled Out By Clouds During 1992-2014

by K. Richard, March 28, 2019 in NoTricksZone

An unheralded but significant 2016 scientific paper – “A Hiatus of the Greenhouse Effect” – is now publicly available.

Scientists have found the greenhouse effect’s (GHE) influence on planetary temperatures went on “hiatus” during 1992-2014.

The estimated GHE radiative influence for these 22 years was a slightly negative -0.04 Wm-2 per year.

The reason why the GHE influence went on hiatus in recent decades is that (a) decadal-scale changes in cloud cover exert dominant radiative control in longwave forcing (GHE) efficacy, and (b) the shortwave effects of cloud cover changes override the radiative longwave effects, meaning that a decrease in cloud cover will allow more direct shortwave radiation to be absorbed by the Earth system, eliciting a net positive imbalance in the energy budget.

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unclassified

L’art de gommer les incertitudes

by Jean, N. 2 mars 5019 in ScienceClimatEnergie

Comme déjà mentionné dans un article précédent publié sur SCE, la variation de la couverture nuageuse a probablement un effet majeur sur la température moyenne globale de la basse atmosphère. Si l’on veut prédire le climat du futur comme le prétend le GIEC il faut savoir modéliser la formation des nuages. Que nous dit le dernier rapport scientifique (AR5) du GIEC à ce sujet? Le but du présent article est simplement de vous présenter quelques phrases tirées de ce rapport. La science est-elle dite?

1. Le chapitre 7 du rapport AR5 publié par le GIEC en 2013

Le chapitre 7 du rapport AR5 du GIEC[1] fait 60 pages et est consacré aux nuages et aux aérosols (le rapport AR5 complet fait au total 1535 pages). Ce chapitre 7 comporte 22 pages de références et cite plus de 1100 articles scientifiques publiés dans des revues aussi prestigieuses que Science, Nature ou PNAS. Le chapitre 7 a été écrit sous la direction de Olivier Boucher (France) et David Randall (USA), deux spécialistes du domaine. Nous n’allons pas ici remettre en question la validité de ce chapitre. Nous allons simplement vous présenter quelques phrases tirées du rapport. Comme le rapport est écrit en anglais nous vous proposerons ci-dessous une “traduction maison” des phrases qui nous paraissent les plus importantes, assorties parfois de quelques explications pour bien les comprendre. Les lettres entre crochets ([A] à [P]) renvoient simplement au texte original en anglais, donné en Annexe du présent article.

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climate-debate

Striking study finds a climate tipping point in clouds

by Scott K. Johnson, February 25, 2019 in WUWT

The word “hysteresis” doesn’t immediately seem threatening; it hints at a portmanteau of “history” and “thesis”—a dense read, perhaps, but those never killed anyone. But that’s not what the word means. Hysteresis is a profound behavior some systems can display, crossing a sort of point-of-no-return. Dial things up just one notch, and you can push the system through a radical change. To get back to normal, you might have to dial it down five or six notches.

Earth’s climate system can provide examples. Take the conveyor-belt-like circulation of water in the Atlantic Ocean. Looking back at the past, you can see times that the circulation seems to have flipped into an alternate pattern regarding climatic consequences around the North Atlantic. Switching from one pattern to the other takes a significant nudge, but reversing it is hard—like driving up to the top of a ridge and rolling down into the next valley.

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Stratocumulus clouds, like those in the lower two-thirds of this image, are common over the oceans.

NASA Earth Observatory

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climate-debate

Aerosol-driven droplet concentrations dominate coverage and water of oceanic low-level clouds

by  D. Rosenfeld et al., February 8, 2019 in Science

Reflections on cloud effects

How much impact does the abundance of cloud condensation nuclei (CCN) aerosols above the oceans have on global temperatures? Rosenfeld et al.analyzed how CCN affect the properties of marine stratocumulus clouds, which reflect much of the solar radiation received by Earth back to space (see the Perspective by Sato and Suzuki). The CCN abundance explained most of the variability in the radiative cooling. Thus, the magnitude of radiative forcing provided by these clouds is much more sensitive to the presence of CCN than current models indicate, which suggests the existence of other compensating warming effects.

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