Archives par mot-clé : Warming

CMIP6 GCM ensemble members versus global surface temperatures

by N. Scafetta, Sep 18, 2022 in Springer


Abstract

The Coupled Model Intercomparison Project (phase 6) (CMIP6) global circulation models (GCMs) predict equilibrium climate sensitivity (ECS) values ranging between 1.8 and 5.7 C. To narrow this range, we group 38 GCMs into low, medium and high ECS subgroups and test their accuracy and precision in hindcasting the mean global surface warming observed from 1980–1990 to 2011–2021 in the ERA5-T2m, HadCRUT5, GISTEMP v4, and NOAAGlobTemp v5 global surface temperature records. We also compare the GCM hindcasts to the satellite-based UAH-MSU v6 lower troposphere global temperature record. We use 143 GCM ensemble averaged simulations under four slightly different forcing conditions, 688 GCM member simulations, and Monte Carlo modeling of the internal variability of the GCMs under three different model accuracy requirements. We found that the medium and high-ECS GCMs run too hot up to over 95% and 97% of cases, respectively. The low ECS GCM group agrees best with the warming values obtained from the surface temperature records, ranging between 0.52 and 0.58 C. However, when comparing the observed and GCM hindcasted warming on land and ocean regions, the surface-based temperature records appear to exhibit a significant warming bias. Furthermore, if the satellite-based UAH-MSU-lt record is accurate, actual surface warming from 1980 to 2021 may have been around 0.40 C (or less), that is up to about 30% less than what is reported by the surface-based temperature records. The latter situation implies that even the low-ECS models would have produced excessive warming from 1980 to 2021. These results suggest that the actual ECS may be relatively low, i.e. lower than 3 C or even less than 2 C if the 1980–2021 global surface temperature records contain spurious warming, as some alternative studies have already suggested. Therefore, the projected global climate warming over the next few decades could be moderate and probably not particularly alarming.

Activist Scientists Have Now Officially Changed A -0.5°C Global Cooling Trend Into A Warming Trend

by K. Richard, Aug 15, 2022 in NotricksZone


Back in the days when data manipulation was still strictly forbidden, scientists reported the globe cooled significantly for decades even as CO₂ concentrations increased.

The global cooling amplitude was -0.5°C from 1960-1965, and 1976 was reported to be the coldest year of any year measured since 1958 (Angell and Korshover, 1978).

Today these recorded 1960-1965 and 1958-1963 cooling trends have been fully erased and replaced with a slight warming or pause.

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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Tonga Eruption Blasted Unprecedented Amount of Water Into Stratosphere

by C. Rotter, Aug 3, 2022 in WUWT


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This looping video shows an umbrella cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022. The GOES-17 satellite captured the series of images that also show crescent-shaped shock waves and lightning strikes.
Credit: NASA Earth Observatory image by Joshua Stevens using GOES imagery courtesy of NOAA and NESDIS

The huge amount of water vapor hurled into the atmosphere, as detected by NASA’s Microwave Limb Sounder, could end up temporarily warming Earth’s surface.

When the Hunga Tonga-Hunga Ha’apai volcano erupted on Jan. 15, it sent a tsunami racing around the world and set off a sonic boom that circled the globe twice. The underwater eruption in the South Pacific Ocean also blasted an enormous plume of water vapor into Earth’s stratosphere – enough to fill more than 58,000 Olympic-size swimming pools. The sheer amount of water vapor could be enough to temporarily affect Earth’s global average temperature.

“We’ve never seen anything like it,” said Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California. He led a new study examining the amount of water vapor that the Tonga volcano injected into the stratosphere, the layer of the atmosphere between about 8 and 33 miles (12 and 53 kilometers) above Earth’s surface.

Why the Sun, Not CO2, Heats the Oceans Revisiting the Debate: Does Greenhouse Back-radiation Warm the Oceans?

by J. Steele, Aug 1, 2022 in WUWT


About a decade ago there was a heated and unresolved debate on whether infrared back radiation from greenhouse gases is heating the oceans. Because infrared penetrates less than a millimeter into the ocean’s surface, many skeptics argued it is impossible to blame rising CO2 for ocean warming. However, several prominent skeptic scientists, people who I have great respect for, also weighed in arguing it was silly and useless to argue infrared heat can’t warm the ocean.

After analyzing the physics detailed in this video, I’m convinced it is solar energy that drives the observed ocean heating, and any infrared ocean heating is insignificant at best. If this analysis holds, it is another significant strike against the prevailing CO2 driven global warming theory

To ensure lay people are brought up to speed, here’s a quick summary of where consensus climate science stands today.

A Tropical Plant’s Warmth Threshold Affirms Mid-Holocene Temps Were ‘7.7°C Higher Than Today’

by K. Richard, July 25, 2022 in NoTricksZone


A warmth-demanding plant can provide us with solid evidence of a much warmer than today Mid-Holocene climate.

Growth of the tropical aquatic plant ceases when air temperatures fall below 10°C.

A new study says that from about 8000 to 5000 years ago it was warm enough in winter that could grow at the 40°N latitude in northern China. Today its warmth threshold growth limit is ~34°N.

Scientists can therefore deduce the Mid-Holocene winter temperatures needed to have been “7.7°C higher than today” at that time.

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Radiosonde Temps Show Northern Hemisphere, Tropical Warming Has Mostly Paused Since 1998

by K. Richard, May 22, 2022 in NoTricksZone


A new study indicates nearly all the Northern Hemisphere and Tropical warming in the last 40 years occurred by the late 1990s.

CO2 has risen by about 50 ppm since 1998 (367 to 418 ppm).

Interestingly, upper-air measurements of temperature from balloon-borne sensor radiosonde data, shown below in the image from a new study (Madonna et al., 2022), suggest there was more warming from the early 1980s to late 1990s – when CO2 only rose about 25 ppm (341 to 367 ppm) – than there has been this century.

Radiosonde measurements appear to depict mostly flat temperatures trends since 1998 in both the Northern Hemisphere (25°N to 70°N) and tropics (25°S to 25°N).

 

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Image Source: Madonna et al., 2022

 

Doomsday Climate Studies Turn Out To Be Overblown Nonsense

by Washington Are Beacon Staff, Feb 17, 2022  in The WashigntonFreeBeacon


For over a decade, scientists have warned that the acidification of ocean water could decimate fish populations. Acidification changed fish behavior, several studies found, making them less likely to evade predators.

As carbon emissions pushed pH levels higher and higher, climate advocates sounded an apocalyptic tone. Fewer fish would mean fewer fisheries, which would imperil the livelihoods of millions of fishermen across the globe. It could also mean fewer medicines, many of which are derived from marine life.

 

According to a new paper in a top-ranked biology journal, these concerns are vastly overblown.

The paper, published in PLOS Biology on Feb. 3, reviewed 91 studies of the effect of ocean acidification on fish behavior. It found that better-quality studies tended to find smaller effects on fish behavior—and that the studies with the most dramatic results tended to have low sample size, making them less statistically reliable.

The Arctic Ocean began warming decades earlier than previously thought, new research shows

by P. Homewood, Nov 27, 2021 in NotaLotofPeopleKnowThat


A new study throws doubt on the theory that Arctic warming is man made.

The Arctic Ocean has been warming since the onset of the 20th century, decades earlier than instrument observations would suggest, according to new research.

The study, published Wednesday in the journal Science Advances, found that the expansion of warm Atlantic Ocean water flowing into the Arctic, a phenomenon known as “Atlantification,” has caused Arctic water temperature in the region studied to increase by around 2 degrees Celsius since 1900.

Francesco Muschitiello, an author on the study and assistant professor of geography at the University of Cambridge, said the findings were worrisome because the early warming suggests there might be a flaw in the models scientists use to predict how the climate will change.

Physicists: Climate Model Error Overestimates CO2 Impact On Global Temps By Factor Of 5

by K. Richard, Nov 22, 2021 in NoTricksZone


A new study suggests CO2 molecules have little consequential impact affecting outgoing radiation, and that climate models attribute global temperature effects to CO2 that are fundamentally erroneous.

Russian physicists (Smirnov and Zhilyaev, 2021) have published a peer-reviewed paper in the Advances in Fundamental Physics Special Issue for the journal Foundations.

They assesses the role of CO2 molecules in the standard atmosphere and assert “we have a contradiction with the results of climatological models in the analysis of the Earth’s greenhouse effect.”

Key points from the paper include the following:

1. Climate model calculations of CO2’s impact on global temperatures are in error by a factor of 5 as a result of “ignoring, in climatological models, the Kirchhoff law” which says radiators are “simultaneously the absorbers.”

2. Change in the concentration of an optically active atmospheric component (like CO2) “would not lead to change in the outgoing radiative flux.”

3. CO2 molecules “are not the main radiator of the atmosphere.” Water vapor molecules are, and thus they “may be responsible for the observed heating of the Earth.”

The anatomy of past abrupt warmings recorded in Greenland ice

by C. Rotter, Apr 19, 2021 in WUWT/Nature


New paper at Nature Communications

Abstract

Data availability and temporal resolution make it challenging to unravel the anatomy (duration and temporal phasing) of the Last Glacial abrupt climate changes. Here, we address these limitations by investigating the anatomy of abrupt changes using sub-decadal-scale records from Greenland ice cores. We highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters. This diversity in the sequence of changes seen in ice-core data is also observed in climate parameters derived from numerical simulations which exhibit self-sustained abrupt variability arising from internal atmosphere-ice-ocean interactions. Our analysis of two ice cores shows that the diversity of abrupt warming transitions represents variability inherent to the climate system and not archive-specific noise. Our results hint that during these abrupt events, it may not be possible to infer statistically-robust leads and lags between the different components of the climate system because of their tight coupling.

Committed warming and the pattern effect

by Nic Lewis, Jan 19, 2021 in ClilmateEtc.


Key points

  • The pattern effect is the dependence of outgoing radiation to space on the spatial pattern of surface warming.
  • A pattern effect, relative to that in equilibrium, can be caused both by evolution over time in the climate system’s response to forcing and by its internal variability.
  • The paper fails to distinguish between a historical period pattern effect that is forced, which will unwind very slowly, and one that is caused by internal variability, which can quickly unwind, causing rapid warming.
  • The forced pattern effect is very small in CAM5.3
  • The pattern effect found in the paper is greatly affected by being estimated during the hiatus.
  • The estimated post-hiatus unforced historical pattern effect is non-negligible in CAM5.3 when using the AMIP2 sea surface temperature dataset, as in the paper, but negligible when using the UK Met Office HadISST1 dataset.
  • The historical pattern effect is not robust; it varies hugely between models and SST datasets.
  • The paper’s claims about greater committed warming directly reflect its estimate of the size of the historical pattern effect.

Introduction

A new paper “Greater committed warming after accounting for the pattern effect” led by Chen Zhou  (Zhou et al.[1]) has recently been published in Nature Climate Change. Here is the accompanying press release.

New Study: East Antarctica Was Up To 6°C Warmer Than Today During The Medieval Warm Period

by K. Richard, Oct 15, 2020 in NoTricksZone


As recently as 2000 to 1000 years ago, spanning the Roman to Medieval Warm Periods, East Antarctica was 5-6°C warmer than it is today. The consequent ice melt resulted in >60 meters higher water levels in East Antarctica’s lakes.

East Antarctica has been rapidly cooling in recent decades, with magnitudes reaching -0.7°C to -2.0°C per decade since the mid-1980s (Obryk et al., 2020).

A new study (Myers et al., 2020) reports that until about 15,000 years ago and throughout the Last Glacial Maximum, East Antarctica was 4-9°C colder than it is today.

Antarctica then abruptly warmed 15°C within centuries. From 12,000 to 6,000 years before present, East Antarctica was about 5°C warmer than it is today.

New confirmation that climate models overstate atmospheric warming

by Dr. Judith Curry, August 27, 2020 in WUWT


Reposted from Dr. Judith Curry’s Climate Etc.

Posted on August 25, 2020

by Ross McKitrick

Two new peer-reviewed papers from independent teams confirm that climate models overstate atmospheric warming and the problem has gotten worse over time, not better.

The papers are Mitchell et al. (2020) “The vertical profile of recent tropical temperature trends: Persistent model biases in the context of internal variability” Environmental Research Letters, and McKitrick and Christy (2020) “Pervasive warming bias in CMIP6 tropospheric layers” Earth and Space Science. John and I didn’t know about the Mitchell team’s work until after their paper came out, and they likewise didn’t know about ours.

Mitchell et al. look at the surface, troposphere and stratosphere over the tropics (20N to 20S). John and I look at the tropical and global lower- and mid- troposphere. Both papers test large samples of the latest generation (“Coupled Model Intercomparison Project version 6” or CMIP6) climate models, i.e. the ones being used for the next IPCC report, and compare model outputs to post-1979 observations. John and I were able to examine 38 models while Mitchell et al. looked at 48 models. The sheer number makes one wonder why so many are needed, if the science is settled. Both papers looked at “hindcasts,” which are reconstructions of recent historical temperatures in response to observed greenhouse gas emissions and other changes (e.g. aerosols and solar forcing). Across the two papers it emerges that the models overshoot historical warming from the near-surface through the upper troposphere, in the tropics and globally.

Mitchell et al. 2020

Mitchell et al. had, in an earlier study, examined whether the problem is that the models amplify surface warming too much as you go up in altitude, or whether they get the vertical amplification right but start with too much surface warming. The short answer is both.

CLAIM: 100 degrees in Siberia? 5 ways the extreme Arctic heat wave follows a disturbing pattern

by C. Rotter, June 28, 2020 in WUWT


This essay from director of NSIDC, Mark Serreze, is provided for reference. You may remember Serreze who once said “the Arctic is screaming” while botching and then backpedaling on claims of “ice free summers” on the near horizon for the Arctic that never happened. Give it all the consideration it is due. For some perspective, see my article on a previous 100 degree event above the Arctic circle over 100 years ago. By the way, with 24 hours daylight above the Arctic circle, and near 24 hour daylight in Siberia this time of year, (the first day of summer aka  the summer solstice) is it any surprise it would get warm?

This Arctic heat wave has been unusually long-lived. The darkest reds on this map of the Arctic are areas that were more than 14 degrees Fahrenheit warmer in the spring of 2020 compared to the recent 15-year average. Joshua Stevens/NASA Earth Observatory

CMIP6 Climate Models Show 50% More Warming Than Observations Since 1979

by Roy W. Spencer, June 26, 2020 in ClimateChangeDispatch


Those who defend climate model predictions often produce plots of observed surface temperature compared to the models which show very good agreement.

Setting aside the debate over the continuing adjustments to the surface temperature record which produce ever-increasing warming trends, let’s look at how the most recent (CMIP6) models are doing compared to the latest version of the observations (however good those are).

First, I’d like to explain how some authors get such good agreement between the models and observations. Here are the two “techniques” they use that most annoy me.

  1. They look at long periods of time, say the last 100+ years. This improves the apparent agreement because most of that period was before there was substantial forcing of the climate system by increasing CO2.
  2. They plot anomalies about a common reference period but do not show trend lines. Or, if they show trend lines, they do not start them at the same point at the beginning of the record. When you do this, the discrepancy between models and observations is split in half, with the discrepancy in the latter half of the record having the opposite sign of the discrepancy in the early part of the record. They say, “See? The observed temperatures in the last few decades nearly match the models!”

In the following plot (which will be included in a report I am doing for the Global Warming Policy Foundation) I avoid both of those problems.

During the period of strongest greenhouse gas forcing (since 1979), the latest CMIP6 models reveal 50% more net surface warming from 1979 up to April 2020 (+1.08 deg. C) than do the observations (+0.72 deg. C).

 

Continuer la lecture de CMIP6 Climate Models Show 50% More Warming Than Observations Since 1979

Scientists Panic, Because Arctic Is 0.4F Warmer Than In 1915!

by P. Homewood, June 21, 2020 in NotaLotofPeopleKnowThat


The Arctic is thought to have recorded its hottest ever temperature of 100.4F (38C) in Siberia, an astonishing 32F (18C) above the normal level for this time of year.

The mercury shot up to the unprecedented level in Verkhoyansk, 3,000 miles east of Moscow, as the region endures a summer heatwave.

Scientists had predicted the Arctic wouldn’t reach these levels until 2100, meaning it is warming 80 years faster than previously thought.

If the record is confirmed it will represent a new high. The current record for hottest temperature in the Arctic is held by Prospect Creek, Alaska, which recorded 100F (38C) in 1915.

Weatherman for CBS, Jeff Beradelli, said on Twitter yesterday: ‘Likely the hottest temperature ever recorded in the Arctic happened today.

‘What’s happening in Siberia this year is nothing short of remarkable. For perspective, Miami has only reached 100F (38C) once on record.’

https://www.dailymail.co.uk/news/article-8444319/Arctic-records-hottest-temperature-mercury-hits-100F-town-Verkhoyansk-Siberia.html?login#readerCommentsCommand-message-field

 

Even the babies who write for the Mail could surely spot the fly in the ointment – that this new record is only 0.4F higher than the previous one set in 1915! Hardly the apocalypse they are trying to present.

As for Verkhoyansk itself, temperatures there reached 37.3C (99.1F) in 1988 during a succession of 30C+ days, so again there is nothing remarkable about the latest weather at all :

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.

 

 

Extra warm U.S. winter had nature’s thumbprint on it–Joe Bastardi

by P. Homewood, April 3; 2020 in NotaLotofPeoppleKnowThat


Joe Bastardi explains why this winter has been so mild in the US, but also across N Europe, at CFACT.

Two points:

1) I will make the case for why such winters like this happen

2) I will point out that nowhere in this article did the massive natural physical drivers that far outweigh the effect of CO2, which is only .041% of the atmosphere. Pointedly, of which man is only responsible for  25% and the US only 15% of that total.

I am not going to waste time attacking here, except to say this kind of one-sided journalism and the fact that nowhere did anyone show what I am about to reveal to you, should raise questions of any objective person.

Basically the rules of the game are, if its warm like this winter, its climate change, if it is cold, its climate change. It is typical of everyone gets a trophy in that any answer even if opposite, means you get credit.

I won’t copy the whole article as it is a bit technical, but it can be seen here. However these are the main points Joe raises, starting with the role of El Nino and water vapour:

Water vapor is by far the most important greenhouse gas when it comes to the planetary weather and climate. Meteorologist look at “saturation mixing ratios” which show a correlation of water vapor to temperature. Basically the colder and drier the air mass, the more the introduction of water vapor will lead higher temperatures, there is no place like the arctic to prove this is the case. The cyclically warmed oceans have put more water vapor (and CO2) into the air. When Super El Niño’s go off, the immense amounts dispersed lead to a step up of the temperature. The colder regions leading the way as will be opined on below.

NOAA Relies on ‘Russian Collusion’ to Claim January Was Hottest Month on Record

by Anthony Watts, February 29, 2020 in WUWT


In a report generating substantial media attention this month, the National Oceanic and Atmospheric Administration (NOAA) claimed January 2020 was the hottest January on record. In reality, the claim relies on substantial speculation, dubious reporting methods, and a large, very suspicious, extremely warm reported heat patch covering most of Russia.

The January 2020 Climate Assessment Report, released by NOAA’s National Center for Environmental Information (NCEI), was accompanied by a map showing a giant red menace of extraordinary asserted warmth extending from the Russian border with Poland well into Siberia. Yet, the asserted hot spot appears nowhere else.

 

Figure 1: Map of temperature departure provided by NOAA/NCEII. Note the huge red spot over Russia.

Continuer la lecture de NOAA Relies on ‘Russian Collusion’ to Claim January Was Hottest Month on Record

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

by Shaviv, December  19, 2017 in ScieneBits/fromNature


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.

Climatologist: Climate Models Are Predicting Too Much Warming

by Dr. Benny Peiser, May 23, 2019 in GWPF


A leading climatologist has said that the computer simulations that are used to predict global warming are failing on a key measure of the climate today and cannot be trusted.

Speaking to a meeting in the Palace of Westminster in London, Professor John Christy of the University of Alabama in Huntsville told MPs and peers that almost all climate models have predicted rapid warming at high altitudes in the tropics:

A paper outlining Dr. Christy’s key findings is published today by the Global Warming Policy Foundation.

CBC Claims Canada Warming Twice As Fast As Globe, Yet Data Tell A Different Story: No Warming In 25 Years!

by P. Gosselin, April 3, 2019 in NoTricksZone


Canada’s CBC here recently cited “a leaked report” which claimed Canada is “warming at twice the global rate.”

According to the “leaked report”, Canada’s annual average temperature over land has warmed 1.7 C when looking at the data since 1948. But that claim is misleading when recent data is considered.

Over the past 25 years, since scientists began to warn that the planet was warming in earnest, there has not been any warming when one looks at the untampered data provided by the Japan meteorology Agency (JMA) that were measured by 9 different stations across Canada. These 9 stations have the data dating back to around 1983 or 1986, so I used their datasats.

Looking at the JMA database and plotting the stations with longer term recording, we have the following chart:

Le réchauffement climatique d’origine anthropique

by G. Geuskens, 14 février 2019, in ScienceClimatEnergie


Le climat peut changer, comme il l’a toujours fait et continuera à le faire sous l’action de variables naturelles. Les activités humaines peuvent-elles avoir une influence comme le prétend la théorie du réchauffement climatique d’origine anthropique ? Cette théorie est basée sur l’existence d’un hypothétique effet de serre défini comme un phénomène radiatifcausé par des gaz tels la vapeur d’eau ou le CO2 qui absorbent une fraction du rayonnement infrarouge émis par la Terre et le réémettent  ensuite dans toutes  les directions et notamment vers la surface terrestre dont la température serait, de ce fait, plus élevée qu’en l’absence de gaz absorbant l’infrarouge. L’effet de serre résulterait donc essentiellement de l’émission par les molécules de CO2 d’un rayonnement  de fluorescence  dans le domaine infrarouge [1]. Cette définition est claire et scientifiquement valable car conforme au principe de réfutabilité défini par Karl Popper. Nous l’examinerons à la lumière de théories physiques bien établies et de faits expérimentaux connus.

1. Le CO2 dans les basses couches atmosphériques