Atmospheric Scientists Slam Fundamentals
of the Anthropogenic Global Warming Theory
Scafetta et al., 2017 Natural climate variability, part 1: Observations versus the modeled predictions
[T]he AGWT [Anthropogenic Global Warming Theory] was globally advocated by the IPCC in 2001 because it appeared to be supported by the ‘infamous’ Hockey Stick temperature reconstructions by Mann et al. * and by specific computer climate models mainly based on radiative forcings [4,11]. Those temperature reconstructions claimed that only a very modest change in the Northern Hemispheric climate had occurred during the pre-industrial times from A.D. 1000 to 1900, while an abrupt warming did occur just in the last century. Energy balance and general circulation climate models (GCM) were used to interpret the Hockey Stick climatic pattern as due mostly to anthropogenic greenhouse gas emissions such as CO2 because of coal and oil fuel consumption, which has been accelerating since the beginning of the 20th century .
However, since 2005 novel Northern Hemisphere proxy temperature reconstructions were published revealing the existence of a large millennial oscillation that contradicts the Hockey Stick temperature pattern
* see reference list
The new findings were consistent with alternative climatic and solar activity records showing that a quasi-millennial oscillation occurred throughout the entire Holocene for the last 10,000 years [16, 17].
The severe discrepancy between observations and modeled predictions found during the 1922-1941 and 2000-2016 periods further confirms, according to the criteria proposed by the AGWT advocates themselves, that the current climate models have significantly exaggerated the anthropogenic greenhouse warming effect.
In 2009 AGWT advocates acknowledged that: “Near-zero and even negative trends are common for intervals of a decade or less in the simulations, due to the model’s internal climate variability. The simulations rule out (at the 95% level) zero trends for intervals of 15 year or more, suggesting that an observed absence of warming of this duration is needed to create a discrepancy with the expected present-day warming rate” . Thus, according to the AGWT advocates’ own criteria, a divergence between observations and climate models occurring at the bi-decadal scale would provide strong convincing evidences that the GCMs used to support the AGWT are severely flawed.
In conclusion, the temperature records clearly manifest several fluctuations from the inter-annual scale to the multidecadal one. Detailed spectral analyses have determined the likely existence of harmonics at about 9.1, 10.5, 20 and 60- year periods [7, 8, 9]. By contrast, the CMIP5 GCMs simulations used by the IPCC (2013) to advocate the AGWT show a quite monotonic accelerating warming since 1860, which is at most temporarily interrupted by volcano eruptions and only slightly modulated by aerosol emissions. Thus, the models are not able to reproduce the natural variability observed in the climate system and should not be trusted for future energy planning .
It has been suggested that non-radiative physical processes connected with solar activity and the “resonant” orbital motions of the moon and the planets can cast light on the otherwise incomprehensible temperature fluctuations [34, 35]. In fact, the magnetic activity of the sun and, probably, also the planetary motions modulate both the solar wind and the flux of the cosmic rays and interstellar dust on the earth with the result of a modulation of the clouds coverage.
Scafetta et al., 2017 Natural climate variability, part 2: Observations versus the modeled predictions
Several studies based on general circulation model (GCM) simulations of the Earth’s climate concluded that the 20th century climate warming and its future development depend almost completely on anthropogenic activities. Humans have been responsible of emitting in the atmosphere large amount of greenhouse gases (GHG) such as CO2 throughout the combustion of fossil fuels. This paradigm is known as the Anthropogenic Global Warming Theory (AGWT).
[S]ince 2001 AGWT was actually supported by the belief that the “hockey stick” proxy temperature reconstructions, which claim that an unprecedented warming occurred since 1900 in the Northern Hemisphere, were reliable [2,5] and could be considered an indirect validation of the available climate models supporting the AGWT . However, since 2005 novel proxy temperature reconstructions questioned the reliability of such hockey stick trends by demonstrating the existence of a large millennial climatic oscillation [7-10]. This natural climatic variability is confirmed by historical inferences  and by climate proxy reconstructions spanning the entire Holocene [12, 13]. A millennial climatic oscillation would suggest that a significant percentage of the warming observed since 1850 could simply be a recovery from the Little Ice Age of the 14th – 18th centuries and that throughout the 20th century the climate naturally returned to a warm phase as it happened during the Roman and the Medieval warm periods [9, 11, 14-16].
We … critically analyze the year 2015-2016, which has been famed as the hottest year on record. We show that this anomaly is simply due to a strong El-Niño event that has induced a sudden increase of the global surface temperature by 0.6 °C. This event is unrelated to anthropogenic emissions. In fact, an even stronger El-Niño event occurred in 1878 when the sudden increase of the global surface temperature was 0.8 °C.
Herein, the authors have studied the post 2000 standstill global temperature records. It has been shown that once the ENSO signature is removed from the data, the serious divergence between the observations and the CMIP5 GCM projections becomes evident. Note that Medhaug et al.  claim that the models agree with the post 2000 temperature trend. However, these authors did not remove the ENSO signal and used annual mean temperature records up to 2015 that camouflage the real nature of the 2015-2016 ENSO peak.
Moreover, a semi-empirical model first proposed in 2011 based on a specific set of natural oscillations suggested by astronomical considerations plus a 50% reduced climatic effect of the radiative forcing, which includes the anthropogenic forcing, performs quite better in forecasting subsequent climate changes. Thus, the GCMs used to promote the AGWT have been also outperformed [by a natural oscillation/astronomical/anthropogenic “semi-empirical” model]. This result is indeed consistent with recent findings. In fact, although the equilibrium climate sensitivity (ECS) to CO2 doubling of the GCMs vary widely around a 3.0°C mean [3,4], recent studies have pointed out that those values are too high.
Since 2000 there has been a systematic tendency to find lower climate sensitivity values. The most recent studies suggest a transient climate response (TCR) of about 1.0 °C, an ECS less than 2.0 °C  and an effective climate sensitivity (EfCS) in the neighborhood of 1.0 °C .
Thus, all evidences suggest that the IPCC GCMs at least increase twofold or even triple the real anthropogenic warming. The GHG theory might even require a deep re-examination .