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LOGOTIPO8

CLOUD COVER & GLOBAL CLIMATE

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International Satellite Cloud Climatology Project

The International Satellite Cloud Climatology Project (ISCCP) shows that from the beginning of data analysis up to 1999/2000, global cloud coverage has been reduced by 5% (Figure 1). The planetary albedo is the fraction of solar radiation flux that is reflected (rejected) by the planet into outer space and consequently does not participate in the biogeophysical processes that occur in it. The current planetary albedo is about 30%, and the cloud cover is responsible for half (15%) of this percentage. According to Trenberth et al (2009), an average flow of 341 w/m2 falls “on top” of the planet’s atmosphere, of which 102 w/m2 are reflected into space.

Global Cloud Cover

Therefore, 51 W/m2 of these are reflected by clouds. Considering an initial cloud coverage of 69% and the reflected flux varying linearly with the total coverage, a simple “rule of 3” would lead to an increase of approximately 4 W/m2 in the solar radiation flow absorbed by the planet in 1999/2000. According to the Intergovernmental Panel on Climate Change (IPCC), climate sensitivity (λc) is a totalizer parameter used in the equation

Fórmula

where ΔF is the variation of radiative forcing (W/m2) due to a variation of a controlling variable of the global climate, for example the concentration of greenhouse gases, and ΔT (°C) is the variation of the temperature corresponding to this variation. In the E version of the global climate model of the Goddard Institute for Spatial Studies/NASA (GISS/NASA), the value of λc is equal to 0.7° C/W/m2 (Hansen et al, 2007), which means that for every 1 W/m2 of change in the forcing one would have a variation of 0.7° C in the average global temperature.  As indicated above, a reduction of 5% in the total cloud coverage would lead to an increase of 4 w/m2 in the radiation flux absorbed by the Earth in 2000, which would represent a mean flux (ΔF) of 2 w/m2 in this 18-year period. This value, inserted into the above equation would result in an increase of ΔT = 1, 6°C in the average global temperature. Figure 2 shows data on the variation in the average global temperature of the low troposphere obtained by microwave sensors onboard satellites (MSU) and processed at the University of Alabama in Huntsville (Spencer, 2018) for the same period.

Dados

As can be seen in Figure 2, the dotted line showing the temperature trend measured by the MSU varies between-0.2°C and 0.2°C, an ΔT less than 0.4°C throughout the period, which includes the 1997/1998 Super El Niño, which raised the average global temperature by 0.74°C in April 1998, and other moderate El Niño events occurring in 1986/1987 and 2006/2007 and 2009/2010. It is known that El Niño events inject large amounts of heat into the atmosphere both in the form of sensible and latent heat, affecting global temperature and climate. The conclusion one reaches is that something must be wrong with the global climate models used by the IPCC. According to the latter, an average increase of about 2 W/m2 due to the reduction in global cloud coverage should have caused an increase of 1.6°C in the average temperature. However, according to MSU observations, an increase of less than 0.4°C was observed, which would result in a climatic sensitivity parameter (λc) lower than 0.2°C/W/m2 rather than the 0.7°C/W/m2 resulting from the GISS/NASA’s E model. By doubling the CO2 concentration in the atmosphere, the increase in radiative forcing would be 4 W/m2, which would increase the overall temperature by about 3°C as per the  /NASA model. However, if the planet’s climate sensitivity is similar to the one found here, the global temperature increase would be about 0.4° C, therefore within the natural variability of the climate and with nothing catastrophic about it, contrary to what the IPCC has been trumpeting.

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