The very strong influence of clouds in the climate system

Clouds are poorly represented in climate models, yet clouds are known to have a very strong effect on the climate system, this effect operating mainly through albedo changes. A small change in albedo has a strong effect on the temperature of the Earth, and if the change persists, this will also cause climate change. The Earth’s albedo changes can best be measured by earthshine; simply by measuring how much light the Moon receives from Earth on its unlit side. In this way, a strong negative feedback though cloud changes was measured in response to the warming of the 1998 El Nino (Pallé et al., 2009) clouds were found to increase the Earth’s reflectance beginning in late 1998 until mid-2000, so countering the warming effects of the El Nino. There were also found to be large decadal changes occurring in the albedo or reflectance of the Earth, which could be a negative feedback mechanism controlling the planet’s temperature. A strong negative feedback mechanism is seen in the outgoing longwave radiation (OLR) (Figure 3.60).

Another recent and perhaps surprising discovery is that the Northern Hemisphere and the Southern Hemisphere’s albedos are equal to within 0.2 W/m² (Stephens et al., 2015). There are large differences between the Northern and the Southern Hemispheres;

82 REDUCING CLIMATE CHANGE RELATED FUGITIVE GHG EMISSIONS FROM OPERATIONAL LONGWALL COAL MINES the reflective north being mostly land and the darker and so more absorbent south being mostly oceans, and overall of course, the surfaces have vastly different albedos – so their surface temperatures should on average be very different. Yet when clouds are included, their albedos are virtually the same, which mostly evens out their temperatures. This can only be a result of a strong negative feedback mechanism; the close symmetry in hemispheric albedos, is caused by the buffering of the clouds themselves.

Another buffering effect has also been found; it is known that there is a seasonal cycle of solar flux caused by the eccentricity of the Earth’s orbit. The Earth’s orbit is egg- shaped, this means that every year the distance to the Sun varies from 147.5 M km at perihelion to 152.6 M km at aphelion (Table 3.2). Perihelion (closest approach) occurs each year on January the 3rd _{and at that time the top-of-atmosphere (henceforth TOA) insolation}

is 1,413 W/m². aphelion (greatest distance) occurs each year on July 3rd _{and at that time the}

TOA insolation is 1,321 W/m².

Table 3.2 Seasonal surface insolation changes (Taube, M. 2012). Position Insolation W/m² Earth sphere W/m² Albedo 29% W/m²

Perihelion Jan 3 1,413 353.25 250.8

Aphelion July 3 1,321 330.25 234.48

When allowances are made for the shape of the Earth, and a 29% albedo, the average surface insolation is expected to be 250.80 W/m² at closest approach and 234.48 W/m² at greatest distance; that is, a difference every 6 months of 16.32 W/m². This is one thousand six hundred times the average change in forcing, estimated to have been caused by human GHG (which is of order ~0.01 W/m²) over the same time period (Feldman et al., 2015), and eccentricity is just one contributor out of many, to natural climate variability. This puts the alleged anthropogenic CO₂ forcing into better context, and perhaps goes some way towards explaining just why this forcing has been so difficult to measure.

It will be noted that a change in albedo of just 1% leads to a net surface change in forcing of at least 3.31 W/m², which is still greater than the total net anthropogenic forcing listed in AR5 (Team et al., 2014) of 2.29 W/m² in the 261 years since 1750. Albedo has been found to have a seasonal variability of over 3%, with a higher albedo occurring in the southern summer, and a lower albedo occurring in the northern summer (Stephens et al., 2015), little research has been done yet into these large negative feedback mechanisms.

Seasonal variations in insolation due to eccentricity can also be used to estimate the climate sensitivity. Original work by Cederlof (Cederlöf, 2014) uses empirical data to

83 REDUCING CLIMATE CHANGE RELATED FUGITIVE GHG EMISSIONS FROM OPERATIONAL LONGWALL COAL MINES create a simple climate model to estimate the impact of doubling atmospheric CO₂, using the IPCC’s forcing figure of 3.7 W/m². The key is to separate the Northern Hemisphere from the Southern Hemisphere and treat them separately, because their responses to the seasonal forcing changes are very different. A hysteresis due to inertia of perhaps one month was found to exist after the regular 16.32 W/m² seasonal surface insolation forcing change (caused by the Earth’s eccentricity); but the temperature change was muted in the Southern Hemisphere – the Northern Hemisphere experiences a much greater temperature swing in response. The resultant global climate sensitivity to CO₂ as per these model results, is in the very low range of 0.23°C to 0.32°C; this would probably be too low to measure.

Figure 3.25 Northern Hemisphere irradiance changes vs cloud cover (Cederlöf, 2014) Further work by Cederlof (Principia Scientific, 2017) into the eccentricity-induced seasonal insolation change and cloud cover changes led to an examination of NASA’s CERES data to explore any possible links between the two (CERES, 2017). The result is Figures 3.25 and 3.26 which show a previously unknown and strong correlation between the seasonal irradiance variation and cloud cover changes in each hemisphere when assessed separately; no significant correlation is seen when assessed globally. The importance of this discovery cannot be understated since it means that there exists a strong

negative feedback mechanism in the climate system, which operates through clouds to

reduce the effects of large seasonal insolation changes on the Earth’s surface. This has problematic connotations for the positive water vapour and cloud feedback, which is an integral part of the EGGWH.

84 REDUCING CLIMATE CHANGE RELATED FUGITIVE GHG EMISSIONS FROM OPERATIONAL LONGWALL COAL MINES Figure 3.26 Southern Hemisphere irradiance changes vs cloud cover (Cederlöf, 2014)

Also, to be noted is that the Northern Hemisphere is warmer than the Southern Hemisphere, despite the fact that the Southern Hemisphere’s surface insolation is on average, higher. The reason for this discrepancy is because there is a far higher average cloud cover in the Southern Hemisphere. According to CERES data, the Southern Hemisphere averages 65.5% cloud cover, and the Northern Hemisphere averages 57.6%. From the differences in cloud cover and insolation, Cederlof calculates from this, a climate sensitivity to CO₂ of 0.4°C which compares well with the 0.3°C from the previous work on seasonal variations.

Climate models used by the IPCC researchers do not have the same regulation of albedo or degree of hemispheric symmetry that is created by the action of clouds. The obvious and strong negative feedback that is displayed here by clouds on a global and hemispheric scale, is completely at odds with the proposition that clouds do the exact reverse where CO₂ is involved; namely, that they positively reinforce the initial warming from CO₂ rather than act to mitigate it. It is difficult to maintain the proposition of positive feedback from clouds to a CO₂ forcing, if a measured solar forcing produces a measured negative feedback from clouds. Why should they be different? Invoking a large positive feedback through water vapour to any CO₂ forcing, also flies in the face of logic, since this would mean that the climate system has to be intrinsically unstable, and this instability is not seen anywhere in the climate record.