By Kenneth Richard on 24. April 2023
A new study exposes the uncertainty in solar activity reconstructions, but suggests solar models explain climate changes far better than atmospheric CO2 concentrations.
Proxy model estimates of the impact of solar variability on climate are highly uncertain. For example, estimations of the increase in solar irradiance over the last 400 years range anywhere from 0.75 W/m² to 6.3 W/m² (Scafetta and Bianchini, 2023).
Even satellite measurements of recent solar irradiance changes are controversial and conflicting. One composite (ACRIM) shows an increase in solar activity from 1980 to 2000, whereas another (PMOD) depicts a decrease. If even modern-day measurements of solar activity contradict each other, then we cannot assume the estimations of past variations from proxies are any more accurate.
On the other hand, the Northern Hemisphere proxy temperature record (shown in black in the image below, extended to 1999) has been linked to the periodicity of an interplanetary solar activity model devised by Dr. Nicola Scafetta and others. Notice the proxy temperature reconstruction depicts nearly all of the warming in the last 400 years occurring prior to 1950.
Image Source: Scafetta and Bianchini, 2023
In contrast, there is almost no link between CO2 and temperature that could lead to the conclusion CO2 is a driver of climate.
CO2 changes lag behind temperature changes by hundreds of years in paleoclimate reconstructions, and CO2 variations “significantly depend on the surface temperature of the oceans.” If the CO2 variations are dependent upon temperature variations, the CO2 cannot be the driver of temperature variations.
“It is worth noting that the link between atmospheric CO2 content and global temperature has been fairly poor throughout the last 600 million years [2,22,23]. CO2 concentration, for example, has also lagged for centuries behind temperatures during deglaciation and glaciation periods, as occurred during the last 420,000 years, as shown in the Vostok ice core record ; although, if the data are processed in some way and some specific places are analyzed, the two variables appears much more tightly coupled [20,25].
Hence, carbon dioxide cannot have typically been the primary driver of climate changes for nearly all of Earth’s history, but rather, it worked as one of the climate (positive) feedback mechanisms in response to solar, astronomical, orbital, and other natural forcings, although it was likely less important than water vapor and clouds. In fact, the atmospheric CO2 concentration significantly depends on the surface temperature of the oceans and on the status of the biosphere, although it might also be suddenly altered by volcanic activity.”
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