Ice core records from Greenland reveal substantial solar irradiation variability parameters over millennial timescales. After the year 1000 the ice core records have identified five solar irradiation minima. These solar minima are commonly referred to as the Oort (1010–1070), Wolf (1270–1340), Spörer (1390–1550), Maunder (1640–1720), and Dalton (1790–1820) minima (Usoskin et al., 2007).

The five solar minima suggest a possible periodic solar irradiation minima. Periodic radiation from the Sun implies that a cold climate period may follow a warm period. The Maunder Minimum in the 1700s was among the coldest periods recorded. This raises the question of whether we can expect a new Maunder-type minimum, or a milder Dalton-type minimum 

Satellite TSI monitoring

The atmosphere affects the radiation received from the Sun. In 1978, NASA initiated satellite-based measurements of total solar irradiance (TSI). After about 30 years, a reconstructed TSI data series was published in 2014, extending back to the year 1700. The data indicate that solar radiation increased by about 0.3% over 300 years (Scafetta and Willson, 2014).

These results confirm that TSI varies over time and may influence climate variability. A 300-year TSI record also contains information about the sources of solar variability. If solar radiation varies periodically, it may provide insight into both past and future TSI changes.

The Planet Hypothesis

The language of nature is mathematics. A data series has a unique signature. A fingerprint that may reveal the source of variability. Analysis of the NASA TSI data series revealed that solar radiation contains signatures associated with the major planets: Jupiter, Saturn, Uranus, and Neptune (Yndestad and Solheim, 2017).

As the planets orbit the Sun, the Sun moves around the solar system barycenter. The elliptical planetary orbits cause variations in this motion. Changes in the Sun’s motion may influence the solar dynamo. This, in turn, may affect solar irradiance. TSI minima occur when Uranus and Neptune are closest to the Sun. Deep minima occur when Saturn, Uranus, and Neptune align (Yndestad, 2022).

The First Little Ice Age

The TSI signature indicates minima and maxima within an envelope period of about 4450 years. Within this envelope, a Little Ice Age spans approximately 1100 years. TSI minima occur at intervals of about 165 and 500 years. A typical minimum lasts about 50 years. A deep minimum may last 50–70 years. The 1100-year period defines the Little Ice Age structure. There have been two such periods since the last major glaciation ended about 10,000 years ago. The first lasted from about 3300 BC to 2200 BC. During this period, three TSI minima and four deep minima were identified.

A deep TSI minimum lasting 50–70 years may influence climate and sea surface temperature. Lower ocean temperatures affect Arctic ice extent and wind patterns. During cold periods, ecosystems show reduced productivity. Food production declines. This may lead to migration and societal stress. Populations may also become more vulnerable to pandemics. This framework may explain why early civilizations developed between deep TSI minima.

The Last Little Ice Age

The last Little Ice Age is computed to span from about 1100 to 2200. Within this period, TSI minima are calculated for the years 1535 and 2035. Deep minima are estimated for the years 1214, 1384, 1710, 1889, and 2215. These deep minima coincide with historical reports of poor harvests, pandemics, and migration. The minimum around 1384 started with the Black Death and prolonged cooling. The minimum around 1710 corresponds to “The Deep Freeze”. The coldest periods in recent millennia. The minimum around 1889 coincides with agricultural stress and migration to America. A TSI maximum is identified around 2018. This corresponds to the recent warming period. The next estimated minimum around 2035 may initiate a cooling trend toward 2074.

Estimated sea surface temperature

Figure 1. Estimated global sea surface temperature, 1850–2020.

Most of the Earth’s surface is covered by oceans. Ocean heat capacity introduces a delay between changes in solar radiation and observed temperature. Global sea surface temperature data (1850–2020) show such a delay. A deep TSI minimum around 1889 is followed by a temperature minimum around 1910. A maximum occurs around 1945, a minimum around 1970, and a new maximum around 2018 (Figure 1).

Computed sea surface temperature

The TSI signature is reflected in global sea surface temperature. Maximum temperature growth occurs near TSI maxima, followed by delayed warming. Calculated temperature minima occur around the years 1248, 1383, and 1911. Deep minima around the years 1070, 1570, 1745, and 2071. The minimum around 1745 coincides with maximum glacier extent in Norway. The calculated minimum in 1911 aligns with observed data from 1910.

A temperature maximum around 2025 appears as a 500-year event, comparable to a maximum around 1570. This may explain the rapid warming observed in recent decades. A deep minimum around 2071 represents a corresponding large-scale event.

Figure 2. Computed global sea surface temperature, 1900–2100. The Neptune period (black), the Uranus period (green), and the temperature index (red), represented as the sum of the periods.

The sea surface temperature signal includes multiple planetary periods. Contributions from Uranus and Neptune are illustrated for 1900–2100. Their sum forms a temperature index. The index increases from a minimum around 1908 to a maximum around 1952. It declines toward the 1960s, rises to a maximum around 2025, and then decreases toward a deep minimum around 2074.

The transition from maximum (2025) to deep minimum (2074) spans about 50 years. This may seem rapid. However, climate change is not linear. Climate variability reflects the sum of interacting periodic processes with astronomical origins.

Turning points

Analysis of climate data suggests a signature linked to solar system dynamics. The pattern indicates that cold periods may follow warm periods. The results suggest a turning point around 2025 and a potential cooling over the next 50 years.

Ecosystems tend to expand during warm periods and contract during cold periods. If a climatic transition is approaching, adaptation in ecosystems, food production, and energy systems will be required. The key question is whether society is prepared for a prolonged cold period.

Post song: The Climate Turning

References

1. Usoskin, I.G., Solanki, S.K. and Kovaltsov, G.A., 2007, Grand minima and maxima of solar activity: new observational constraints A& A, 471, 301-309.
2. Scafetta N. and Willson R.C., 2014, ACRIM total solar irradiance satellite composite validation versus TSI proxy models. Astrophys. Space Sci., 350(2), 1040, 421-442. DOI 10.1007/s10509-013-1775-9.
3. Yndestad, H., & Solheim, J. (2017). The influence of solar system oscillation on the variability of the total solar irradiance. New Astronomy, 51, 135–152. doi.org/10.1016/j.newast.2016.08.020.
   https://ntnuopen.ntnu.no/ntnu-xmlui/handle/11250/2473902
4. Yndestad H. 2022. Jovian Planets and Lunar Nodal Cycles in the Earth’s Climate Variability Frontiers in Astronomy and Space Sciences. May 10. 2022. https://doi.org/10.3389/fspas.2022.839794.