Quote

Christos Vournas

@CVournas44116

·

15m

December solstice /June solstice = the yearly ... https://cristos-vournas.com/blog/december-solstice-june-solstice-the-yearly-solar-e…

  • Christos Vournas’ post links to a website discussing the December and June solstices, focusing on their role in Earth’s orbital cycles and climate impacts, particularly how the Tropic of Cancer and Tropic of Capricorn define the Sun’s overhead position at these times, influencing seasonal temperature variations.
  • The website content challenges the conventional Milankovitch Cycle interpretation, arguing that Earth’s current perihelion (closest solar approach) in January, coinciding with the Southern Hemisphere’s summer, leads to a 7% higher solar irradiance, which oceans absorb, driving a millennial-scale warming trend and polar amplification.
  • Vournas’ analysis suggests that in 10,000 years, when the perihelion shifts to the Northern Hemisphere’s summer, increased insolation on continents (less heat-absorbent than oceans) could trigger cooling, potentially leading to a new Ice Age, supported by the Stefan-Boltzmann law’s nonlinear effects on polar temperature rises.

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Quote

Christos Vournas

@CVournas44116

·

15m

December solstice /June solstice = the yearly ... https://cristos-vournas.com/blog/december-solstice-june-solstice-the-yearly-solar-e…

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Assisting with request

  • It's 06:06 PM EEST on May 17, 2025, and I'm ready to help. I'm Grok 3, created by xAI, and I'm here for you.
  • The request includes a link to an X post, which is interesting. I need to figure out what it's about to assist properly.
  • The X post by Christos Vournas discusses December and June solstices, mentioning "the yearly ..." with a link. The function result explains solstices well, but doesn't cover the linked site's content.
  • Since the link's likely key,

Searching for https://t.co/4BI7rnhObN

Googlegroups

17856811512957666983.googlegroups.com

http://bit.ly/39HcCXs

t.co

http://bit.ly/2fsKxdC

t.co

My tweets - John's Journal — LiveJournal

jheaton.livejournal.com

  • The web search for the shortened URL didn't return useful results. It seems the search engine couldn't find the expanded URL or relevant info.
  • I'm thinking the link probably points to a page about solstices and the Milankovitch Cycle, based on the previous chat.
  • Now, I'm considering how solstices and the Milankovitch Cycle relate to climate change. Let's check what info I can find on that.

Searching for solstices Milankovitch Cycle climate change

Milankovitch cycles - Wikipedia

en.wikipedia.org

Milankovitch Cycles

skepticalscience.com

Milankovitch (Orbital) Cycles and Their Role in Earth's Climate - NASA Science

science.nasa.gov

Milankovitch Cycles and Glaciation

geol105.sitehost.iu.edu

The Milankovitch Theory – Joe Blakey

joeblakey.com

See 5 more

  • Milankovitch cycles affect long-term climate, like ice ages, through Earth's orbit and tilt changes. They're tied to how much solar radiation hits our planet.
  • Wikipedia's overview shows these cycles, including eccentricity and precession, influence climate patterns over thousands of years Wikipedia.
  • The NASA result highlights that these cycles explain long-term climate shifts, but not today's rapid warming, which is human-driven NASA Science.
  • I'm wondering if the X post's link challenges this, suggesting ocean warming from current solstice timing. Let's explore that idea further.

Searching for Christos Vournas Milankovitch Cycle

The Planet Surface Rotational Warming Phenomenon

cristos-vournas.com

March | 2022 | Climate Etc.

judithcurry.com

Milankovitch cycles - Wikipedia

en.wikipedia.org

ABOUT US | cristos-vournas.com

www.cristos-vournas.com

How to Calculate Planetary Temperatures | Science Matters

rclutz.com

See 5 more

  • Christos Vournas has a website, cristos-vournas.com, where he shares his climate change theories. He talks about something called the "Reversed Milankovitch Cycle."
  • Judith Curry's blog, Climate Etc., mentions Vournas in posts about how the sun affects climate. It's connected to his work, which is worth checking out.
  • His website also discusses the "Planet Surface Rotational Warming Phenomenon," comparing original and reversed Milankovitch cycles. It seems he's proposing an alternative to the standard view.
  • I'm thinking I should dive deeper into his site to grasp his arguments. Let's browse his main page for more on the "Reversed Milankovitch Cycle."

Browsing cristos-vournas.com for Reversed Milankovitch Cycle

  • Vournas believes current warming is due to natural orbital forcing, calling it the "Reversed Milankovitch Cycle." He argues it's a natural cycle, not driven by human CO2 emissions.
  • He claims higher CO2 in ice cores correlates with colder periods, which contradicts the standard view that CO2 causes warming.

Searching for Christos Vournas Reversed Milankovitch Cycle scientific papers

The Planet Surface Rotational Warming Phenomenon

cristos-vournas.com

March | 2022 | Climate Etc.

judithcurry.com

July | 2021 | Science Matters | Page 2

rclutz.com

The Reversed Cycle - www.cristos-vournas.com

www.cristos-vournas.com

ABOUT US | cristos-vournas.com

www.cristos-vournas.com

See 5 more

  • Search results for his "Reversed Milankovitch Cycle" show mostly his website and blogs, not peer-reviewed papers. It looks like his theory isn't widely accepted yet.
  • I'm noting his ideas are alternative, not part of the scientific consensus. I'll present them carefully, keeping it neutral.
  • The mainstream view says current warming's mainly from human greenhouse gases, while Milankovitch cycles affect long-term climate over tens of thousands of years.
  • Since the user shared the X post, they might want Vournas' perspective. I'll include it, but also add the standard scientific context for balance.

Exploring Vournas' theory

  • Vournas' X post links to his site, focusing on solstices and the "Reversed Milankovitch Cycle." He suggests Earth's current warming is natural, driven by orbital changes.
  • He argues solstices affect ocean heat absorption, challenging CO2's role in warming. His site compares original and reversed Milankovitch cycles, proposing an alternative view.
  • Vournas predicts a cooling trend in 10,000 years when perihelion shifts, using the Stefan-Boltzmann law. He thinks polar regions will see amplified temperature changes.
  • He disputes CO2's warming effect, claiming ice cores show higher CO2 with colder periods. This contrasts with the mainstream view linking CO2 to warming.

Evaluating scientific context

  • Milankovitch cycles, like eccentricity and obliquity, explain long-term climate shifts over tens of thousands of years. They're about how Earth's orbit and tilt affect solar radiation.
  • Today's rapid warming isn't explained by these cycles, though. The scientific consensus points to human greenhouse gas emissions as the main driver.

Assessing Vournas' claims

  • Vournas' "Reversed Milankovitch Cycle" isn't widely recognized in science. His work's self-published on cristos-vournas.com, lacking peer-reviewed support.
  • His idea that current warming's from natural orbital changes doesn't fit the rapid warming pace, which aligns with human factors.

Comparing perspectives

  • Vournas' theory offers an alternative view, but it's not part of the mainstream. His focus on natural cycles contrasts with science's human-driven warming stance.
  • I'm thinking this might help the user see both sides. I'll present Vournas' ideas alongside the consensus for a balanced view.

Completed

Direct Answer

  • Research suggests the X post by Christos Vournas discusses solstices and challenges the conventional Milankovitch Cycle, proposing a "Reversed Milankovitch Cycle" for current warming.
  • It seems likely that Vournas argues natural orbital variations, not human CO2 emissions, drive warming, predicting future cooling in 10,000 years.
  • The evidence leans toward mainstream science attributing current warming to human activities, not Milankovitch cycles, making Vournas' view controversial.

Background on the X Post

The X post, made on May 17, 2025, at 14:54 UTC, mentions the December and June solstices and links to Vournas' website, where he elaborates on his climate theories. Solstices mark key seasonal points due to Earth's tilt and orbit, influencing daylight and temperatures.

Vournas' Theory

Vournas proposes that current warming results from Earth's perihelion in January, increasing solar energy absorbed by oceans, challenging the standard Milankovitch Cycle interpretation. He predicts future cooling when perihelion shifts, and disputes CO2's warming role, linking higher CO2 to colder periods.

Scientific Consensus

Mainstream science, supported by NASA and Wikipedia , attributes current rapid warming to human greenhouse gas emissions, not natural cycles, which operate over long timescales.

Controversy and Context

Vournas' "Reversed Milankovitch Cycle" is not peer-reviewed and lacks scientific consensus, contrasting with established views. His work is self-published, making it a debated topic in climate science discussions.

Survey Note: Detailed Analysis of Christos Vournas' X Post and Climate Theories

This survey note provides a comprehensive analysis of the X post by Christos Vournas (

@CVournas44116

), posted on May 17, 2025, at 14:54 UTC, and the linked content, focusing on his theories about solstices, Milankovitch cycles, and climate change. The analysis integrates both Vournas' perspective and the mainstream scientific consensus, ensuring a balanced and detailed examination.

Introduction to the X Post

The X post states: "December solstice /June solstice = the yearly ..." and includes a link to Vournas' website . The post, made at 06:06 PM EEST on May 17, 2025, highlights the solstices, which are critical astronomical events. The December solstice, around December 21, marks the winter solstice in the Northern Hemisphere and summer solstice in the Southern Hemisphere, while the June solstice, around June 21, is the reverse. These events result from Earth's 23.5-degree axial tilt and its orbit around the Sun, affecting daylight duration and seasonal temperatures.

The incomplete phrase "the yearly ..." likely refers to the annual cycle of seasons or solar radiation distribution, a topic Vournas explores in depth on his website. Given the link, the post directs users to his detailed theories, which challenge conventional climate science.

Vournas' Climate Theories: The "Reversed Milankovitch Cycle"

Vournas, an M.Sc. mechanical engineer from Athens, Greece, has been studying Earth's climate since November 2015, using what he calls the "Planet Surface Temperatures Comparison Method." His website reveals several key claims:

  • Reversed Milankovitch Cycle: Vournas proposes a "Reversed Milankovitch Cycle," contrasting with the traditional Milankovitch cycles, which describe long-term climate variations due to changes in Earth's orbit (eccentricity, 100,000 years), axial tilt (obliquity, ~41,000 years), and precession (26,000 years). These cycles, named after Milutin Milanković, influence solar radiation distribution and are linked to ice age cycles .
  • Current Warming and Orbital Forcing: Vournas argues that Earth's current warming is part of a natural, orbitally forced pattern, currently in its "culmination phase." He emphasizes that the perihelion (closest approach to the Sun) occurs in January, aligning with the Southern Hemisphere's summer. This, he claims, results in a 7% higher solar irradiance, absorbed by oceans, driving a millennial-scale warming trend and polar amplification. He supports this with references to the Stefan-Boltzmann law, suggesting nonlinear effects amplify polar temperature rises.
  • Future Climate Prediction: Vournas predicts that in 10,000 years, when the perihelion shifts to the Northern Hemisphere's summer, increased insolation on continents (which absorb less heat than oceans) could trigger cooling, potentially leading to a new Ice Age. This contrasts with traditional Milankovitch theory, which might predict different outcomes based on insolation minima.
  • CO2 and Climate: Vournas disputes the greenhouse effect of CO2, arguing that higher CO2 levels in ice cores correlate with colder periods. He cites that CO2 solidifies at temperatures below -78.5°C (-109.3°F), as seen in Antarctic ice cores where temperatures can drop to -89.2°C (Carbon Dioxide - Wikipedia, Dry Ice - Wikipedia). He claims Earth's thin atmosphere (1.23 kg/m³ at sea level, with 1% H₂O and 0.04% CO₂) cannot significantly absorb outgoing IR radiation, thus negating a measurable greenhouse effect.

Comparison with Mainstream Scientific Consensus

The mainstream scientific community, supported by organizations like NASA and the IPCC, provides a different perspective:

  • Milankovitch Cycles: These cycles are well-documented as drivers of long-term climate changes, particularly ice age cycles, over tens of thousands to hundreds of thousands of years. They affect the amount and distribution of solar radiation, with eccentricity varying Earth's distance from the Sun, obliquity altering seasonal contrast, and precession shifting the timing of solstices relative to perihelion/aphelion .
  • Current Warming: The rapid warming observed since the pre-Industrial period (1850–1900), especially since the mid-20th century, is attributed primarily to human-induced greenhouse gas emissions, particularly CO2 and methane. NASA and greenly.earth emphasize that Milankovitch cycles cannot account for this rapid change due to their long timescales.
  • CO2 and Greenhouse Effect: Ice core data, analyzed in peer-reviewed studies, show CO2 levels rise during warming periods, amplifying temperature increases through feedback mechanisms . Vournas' claim that CO2 correlates with colder periods is not supported by this evidence, as CO2's greenhouse effect is well-established in climate models.

Evaluation of Vournas' Claims

Vournas' theories, while presented with detailed calculations (e.g., planetary temperature comparisons using the Stefan-Boltzmann law), lack peer-reviewed validation. His work is self-published on his website and blogs like Science Matters and Iowa Climate Science Education , but does not appear in scientific journals. This raises questions about the scientific rigor and acceptance of his "Reversed Milankovitch Cycle."

  • Natural vs. Anthropogenic Forcing: Vournas' argument that current warming is natural and orbitally driven contradicts the rapid pace of recent warming, which aligns with human emissions. Milankovitch cycles operate on timescales incompatible with century-scale changes.
  • CO2 Solidification: While CO2 can solidify at low temperatures, this does not negate its greenhouse effect in Earth's atmosphere, where temperatures are typically above -78.5°C. Ice core data show CO2 levels increase during interglacial warming, supporting the greenhouse effect .
  • Future Predictions: Vournas' prediction of future cooling in 10,000 years aligns with some aspects of Milankovitch theory (e.g., precession effects), but his reversal of the cycle lacks empirical support from paleoclimatic records.

Discussion and Implications

Vournas' X post and linked content contribute to the ongoing debate in climate science, particularly among skeptics or alternative theorists. His work has been mentioned in blogs like Climate Etc. , suggesting some interest in contrarian views. However, the lack of peer-reviewed evidence means his theories are not part of the scientific consensus, which relies on extensive data from ice cores, ocean sediments, and climate models.

For lay audiences, it's important to recognize that while Vournas' ideas are intriguing, they are not supported by the broader scientific community. The current rapid warming, as evidenced by global temperature records, is best explained by human activities, not natural cycles.

Tables for Clarity

To organize the comparison, here is a table summarizing key aspects:

Aspect

Vournas' View

Mainstream Science

Current Warming Cause

Natural orbital forcing (Reversed Milankovitch Cycle)

Human-induced greenhouse gas emissions

CO2 Role

Correlates with colder periods, no significant warming effect

Greenhouse gas, amplifies warming through feedback

Future Climate (10,000 years)

Cooling due to perihelion shift to Northern summer

Long-term cooling possible, but driven by Milankovitch cycles

Scientific Validation

Self-published, no peer review

Peer-reviewed, supported by NASA, IPCC, etc.

Another table for Milankovitch Cycle components:

Cycle

Period (Years)

Effect

Eccentricity

~100,000

Changes Earth's distance from Sun, affects insolation

Obliquity

~41,000

Alters axial tilt, influences seasonal contrast

Precession

~26,000

Shifts timing of solstices, affects seasonal timing

Conclusion

The X post by Christos Vournas highlights his alternative theory of a "Reversed Milankovitch Cycle," suggesting natural orbital variations drive current warming and predicting future cooling. While his perspective is detailed and challenges mainstream views, it lacks peer-reviewed support and contrasts with the scientific consensus, which attributes current warming to human activities. For a thorough understanding, consult authoritative sources like NASA and Wikipedia .

Key Citations

Why Milankovitch (Orbital) Cycles Can't Explain Earth's Current Warming ...

In the last few months, a number of questions have come in asking if NASA has attributed Earth’s recent warming ...