Lots of assertions there JD. But STILL not a single concrete piece of evidence.

As usual.
As expected

Now he's asking me to go off and find papers that support his assertions. What a joke.

No, mhaze, I didn't ask you to.

//Now he's asking me to go off and find papers that support his assertions. What a joke.//

I simply pointed out that you were capable of doing so.

(Sounds like someone's getting a little cranky.)

//But STILL not a single concrete piece of evidence.//

I offered to google it for you. Can I take it this is a 'Yes, please do'?

"Henrik Svensmark's ground-breaking theory, often termed cosmoclimatology, offers a compelling explanation for how solar winds influence Earth's climate through cosmic rays. Developed in the 1990s at the Danish National Space Center, it posits that variations in solar activity modulate the influx of galactic cosmic rays, which in turn affect cloud formation and global temperatures.

At its core, the mechanism is elegant: During periods of high solar activity, marked by increased sunspots and stronger solar winds, the Sun's magnetic field intensifies, deflecting more cosmic rays away from Earth. Fewer cosmic rays mean reduced ionization in the atmosphere, leading to fewer cloud condensation nuclei. This results in diminished low-level cloud cover, which normally reflects sunlight back to space. Consequently, more solar radiation reaches the surface, warming the planet. Conversely, low solar activity allows more cosmic rays to penetrate, promoting cloud formation and cooling effects, as seen during the Little Ice Age when solar minima coincided with colder global temperatures.

Empirical evidence bolsters this view. Svensmark's analysis of satellite data revealed a strong correlation—up to 0.92—between cosmic ray flux and global cloud cover variations over solar cycles. Laboratory experiments, such as those at CERN's CLOUD project, have confirmed that cosmic rays enhance aerosol nucleation, supporting the cloud-seeding hypothesis. Historical reconstructions further align solar activity proxies with climate shifts, explaining warming trends since 1750 without over-relying on anthropogenic factors.
This theory amplifies the Sun's role beyond mere irradiance changes, estimating solar forcing at 1.0–1.5 W/m² over cycles—far greater than IPCC estimates. It challenges conventional models by integrating astronomical phenomena with terrestrial climate, fostering a holistic understanding of natural variability. Svensmark's work invites re-evaluation of climate dynamics, emphasizing the Sun's profound, underappreciated influence on our world."

http://www.thegwpf.org/content/uploads/2019/03/SvensmarkSolar2019-1.pdf

mhaze,

The document you linked isn't a journal paper. It's a GWPF policy report. So it hasn't gone through the standard anonymous peer review process that attribution studies in the mainstream literature do.

Svensmark is a serious physicist and the cosmic ray-cloud idea is a legitimate hypothesis. CLOUD at CERN did show that ionisation can enhance nucleation of very small particles in controlled conditions. That part is interesting.

The harder part isn't whether ions can help nucleation. It's what happens next.

Showing enhanced nucleation in a chamber is not the same as demonstrating a sustained, multi-decadal shift in global cloud cover large enough to explain late-20th-century warming. Moving from microphysics to global radiative forcing is the real leap, and that's where the evidence becomes much less clear.

Then there's timing. Cosmic ray flux has been directly measured since the 1950s. It tracks the 11-year solar cycle. What it does not show is a strong long-term trend since the 1970s that mirrors the steady temperature rise. The modern warming curve and the cosmic ray record simply don't line up on that timescale.

As for attribution, this isn't about eyeballing graphs. Models are run with natural forcings only and then with greenhouse gases included. The natural-only runs don't reproduce the late-century warming trend. Add greenhouse gases and the models track the observed rise much more closely. That pattern has been reproduced across multiple modelling groups.

The sun clearly influences climate. The question is whether solar-modulated cosmic rays explain the magnitude and timing of recent warming. At this stage, the peer-reviewed literature says they don't.

In the ongoing debate over the drivers of global warming, two prominent theories emerge: the mainstream CO2-driven greenhouse effect and Henrik Svensmark's cosmic ray hypothesis. While the CO2 theory attributes recent temperature rises primarily to human emissions trapping heat, Svensmark's model offers a more comprehensive, natural explanation that aligns better with historical and empirical data, making it preferable for understanding climate dynamics.

Svensmark's theory holds that galactic cosmic rays (GCRs) play a pivotal role in cloud formation. When solar activity is high, the sun's magnetic field strengthens, deflecting more GCRs from Earth. Fewer GCRs mean reduced ionization in the atmosphere, leading to fewer cloud condensation nuclei and thus thinner cloud cover. This allows more sunlight to reach the surface, amplifying warming. Conversely, low solar activity permits more GCRs, increasing clouds and cooling the planet. This mechanism explains not just 20th-century warming but other climate events, such as the Medieval Warm Period and Little Ice Age, without relying on anthropogenic factors.

Empirical evidence strongly supports Svensmark. Studies show a 0.92 correlation between GCR flux and global cloud cover, far exceeding CO2's explanatory power for pre-industrial variations. Over the solar cycle, energy entering Earth's system is 5-7 times greater than from solar irradiance alone, indicating amplification via clouds. Recent Japanese research on winter monsoons confirms GCRs' "umbrella effect," where increased rays boost low clouds, countering warming trends. In contrast, the CO2 theory struggles with these natural cycles; IPCC estimates solar forcing at a mere 0.05 W/m² since 1750, negligible next to greenhouse gases, yet ignores solar amplification.

"Svensmark's approach is preferable because it integrates astronomical influences with terrestrial climate, offering a holistic view. It suggests lower climate sensitivity to CO2 (around 0.25 K/Wm⁻² versus IPCC's 0.9), implying less alarm over emissions. By substantiating solar-GCR links through experiments like SKY2, it challenges CO2-centric models that overlook cosmic drivers. Ultimately, embracing Svensmark fosters a nuanced, evidence-based climate science, prioritizing natural variability over singular human culpability."

Thanks for the copy-and-paste, mhaze.

//two prominent theories emerge: the mainstream CO2-driven greenhouse effect and Henrik Svensmark's cosmic ray hypothesis.//

That framing is the first problem. This isn't a binary contest where one theory must replace the other. Solar forcing is already included in mainstream attribution work alongside volcanic forcing, aerosols and greenhouse gases. The question has always been magnitude, not existence.

//Studies show a 0.92 correlation between GCR flux and global cloud cover…//

That figure comes from early ISCCP cloud datasets over a limited period. Later work raised calibration issues with those satellite records, and the strength of that correlation weakened once those were addressed. Even Svensmark's own report notes long-term cloud dataset reliability problems. A short-window correlation during part of a solar cycle doesn't establish multi-decadal climate control.

//Over the solar cycle, energy entering Earth's system is 5-7 times greater than from solar irradiance alone…//

Yes, the solar cycle signal in ocean heat content appears larger than TSI alone would imply. That's interesting. But an 11-year oscillation is not the same thing as a sustained century-scale driver. The existence of a cycle does not automatically establish a secular trend.

//This mechanism explains not just 20th-century warming…//

Timing is the sticking point. Since the 1970s there has not been a sustained upward trend in solar activity, nor a sustained downward trend in cosmic ray flux that mirrors the steady rise in global temperature. If GCR modulation were the dominant modern driver, you would expect that alignment to be visible in the data.

//Svensmark's approach is preferable…//

Preference isn't the metric.

Attribution studies test forcings separately. When models are run with natural forcings only (solar + volcanic), they do not reproduce the late-20th-century warming trend. When greenhouse gases are included, the models track the observed rise much more closely. That pattern has been reproduced across multiple modelling groups.

The Sun clearly influences climate. That isn't disputed.

The narrower question is whether solar-modulated cosmic rays explain the magnitude and timing of recent warming better than greenhouse forcing. At present, the broader peer-reviewed literature does not support that conclusion.

Back to you...