Blinded by the Light

Written by Dr. Matthew Wielicki on April 3, 2025. Posted in Current News

I’ve spent most of my career in earth science, working alongside thoughtful, rigorous, and principled scientists, people I deeply respect.

I don’t believe most are dishonest or driven by ideology. Indeed, much of the foundational science in IPCC’s Working Group I, which addresses climate data, physical mechanisms, and processes, appears careful and credible. But even there, there’s a troubling gap: natural variability is consistently underexplored, overlooked, or simply not taken seriously.

But something happens between the technical findings and the public narrative. By the time it reaches policymakers, media, and the general public, nuance disappears. Uncertainty becomes certainty. Debate becomes denial. And science becomes storytelling.

Nowhere is this more obvious than in how the IPCC treats Total Solar Irradiance (TSI), the literal energy source for Earth’s entire climate system.

Each time I write about this, I get closer to saying what I once refused to believe: maybe this isn’t just sloppy communication or bureaucratic overreach. Maybe it’s scientific fraud.

What Is Total Solar Irradiance?

Total Solar Irradiance (TSI) is simply the amount of energy from the Sun that reaches the top of Earth’s atmosphere. It powers literally everything we experience: storms, currents, temperature changes. Without solar energy, Earth’s climate ceases to exist

TSI isn’t constant. It varies slightly over time due to changes in solar activity, like the 11-year sunspot cycle, and more slowly over decades and centuries due to shifts in the Sun’s magnetic behavior.

Even small changes in TSI, on the order of 1 to 2 watts per square meter, represent a huge amount of energy when averaged over the Earth’s surface. So it’s worth asking: if TSI has increased since the 19th century, could that be contributing to recent warming?

The IPCC’s answer is a hard no.

What the IPCC Says

The IPCC insists solar activity has essentially done nothing meaningful to influence climate in the last 270 years. They report solar forcing at an absurdly trivial 0.01 W/m² since 1750. Yet they never fully engage with the wide range of peer-reviewed evidence suggesting far greater variability. Instead, they rely exclusively on one dataset, one interpretation… one that fits neatly with their preferred narrative.

Just a hundredth of a watt? That’s not a minor role… they’re saying the Sun has essentially done nothing for the last 270 years.

What the Science Really Shows

Before satellites, we relied on reconstructions of TSI using sunspot records, cosmogenic isotopes, and magnetic modeling. These reconstructions are not all in agreement, but many show a rise in solar activity from the end of the Little Ice Age (~1850) to the late 20th century.

Even if only part of that increase in TSI translates into net radiative forcing at Earth’s surface, we’re talking about a possible warming contribution of 0.3 to 0.6 W/m². That’s within the same range the IPCC attributes to anthropogenic CO₂. It doesn’t eliminate human influence, but it absolutely complicates the “CO₂ is the sole driver” narrative.

The IPCC doesn’t engage with any of these reconstructions seriously. In fact, they don’t even mention most of them.

A Tale of Two Satellites: ACRIM vs. PMOD

You might assume that satellite measurements since 1978 have settled the question of TSI. But they haven’t. In fact, even the modern satellite record is split.

Two major datasets exist, and they don’t agree:

ACRIM (Active Cavity Radiometer Irradiance Monitor) is a series of instruments launched on NASA satellites that provided direct, largely unadjusted TSI measurements. When combined into a long-term record, they show an upward trend in solar output from 1980 to around 2000.

PMOD (developed by researchers at the Physikalisch-Meteorologisches Observatorium Davos in Switzerland) uses many of the same instruments but applies corrections, particularly during the “ACRIM Gap” (1989–1991) when satellite coverage lapsed. These corrections result in a flattened trend, TSI remains basically flat through the late 20th century.

The IPCC uses PMOD. They ignore ACRIM.

This isn’t just a technical disagreement. It’s a choice with consequences. If the ACRIM dataset is right, solar variability may explain a meaningful part of the late 20th-century warming. If PMOD is right, it doesn’t.

And despite this major disagreement, the IPCC never explains their preference or acknowledges the ongoing debate.

Even Claus Fröhlich, the creator of PMOD, admitted in a 2012 paper that this difference was:

“significant and unresolved.”
— Fröhlich, 2012, DOI: 10.1007/s10712-011-9168-5

Yet the IPCC proceeds as if there’s no debate at all.

What This Really Means

If solar forcing has been underestimated, the whole foundation of modern climate policy shakes. Trillion-dollar decarbonization efforts might be targeting only a fraction of the problem, or worse, addressing the wrong issue entirely. Instead of aggressively dismantling affordable, reliable energy infrastructure, we should reconsider our priorities. History offers cautionary examples, Germany’s ongoing energy crisis is a stark reminder of what happens when policy is guided by incomplete or distorted science.

We’ve seen this selective neglect before. In Forgotten Extremes, I exposed how the IPCC sidesteps or downplays substantial climate variability that occurred naturally, long before human emissions became a convenient scapegoat. The message is clear: if natural variability challenges the prevailing narrative, it’s quietly omitted from serious consideration.

What If We’re Getting the Whole Thing Backwards?

If TSI really did rise through the 20th century, and the models ignored it, then much of the warming we see could be natural. If the PMOD composite is wrong and ACRIM is right, then our entire attribution framework, the central claim of climate science, starts to wobble.

If you’re wondering why the IPCC would lean so hard into one dataset while excluding the other, the answer is simple: it protects the carbon narrative. ACRIM complicates that. PMOD simplifies it.

And so, ACRIM disappears.

🔒 Want to go deeper?
In the next section for paid subscribers, I’ll unpack how climate models are tuned to emphasize CO₂ and what it would mean for energy policy if the IPCC has been downplaying solar variability for decades.

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