By Robert Tracinski - May 1, 2012

I do not deny the reality of climate change. No, this is not a change of mind, reversing my longstanding skepticism toward claims of human-caused global warming. I have never denied climate change—and that is precisely why I reject the global warming hysteria. But a fascinating new scientific contribution from Danish physicist Henrik Svensmark, who is single-handedly blowing away the alleged "consensus" on what drives the climate, has given me a whole new appreciation for climate change.

The term "climate change denier" is obviously objectionable because of the word "denier." That word is carried over from the phrase "Holocaust denial" and is meant to smear global warming skeptics by associating us with the vicious motives of those who airbrush the crimes of the Nazis. But the more substantive objection to this phrase is that we skeptics do not deny the reality of climate change. We embrace it all too thoroughly.

We understand that the climate is changing and that it has always been changing. The four-and-a-half-billion-year history of the Earth is a history of constant, wild swings in global temperatures and weather, from the steamy jungles that nurtured the dinosaurs to the vast equatorial glaciers of "Snowball Earth."

(If you follow the link about Snowball Earth, by the way, you may notice that the theory is controversial and has its own skeptics. Funny how that works. In genuine science, for any new theory there is a competing theory, and the question is settled by more evidence and not by people lining up behind some top-down political "consensus.")

So we're skeptical of any claim that the very small trends in the global temperature record over the past few decades are anything extraordinary, or that they imply a man-made cause rather than natural variation. The measurement of temperatures worldwide with reliable instruments goes back only about a century and a half, a mere blip in the geological time-scales that define ice ages and interglacial warmings. How can we possibly have established, in that short a time, an absolute baseline for what is a "normal" global temperature?

The alarmists who warn about recent man-made global warming are the ones who deny the reality of climate change. They are, in fact, advocates of climate stasis. They assume that the "normal" climate is basically what it was in 1970—not coincidentally, about the time of the first "Earth Day"—and any recent variation from that norm must require some extraordinary explanation.

This was the point, by the way, of Michael Mann's infamous "hockey stick" graph. Mann tried to rewrite paleoclimatology, the history of past climate, by manipulating evidence from various temperature "proxies." (Since we don't have direct thermometer measurements from five hundred or two thousand years ago, we need to use things we can measure, like tree-ring samples from ancient, slow-growing trees, as an imperfect stand-in.) By using a questionable statistical model, Mann made it look like global temperatures had been basically flat over the past two millennia, only moving in the last two decades of the 20th century. Talk about a climate change denier!

This climate-change denial is why one of the fiercest recent critics of the theory of man-made global warming is eminent Australian geologist Ian Plimer. As he told me and Tom Minchin in an interview a few years ago, from the geologist's perspective, "The [current] rate of sea level change, CO2 release, and temperature rise and fall are well within variability," and "it is only if [geological] time is ignored that we can conclude that humans change climate by CO2 emissions."

Ignoring the past is precisely what they have done. The scientific advocates of man-made global warming tend to busy themselves with artificial computer models of the climate. Yet they have little interest in the past climate, and while they presume the ability to project the future climate over a scale of centuries, they have not spent much time showing how their theory—that carbon dioxide is the main driver of global temperatures—would explain the millions and billions of years of the Earth's history.

Henrik Svensmark has once again driven straight through this gap in their theory.

Svensmark's theory of climate change, you may recall, began by targeting a glaring gap in the global warming theory: the inability to account for cloud-formation and its effect on climate. Svensmark formulated the theory that cosmic rays—fast-moving charged particles from outer space—hit the atmosphere and create nucleation sites for the condensation of water vapor, encouraging cloud formation. Thus, an influx of cosmic rays would create more clouds, which bounce more sunlight back to space and cool the Earth, while fewer cosmic rays create fewer clouds, letting more sunlight in to warm the Earth. A key element of this theory, the effect of cosmic rays in creating aerosols in the atmosphere, was recently demonstrated in an experiment at the CERN particle accelerator.

Up to now, Svensmark's theory has focused on the role of the sun in regulating the influx of cosmic rays. When the sun is more active, it's magnetic field is stronger and blocks more cosmic rays, warming the Earth. When the sun is weaker, it blocks fewer cosmic rays and the Earth cools. But now Svensmark has a new study out looking at the other side of the equation, the number of cosmic rays coming from outside the solar system, and using this factor to explain a vast portion of the Earth's past climate variation.

Supernovas create a massive flux of cosmic rays. You can see why. What would be better at ejecting fast-moving charged particles out into space than the violent explosion of a star? So the more supernovae there are and the closer they are to Earth, the larger the number of cosmic rays that will rake our atmosphere.

Here's where a little knowledge of astronomy comes in handy. Just as the planets revolve around the sun, so our solar system as a whole is revolving around the center of our galaxy. Over long periods of time, tens of thousands and millions of years, we move in and out of different neighborhoods in the galaxy, bringing us closer and farther to areas with supernova activity. So over geological time, the Earth is exposed to widely varying levels of cosmic radiation.

Svensmark's new study, described in depth by Nigel Calder by way of Watts Up With That?, correlates what is known about the Earth's past exposure to supernovae with what is known about the Earth's past climate, and his conclusion is that the one largely explains the other.

I had already heard part of this theory: that the ice ages, for example, correspond to the Earth's movement among the spiral arms of the galaxy. As we move into more densely populated neighborhoods, cosmic rays increase, the Earth clouds over, and we go into an ice age. As we move back out to the galaxy's wide-open spaces, cosmic rays fall off, the clouds disperse, and we go into a warm interglacial period.

Svensmark's latest paper goes much further, showing how supernovae and their cosmic rays can explain mass extinctions and other major events in the history of life on Earth. Calder sums up Svensmark's "main results."

• The long-term diversity of life in the sea depends on the sea-level set by plate tectonics and the local supernova rate set by the astrophysics, and on virtually nothing else.

• The long-term primary productivity of life in the sea—the net growth of photosynthetic microbes—depends on the supernova rate, and on virtually nothing else.

• Exceptionally close supernovae account for short-lived falls in sea-level during the past 500 million years, long-known to geophysicists but never convincingly explained.

• As the geological and astronomical records converge, the match between climate and supernova rates gets better and better, with high rates bringing icy times.

Calder also goes into detail about how Svensmark's theory explains the Permo-Triassic Event, a catastrophic mass extinction about 250 million years ago which divides the Paleozoic Era from the Mesozoic Era. Thus, Svensmark describes this paper as a work of "astrobiology," the study of the connection between astronomy and biology.

As co-author of Svensmark's book The Chilling Stars, Calder is naturally a bit of a booster of this theory, so take that into account when you read the sweeping terms in which he frames this latest news.

By taking me back to when I reported the victory of the pioneers of plate tectonics in their battle against the most eminent geophysicists of the day, it makes me feel 40 years younger. Shredding the textbooks, Tuzo Wilson, Dan McKenzie and Jason Morgan merrily explained earthquakes, volcanoes, mountain-building, and even the varying depth of the ocean, simply by the drift of fragments of the lithosphere in various directions around the globe....

A mark of a good hypothesis is that it looks better and better as time passes. With the triumph of plate tectonics, diehard opponents were left redfaced and blustering. In 1960 you'd not get a job in an American geology department if you believed in continental drift, but by 1970 you'd not get the job if you didn't. That's what a paradigm shift means in practice and it will happen sometime soon with cosmic rays in climate physics.

Svensmark's theory still has to face the challenge of testing and criticism from others. And even if it is proven right, it may still take much longer to break through an entrenched establishment supported by billions of dollars in government money and the social pressure of political correctness. But his theory has already gone much farther than anything put forward by the proponents of carbon-dioxide-driven global warming, both in terms of demonstrating its physical basis and in terms of accounting for vast swaths of geological and biological history.

It is certainly a far more "interdisciplinary" theory, drawing in facts from a variety of different fields. Note, in this context, the way in which the man-made global warming alarmists declare that only certified "climatologists" have any authority to speak on the subject, dismissing the legions of skeptics from fields like geology or physics. On a practical level, you can see how this helps preserve the monopoly of the establishment. A relatively small group of academics at a fixed number of universities and research institutes, all supported by the same government agencies with the same agendas, get to decide who joins the closed club of "climatology." Whereas if you have to bring in the geologists and the physicists and the astronomers, they have all come up through independent institutions with sources of funding that tend to be more varied and less political.

But as Calder points out, the measure of a good scientific theory, particularly on a topic this complex, is its ability to integrate knowledge from many other fields. Svensmark has made an impressive effort to do soå. In the process, he has already broken the claim of the man-made global warming "consensus" to be the only scientific explanation of the climate. At the rate he is going, Svensmark will leave them scrambling for relevance as a stronger theory with a broader and deeper foundation in the evidence begins to take over.

In the process, he has also shown us the full scientific reality—in geology, biology, and astronomy—of "climate change."