On July 1, the prestigious Geological Society of America (GSA) released a blockbuster scientific paper that fundamentally challenges the view that carbon dioxide is the principal driver of climate change. Apart from its scientific importance, it has political implications as well, since it pulls the rug out from under the Kyoto accord. Co-authored by University of Ottawa geology professor Dr. Jan Veizer and University of Toronto-trained astrophysicist Dr. Nir J. Shaviv, this study shows that changes in atmospheric carbon dioxide (CO2), the gas most targeted by Kyoto, has had little effect on Earth's long-term temperature variations compared to natural causes.
In a unique cross-disciplinary study, Veizer and Shaviv combined their perspectives of Earth sciences and astrophysics to show the primary driver of Earth's major climate swings over the past half-billion years almost certainly originates with the most violent natural phenomenon known -- supernovas, the cataclysmic explosions that end the normal life of the galaxy's largest stars.
At first glance, such an announcement sounds like sensational fodder for Canadian newspaper editorial pages and TV and radio talk shows. Yet, because of the complexity of the science involved, most media, particularly the CBC, which focused instead on a simpler but less significant pro-Kyoto announcement from Geneva, merely ignored the story. Those in the press who sensed correctly that the GSA paper was crucially relevant to today's climate-change debate were faced with the impossible task of quickly understanding and immediately reporting upon a scientific discovery that would take someone trained in the field many hours to properly interpret. Not surprisingly, the few media reports that did come out on the issue left readers more perplexed than informed. Like the brilliant but short-lived supernovas it references, the study was briefly described in confused articles on several newspaper front pages and then virtually disappeared.
For experts frustrated with the continual dumbing-down of climate science in the Kyoto debate, the media's treatment of the Veizer paper is all too familiar. Without a TV scientist like David Suzuki to simplify and "interpret" the study, tragically few Canadians will give the paper a second thought. Of course, this is partly due to the strong bias against announcements that run counter to the familiar script in the Kyoto debate -- "We must stop disastrous climate change by reducing our emissions of greenhouse gases" has become the international mantra of environmentalists and politicians alike.
But it is also due to the fact that climate is arguably the most complex phenomenon science has ever tackled -- indeed, we are still deeply uncertain about the causes of climate change. Unfortunately for news anchors, politicians and environmentalists dressed in polar bear suits, there are no cheat sheets or one-minute tutorials to help them quickly learn to speak meaningfully about climate change. Canadian professors Chris Essex and Ross McKitrick sum up the situation perfectly in their award-winning book, Taken by Storm: "Non-scientists should stop looking for shortcuts around the hard work of learning the science."
Environment Minister David Anderson has often said he must proceed on the basis of the best science available. Well, luckily for him, science has just advanced again and the potentially revolutionary implications could save us billions. So lets follow Essex and McKitrick's advice and take a closer look at the Veizer/Shaviv paper in an effort to understand how it relates to today's climate-change debate.
Although there is a superficial correlation between rising atmospheric CO2 concentrations and recent temperature records, scientists have also observed a consistent trend linking variations in the output of the sun with terrestrial climate. Like most stars, our sun experiences regular and predictable changes in brightness driven by variations in its speed of rotation, its magnetic field, the incidence of sunspots and the gravitational effect of the major planets. Independent European and Chinese records clearly show significant climactic effects on the Earth when the sun is unusually bright or dim.
Throughout the 20th century, the sun continued to brighten and so, not surprisingly, the Earth warmed. This direct heating effect may be responsible for about a third of the warming observed in the past 100 years. Scientists who have argued that greenhouse gases are causing climate change acknowledge that the sun plays a role, but still insist the majority of the warming has been caused by greenhouse gas increases.
But the computer models used by the Intergovernmental Panel on Climate Change (IPCC) to support the need for Kyoto are weak at modelling changes in cloud cover. This matters acutely because low-lying clouds cool the Earth by reflecting much of the incoming sunlight back into space, while wispy, high clouds tend to trap heat. Overall, clouds are likely a cooling influence, so anything that diminishes cloud cover in general will indirectly warm the Earth, especially if the reduction is mostly in lower clouds. Surprisingly, increases in solar activity tend to reduce cloud cover, so solar effects may be far more important than indicated by direct heating alone.
To begin to appreciate the significance of the Veizer paper, it is important to first understand how increases in the sun's activity diminish cloud cover.
Clouds form more readily when tiny particles in our atmosphere, known as aerosols, pick up electric charges and so act as more effective nuclei for the collection of water droplets. Recent theoretical and experimental studies demonstrate that galactic cosmic rays -- high-energy particles that originate in deep space -- are one of the sources that act to charge aerosols and thereby create more low-lying clouds. So anything that reduces galactic cosmic rays hitting the Earth will indirectly warm the planet.
This is where the sun comes in. When our star is more active, not only does it give off more radiant energy that warms us, but it also emits more solar wind -- a continuous stream of very high-speed charged particles. These particles act to deflect the galactic cosmic rays that would ordinarily hit the Earth, leading to less cloud formation and a diminished cooling effect. In other words, the reduction in cloud cover amplifies direct solar heating, so most of the past century's warming may be completely natural and attributable to changes in the activity of our sun. This would imply that carbon dioxide emissions have had little effect, and will consequently have little impact in the future.
When the IPCC report was being written, specialists in the field knew there was good evidence this natural amplification of the direct heating effect of the sun could explain recent warming. However, the IPCC left the idea aside under the label "Very Low Scientific Understanding," partly because of the short length of time for which good data existed. Even though the solar-cosmic ray climate link appeared to many experts to be more meaningful than the CO2 climate connection, skeptics of the cosmic ray theory have argued we are unable to differentiate between the impact of CO2 and solar activity when the only data we have was during a period when both were increasing in unison.
Thanks to Veizer and Shaviv, the missing data now has been provided.
By analyzing the fossilized remains of seashells, Veizer has been able to reconstruct the Earth's temperature record for the past half-billion years, the period during which there have been hard-shelled sea creatures. Surprisingly, this record displays a repeating cycle of temperature increases and decreases every 135 million years, a period that corresponds with no known terrestrial phenomena. Independently, Shaviv had determined galactic cosmic rays striking the Earth have been varying with about the same periodicity over an even longer time frame. Once Veizer and Shaviv made the connection, they wondered whether they were looking at a reflection of some sort of regular celestial phenomenon in the climate history of the Earth.
Indeed, it appears they were. Our solar system passes through the bright arms of the Milky Way Galaxy with approximately the same regularity as the long-term temperature changes Veizer had discovered. And because interstellar matter bunches up in the galaxy's arms, we see the birth of large, very bright, but short-lived stars that end their lives as supernovas while still inside the arms, giving off powerful bursts of galactic cosmic rays.
The changes in galactic cosmic ray intensity due to our passage through the arms of the Milky Way are much larger than those caused by variations in the output of our sun. Consequently, the corresponding temperature variations were significant enough for Veizer to see in his "seashell thermometers" even though they occurred hundreds of millions of years ago.
So the process works like this:
- When we are in the bright arms of the galaxy, we are relatively close to more supernovas, the galactic cosmic ray intensity is consequently high, we therefore have more cooling clouds, and so we see colder periods on the Earth;
- When we are out of the arms and galactic cosmic ray strength is low, there are less clouds and the Earth is warmer.
Veizer and Shaviv conclude that 75% of the temperature variability in the last half-billion years is explained by cosmic ray changes as we move in and out of galactic spiral arms.
Yet, over the same time frame, the geologic record shows essentially no correlation between CO2 levels and temperature even though CO2 levels have been up to 18 times higher than today. In fact, CO2 concentration was more than 10 times higher than current levels during the Ordovician glaciation, about 440 million years ago.
Veizer and Shaviv use their study results to conclude that a doubling of today's CO2 levels would result in a change in low-latitude sea temperatures of about 0.5C. This translates into a global temperature rise of only about 0.75C instead of the 1.5-to-5.5C global warming predicted by the IPCC. This new forecast compares favourably with other predictions (e.g. MIT's Richard Lindzen, 1997) and matches the rate of change observed by weather satellites over the past 22 years.
Of course, all of this is fabulous news for normal Canadians and the environment. This study, as well as many others that have come out recently, support the contention that the IPCC's conclusions are obsolete and the scientific rationale for Kyoto has evaporated. While reducing the air pollution that threatens our health and damages the natural world continues to be important, no sensible person wants to throw billions down the drain fighting climate change if humanity has essentially no impact.
Unfortunately, as Essex and McKitrick point out, the global-warming "stage is populated by many people whose desire to save the world is deemed an acceptable, even preferable, substitute for technical understanding."
This is no longer good enough. Parliamentarians, the media and indeed all Canadians who want to play a role in the debate must quickly learn more of the relevant science. Only then will we have a chance of developing environmental policy that actually protects the environment while sustaining human progress.
Dr. Tim Patterson, a professor in the Department of Earth Sciences at Carleton University, specializes in Paleoclimatology.
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