|The Week That Was
December 30, 2000
NEW ON THE SEPP WEB:
How providential that Simon Scott e-mailed us the secret diary of the global warming god RA. Now we can find out what goes on behind the scenes.
The Week That Was December 30, 2000 brought to you by SEPP
By Curt Suplee
Just as world leaders are preparing to try to come to grips with global warming, a small but persistent group of scientists has revived an unsettling thought:
What if much, or even most, of the warming seen so far--about 1.2 degrees Fahrenheit since the late 19th century--was not the result of civilization's cumulative spew of "greenhouse gases"? What if, instead, it was caused by electromagnetic changes in the sun, a thermonuclear behemoth 93 million miles beyond human control?
When that idea was proposed in the late 1990s, it was generally dismissed by leading experts. But many researchers have become even more convinced "that the sun may be a much more important contributor to global climate change than previously assumed," according to Paal Brekke of the Goddard Space Flight Center in Greenbelt.
That is emphatically not the mainstream view. True, the total amount of solar radiation striking Earth fluctuates according to 11-year (sunspot) cycles and longer periods. However, it has increased only about 0.1 percent over the past century, according to best estimates--scarcely sufficient to induce substantial warming. Indeed, most climate scientists believe it is small compared with the heat-trapping action of greenhouse gases such as carbon dioxide, methane and chlorofluorocarbons.
However, total radiation is only one way the sun could affect climate. Another, Brekke notes, is "by an increase in ultraviolet and extreme ultraviolet radiation, which could lead to changes in the temperature, dynamics and chemistry of the atmosphere." Those might include heating atmospheric ozone, a gas that absorbs UV radiation and warms up as it does so.
But it is a third possible mechanism that has prompted the most excitement--and the most controversy. In this scenario, changes in the sun's magnetic field alter the amount of cosmic rays that strike Earth, which in turn affects cloud formation.
The hypothesis, pioneered by Henrik Svensmark of the Danish Space Research Institute in Copenhagen, is based on this fact: Magnetic fields deflect electrically charged particles, such as the incessant barrage of protons and atomic nuclei misleadingly known as cosmic "rays."
These particles come screaming toward us from various places in our galaxy at high energies, and they would pose a significant threat to life on Earth were it not for the magnetic fields of our planet and the sun, which together divert much of the cosmic fusillade.
The rest penetrate the atmosphere, where the shower turns electrically neutral air molecules and airborne vapors into charged ions. In that condition, two UCLA scientists argued in Geophysical Research Letters earlier this year, molecules are more prone to cluster into aggregations that make dense, low-level clouds that shade the planet's surface. High, thin clouds typically warm the planet by trapping outgoing heat in the sky. But thick, umbrella-like low clouds have a net cooling effect.
By this logic, when the sun's magnetic field is stronger--as it is, for example, during high sunspot activity--it deflects more cosmic rays, preventing them from hitting air molecules. Fewer cosmic rays mean fewer clouds, which means more warming.
Svensmark and colleagues reported their latest results at a conference two weeks ago in Spain on "The Solar Cycle and Terrestrial Climate." Using data from the International Satellite Cloud Climate Project, they found that the amount of cloud cover at elevations of two miles or lower is directly related to cosmic ray levels--at least over the period for which satellite data are available.
But Earth has been warming for more than a century. Has the sun's field been strengthening that long? Yes, according to Michael Lockwood and colleagues at the Rutherford Appleton Laboratory in England, who published exactly that result in the journal Nature last year. Analyzing instrument measurements taken since 1868, they conclude that the sun's exterior magnetic field has increased by 230 percent since 1901 and by 40 percent since 1964.
Many veteran climate analysts remain unconvinced.
"In the first place," said Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colo., "there is very good evidence that the amount of low cloud has increased throughout the world in recent decades. This change in cloudiness is primarily responsible for the difference in the increase in maximum versus minimum temperatures. Over land in the past 20 years, minimum temperatures are increasing at about 0.3 C per decade and maximum temperatures are increasing at 0.2 C per decade.
"The way this works is that increased low cloud is bright. So it reflects solar radiation during the day, keeping the daytime heating down somewhat, while providing a blanket at night: a greenhouse effect that keeps the nighttime temperature up. Overall increase in low cloud is, however, a negative heating effect because of [shading]. So the observed changes in cloud [should be] responsible for a cooling, not a warming."
Moreover, Trenberth says, the cloud-changing effect of "aerosols" (chemical particles and pollutants that affect cloud density, longevity and droplet size) are probably at least 10 times "greater than anything from cosmic rays."
Svensmark believes that the cloud record--based on human ground observations--is "unreliable." When simultaneous records exist for human observations and satellite data, he found, they disagree. "There is no real evidence from ground observations what the cloud cover has been doing."
Moreover, he notes, "the apparent link between cosmic rays and low clouds is strongest over the ocean--about 70 percent of Earth. However, nearly all ground observations are over land."
James E. Hansen of NASA's Goddard Institute for Space Studies in New York believes that "the sun has probably been a significant contributor to past climate change," accounting for a fraction of 20th century warming. As for the cosmic ray theory, however, "there are no convincing data." Certainly the cloud data are not good enough and don't cover a long enough period for any significant conclusion," Hansen says.
A consortium of more than 50 scientists has petitioned CERN, the European particle physics facility in Geneva, to conduct an experiment that could help settle the issue. The researchers want to use one of CERN's particle beams as a source of artificial cosmic rays that would strike a "cloud chamber" containing the equivalent of air in the lower atmosphere. If there is a clear link between cosmic rays and cloud formation, the experiment should reveal it.
There is evidence from Greenland ice cores that cosmic-ray bombardment has declined over the past century. "If the link between cosmic rays and clouds is confirmed," the scientists write in their proposal, "the consequent global warming could be comparable to that presently attributed to greenhouse gases from the burning of fossil fuels."
SEEDING OCEANS WITH IRON COULD REDUCE ATMOSPHERIC CO2
Seeding the oceans with iron could potentially trap several hundred million tons of the greenhouse gas carbon dioxide (CO2) from the air each year, scientists report in Nature. Moreover, the world's fisheries could expand if the process is commercially exploited, as some firms hope to do.
In an experiment conducted last year between Tasmania and Antarctica, researchers released three and a half tons of dissolved iron over about 30 square miles of sea.
The addition of iron, an essential element lacking in vast, barren stretches of the Pacific and Antarctic oceans, caused an estimated 10-fold rise in the amount of phytoplankton -- one celled plants that live near the surface. The patch eventually covered 660 square miles, pulling perhaps several thousand tons of carbon dioxide from the air.
The response far exceeded predictions and persisted for more than six weeks. Previous blooms created in the tropics dissipated in half that time.
The phytoplankton could sink to the ocean bottom, reducing atmospheric CO2, a heat-trapping gas implicated in global warming. The cold ocean water sinks to great depths, where it can remain for centuries.
Using computer models incorporating the results from the experiment, Andrew J. Watson, a geochemist at the University of East Anglia in Norwich, England, found the effect was consistent with changes in past geological periods when iron dust blown from the continents enriched the southern seas, causing plankton blooms that appear to have reduced atmospheric CO2 levels.
Several companies are planning to fertilize the sea with iron, both to attack global warming and to stimulate fisheries. And the United States Department of Energy is considering partially underwriting a proposal from the University of Hawaii and Greensea Ventures to conduct a larger test of the iron fertilizing process west of the Galapagos Islands.
Source: Andrew C. Revkin, "Antarctic Test Raises Hope on Earth Warming; Iron-Fed Plankton Absorbs Greenhouse Gases," New York Times, October 12, 2000.
HYDRO RESERVOIRS EMIT GH GASES
The UK Observer of Oct 13 reports that rotting vegetation in reservoirs is an abundant source of methane
Vincent St Louis of the University of Alberta has calculated that 20% of manmade methane comes from the thousands of reservoirs around the world, covering a total area of 1.5 million square kilometers. (Sept. issue of the journal BioScience).
Comment: Might as well burn fossil fuels
LEADING AUTO INSURER TO CUT RATES FOR DRIVERS OF BIGGEST
State Farm, the nation's biggest auto insurer, plans to announce a shift in its pricing policies that will cut rates for drivers of the biggest cars, trucks and sport utility vehicles based on claims data showing them to be the safest for their occupants.
After reaching record-breaking proportions earlier this year the ozone hole over Antarctica has made a surprisingly hasty retreat.
Comment: But did you read about it in the newspapers?
A CANADIAN PERSPECTIVE ON GLOBAL WARMING
Check out Tom Harris and Prof Tim Patterson on (www.iosphere.net/~tharris), as they strive mightily to inform the Canadian public and counter the hype of David Suzuki and others.
The AGU is the major professional scientific society for all of geophysics and planetary sciences. Its main meeting takes place in San Francisco every December.
1. It is disconcerting therefore to find that Dr. Ben Santer delivered
a 20-minute paper, defending his record as lead author of the notorious
Chapter 8 of the 1996 IPCC report. It formed the basis for the enigmatic
and misused political conclusion about a "balance of evidence suggesting
a human influence " on climate. For details on what
Santer really did, click here.
Comment: Think about this as we face a cold winter.