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When a Greenhouse Gas Goes Swimming

How the Earth's magnetic field influences our climate

Munich, 10/06/2008

For years, it has been suspected that the Earth's magnetic field influences the climate and temperatures on the planet. Exactly what this correlation is, however, has always been disputed. Researchers from Ludwig-Maximilians-Universität (LMU) München have now discovered a possible mechanism that could explain the geomagnetic field's influence on the climate. Biophysicist Alexander Pazur and geophysicist Michael Winklhofer observed that seawater can absorb less carbon dioxide if there is a weaker magnetic field acting on it. This could result in more CO2 escaping into the earth's atmosphere. Carbon dioxide is considered a greenhouse gas that contributes towards global warming. While the CO2 amounts observed from this phenomenon are dwarfed by the carbon dioxide emissions caused by man, it may well exceed the amount of CO2 released from volcanoes, for example. "Granted, the earth's magnetic field doesn't influence the Earth's temperature all that much," Winklhofer says. "But taking this factor into account could help improve our climate models," he concludes.

Recent geo-archeological and archeomagnetic studies have provided good evidence for the theory of a correlation between the geomagnetic field and climatic conditions. It was seen, for example, that during the last four millennia before Christ, abrupt strengthenings of the Earth's magnetic field corresponded with a cooling of temperatures on earth. A correlation has also been observed between a stronger geomagnetic field and colder periods in the time since 700 AD. Geoscientists established this by analyzing archeological finds from various different ages and drawing conclusions from their magnetization on the strength of the magnetic field prevailing at the time. Researchers also observed that the strength of the earth's magnetic field has been continually diminishing since they started taking measurements 150 years ago. Yet it had never been very clear by what mechanisms the Earth's magnetic field could be influencing the cooling or warming of the globe.

Pazur and Winklhofer are now the first to have investigated how the earth's magnetic field affects the solubility of carbon dioxide in seawater. Carbon dioxide is a known greenhouse gas, and its quantities in the oceans and atmosphere play an important part in governing the temperatures of the Earth. The researchers experimented on seawater. First, they removed the gas from it. Then they subject it to magnetic fields of various strengths in the order of magnitude of the geomagnetic field as it fluctuates over time. Pazur and Winklhofer then measured how much gas the liquid absorbed when they exposed it to normal air. The temperature of the seawater was kept at a constant four degrees Celsius during the experiment.

The results showed that even small changes in the magnetic field affect the solubility of gases in water. "The solubility of air in seawater was found to be 15 percent lower under reduced magnetic field compared to when the field was stronger," explains Winklhofer. "The observed effect was even twice as strong for carbon dioxide." In their experiment, the scientists applied a magnetic field of 50 microtesla field strength, which is equivalent to the Earth's normal magnetic field at mid latitudes, and a magnetic field of 20 microtesla to simulate a weakened field. "From the results, we surmise that geomagnetic field variations modulate the gas exchange between ocean and atmosphere," states Winklhofer.

Working from their results, the scientists projected how much more CO2 would escape into the atmosphere if the earth's magnetic field weakened by a certain amount. Their analyses suggest that a weakening of just one percent per decade would lead to a release of 0.35 billion metric tons more CO2 per year. This effect is significantly greater than the CO2 emission from volcanoes, which is 0.03 billion metric tons of carbon dioxide per year. "Yet this figure is dwarfed by man's contribution of CO2 emissions into the atmosphere," stresses Winklhofer. "Our contribution is seven billion metric tons of carbon dioxide every year."

In light of this, it would be absurd to make the weakening geomagnetic field responsible for climate change, says the geoscientist. Nevertheless, the effect does act in line with the emissions caused by man, and should be factored into the climate models accordingly. "This could help increase the precision of predictions," Winklhofer says. The geophysicist is optimistic that, with this study, he has struck upon a new field of research: "I think the results will arouse the interest of many scientists."

Winklhofer and colleagues also plan to do more studies to examine the geomagnetic field effect more closely. "Next, we intend to use even finer analytical methods to systematically investigate the conditions under which the effect occurs," the geophysicist tells us. "It would be important, for example, to examine the gas exchange at different water temperatures and pressures, as well as at different salt contents and acidities of the seawater. Aside from that, experiments should also be conducted under natural conditions – that is, at sea."

Publication:
“Magnetic effect on CO2 solubility in seawater: A possible link between geomagnetic field variations and climate”
Alexander Pazur and Michael Winklhofer
Geophysical Research Letters, Vol. 35, No. 16, L16710, 2008
doi: 10.1029/2008GL034288.

Contact:
Michael Winklhofer
Department for Earth and Environmental Sciences at LMU Munich
Tel.: +49 (89) 2180-4207
Fax:  49 (89) 2180-4205
E-mail: michael.winklhofer@geophysik.uni-muenchen.de
Internet: http://www.geophysik.uni-muenchen.de/~michael

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