By: GZ on Giovedì 21 Giugno 2007 15:20
Scienziati allarmati dai rischi di RAFFREDDAMENTO del pianeta dovuti al ciclo solare
(R. Timothy Patterson is professor and director of the Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University)
....Our finding of a direct correlation between variations in the brightness of the sun and earthly climate indicators (called "proxies") is not unique. Hundreds of other studies, using proxies from tree rings in Russia's Kola Peninsula to water levels of the Nile, show exactly the same thing: The sun appears to drive climate change.
However, there was a problem. Despite this clear and repeated correlation, the measured variations in incoming solar energy were, on their own, not sufficient to cause the climate changes we have observed in our proxies. In addition, even though the sun is brighter now than at any time in the past 8,000 years, the increase in direct solar input is not calculated to be sufficient to cause the past century's modest warming on its own. There had to be an amplifier of some sort for the sun to be a primary driver of climate change.
Indeed, that is precisely what has been discovered. In a series of groundbreaking scientific papers starting in 2002, Veizer, Shaviv, Carslaw, and most recently Svensmark et al., have collectively demonstrated that as the output of the sun varies, and with it, our star's protective solar wind, varying amounts of galactic cosmic rays from deep space are able to enter our solar system and penetrate the Earth's atmosphere. These cosmic rays enhance cloud formation which, overall, has a cooling effect on the planet. When the sun's energy output is greater, not only does the Earth warm slightly due to direct solar heating, but the stronger solar wind generated during these "high sun" periods blocks many of the cosmic rays from entering our atmosphere. Cloud cover decreases and the Earth warms still more.
The opposite occurs when the sun is less bright. More cosmic rays are able to get through to Earth's atmosphere, more clouds form, and the planet cools more than would otherwise be the case due to direct solar effects alone. This is precisely what happened from the middle of the 17th century into the early 18th century, when the solar energy input to our atmosphere, as indicated by the number of sunspots, was at a minimum and the planet was stuck in the Little Ice Age. These new findings suggest that changes in the output of the sun caused the most recent climate change. By comparison, CO2 variations show little correlation with our planet's climate on long, medium and even short time scales.
In some fields the science is indeed "settled." For example, plate tectonics, once highly controversial, is now so well-established that we rarely see papers on the subject at all. But the science of global climate change is still in its infancy, with many thousands of papers published every year. In a 2003 poll conducted by German environmental researchers Dennis Bray and Hans von Storch, two-thirds of more than 530 climate scientists from 27 countries surveyed did not believe that "the current state of scientific knowledge is developed well enough to allow for a reasonable assessment of the effects of greenhouse gases." About half of those polled stated that the science of climate change was not sufficiently settled to pass the issue over to policymakers at all.
Solar scientists predict that, by 2020, the sun will be starting into its weakest Schwabe solar cycle of the past two centuries, likely leading to unusually cool conditions on Earth. Beginning to plan for adaptation to such a cool period, one which may continue well beyond one 11-year cycle, as did the Little Ice Age, should be a priority for governments. It is global cooling, not warming, that is the major climate threat to the world, especially Canada. As a country at the northern limit to agriculture in the world, it would take very little cooling to destroy much of our food crops, while a warming would only require that we adopt farming techniques practiced to the south of us.
Meantime, we need to continue research into this, the most complex field of science ever tackled, and ^immediately halt wasted expenditures on the King Canute-like task of "stopping climate change." #http://www.canada.com/nationalpost/financialpost/comment/story.html?id=597d0677-2a05-47b4-b34f-b84068db11f4&p=4^