by Playfuls Staff |
12th September 2006
Does “El Nino” mean anything to you? If not, you certainly remember the violence of Katrina hurricane, which swept New Orleans. Well, prepare for worse because Pacific and Atlantic storms are gaining strength.[more]
I’m sure global warming is no enigma to anyone these days, since signs that confirm it are to be found in any news posted on any TV channel. From last year’s hurricane seasons in the US, to the drought that parched Portugal in the same year and burned almost a third of the country’s forests, to this year’s fires in Greece and the hot air wave that raised temperatures in Europe to the highest level in five years, all are demonstrations of how Earth’s atmosphere suffers from pollution.
The consequences of global warming and the green house effect are even worse than previously anticipated. According to a study by 19 climate researchers published in the journal Proceedings of the National Academy of Sciences polluting particles emitted from car tailpipes and power plants that work with fossil fuel are making the surface of the Pacific and Atlantic Oceans warmer, acting like a catalyst for stronger and more devastating hurricanes that form there.
The recent results came after a long and complicated scientific adventure at Lawrence Livermore National Laboratory in California, where more than 22 climate models were put to test on the powerful computers installed there, each model being run several times with slightly different initial conditions. For example, climate models included the global effects of the “El Nino” phenomenon, the possible implications of a catastrophic volcano eruption (like the one that took place in August 25-27, 1883 in Krakatoa, when the volcano ejected more than 25 cubic kilometres of rock, ash, and pumice, and generated the loudest sound ever historically reported) and even a possible modification in the light emitted by the Sun.
All tests indicated that a simple and natural climate change is unacceptable and that pollution must play the most important role for the heating of oceans’ surface.
"There is no way the observed changes could be related just to natural variables," said Tom Wigley, a National Center for Atmospheric Research researcher and a co-author of the journal, published by the National Academy of Sciences.
The main hypothesis from which researchers started was the rise in sea surface temperatures of up to 0.67C in the Atlantic and Pacific tropics from 1906 to 2005. The scientists, led by Ben Santer, found that tiny particulates from volcanoes and sulphates from industrial plants blocked the sun, and so cooled the oceans. But the effect was swamped by the rise in greenhouse gases, which led to warmer oceans.
Nathan Gillett, a co-author of the study at the climatic research unit at the University of East Anglia, said: “We know the oceans have been warming in these regions and some scientists have said it was because of natural events. But this study confirms that it cannot be explained by a natural cycle.”
The scientists estimated an 84 percent chance that at least two-thirds of the sea surface temperature increase were due to human activity. They started the work on the project soon after Hurricane Katrina slammed into the US Gulf Coast a year ago, said Santer.
The recent study completes a series of other studies published in the past two years about climate changes and its causes and is supported by many climatologists. But other scientists are skeptical saying that more data needs to be gathered in order to have the full picture of what awaits us.
Meteorologist and researcher Chris Landsea of the National Hurricane Center in Miami is not convinced that the warming of ocean surfaces detected to date has spawned fiercer hurricanes.
In addition, an analysis Landsea and others published last year concluded that some hurricanes in the past may have been more powerful than recognized. Observational tools, especially satellite imaging, capture detail invisible to earlier observers.
Landsea has said a different sort of pattern might be at work -- alternation between a period of lower intensity hurricanes for 25 to 40 years, then a period of higher activity for a similar length of time. During the past century, he said, the '40s, '50s and '60s were intense hurricane periods, while the '70s '80s, and '90s were fairly quiet, with the recent intensity picking up the past 11 years.
The new results linking water temperature to greenhouse gases don't answer those criticisms. "I don't think this really advances the debate," Landsea said.
But supporters of global warming and its devastating effects think the contrary and claim that arguments brought by independent studies cannot be rejected and that a warning signal is necessary. About one dozen peer-reviewed research articles published since 2005 detected links to the latest study, they note.
"This is a complex problem that you can't just think about or solve with brainstorming," Wigley said. "You need to have mathematically complex models."
Peter Webster of the Georgia Institute of Technology has observed that in the Atlantic Ocean, the average number of named storms was higher between 1995 and 2005 than in a previous decade of high hurricane activity, from 1945 to 1955. Category 4 and 5 hurricanes rose to an average of nearly three a year, compared to less than one a year in 1945-55.
But University of Colorado climatologist Roger Pielke Sr. said the claim that humans are responsible for at least 67 percent of the warming "overstates the capabilities of the (climate) models."
"No one has demonstrated any ability for these models to skillfully predict on the regional scale," he said.
Gray said that changes in deep- ocean circulation, not the buildup of greenhouse gases, likely explain the observed rise in sea-surface temperatures. "The big question they don't answer is this: Even if SSTs go up, does that make hurricane activity more frequent and more intense? They imply that it does, but we have no observations to show that it's true," said Gray, a global warming skeptic.
According to Gray, the Atlantic Ocean is in a period of increased hurricane activity that began around 1995 and could last another 15 or 20 years before tapering off. The recent surge of activity is part of a natural cycle and has little to do with global warming, he contends. "This paper is going to carry a lot of weight because it has such prominent authors," he said. "But I'm sure they're going to be proven wrong."
But as Benjamin Santer and Tom Wigley point out, what other tools are there for projecting the future?
"In the real world, we are performing an unprecedented and uncontrolled geophysical experiment," they write. "We know, beyond a shadow of doubt, that [human] activities have changed the chemical composition of the Earth's atmosphere.
