Title: Scorched Earth in the Tropics Linked to Europe's StormsSource: c2000 San Francisco ChronicleDate: January 1, 2001Byline: Keay DavidsonTropical forest fires may be worsening rainstorms far, far away --in northern Europe, of all places.It's the latest sign that when it comes to weather, all Earth is a"global village": A climate upset in one region can set off adifferent upset thousands of miles away.The most famous example is El Nino, the quasi-cyclical warming ofPacific waters routinely blamed for many of the globalmeteorological headaches of recent decades.El Nino is an all-natural phenomenon whose long history can betracked in the alternating thin and thick stripes in tree ringsover thousands of years. By contrast, a phenomenon for whichhumans are largely responsible may deserve some of the blame forthe recent heavy storms off northern Europe, scientists suggest.Over the last three to four decades, northern Europeans havecomplained that regional storms appear to be worse than ever.Winds are stronger; waves are higher.Why? The probable causes are diverse, climatologists say. One maybe global warming, prime among climatology's "usual suspects."But another, more surprising factor may also be at work,scientists said recently at the American Geophysical Unionconference in San Francisco: burning forests in lush tropicallands thousands of miles from the urban jungles of Europe.The burning lands include regions of South America, Africa,Thailand and Indonesia where farmers burn down forests to clearland for farming.These tropical blazes unleash mountainous smoke clouds that set inmotion atmospheric effects, including a shift in storm tracks,that could partly explain why ocean storms have pounded northernEurope so relentlessly in recent decades, atmospheric scientistsDaniel Rosenfeld and Hans-Friedrich Graf said.Rosenfeld, a cloud physicist, works at the Hebrew University inJerusalem. Graf, a meteorologist, is based at the Max PlanckInstitute in Germany.While the causes of rainfall are complex, the fundamentalexplanation is clear. Rain falls when water vapor in cloudsaccumulates into droplets large enough to overcome their naturalbuoyancy in updrafts and, thus, to fall to Earth.The accumulation of droplets is greatly accelerated by "aerosol"particles such as dust and smoke. Water vapor readily condensesonto aerosols.Forest fires, however, fill rain clouds with an unnaturally largenumber of smoke particles, and water vapor condenses into so manyparticles that the water in the cloud remains, in effect,hopelessly subdivided. No large droplets accumulate, and no rainfalls.The capacity of air pollutants, including smoke, to suppressrainfall was described by scientists at last year's meeting of theorganization, held in San Francisco in December 1999. Thatdiscovery was surprising enough in its own right: It suggestedthat tropical fires could suppress rainfall in those regions,worsening droughts."Clouds produce as little as half the rain when polluted as when'clean,' " Rosenfeld noted at a press conference at this year'smeeting.At the latest conference, Rosenfeld and Graf proposed an even morefar- reaching consequence of tropical burning. They theorize thatfire-triggered suppression of rainfall sets in motion acomplicated chain of atmospheric events -- among them, a shift instorm tracks over the north Atlantic.That is the reason storms have clobbered northern Europe in recentdecades, Graf's computer model suggests. "If it doesn't rain inone place, it rains in another place more," Rosenfeld explained.Global warming and the climatic effects of recent major volcaniceruptions, according to Graf's model, contributed more toincreasing the frequency of storms in northern Europe thantropical burning.Still, Rosenfeld and Graf's research illustrates how environmentalchanges in one region -- including those that can be blamed onhumans, like burning -- may affect weather on a distant continent."Weather is like a global village," Rosenfeld said.