According to
The New York Times, human influence on the atmosphere (effects of greenhouses gases released by human activities) is at least partly responsible for increased heavy precipitation:
An increase in heavy precipitation that has afflicted many countries is at least partly a consequence of human influence on the atmosphere, climate scientists reported in a new study.
In the first major paper of its kind, the researchers used elaborate computer programs that simulate the climate to analyze whether the rise in severe rainstorms, heavy snowfalls and similar events could be explained by natural variability in the atmosphere. They found that it could not, and that the increase made sense only when the computers factored in the effects of greenhouse gases released by human activities like the burning of fossil fuels.
As reflected in previous studies, the likelihood of extreme precipitation on any given day rose by about 7 percent over the last half of the 20th century, at least for the land areas of the Northern Hemisphere for which sufficient figures are available to do an analysis.
The principal finding of the new study is “that this 7 percent is well outside the bounds of natural variability,” said Francis W. Zwiers, a Canadian climate scientist who took part in the research. The paper is being published in Thursday’s edition of the journal Nature.
NatureNews says about the study (Published online 16 February 2011 | Nature 470, 316 (2011) | doi:10.1038/470316a):
Increased flood risk linked to global warming
Likelihood of extreme rainfall may have been doubled by rising greenhouse-gas levels.
Climate change may be hitting home. Rises in global average temperature are remote from most people's experience, but two studies in this week's Nature1,2 conclude that climate warming is already causing extreme weather events that affect the lives of millions. The research directly links rising greenhouse-gas levels with the growing intensity of rain and snow in the Northern Hemisphere, and the increased risk of flooding in the United Kingdom.
Insurers will take note, as will those developing policies for adapting to climate change. "This has immense importance not just as a further justification for emissions reduction, but also for adaptation planning," says Michael Oppenheimer, a climate-policy researcher at Princeton University in New Jersey, who was not involved in the studies.
There is no doubt that humans are altering the climate, but the implications for regional weather are less clear. No computer simulation can conclusively attribute a given snowstorm or flood to global warming. But with a combination of climate models, weather observations and a good dose of probability theory, scientists may be able to determine how climate warming changes the odds. An earlier study3, for example, found that global warming has at least doubled the likelihood of extreme events such as the 2003 European heatwave.
According to The New York Times article,
...the paper covers climate trends from 1951 to 1999 and therefore does not include any analysis of last year’s extreme precipitation, including catastrophic floods in Pakistan, China and Australia as well as parts of the United States, including Tennessee, Arkansas and California. However, the paper is likely to bolster a growing sense among climate scientists that events like the 2010 floods will become more common.
<snip>
Scientists have long been reluctant to attribute any specific weather event to global warming, but a handful of papers that do so are beginning to appear in the scientific literature. One such installment is being published on Thursday in Nature as a companion piece to the broader paper. It finds that severe rains that flooded England and Wales in 2000, the wettest autumn since record-keeping began there in 1766, were made substantially more likely by the greenhouse gases released by human activity.
In that analysis, scientists at the University of Oxford used computer time donated by the public to analyze the climate of Britain in 2000 as it actually existed and to compare that with a hypothetical climate in which the Industrial Revolution never happened and few greenhouse gases were released.
The computers found that the chances of those memorable floods, which sent geese swimming through city streets, were roughly doubled in a climate with the greenhouse gases.
That it took a decade to come to that conclusion illustrates one of the major problems of climate science at the moment. Researchers are barraged with questions about weather extremes like the recent winters in Europe and the United States and the heat waves and droughts of last summer.
Yet, even when adequate weather statistics are available for an affected region, the scientists need years to run computer analyses of any specific event and calculate whether it was made more or less likely by global warming.
So even more reports on effects of AGW Or global warming. Or global weather change. Whatever they call it, the stuff where we've screwed up the atmosphere and aren't doing anything much about it, if it weren't too late for any substantive change in the near future anyway. That stuff. That experts are studying from different angles and for different reasons (duh! I never even thought about insurance, much less aid to countries more severely impacted by AGW effects). Even more interesting than the studies (which I can only understand vaguely) is the mention of the difficulties in researching this area.
I hadn't realized the time scales needed to analyze data (assuming data are even available for the area being studied). Is that an exaggeration, or does it really take
years to run computer analyses of specific events to calculate whether global warming made it more or less likely? And what kind of times are involved in modeling future trends? Is that a years-long proposition as well? I had assumed (yes, I know) that computer programs took maybe months to set up and run, but
years?? How does that work? Is it because computer time is in dribs and drabs or is this years of constant running the program?
Is this time-frame common in science? If so, why doesn't stuff like this get mentioned (unglamorous, I know) so ordinary people have some idea of the difficulties and magnitudes of work involved. A writer researches a biography for years and we're impressed. Scientific studies come out and may elicit headlines and sound-bites. No mention of the massive amounts of time and work involved. So maybe all the other scientists already know this, but you're trying to sell science to the average Joe. And right now, Science needs a better PR guy. It's not just amazing that anything gets done, it's a freaking miracle (in any non-theistic, theistic, figural, or actual sense you want).
And what is the bit about computer time donated by the public? Don't scientists get government money for computer time in the UK? Or only some programs, or some institutions or what do they mean? They make it sound like anyone can call up some anonymous "them" and say "give global warming my 5 minutes on Saturday; research into cancer can have 10 minutes on Monday." Is this the normal way to allocate computer time, kind of a popularity contest with the public as to which subjects are "hottest" and beat out the others? Or is it just a terminology thing, and scientists don't have problems getting computer time to do studies?
.
.
