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The heat is on: predicting British weather
David Adam, The Guardian
…Weather forecasts start life as measurements of sunshine, rainfall, wind speed and air pressure, which are then extrapolated to predict how all those things will interact and change. But it is not an exact science: forecasts can only be made for a few days ahead because chaos theory – which says that a small change can lead to huge and unpredictable disruption further down the line – applies to the weather.
Climate models are less concerned with small day-to-day changes, and instead analyse long-term trends, which tend to smooth out short-term fluctuations. These models simulate the global atmosphere by dividing it into a 3D mesh of thousands of manageable chunks. Once you run simultaneous forecasts for each of these independent blocks, a bigger picture starts to emerge. Repeat the exercise for half-hour chunks over the next 100 years (hence the supercomputers) and clear signals on the direction of the climate start to emerge.
Most climate models run on a global scale, and the results are averaged out over the entire planet. But that can be misleading when it comes to specific regions such as the UK, as the way world weather systems work means that the largest impacts will be felt towards the poles. Calculating a more specific impact on Britain is the responsibility of the UK Climate Impacts Programme, a government-funded group based at Oxford University. The programme publishes “scenarios” intended to offer a snapshot of changing weather in Britain over the next century – its next scenario is due to be published in October next year.
Richard Westaway, a scientist with the programme, says that the new forecast will be the best yet because it will reflect more accurately the range of possible outcomes. Rather than just offering a best-guess temperature rise of, say, 2C by a certain date, the new scenario will be more specific, able to state, for example, that there is a 10% or so chance of a rise up to 4C. “That sort of attitude towards risk is much more useful to people planning things like the renewal of the Thames barrier,” he notes.
(21 May 2007)
Scorching summer forecast in USA
Patrick O’Driscoll, USA TODAY
Drought to persist in West, Southeast; fire danger a big worry
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DENVER – As Memorial Day weekend beckons, federal climate scientists predict drought will intensify in much of the West this summer and persist in the fire-scorched Southeast despite recent rain.
People heading out this holiday to fish and boat in the Southeast could find lakes and reservoirs so low that sandbars and stumps pose hazards. Campers and hikers in the Southwest may see restrictions in national forests dangerously dry from years of drought.
In its drought outlook for June, July and August, the federal Climate Prediction Center foresees some improvement in the Gulf Coast states, including central and South Florida and the state’s Panhandle. But southern Georgia and northern Florida, raked by wildfire this month, “may see deterioration” even though the rainy season is due to start, the center reports.
“Fire is the big story,” says Mark Svoboda of the National Drought Mitigation Center in Nebraska. “The lack of spring rains has increased fire incidence.”
The climate center outlook also expects little lasting relief in dry areas of the West, from California across Nevada and Utah, and new drought areas developing in large parts of Idaho and Oregon.
(21 May 2007)
It’s Not Your Imagination: Fires Are More Common (text and audio)
Elizabeth Shogren, National Public Radio
In the Southeast this week, extreme drought created the perfect conditions for wild fires, including the largest one ever recorded in Georgia. And across the country, Southern California is facing its driest weather on record; the wildfires season is starting early there.
The fire-friendly conditions are partly the result of climate change. And it looks like there is more parched weather, and fires, on the way.
Scientists who study long-term weather patterns say that the United States were due for a dry spell: The past century was unusually wet when compared to averages of the past two millennia.
Government officials say they can’t say that the current droughts are caused by global climate change. But epidemics of tree-killing insects, droughts and wild fires are some of symptoms of global warming.
And scientists say they’ll become much more common in coming years.
Jay Lawrimore, who tracks droughts for the National Oceanic and Atmospheric Administration, is working on a study to see if climate change is responsible for making recent droughts worse.
(13 May 2007)
