First today we have the final episode of Earth: The Climate Wars – New Challenges.
Professor Iain Stewart looks at some of the methods used to predict climate behaviour, starting with a simple dishpan, with water, ice in the centre to represent the polar icecap, and a bunsen burner next to it to mimic the sun. “But in the 1950s, scientists became real experts at this technique. They used it to recreate complex circulation patterns in the atmosphere, and their experiments proved something vital. The behaviour of the atmosphere followed some simple fundamental laws.”
The move to using computers to model the weather and climate is illustrated by Professor Stewart walking into a noisy server room, and having equations projected all over him.
One of the first chances to actually test their climate models came when Mount Pinatubo volcano erupted, throwing millions of tons of debris and gases into the atmosphere. Climate scientist Jim Hansen ran his models to predict what effect it would have. “He knew that the Pinatubo eruption was so big it might well have an effect on global temperatures. Huge volcanic eruptions on this scale can cool the climate because they send a cloud of dust and gases into the upper atmosphere, which reflect the sun’s rays back into space.” And his models were very accurate when compared with the actual global temperatures.
He visits Greenland with Professor Konrad Steffen, studying how glaciers there have been speeding up over time, because of warming.
Next he explains why it’s so difficult to predict weather over the long term, by relating the story of Edward Lorenz, a pioneer in computer modelling, who made a discovery in 1961. He wanted to re-run a forecast, and to save time, rather than start from the beginning of the run with the original variables, he started with the state of the variables partway through its first run. But when he input these starting figures, and ran the simulation, it generated a completely different forecast.
Professor Stewart explains why while sitting in Ed’s Easy Diner. I wonder which one that was. It’s not the one I used most, in Old Compton Street, but it could be the one near the Trocadero. None of them are there any more, and it makes me sad. Sorry, I got distracted. The reason Lorenz’s simulation produced vastly different results over time is that the initial conditions he used on the second run were rounded to a few decimal points, while in the original run they would have been at full precision. And it’s this high sensitivity to the initial conditions that launched the whole idea of chaos theory.
Naturally, he discusses the Butterfly Effect.
Not just butterflies. The pattern of which beetles were plentiful in different layers show the end of a period of cooling called the Younger Dryas. After a long perios of beetles which thrive in the cold, then were quite suddenly replaced by beetles which loved the warmth.
Other clues about ancient temperatures comes from ice cores cut in Greenland.
Professor Jim White explains how the cores show that the end of the Younger Dryas cold period was very sudden indeed – probably less than two years during which temperatures rose by five degrees.
Professor Stewart visits the magnificent city of the Azasazi people, who had to abandon their homes carved into the rock face, when the rainfall rates dropped sharply and they could no longer survive there.
He visits Lake Mead, held above the Hoover Dam, and the source of water and hydroelectric power to Las Vegas. He speaks to Tim Barnett, who is slightly pessimistic of the lake’s ability to survive a continuing drought. “I think the human beings in this part of the world don’t understand what the word sustainability means.”
Summing up: “You know, I was thinking it would have been lovely to have made a programme about how science had got it all wrong, that actually we’ve got nothing to worry about. But unfortunately it’s the opposite. Most of the climate scientists I talk to are actually genuinely scared by the future.”
Media Centre Description: Having explained the science behind global warming, and addressed the arguments of the climate change sceptics earlier in the series, in this third and final part Dr Iain Stewart looks at the biggest challenge now facing climate scientists. Just how can they predict exactly what changes global warming will bring? It’s a journey that takes him from early attempts to model the climate system with dishpans, to supercomputers, and to the frontline of climate research today: Greenland.
Recorded from BBC TWO on Sunday 21st September 2008 20:58
BBC Genome: BBC TWO Sunday 21st September 2008 21:00
The other recording today is an episode of Fossil Detectives – South West England.
Hermione Cockburn starts by talking about one of the more famous fossil hunters, Mary Anning, and she drops a fact I don’t think I knew – that the rhyme “She sells sea shells on the seashore” was written about Anning.
Dr Tim Ewin talks about one of the largest fossils found on the Jurassic Coast, a fossil of a Scelidosaurus. He explains how it was fossilised after being swept out to sea by a flash flood.
The CG model they use makes it look like a pokemon.
Dr Anjana Khatwa explains the massive timescale that visible in the cliffs of the Jurassic Coast. “It’s one of the most incredible coastlines in the world because you can see 185 million years of geological time in just 95 miles of coastline.”
It wouldn’t be a fossil programme without an ammonite, would it?
Dr Phil Manning explains the close relationship between dinosaurs and birds.
Talking of fossils, the oil industry is still extracting oil from the coast.
Alex James makes another appearance on the blog, talking about his enthusiasm for fossil hunting as a boy. “When you see a fossil, it’s like you’re coming face to face with the past. It’s like the past is still kissing the present somehow. It just makes you aware of what a kind of ever-changing, infinite universe we live in. It’s a really important thing to hold on to.”
Here’s the whole episode.
Media Centre Description: Series in which lecturer Hermione Cockburn leads a team of fossil experts and geologists around different regions of Britain to search for its best fossil treasures and mysteries. In the south west of England, the team see Britain’s best-preserved dinosaur and discover why the Jurassic Coast is one of the most dynamic shorelines in the world. They meet a relative of the dinosaurs which is alive and well today and, at Lulworth Cove, former Blur bassist Alex James explains his love of fossils.
Recorded from BBC FOUR on Monday 22nd September 2008 00:58
BBC Genome: BBC FOUR Monday 22nd September 2008 01:00
After this there’s a trail for Classical Legends.