It was a lovely atmospheric evening t'other night
Another atmospheric evening . I've no idea why some evenings and nights feel this way and others don't. there ws nothing to suggest that it should fel that way this evening. It felt very mild but it also appred to be trying to rain now and then and I wanted to get back to the flat befow it did if it was going to so I wasn't walking along in any kind of dream state More a let's get back quickly kind of mood just incase the very, very few drops of rain developed into anything more . But I could still feel a kind of quiet dreamy atmosphere.
Still had last week's New Scientist on the sofa and re read an article about a very, very cold winter back in 1709 .. this is interesting sientist at the moment beause they are trying to map european climate history and they an't find any explanation why this happened. What series of events changed things so dramatially. They do know that the winds changed direction suddenly but just why this happened isn't known.
The European Millenium Project links
http://www.geogr.muni.cz/millennium
Ha! the article's up on the net
http://www.newscientist.com/article/mg20126942.100-1709-the-year-that-europe-froze.html
Reading that people might wonder why there is any conern about the climate today ... after all it's not that severe and the climate recovered from that disaster.
The person who wrote it mentioned that conditions now as far as climate change goes are different than they were then. One difference is that this happend very suddenly rather than it being a gradual change ... though gradual is relative here ... within 100 years ( In connection with the present problem) rather than, say, within 10 or so. Most slow factors in climate change happen very, very slowly.
Natural slow factors in climate change were noted by a guy called Milutin Milankovitch. He named them 1) Eccentricity ... when the earth's orbit round the sun changes from an oval to a cirular shape and back again. The change from one to the other takes round 100,000 years. This means that with an oval (elliptical) orbit the weather will be more variable in this respect because of the difference in the amount of solar radiation (heat) that reaches the earth cause of the way the shape of the orbit takes the earth nearer and further way from the sun. With a circular shape the earth is orbiting roughly the same distance away from the sun.
Modern day studies of coral reefs have shown that Milankovitch was right in this theory though it doesn't explain everything. At the moment there is very little difference in the shape of the earth's orbit round the sun. His theory has shown that this eccentricity is responsible for some very long term changes in the earth's limate ... but.not all .. there is something else affecting the pattern of ice ages which has yet to be discovered. His original work has been like a base for other scientists to work from .. the circular and oval orbits round the sun have been shown to alter the climate but variations on his original theory have also come up.
I suppose the Milankovitch theory was really the start of lot of scientific work being done .. it was like a base to start off the work from ... but the basis of his work appears to be correct.
Gonna turn in now cause it's getting late ... mug of soup then off to bed.
2 ... Precession .. which I used to call precision by mistake .. this is often referred to as axis wobble and takes about 23,000 years to complete .. um ... not quite precision ... huh!!!!
If you imagine the earth As a spining top the axis spins in a kind of a circular motion ... not in a pin prick one staying in the same spot all the time it spreads out ... you can imagine this as a cone with the pin prick being where the imaginary line of the axis pokes through the earth's crust and is virtually still ... it then spreads out in a cone shape where it draws a circle while rotating.
Now if it just rotated there for ever with no forces having an effect on it there would be no wobbling. But just as the Earth rotates round the sun so the moon rotates round the Earth and it pulls at the earth with it's gravitational force making the axis wobble a bit. If you gave the earth a little prod instead if the Moon's gravity pulling it it would just draw out small circles but if you gave it a bigger push it would draw out bigger circles like pushing a toy top. There are also other gravitational pulls from other objects in space on the Earth but I have used the moon as an example.
If you think of the axis drawing the circle you will see that it is changing the direction it is tilted in ... this will change the seasons so that summer will become winter half way through the cycle and then slowly return to winter again. So, now in December it's cold ... eventually December will be summer here and then go back to being cold again. This takes around 23,000 years to complete.
3 ... Obliquity ... this is a change in the degree of tilt in the Earth's axis of rotation. This takes about 41,000 years and the tilt of the axis changes from 22 degrees to 24.5 degrees and then goes back again to 22 degrees. a small tilt ... 22 degrees .. means mider winters because more solar energy would reach the planet and cooler summers because less solar energy would reach the planet. A larger tilt increases the differences between the seasons.
The earth's axis is an imaginary line that stretches from the north pole to the south pole ... it is then tilted to show the changes of the seasons as the earth revolves round the sun. Without using the conept of an axis this wouldn't be so easy to show.
It is thought, given these three concepts that we should be heading for another ice age ... though not for many thousands of years ..it's not known how many ... but it's thought that it may be in about 30,000 years but some scientists say that this will be delayed further by human influenced climate change.
The movement of the plates that form the earth's crust also give rise to climate change but as this takes millions of years I think we can count that out for now!!!!
Those are slow factors influencing climate change.
Faster influences on climate change include volanic eruptions, changes in the tides and sun spots.
Sun spots have been said to be the cause of the changes in the climate in recent years. Sun spots cool the sun down and there has been less activity recently after a period of high activity. It has been said that this is what has caused the planet to warm up.
BUT ... it has also been said that sunspots are surrounded by glowing higher levels of solar output (heat output) which means that if there are lots of sunspots which, by themselves, could be seen as cooling the sun and therefore the planet down ... with this glowing boarder it could actually be a time of more rather than less heat being released from the sun. In the middle of the mini ice age (1645 - 1715) there was relatively little sun spot activity which just taking sunspot data by itself would have meant the planet should be heating up ... but it cooled down .... see article in New Scientist about 1709!!!!!
It has also been suggested, however, that sunspot activity has relatively little change on the planet.
It was thought that the Gulf Stream was changing direction because of the melting ice influencing it ... but this is a result of climate change not something that started it all off.
Neither is the ice melting 'cause of volanic activity.
The changes in wind activity have been put down to human influences climate change.
Well, they are the major natural causes of climate change.
In general it's said that they either point towards an ice age ... though far in the future or aren't significant enough, as far as anyone knows, to cause the climate change we are experiencing right now as an overall trend which is very apparent through the melting Arctic.
(I suppose, if just by a very, very, minor chance that climate change somehow isn't caused by greenhouse gasses we could still collect and contain carbon emissions and then if by some chance it's found that it wasn't necessary ... just release them again if anyone wants to)
Well, off to get a mug of soup.
Still had last week's New Scientist on the sofa and re read an article about a very, very cold winter back in 1709 .. this is interesting sientist at the moment beause they are trying to map european climate history and they an't find any explanation why this happened. What series of events changed things so dramatially. They do know that the winds changed direction suddenly but just why this happened isn't known.
The European Millenium Project links
http://www.geogr.muni.cz/millennium
Ha! the article's up on the net
http://www.newscientist.com/article/mg20126942.100-1709-the-year-that-europe-froze.html
Reading that people might wonder why there is any conern about the climate today ... after all it's not that severe and the climate recovered from that disaster.
The person who wrote it mentioned that conditions now as far as climate change goes are different than they were then. One difference is that this happend very suddenly rather than it being a gradual change ... though gradual is relative here ... within 100 years ( In connection with the present problem) rather than, say, within 10 or so. Most slow factors in climate change happen very, very slowly.
Natural slow factors in climate change were noted by a guy called Milutin Milankovitch. He named them 1) Eccentricity ... when the earth's orbit round the sun changes from an oval to a cirular shape and back again. The change from one to the other takes round 100,000 years. This means that with an oval (elliptical) orbit the weather will be more variable in this respect because of the difference in the amount of solar radiation (heat) that reaches the earth cause of the way the shape of the orbit takes the earth nearer and further way from the sun. With a circular shape the earth is orbiting roughly the same distance away from the sun.
Modern day studies of coral reefs have shown that Milankovitch was right in this theory though it doesn't explain everything. At the moment there is very little difference in the shape of the earth's orbit round the sun. His theory has shown that this eccentricity is responsible for some very long term changes in the earth's limate ... but.not all .. there is something else affecting the pattern of ice ages which has yet to be discovered. His original work has been like a base for other scientists to work from .. the circular and oval orbits round the sun have been shown to alter the climate but variations on his original theory have also come up.
I suppose the Milankovitch theory was really the start of lot of scientific work being done .. it was like a base to start off the work from ... but the basis of his work appears to be correct.
Gonna turn in now cause it's getting late ... mug of soup then off to bed.
2 ... Precession .. which I used to call precision by mistake .. this is often referred to as axis wobble and takes about 23,000 years to complete .. um ... not quite precision ... huh!!!!
If you imagine the earth As a spining top the axis spins in a kind of a circular motion ... not in a pin prick one staying in the same spot all the time it spreads out ... you can imagine this as a cone with the pin prick being where the imaginary line of the axis pokes through the earth's crust and is virtually still ... it then spreads out in a cone shape where it draws a circle while rotating.
Now if it just rotated there for ever with no forces having an effect on it there would be no wobbling. But just as the Earth rotates round the sun so the moon rotates round the Earth and it pulls at the earth with it's gravitational force making the axis wobble a bit. If you gave the earth a little prod instead if the Moon's gravity pulling it it would just draw out small circles but if you gave it a bigger push it would draw out bigger circles like pushing a toy top. There are also other gravitational pulls from other objects in space on the Earth but I have used the moon as an example.
If you think of the axis drawing the circle you will see that it is changing the direction it is tilted in ... this will change the seasons so that summer will become winter half way through the cycle and then slowly return to winter again. So, now in December it's cold ... eventually December will be summer here and then go back to being cold again. This takes around 23,000 years to complete.
3 ... Obliquity ... this is a change in the degree of tilt in the Earth's axis of rotation. This takes about 41,000 years and the tilt of the axis changes from 22 degrees to 24.5 degrees and then goes back again to 22 degrees. a small tilt ... 22 degrees .. means mider winters because more solar energy would reach the planet and cooler summers because less solar energy would reach the planet. A larger tilt increases the differences between the seasons.
The earth's axis is an imaginary line that stretches from the north pole to the south pole ... it is then tilted to show the changes of the seasons as the earth revolves round the sun. Without using the conept of an axis this wouldn't be so easy to show.
It is thought, given these three concepts that we should be heading for another ice age ... though not for many thousands of years ..it's not known how many ... but it's thought that it may be in about 30,000 years but some scientists say that this will be delayed further by human influenced climate change.
The movement of the plates that form the earth's crust also give rise to climate change but as this takes millions of years I think we can count that out for now!!!!
Those are slow factors influencing climate change.
Faster influences on climate change include volanic eruptions, changes in the tides and sun spots.
Sun spots have been said to be the cause of the changes in the climate in recent years. Sun spots cool the sun down and there has been less activity recently after a period of high activity. It has been said that this is what has caused the planet to warm up.
BUT ... it has also been said that sunspots are surrounded by glowing higher levels of solar output (heat output) which means that if there are lots of sunspots which, by themselves, could be seen as cooling the sun and therefore the planet down ... with this glowing boarder it could actually be a time of more rather than less heat being released from the sun. In the middle of the mini ice age (1645 - 1715) there was relatively little sun spot activity which just taking sunspot data by itself would have meant the planet should be heating up ... but it cooled down .... see article in New Scientist about 1709!!!!!
It has also been suggested, however, that sunspot activity has relatively little change on the planet.
It was thought that the Gulf Stream was changing direction because of the melting ice influencing it ... but this is a result of climate change not something that started it all off.
Neither is the ice melting 'cause of volanic activity.
The changes in wind activity have been put down to human influences climate change.
Well, they are the major natural causes of climate change.
In general it's said that they either point towards an ice age ... though far in the future or aren't significant enough, as far as anyone knows, to cause the climate change we are experiencing right now as an overall trend which is very apparent through the melting Arctic.
(I suppose, if just by a very, very, minor chance that climate change somehow isn't caused by greenhouse gasses we could still collect and contain carbon emissions and then if by some chance it's found that it wasn't necessary ... just release them again if anyone wants to)
Well, off to get a mug of soup.
posted by Zeb at 3:27 PM
<< Home