Tree rings are the result of the seasonal growth of trees, during each growing season a new layer of cellulose matter grows around the tree and in cross-section this is seen as a single tree ring. Over the years more rings are added.
When conditions are favourable, such as a milder climate, tree growth accelerates and so the tree rings are larger. If conditions are unfavourable, such as during colder weather or periods of drought, then tree growth is stunted and the rings are more tightly packed.
By examining tree rings from ancient trees it’s possible to piece together some idea of what the historical climates were like.
However, there’s a better way to use trees to determine past climates, something that many people are perhaps unaware of. This involves analyses of the maximum latewood density (MXD), essentially it’s looking specifically at the part of the tree that grew toward the end of the growing season.
A typical tree grows in temperatures of 6°C and above, when temperatures fall below this the tree effectively shuts down for the winter. During periods of warmer average global temperatures this 6°C threshold isn’t reached until later in the season. Similarly, during the spring the threshold is reached sooner.
By concentrating more on tree growth late in the season we can get a better picture of how long the annual growing season was and what the climatic conditions were like at the time.
It’s worth noting that reconstructed dendroclimatologies and dendrochronologies have multiple inherent uncertainties and the data from a single analysis can only give an indication of past climates. It is necessary therefore to conduct multiple studies at sites around the world in order to reduce the margin of error.
Basically a tree grows a "layer" every year or so. The new layer hides the old layer inside. A small ring could mean drought or low sunlight for that estimated year. A large ring, extra water and sunlight. It can also hide "scars" from things such as fires. Scientist know what the weather, climate, natural disasters were like around that period the ring is from/.
Poorly
If the tree gets rain they are thick , no rain thin temperatures and daily factors
unknown .
Theoretically, they can tell the yearly temperature by the thickness if the rings on a year by year basis.
http://en.wikipedia.org/wiki/Tree_rings#... heres a site with some info. i don't feel like reading it and explaining it to you. its your homework, you do it.
