what challenges face climatologists interested in reconstructing the climate of the past?

Answer 1

By far, the greatest impediment to reconstructing the climate of the past is not understanding what produces the climate of the present. As egotistical as man can be, especially scientists who may not want to feel overwhelmed by an embarrassing lack of knowledge, you can understand why as a society, we are led to believe that the "experts" know just about all there is to know. Or at least the idea that SOMEONE must know.

Not only do we NOT know everything, we don't really know how much we don't know.

Answer 2

It depends how far back in time you go. For the last 30 years we have very precise readings from across the globe obtained from staellite telemetry. Going back another 100 or so years and we have accurate records taken from first hand observations, primarily thermometers. In some parts of the world accurate records extend as far back as 1659, in most places the records begin in the 19th century.

Going further back we use a number of different methods to reconstruct the climate. There's hundreds of different things we can look at including sedimentary deposits, glaciation, the fauna and flora records, dendrology (tree rings) etc. Because we have many different ways of reconstructing the climate the results can be compared side by side, if the results match then it's safe to say we have an accurate record. Sometimes results don't match and we need to look at reasons why, often it's the result of some localised variation perhaps caused by microclimates or human influence of some kind.

Once we start going back many thousands and hundreds of thousands of years we are relying more on the analysis of ice core samples. These contain air that has been trapped in the ice for millenia and analysis can provide us with a record of the past climate. This can be matched with the work of hydrologists, geologists, oceanographers etc for comparison pruposes. We can also obtain ice core samples from many locations around the world - not just the polar regions and this enables us to build up a bigger picture.

The current ice core record extends back nearly 750,000 years, once we start going further back we're getting into the realms of oxygen isotope analysis and this is where things aren't quite so clear. We can run many experiments and again compare the results but there's a greater deviation from the mean than using the more recent analytical methods. This record can be extended back some 542 million years, any further and the only lifeforms on the planet were single celled organisms and thus not suitable for accurate climate reconstruction.

In summary, for the last few decades we have extreme accuracy (99.999%) within hundred of years we can reconstruct climate with a very high degree of accuracy (99.9%), going back thousands of years we can be pretty accurate (99%), going back millions of years we have a reasonable accuracy but not precision (95%).

Answer 3

They already have reconstructed the climate over the past century quite accurately:

http://en.wikipedia.org/wiki/Image:Climate_Change_Attribution.png

As you get further back in time, data becomes less reliable because you're getting information about the conditions from ice core samples and tree rings and things like that. The important thing is that they can match their climate models to the global temperatures when we know them the most accurately - over the past century.

Answer 4

I'm interested in this as well

Answer 5

Wow, Thank you! exactly what I was searching for. I tried looking for the answers on other websites but I couldn't find them.

Answer 6

Our weather man can not predict the weather for a week ,but for the whole world it is impossible.

Answer 7

Their own biases that get in the way of good data analysis.