An Introduction to Paleoclimatology
I've had a number of comments and reader e-mails lately asking what we know about past climate and how we know it. So I thought now would be a good time to talk a little big about the field of paleoclimatology, that is, the study of past climate. The link that I've provided gives a fairly comprehensive overview from NOAA, covering how climate is studied and what we know.
A foundational tool of paleoclimatology is proxy records. A wide network of instrument records of the weather extends back only slightly more than 100 years. How can we know what the weather was in the more distant past? Paleoclimatologists study natural recorders of climate - tree rings, ice cores, corals, fossil records - things which capture information about temperature and precipitation which can be studied and turned into a climate reconstruction.
NASA has an interesting "chapter" history and desciption of paleoclimatology which explains some of the methods of the science and explaining why it is important to understand the past in order to predict the future.
Comments (3)
The study of past climate using proxy data obtained from ice cores, tree rings and the like is interesting. It is also problematic in that much of this historic evidence and the assumptions scientists made about the climate conditions that produced it thousands of years ago is �under further review.� Computer programs which take this historic data and predict future climatic conditions rely heavily on the accuracy of these findings. But, what if assumptions about past climates were wrong; wouldn�t predictions also be necessarily wrong?
Two recent reports demonstrate that what we thought we knew may not be correct. AGW produces reduced snow cover and melting ice. Right? Well, not always, according to Ian Howat of the Department of Earth Sciences at the University of California, Santa Cruz and four of his colleagues. They found that just the opposite was occurring on Mount Shasta. The warmer temperatures produced increased precipitation and thus more snow and ice, not less. They used actual data, not proxy data, and got some, perhaps, unexpected results. What kind of results would proxy data have generated? Not accounting for the effects of precipitation on snow and ice formation calls into question a whole range of AGW assumptions. Here is the article from World Climate Report: http://www.worldclimatereport.com/index.php/2007/02/20/more-ice-for-your-shasta/
The second report questions tree rings and assumptions made about their growth and the associated climate. The IPCC postulated, based on Michael Mann�s now discredited �hockey stick� graph, a linear relationship between tree growth and temperature. Cold temps produce narrow tree rings while warm temps produce wider ones. But, what if the relationship is nonlinear? Here is some work that calls this proxy data into question: http://ff.org/centers/csspp/library/co2weekly/20051027/temperature.htm
It�s important to keep studying this but it is equally important to recognize the limitations of proxy data. We make a huge mistake if we jump to conclusions without a complete picture of what contributed to the make up of ice cores and tree rings. Sadly, that is what is happening with global warming theories where proxy data has become sacrosanct.
Posted by Rick Ressler | February 21, 2007 10:44 AM
rick,
exactly...nice post...
Posted by sam | February 21, 2007 2:14 PM
So if global warming is actually causing more snow, wouldn't that additional snow pack/depth help to counter the warmth and keep the earth cool? Sounds like a natural balancing act.
Posted by Anonymous | February 22, 2007 12:17 PM