?There is a lot that needs to be done to create long-term precise records?
24 May, 2006 04:14 pm
John Christy, one of the 21 authors of the last Climate Change Science Report commissioned by the US White House, answers Scitizen?s questions.
What is the Climate Change Science Program?
The Climate Change Science Program presented a set of questions or issues that the Government of the United States wants answers to. This was the very first one and was looking at the issues of how the temperature above the surface, in what we call the troposphere, vary relative to the temperature of the surface where people live?
This report state that "The evidence continues to support a substantial human impact on the global temperature increase". How did you come to this conclusion?
The conclusion is not quite that strong. What it says is that temperature has risen for the past five decades and to explain that climate models require a human influence so the evidence indicates that there is a human influence on the surface temperature increase. Now over the last 26 to 27 years troposphere temperature is more difficult to measure and there is a pretty wide range of results. A few of those results tend to agree with the way climate models project the atmosphere to behave but a number of those observations don't quite do that. So because we have differences in the troposphere temperature observations and the trends of those, there is still an uncertainty and an open question on how the earth troposphere is really changing.
Thomas Karl, the report chief editor declared to Science that "For the first time we had people, who initially disagreed, sitting down across the table". How did you worked altogether?
We had many meetings together, we agreed on the words on this report. If you read the report it describes this differences among the data sets that just mentioned. So it wasn't the case that the group all agreed that one particular data set described the troposphere accurately, it was that the group agreed that there was a range of realizations and results, some of which tend to agree with climate model output expectations for global warming but there are some that do not.
What are the new questions that this study raised?
The new questions or recommendations are the ways in which we should start to monitor the atmosphere. The way we monitor the atmosphere now, to a large extent, is not in a way that allows for long-term precision of the measurements. So our recommendation, what we need to learn, is how to build a system that will give accurate readings. Right now the instruments we have, in the past especially, have lots of faults. At times, instruments are changed, sometimes the calibration of those instruments changes and sometimes they change location and these all create problems for putting together a long term precise record. What we learned is that there is a lot that needs to be done to create long-term precise records.
What are you looking at now?
Right now I’m working on various ways to determine which of the data sets out there are most consistent with the true atmosphere and our initial work is indicating that it looks like the warming rates are more modest that what climate models are projecting.
Dr. John Christy thank you.
Interview By Francesca Gilibert