I've discussed this at some length with some of the people who maintain the surface record.
The large drop off occuring circa 1990 is not real, but rather is an artifact of how the data is collected and transmitted. Much of the data being collected in poorer parts of the world (e.g. Africa and Asia) are still being recorded on paper. Those records are collected (and if necessary translated) into a collected volume known as the World Weather Record that is published only once a decade and has a substantial lag time. The WWR for the 1990s was only published in the last 6 months. So a significant number of records took more than 15 years to become available for researchers. On top of this, there are a variety of geopolitical issues involved whenever it comes to considering the cooperation between nations. For example, India has decided to classify their collected climate data on national security grounds, and will release only a sparse subset of what really was collected. My understanding is that the true number of ground based monitoring stations has not changed dramatically, but that the appearance of dramatic change simply reflects delays in data availability. It is worth keeping in mind that when someone makes a pronouncement that X year was the Y hottest ever, that such announcements will reflect only reports from the ~20% of the temperature stations that transmit their data in near real time, and such pronouncments may be revised as additional data becomes available. On the plus side though, the data that is available quickly does at least give some sampling across most of the world, and satellite observations can now augment that. -Robert A. Rohde http://www.globalwarmingart.com/ On Mar 18, 3:57 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > http://www.magazine.noaa.gov/stories/mag142.htm > > http://data.giss.nasa.gov/gistemp/station_data/ > > http://groups.google.com/group/de.soc.umwelt/browse_thread/thread/995... > > Is it true that weather station coverage has significantly > deteriorated over the last 20 years (impressive graphic in second link > above)? > > If so, why? > > Wouldn't we want better coverage to get a more accurate and detailed > measure of surface temperature trends? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/globalchange -~----------~----~----~----~------~----~------~--~---
