Hemmer: “Recently leaked emails reveal that scientists use, quote, 'tricks' to hide evidence of a decline in global temperatures”

From the December 3 edition of Fox News' America's Newsroom:

HEMMER: Have you followed this story? Republican lawmakers now demanding the White House halt efforts to combat global warming until the controversy is resolved. Recently leaked emails reveal that scientists use, quote, “tricks” to hide evidence of a decline in global temperatures over the past, say, few decades. In a letter to the Environmental Protection Agency, lawmakers writing, in quoting now: “The answers to each of these questions are of great importance. The suggestion that these scientists prevented the dissemination, peer review, and publication of dissenting views is particularly alarming.” We're going to have more on that next hour. [America's Newsroom, 12/3/09]

“Decline” in email -- written 10 years ago after warmest year on record -- does not refer to actual global temperatures

“Decline” refers to unreliable tree ring data, not actual global temperatures. In a November 26 article, The Morning Call of Allentown, Pennsylvania, reported that Penn State scientist Michael Mann -- whose “trick” was referenced in the email Hemmer cited -- “said his trick, or 'trick of the trade,' for the Nature chart was to combine data from tree-ring measurements, which record world temperatures from 1,000 years ago until 1960, with actual temperature readings for 1961 through 1998” because “scientists have discovered that, for temperatures since 1960, tree rings have not been a reliable indicator.” Jones has also stated that it is “well known” that tree ring data “does not show a realistic trend of temperature after 1960,” and the CRU has said that "[t]he 'decline' in this set of tree-ring data should not be taken to mean that there is any problem with the instrumental temperature data." In a November 20 post, RealClimate.org's staff, which is comprised of several working climate scientists, including Mann, similarly stated:

As for the 'decline', it is well known that Keith Briffa's maximum latewood tree ring density proxy diverges from the temperature records after 1960 (this is more commonly known as the “divergence problem”-see e.g. the recent discussion in this paper) and has been discussed in the literature since Briffa et al in Nature in 1998 (Nature, 391, 678-682). Those authors have always recommend not using the post 1960 part of their reconstruction, and so while 'hiding' is probably a poor choice of words (since it is 'hidden' in plain sight), not using the data in the plot is completely appropriate, as is further research to understand why this happens.

Jones' email written 10 years ago, after warmest year on record and prior to warmest decade. Hemmer's claim that the emails show efforts to “hide evidence of a decline in global temperatures over the past, say, few decades” is undermined by the fact that Jones' email was sent in 1999, following the warmest year on record, 1998. Jones sent the email November 16, 1999. According to the UK's Met Office Hadley Center, 1998 was the warmest year globally. Moreover, eight of the 10 warmest years on record have occurred this decade, and the 20 warmest years have occurred since 1981.