{"id":2195,"date":"2009-12-10T17:52:08","date_gmt":"2009-12-10T17:52:08","guid":{"rendered":"0"},"modified":"2009-12-10T17:52:08","modified_gmt":"2009-12-10T17:52:08","slug":"heres_what_hide","status":"publish","type":"post","link":"http:\/\/marcdanziger.com\/?p=2195","title":{"rendered":"Here’s What “Hide The Decline” Is About"},"content":{"rendered":"

From Jones\/Briffa et al “High-resolution palaeoclimatology of the last millennium: a review of current status and future prospects<\/a>” (pdf) – a very interesting paper.<\/p>\n

Recent divergence between tree-ring growth and temperature<\/b><\/p>\n

The final aspect of tree-ring studies that needs to be highlighted is what has become known as the ‘divergence’ issue. This refers to the apparent failure of some (established as temperature-responsive) tree-ring data to follow the trend in instrumental temperatures observed over the latter part of the twentieth century. Chronology time series that vary largely in parallel with changing temperature in earlier periods progressively fail to show the increasing trends that would represent a continuing positive response to the strong warming observed during recent decades. Originally this was noted primarily in certain northern high-latitude areas for ring-width data in Alaska (Jacoby and D’Arrigo, 1995) and in ring-width and particularly ring-density data, in more extensive regions of northern Europe and Russia (Briffa et al., 1998). In the earlier work, it was suggested that the cause of the North American observations was a shift from a direct dominant temperature control on tree growth to one where lack of available moisture becomes increasingly influential, possibly to an extent where the sign of the temperature influence becomes negative rather than positive (Jacoby and D’Arrigo, 1995; D’Arrigo et al., 2004).<\/i><\/p><\/blockquote>\n

Subsequently, various studies focused mainly on recent treegrowth in Alaska and Canada support the idea that current tree growth may no longer be responding positively to increased warming (Barber et al., 2000; Lloyd and Fastie, 2002; Davi et al., 2003; Wilmking et al., 2004; Driscoll et al., 2005; Pisaric et al., 2007). Other suggestions have been offered as the cause of the widely observed loss of temperature response over northern Eurasia. The increasing influence of drought has also been suggested as the cause (Jacoby et al., 2000), though other suggestions include possible reduced atmospheric clarity, localized persistence of spring snow cover and seasonal changes in ozone-related surface UV concentrations (Briffa et al., 1998, 2004; Vaganov et al., 1999; D’Arrigo et al., 2008).<\/p>\n

The IPCC recently laid particular stress on this issue, pointing out that any significant shift in the recent growth response of trees would invalidate the assumptions that underlie the simple regression-based approach to reconstructing past temperature changes. This would imply an inability to recognize potential underestimates of the degree of warmth in earlier periods of reconstructions (Jansen et al., 2007)<\/u>. It is important to stress that not all high-latitude regions display this apparent decoupling between observed and dendroclimatically estimated temperatures (Briffa et al., 2007; Wilson et al., 2007).<\/p>\n

However, the issue remains a crucial one. Unfortunately, a comparative scarcity of recent (ie, post-1980) tree-ring data remains a major obstacle to further exploration of the extent and causes. Hence we stress the vital requirement for widespread updating of major treering networks, as well as for the acquisition of data for new regions. <\/p>\n

[emphasis<\/u> added]<\/i><\/p><\/blockquote>\n

Go read the whole thing.
\n–<\/p>\n","protected":false},"excerpt":{"rendered":"

So the tree-ring data doesn’t match recent thermometer data…what does that mean for AGW, exactly??<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/marcdanziger.com\/index.php?rest_route=\/wp\/v2\/posts\/2195"}],"collection":[{"href":"http:\/\/marcdanziger.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/marcdanziger.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/marcdanziger.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/marcdanziger.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2195"}],"version-history":[{"count":0,"href":"http:\/\/marcdanziger.com\/index.php?rest_route=\/wp\/v2\/posts\/2195\/revisions"}],"wp:attachment":[{"href":"http:\/\/marcdanziger.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2195"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/marcdanziger.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2195"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/marcdanziger.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2195"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}