Why ‘Hide The Decline’?
There Has Been No Net NH Warming Since The 1940s
In the press release for a newly published and controversial peer-reviewed scientific paper, Australian scientist Dr. Jennifer Marohasy unveiled one of climate science’s better-kept secrets.
She and her colleagues are well aware that the post-1940s Northern Hemisphere (NH) proxy evidence from tree-rings, bore holes, pollen, etc., consistently fails to affirm sharply rising temperatures from the late 20th century onwards.
In fact, Marohasy points out that a lack of rising temperatures for recent decades is so common in paleoclimate reconstructions that tendentious climate scientists have necessarily added heavily adjusted, hockey-stick-shaped instrumental records (e.g., from NASA GISS, HadCRUT) on to the end of the trend so as to maintain the visualization of an ongoing dangerous warming.
The lack of recently rising temperatures in proxy evidence is somewhat furtively referred to as the “divergence problem”, and the “trick” of adding instrumental records is utilized to “hide the decline”.
Dr. Jennifer Marohasy, The Spectator (Australia):
Marohasy’s conclusions about proxy temperatures are routinely verified in the scientific literature.
Last year, for example, Dr. Pei Xing and co-authors unveiled a new method (MVDM) for calibrating low-frequency NH tree-ring data for the last 1,200 years in The Extratropical Northern Hemisphere Temperature Reconstruction during the Last Millennium Based on a Novel Method. Using a large volume of 126 proxy temperature records from the Northern Hemisphere, they found (1) a clearly discernible Medieval Warm Period (MWP) (950-1150) and Little Ice Age (LIA) (1450-1850), (2) “likely unprecedented” modern temperatures (relative to the last 1,000 years), as well as a (3) “significant” link between the high temperatures of the MWP and recent times and the high solar activity that characterized both periods (the Medieval Maximum and the Modern Grand Maximum).
“The smoothed MDVM reconstruction exhibited a general agreement with the variation of the reconstructed total solar irradiance (TSI), and the correlation between the two series during the common period 849–2000 AD was significant (r = 0.498). Specially, the records shared high correlation coefficients in the epochs of the solar maximum (i.e. during the Medieval and Modern age)“
Interestingly, when examining the Xing et al. (2016) reconstruction of the Northern Hemisphere from Figure 7, the lack of sustained proxy temperature warming for the more recent decades is clearly detectable. There is a very noticeable temperature decline after 1980. The Xing et al. (2016) reconstruction also documents a lack of any net NH warming for the 60 years following the 1930s and 1940s peak.
Image Source: Xing et al., 2016 (MDVM Reconstructed NH Temperature)
Now consider the instrumental record and its conducivity to hiding the post-1980s decline. Notice the amplitude of the HadCRUT data not only raises the 1980s temperatures well above the tree-ring data, it reduces the 1960s cooling by a few tenths of a degree too. A similar divergence can be found in Briffa et al., 2002, who used 387 NH proxy records in showing that temperatures cooled as instrumental temperatures showed abrupt warming after the 1960s. It’s the illustrated version of “Mike’s Nature Trick”.
Flashback: The leaked Hide the Decline conversations with temperature data overseers…
“…you really ought to replace the values from 1961 onwards with observed [instrumental] temperatures due to the decline.”
“I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) amd from 1961 for Keith’s to hide the decline.”
“Also we have applied a completely artificial adjustment to the data after 1960, so they look closer to observed temperatures than the tree-ring data actually were” …. “Also, we set all post-1960 values to missing in the MXD data set (due to decline), and the method will infill these, estimating them from the real temperatures – another way of ‘correcting’ for the decline, though may be not defensible!”
The D’Arrigo et al. (2006) Northern Hemisphere reconstruction derived from “66 high elevation and latitudinal treeline North American and Eurasian sites” also reveals a NH temperature decline after the 1940s and again after the 1980s.
Christiansen and Lungqvist (2012) utilize proxies from 91 locations across the extra-tropical Northern Hemisphere to reveal no net warming since the 1940s.
Schneider et al., 2015 use proxy evidence from 15 IPCC-referenced locations in the Northern Hemisphere to document no net warming since the 1940s and a flattening after the 1980s.
Stoffel et al., 2015 used proxy data from 22 Northern Hemisphere locations to illustrate there has been no net warming since the 1940s.
Of note, consider how closely the Stoffel et al. (2015) NH reconstruction resembles the trends in total solar irradiance since the 18th century, including almost identical timings and amplitudes for the 20th century.
Below are selections from a much larger collection of graphs taken from recently published papers that also document a lack of any net warming since the mid-20th century…from both hemispheres.
With the large and growing discrepancy between the instrumental record that hides the decline and the proxy evidence from tree-rings and ice cores that doesn’t, one wonders how much longer the illusion of a linearly warming Earth may continue to be promulgated.
“Occupying about 14% of the world’s surface, the Southern Ocean […] … a cooling trend since 1979.”