Archives par mot-clé : Proxies

Hockey Stick Groundhog Day

by P. Homewood, August, 1, 2019 in NotaLotofPeopleKnowThat

Some ancient history

Fifteen to twenty years ago, Michael Mann and colleagues wrote a few papers claiming that current warming was unprecedented over the last 600 to 2000 years.  Other climate scientists described Mann’s work variously as crap, pathetic, sloppy, and crap.  These papers caught the interest of Stephen McIntyre and this led to the creation of his Climate Audit blog and the publication of paperspointing out the flaws in these hockey stick reconstructions. In particular, Mcintyre and his co-author Ross McKitrick showed that the method used by Mann and colleagues shifted the data in such a way that any data sets that showed an upward trend in the 20th century would receive a stronger weighting in the final reconstruction.  With this method, generation of a hockey-stick shape in the temperature reconstruction was virtually guaranteed, which M&M demonstrated by feeding in random numbers to the method.

Réchauffement climatique : le CO2 atmosphérique n’a pas toujours été le coupable

by Alex Barral et al., 2017 (U. Lyon-CNRS)

La comparaison des fluctuations du CO2 atmosphérique retracées à partir de ces estimations avec des courbes des changements de température a révélé de fortes baisses du CO2 atmosphérique (200-300 ppm), couplées à de fortes hausses de la température moyenne à la surface du globe (5-8°C) à l’échelle de quelques millions d’années.

Warm periods in the 20th century are not unprecedented during the last 2,000 years

by Prof. Quansheng Ge, August 8, 2017 in ClimateChangeDispatch

Prof. Quansheng Ge and his group from the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, collected a large number of proxies and reconstructed a 2000-year temperature series in China with a 10-year resolution, enabling them to quantitatively reveal the characteristics of temperature change in China over a common era.

See also here

The 2400-year Bray cycle

by Javier, July 11, 2017 in ClimatEtc.

In our attempt to better understand the nature of our planet’s abrupt climate changes I have already reviewed the glacial-interglacial cycle, and the Dansgaard-Oeschger cycle’s that take place during glacial periods. I now start reviewing the millennial climate cycles that abruptly impact the slowly changing Holocene climate. The most significant and regular one is the ~ 2400-year Bray cycle.