tag:blogger.com,1999:blog-8216971263350849959.post5953550786845851290..comments2023-08-07T16:41:49.660+02:00Comments on Die Klimazwiebel: Another hypothesis for the origin of the Little Ice Ageeduardohttp://www.blogger.com/profile/17725131974182980651noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-8216971263350849959.post-14103270614977024502014-02-04T14:23:04.922+01:002014-02-04T14:23:04.922+01:00I was commenting on the Kaplan (2011) paper, sorry...I was commenting on the Kaplan (2011) paper, sorry ...Karl Kuhnnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-22733458895547208322014-02-04T14:21:51.604+01:002014-02-04T14:21:51.604+01:00I can't help but feeling that the conclusions ...I can't help but feeling that the conclusions of the paper drip of unjustified hyperbole:<br /><br />"Carbon emissions as a result of anthropogenic land use over the preindustrial Holocene could have had a very substantial impact on the global carbon cycle." <br /><br />What is meant by "very substantial"? The next sentence does not enlighten me:<br /><br />"Even before 1000 bc (3 ka), up to 102 Pg of carbon could have been emitted into the atmosphere caused by human land use." <br /><br />Why is that value not put into any perspective, into relative terms? In the next sentence they row back a bit:<br /><br />"This amount of carbon could have contributed to, but cannot fully explain, the increase in atmospheric CO2 that occurred over the middle Holocene." <br /><br />So to what extent could it explain the temperature rise. I mean, there are estimates of TCR out there ...<br /><br />"By ad 1850, this amount increases to roughly 360 Pg, which equates to a ~25 ppm increase in atmospheric CO2."<br /><br />Aha ... 25 ppm is merely a tenth of the much-feared doubling-of-CO2-content.<br /><br />"[...] As a result, the world is much warmer than it would otherwise be."<br /><br />The world is or has been much warmer? By how much? As a reviewer, I would not have approved such imprecisions and weaseling.<br /><br />Karl Kuhnnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-1697160419082601692014-02-04T11:08:30.479+01:002014-02-04T11:08:30.479+01:00Let us say that the hypothesis, though indeed fasc...Let us say that the hypothesis, though indeed fascinating, is far from being proven.<br /><br />I cannot say much on the dynamics of carbon cycle, but my feeling is that a drop of say 5 to 10 ppm in CO2 concentrations would not be sufficient to cause any detectable drop in Northern Hemisphere or global temperatures<br /><br /><br />From the IPCC Report WG1:<br /><br />One of the possible explanations for the drop in atmospheric CO2 around<br />year 1600 is enhanced land and/or ocean carbon uptake in response<br />to the cooling caused by reduced solar irradiance during the Maunder<br />Minimum (Section 5.3.5.3). However, simulations using Earth System<br />Models of Intermediate Complexity (EMICs)(Gerber et al., 2003; Brovkin<br />et al., 2004) and by complex Earth System Models (ESMs) (Jungclaus<br />et al., 2010) suggest that solar irradiance forcing alone is not sufficient to explain the magnitude of the CO2 decrease. The drop in atmospheric<br />CO2 around year 1600 could also be caused by a cooling from increased<br />volcanic eruptions (Jones and Cox, 2001; Brovkin et al., 2010; Frölicher<br />et al., 2011). A third hypothesis calls for a link between CO2 and epidem-<br />ics and wars associated with forest regrowth over abandoned lands and<br />increased carbon storage, especially in Central America. Here, results are<br />model and scenario dependent. Simulations by Pongratz et al. (2011a)<br />do not reproduce a decrease in CO2, while simulations by Kaplan et al.<br />(2011) suggest a considerable increase in land carbon storage around<br />year 1600. The temporal resolution of Central American charcoal and<br />pollen records is insufficient to support or falsify these model results<br />(e.g., Nevle and Bird, 2008; Marlon et al., 2008).eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-75307772973240017562014-02-04T10:29:31.150+01:002014-02-04T10:29:31.150+01:00The (main?) research putting forward this hypothes...The (main?) research putting forward this hypothesis is here:<br /><a href="http://www.researchgate.net/publication/49459608_Holocene_carbon_emissions_as_a_result_of_anthropogenic_land_cover_change/file/72e7e5236d6be600b7.pdf" rel="nofollow">Kaplan et al., 2010</a><br /><br />This is considered and put into context in WG1-AR5, Chapter 6.<br /><br />This idea is fascinating. Why are ideas fascinating that propose how low-tech humans, by going about their little human occupations, inadvertently but significantly impact global scale environmental systems?hvwnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-78802553543526429252014-02-03T23:48:51.430+01:002014-02-03T23:48:51.430+01:00The hypothesis that a once much more numerous popu...The hypothesis that a once much more numerous population in the New World kept substantial amounts of carbon dioxide in the atmosphere, thus warming the planet during the MWP, and that this was stoppped by smallpox etc, is a bold speculation. I do not believe that could add up. Such huge numbers of people, organized in civilizations, leave sufficient archeological traces ... which do not seem to be there.Karl Kuhnnoreply@blogger.com