AGW Observer

Observations of anthropogenic global warming

New research from last week 52/2010

Posted by Ari Jokimäki on January 3, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Weekly cycle in Spanish CO2 measurements

Persistence analysis of CO2 concentrations recorded at a rural site in the upper Spanish plateau – Pérez et al. (2010) “Persistence of CO2 daily means recorded at a rural site over three years was analysed using three procedures: the ST method, rescaled range analysis and detrended fluctuation analysis. Four series were previously considered, since the original series was detrended and gaps were filled. The detrending procedure comprised four steps: a linear evolution of about 3 ppm per year, a quadratic function with a maximum yearly range of 11 ppm, and two harmonic functions, the first with yearly and semi-yearly cycles and the second with a weekly cycle. Yearly ranges of both functions increased with time, their maxima being about 5 and 2 ppm, respectively. Gaps were filled with a method based on previous observation and a Gaussian function, whose standard deviation was fitted so as to resemble original data. The ST method proved extremely sensitive to the detrending procedure. A detailed analysis of the Hurst exponent allowed us to establish four regions where persistence gradually decreased. Finally, detrended fluctuation analysis provided a similar result to rescaled range analysis. From these methods, persistence was high in an interval of about three weeks.” Isidro A. Pérez, M. Luisa Sánchez, M. Ángeles García and Vanessa Paredes, Atmospheric Research, 2010, doi:10.1016/j.atmosres.2010.12.025.

Mankind affected atmospheric CO2 already 3000 years ago

Holocene carbon emissions as a result of anthropogenic land cover change – Kaplan et al. (2010) “Humans have altered the Earth’s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities, and later to provide agricultural cropland. In the Holocene, agriculture was established on nearly all continents and led to widespread modification of terrestrial ecosystems. To quantify the role that humans played in the global carbon cycle over the Holocene, we developed a new, annually resolved inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (AD 1850). This inventory is based on a simple relationship between population and land use observed in several European countries over preindustrial time. Using this data set, and an alternative scenario based on the HYDE 3.1 land use data base, we forced the LPJ dynamic global vegetation model in a series of continuous simulations to evaluate the impacts of humans on terrestrial carbon storage during the preindustrial Holocene. Our model setup allowed us to quantify the importance of land degradation caused by repeated episodes of land use followed by abandonment. By 3 ka BP, cumulative carbon emissions caused by anthropogenic land cover change in our new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO2. By AD 1850, emissions were 325–357 Pg in the new scenario, in contrast to 137–189 Pg when driven by HYDE. Regional events that resulted in local emissions or uptake of carbon were often balanced by contrasting patterns in other parts of the world. While we cannot close the carbon budget in the current study, simulated cumulative anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric δ13CO2 and support the hypothesis that anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.” Jed O. Kaplan, Kristen M. Krumhardt, Erle C. Ellis, William F. Ruddiman, Carsten Lemmen, Kees Klein Goldewijk, The Holocene, December 30, 2010, doi: 10.1177/0959683610386983. [full text]

Freshwater measurements from East Greenland Current

Interannual variability of Arctic sea ice export into the East Greenland Current – Cox et al. (2010) “Observations since the 1950s suggest that the Arctic climate system is changing in response to rising global air temperatures. These changes include an intensified hydrological cycle, Arctic sea ice decline, and increasing Greenland glacial melt. Here we use new δ18O data from the East Greenland Current system at Cape Farewell and Denmark Strait to determine the relative proportions of the freshwater components within the East Greenland Current and East Greenland Coastal Current. Through the comparison of these new data with historical studies, we gain insight into the changing Arctic freshwater balance. We detect three key shifts in the net freshwater component δ18O values, these are (1) a shift to lighter values in the late 1990s that possibly indicates an increased Greenland glacial melt or a reduced sea ice melt admixture and (2) a short-term shift to a ∼10‰ heavier value in 2005 followed by (3) a shift back to the historic average value in 2008. The latter fluctuation reflects a short-term dramatic rise and fall of sea ice meltwater addition into the East Greenland Current system. We infer that this anomalously large inclusion of sea ice meltwater resulted from a short-term peak in Arctic sea ice export via Fram Strait. Our findings, therefore, suggest that the freshwater carried in the East Greenland Current system is susceptible to short-term, high-amplitude changes in the upstream freshwater balance, which may have important ramifications for the global thermohaline circulation through the suppression of deep water formation in the North Atlantic.” Cox, K. A., J. D. Stanford, A. J. McVicar, E. J. Rohling, K. J. Heywood, S. Bacon, M. Bolshaw, P. A. Dodd, S. De la Rosa, and D. Wilkinson (2010), J. Geophys. Res., 115, C12063, doi:10.1029/2010JC006227.

Rocket science – black carbon emissions

Potential climate impact of black carbon emitted by rockets – Ross et al. (2010) “A new type of hydrocarbon rocket engine is expected to power a fleet of suborbital rockets for commercial and scientific purposes in coming decades. A global climate model predicts that emissions from a fleet of 1000 launches per year of suborbital rockets would create a persistent layer of black carbon particles in the northern stratosphere that could cause potentially significant changes in the global atmospheric circulation and distributions of ozone and temperature. Tropical stratospheric ozone abundances are predicted to change as much as 1%, while polar ozone changes by up to 6%. Polar surface temperatures change as much as one degree K regionally with significant impacts on polar sea ice fractions. After one decade of continuous launches, globally averaged radiative forcing from the black carbon would exceed the forcing from the emitted CO2 by a factor of about 105 and would be comparable to the radiative forcing estimated from current subsonic aviation.” Ross, M., M. Mills, and D. Toohey (2010), Geophys. Res. Lett., 37, L24810, doi:10.1029/2010GL044548.

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