Andrew et al., To be sure this "may" be game changing, but these effects are highly uncertain, primarily because there is no agreement (or direct measurement) on whether soot from aircraft can act as ice nuclei (even when processed through contrails) and there is no agreement on the fraction and composition of particles that act as ice nuclei in the background (pre-aircraft) atmosphere. I tried to emphasize this in my talk (and in the submitted paper). The result can range from near zero forcing (my value in the abstract of -0.2 W/m2 is not statistically significant) up to the -0.8 W/m2.
Best, Joyce On Jul 11, 2013, at 6:23 PM, Andrew Lockley wrote: > Poster's note : This is a game-changing piece of research. Finding > we have up to 0.8 W/m2 of previously 'hidden' warming is a spectacular > result. It also suggests a possible contradiction with Kravitz' > result on the use of soot, albeit his paper was analysing > stratospheric (not tropospheric) soot injections. > > NB Link is to abstract only. Paper will hopefully be in PNAS > http://www.daca-13.org/wsl/daca13/program/DACA-13_Abstract_Proceedings.pdf > > Radiative forcing by aircraft: effects of soot on large-scale clouds > Joyce Penneret al > > Radiative forcing by aircraft soot in large-scale clouds has been > estimated to be both positive and > negative, while forcing by contrails and contrail cirrus (i.e. > spreading contrails) is positive. Here we use > an improved model to estimate the forcing in large-scale clouds. We > assume that the fraction of soot > particles that have been processed through contrails are good > heterogeneous ice nuclei (IN) and use > the average fraction determined from the CoCiP model. The calculated > total all-sky radiative climate > forcing ranges between -0.2 and -0.8 Wm-2 > , with the range determined by whether sulfate on soot > decreases their ability to act as IN as well as the treatment used for > precipitation scavenging. We > discuss what is needed to narrow the range. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/groups/opt_out.
