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Saturday, October 3, 2015

Notes on Obliquity

It is usual, when discussing Milankovitch cycles, to dismiss any effect of obliquity on global, annual mean insolation based on the fact that the Earth is a sphere.  I did it myself in a comment on Skeptical Science.  As the Earth is an oblate spheroid, however, it is not strictly accurate.  In particular, on the equinoxes, the Earth presents its minimum aspect to the Sun, showing an eclipsed area of 1.2737 x 1014 m2 to the Sun.  As the Earth moves to the solstice (either winter or summer) it presents its maximum aspect, showing an eclipsed area of 1.2744 x 1014 m2.  That represents a difference of 0.05% in recieved sunlight, or approximately 0.12 W/m2.  That seasonal variation is much less than the 6.8% (16.2 W/m2) seasonal variation due to the eccentricity of the Earth's orbit.

Saturday, September 19, 2015

New Blog

Just a small notice of my new blog, which will be of a more personal nature than By Brisbane Waters.  I am also using it to discuss important issues not related to climate change.

Friday, May 29, 2015

Monday, May 25, 2015

Grantham and the media

I haven't written a post on the Queensland 2011 floods for a while.  It is, however, back in the news due to issues relating to events at Grantham.  I have very little to say about that in particular.  Those issues turn on detailed matters of topography and hydrology on which neither I, nor the residents of Grantham have the necessary knowledge to have an informed opinion.  The residents of Grantham do, of course, have the relevant expertise on what they saw; and what they saw must inform any hydrological assessment of the effects of the flood on Grantham.  Knowing what you saw, and interpreting its significance, however, are not the same thing.  Therefore the claims of the Grantham residents do not determine what happened in 2011, and should not by themselves determine the results of the current inquiry.

The task of the inquiry is being made harder by bad reporting on the floods.  I discuss below the fold one such example of bad reporting by Channel Nine, echoed by the Sydney Morning Herald.  Once again I have copied a comment from SkS for convenience, and in this case the first part of the comment is not directly relevant to the issue of bad reporting by media.  I have retained it, however, as it does give useful background on the general situation in the Lockyer Valley at the time of the Grantham flood of Jan 10, 2011.

Thursday, October 30, 2014

Observed enhanced greenhouse effect

In 2001, Harries et al published an article claiming to infer changes in greenhouse radiative forcing from changes in the Outgoing Longwave Radiation (OLR).  Here is the crucial data from that paper:

The graph shows the difference in OLR between April-June, 1970 and April-June 1997 over the eastern central tropical pacific (10 S to 10 N; 130-180 W).  It shows that the OLR has increased slightly (top), but that the observed increase was matched by an predicted increase in the models (middle).  The graphs are offset to allow easy comparison.

Saturday, October 4, 2014

The straight line hockey stick

This is an extended post from Skeptical Science.  It discusses where I am at in dissecting McIntyre and McKitrick (2005).  That is something I had been holding of on until I completed the analysis, but I raised some points of the analysis in discussion at And Then There's Physics, so thought a fuller statement of the results to date was in order.  Full discussion below fold:

Friday, September 12, 2014

Some knowledge is not certain (or why the spurious rejection of reasonable inductive inferences is itself a fallacy of reasoning)

One of the common themes of the creation wars and the climate war is the attempt by the anti-science side of each debate (ie, creationists and AGW deniers) to make their position appear more reasonable than it is by arguing that it is accepted by a large number of scientists.  Thus we have lists of scientists who do not accept evolution such as that compiled by the Discovery Institute, and equivalent lists of scientists who do not accept Anthropogenic Global Warming such as the OISM petition from the forces of anti-science.

To counter this spurious argument, defenders of science have emphasized how small a proportion of scientists accept these pseudo-scientific positions.  The NCSE does this with some humour, through their Project Steve.  Defenders of the theory of AGW are a bit more dour, and have produced a series of surveys and other studies showing that rejection of AGW is confined to about 3% of climate scientists.

The curious thing is that these studies are rejected in turn by AGW deniers as an appeal to authority, ie, and invalid argument.  Their intention is nothing of the sort.  Rather, they are a rebuttal of the spurious appeal to authority represented by such phenomenon as the OISM petition.  Ignoring that important subtlety, however, the fact remains that an appeal to relevant authority is in fact a valid way of justifying beliefs.  I recently explained why in some detail in a comment at Skeptical Science, which is reproduced with minor editing below the fold.