Another reponse to James Delingpole

(this response hasn't been posted either as of yet...[edit - it has now been published on the telegraph blogs comments section])

Frank fisher wrote: "That’s all you’re left with? How about natural greenhouse gasses..."

Measured and tracked:

http://www.esrl.noaa.gov/gmd/aggi/

http://gaw.kishou.go.jp/wdcgg/

"... Or reduced albedo.  Or increased cloud cover.

Measured and tracked:

http://gosic.org/ios/MATRICES/ECV/ecv-matrix.htm

"...Or deforestation?"

Measured and tracked:

http://news.mongabay.com/2005/1115-forests.html

Absence of evidence is not evidence of absence.

Absolutely true.  But there are few physical processes capable of heating up the Earth's oceans, atmosphere and land on timescales of multiple decades.  Science, as you know, isn't about certainty.  The point is that we can can analyse all the natural phenomena we know about and we can come to the conclusion that anthropogenic GHG emissions are by far and away the most powerful explanation for the warming we've seen, especially over the past 30 years.  If you want to cross your fingers and hope that the last 30 years' warming is entirely down to something completely outside the scope of modern science and that hopefully it'll stop soon then please don't be surprised if folks like me don't join your club.

There is no proof whatsoever that this past century’s warming is man made.

Er.  I'm not sure what a "proof" would look like in the wild away from pure mathematics.  If you mean "there is no evidence that this past century's warming is man made" then that statement can be easily falsified.  Try this for starters:

http://www.skepticalscience.com/empirical-evidence-for-global-warming.htm

BTW, this century’s warming is not, contrary to Mann’s claims, the most rapid on record.

I'm not sufficiently good at statistics to tell whether or not Mann's claims are robust or not.  As far as I'm concerned, feel free to delete Mann and the hockey stick from the literature if it makes you feel better.  It doesn't change the hypothesis that we will soon be (if we aren't already) in an environment which will be distinctly less habitable than the pre-industrial environment, and that we can do something about that if we wish.

JK: We have a mechanism by which green house gasses decreases heat loss from the planet and the temp rises for the past 100 years are consistent with that mechanism.

FF: And is the fall this past decade consistent? Nope. A “travesty” eh?

There are 2 problems with that statement.

Problem 1: it's simply not true that average global surface temps have fallen this decade.  The trend from 2000 until now is a rise in surface temp (this is shown in both HADCRUh3 and GISSTEMP).

People often ask "how come some people say the planet has cooled and others say the planet has warmed"?  The short answer is that the signal is noisy and you can find any trend you want to find if you cherry pick the start and stop dates and keep the timeslice below about 10 years.  You need to look at trends of, ideally, at least 20-25 years to see the AGW signal behind the noise.  This post is an excellent illustration of the problem:

http://woodfortrees.org/notes.php#trends

Problem 2: even if surface temps had fallen over the course of 10 years, this wouldn't falsify AGW because 10 years is too short a timeslice to produce statistically powerful trends.  Look at the numbers: AGW predicts that average surface temps will increase about 0.2 degrees C per decade or 0.02 degrees C per year.  But natural variation (especially El Nino / La Nina) can cause global temp differences of up to 0.5 degrees C per year.  Hence you really need to look at trends of 20-25 years (this number is not arbitrary; this is basic statistical analysis: 0.5 / 0.02 = 25).  It's worth noting that 1998 was especially hot because of a very strong El Nino (warming) event while a strong La Nina event cooled the planet from 2006-7.

This paper discusses this further:

http://www.pnas.org/content/early/2009/09/09/0908699106.abstract

I’m curious. How was that emitted IR measured a century ago?

Of course emitted IR wasn't measured by man-made satellites a century ago.  But the measured trend for the duration of the measurements (starting in 1970) is consistent with AGW.  Here's a paper discussing this:

http://www.eumetsat.eu/Home/Main/Publications/Conference_and_Workshop_Proceedings/groups/cps/documents/document/pdf_conf_p50_s9_01_harries_v.pdf

Me: In summary: we can rule out solar influences and ocean currents and we have plenty of evidence implicating greenhouse gasses in increasing the heat content of the planet over the past 100 years.

FF: If you ignore all possible alternative mechanisms and evidence, yes. Well done."

Eh?  I was under the impression that I had actually considered many (if not all) of the alternative mechanisms.  You're simply ignoring the facts when you state that I'm ignoring "all possible alternative mechanisms".

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