Did the global temperature trend change at the end of the 1990s?

Tom Quirk

Accepted 7 May 2012 for the Asia-Pacific Journal of Atmospheric Sciences

http://ipa.org.au/library/publication/1339463007_document_break_paper_apjas_ipa.pdf

5 Methane

Atmospheric methane concentrations have been directly measured systematically since 1983 (Cunnold et al, 2002) so it is not possible to see any changes before that time. There are ice core data available covering this period (MacFarling Meure et al., 2006) but atmospheric gases trapped in the ice bubbles are averaged over a number of years and detail is lost. There is a further problem with methane measurements prior to 1990. They may well be contaminated by natural gas leakage from pipelines (Quirk, 2010).

The level of methane in the atmosphere is understood to be controlled by the interplay of natural and anthropogenic sources with an atmospheric sink of OH radicals that removes methane. The level of OH radicals is controlled by ultraviolet solar radiation, ozone and the amount of water vapour present (Bousquet et al. 2006).

The major (95%) sink for methane is OH radicals in the troposphere. These are concentrated in the Tropics as water vapour is their source and water vapour is at a maximum concentration in the Tropics. If there is a change in humidity at about the year 2000 then there should be a change in the rate of removal of methane from the atmosphere. An increase in humidity implies an increase in OH radicals and a consequent increase in the rate of removal and a reduced rate of increase of methane. Figure 8 shows just this effect. For the period 1991 to 2009 the annual increase in methane falls from 5.8 +/- 0.4 ppb per year before 1999 to 1.3 +/- 0.4 ppb per year after 1999.

Methane like other components of the atmosphere has a break in its time series in 1999 +/- 1 year.

It follows then, that he would probably exit from a group (us) that addresses feedbacks, empirical observations, IPCC AR veracity, thermodynamics and spectroscopy etc.

So who’s left for him to “communicate” with beyond his institution and govt? His like-minds at Oxford? A compliant but ignorant NZ public?

At least he managed to raise the level of HT to-and-fro above the gutter for a while and as comments go, that would have rate as one of the more comprehensive. This was interesting:-

As for the position that “GHG concentrations are already at the 450 ppm” This conflates short- and long-lived gases. It’s overly pessimistic to redenominate methane (for instance) forcing as though it were much more permanent (ie CO2). It gives a false picture of where we are (and, regrettably, can lead to perverse policy incentives).

He basically dismisses GWP and I don’t think the few of us here that have had a look at GWP would disagree with him, Jim McKinlay in particular.

http://hot-topic.co.nz/groser-underplays-the-real-risks/#comment-33125

..”……and found the calculations somewhat wanting”

The IPCC random number generator got stuck on 23 in about 2004.

I am very hopeful this time, well spotted Richard.

Seasonal variation of methane, water vapor, and nitrogen oxides near the tropopause:
Satellite observations and model simulations

http://acd.ucar.edu/~dkin/Documents/Park_2003JD003706.pdf

“The seasonal comparisons shown here highlight the
importance of the NH summer monsoon circulations for
contributing to STE, as discussed in Dethof et al. [1999]. In
particular, the CH4 and H2O fields in both HALOE and
MOZART show the localized impact of the South Asian
monsoon in the tropopause region, and the MOZART cross
sections (Figures 5, 10, and 11) suggest direct transport of
constituents into the lower stratosphere via monsoon circulations”

Rapid descent of mesospheric air into the stratospheric polar vortex

Abstract
Wind fields from a numerical simulation are used to give a detailed Lagrangian picture of air flow in the middle atmosphere of the southern hemisphere in winter and early spring 1991. Trajectories for many thousands of air particles exhibit rapid descent of mesospheric air into the stratospheric polar vortex, revealing its organizing and structure‐preserving properties. Results are used to account for measurements of low methane concentrations in the vortex made by the HALOE instrument on board the Upper Atmosphere Research Satellite.

http://www.agu.org/pubs/crossref/1993/93GL01104.shtml

Behind paywall so I don’t know how the low concentration of methane was accounted for.

Discovered linked at the WUWT Polar Vortex Reference Page http://wattsupwiththat.com/2011/10/29/new-wuwt-polar-vortex-reference-page/, article also reads:-

“The walls of the polar vortex act as the boundaries for the extraordinary changes in chemical concentrations. Now the polar vortex can be considered a sealed chemical reactor bowl, containing a water vapor hole, a nitrogen oxide hole and an ozone hole, all occurring simultaneously (Labitzke and Kunze 2005)” Stratosphere troposphere interactions: an introduction [linked]

Also re NH heat waves:-

Current Global Weather Patterns Normal Despite Government and Media Distortions

by Dr. Tim Ball on June 28, 2012

The dome of cold air over polar regions is expanding as the world has cooled since 1998. Rossby Waves in the Circumpolar Vortex that circles from west to east in the middle latitudes switched from Zonal to Meridional flow creating different weather patterns in the middle and high latitudes.

[See graphics]

Rossby Waves migrate from west to east on a 4 to 6 week basis. However, when the Meridional Wave amplitude gets deep, with cold air pushing toward the Equator and warm air toward the Poles the system blocks. Now the weather pattern migration becomes 8 to 10 weeks and people become nervous. That is what is happening in North America now, but all we hear about is the warm weather across the eastern half of the continent, with little mention of the cold and wet conditions in the west.

http://drtimball.com/2012/current-global-weather-patterns-normal-despite-government-and-media-distortions/

“Media distortions” would include the Trenberth/Borestein beat-up

This figure of GWP=23 seems to get bandied around like it is a fundamental constant of the universe – like the speed of light or Boltzmann’s constant, yet when pushed, no one knows what it means or how it was derived.