Saturday, February 22, 2014

Consensus? What consensus?

The American Physical Society has just held an extraordinary meeting. It has a Subcommittee looking at climate change. The Subcommittee found it necessary to understand the IPCC consensus on climate science through a workshop which dived deeply into some of the more uncertain aspects. In doing so, it hoped "to illuminate for itself, for the APS membership, and for the broader public both the certainties and the boundaries of current climate science understanding."

People taking part in the workshop included the great climate modeller, Ben Santer of Lawrence Livermore Laboratory; the climatologist Judith Curry from Georgia Tech; the atmospheric physicist Richard Lindzen of MIT; and climate scientist John Christy from the University of Alabama. Each of the specialists would be given a chance to address a set of issues drawn up by the APS panel; the panel would ask questions; there would be a general discussion; and they would move on to the next specialist.

I read the 500-odd pages of transcript.  I think there must be something masochistic in the desire to capture every word, even the announcement that cake was served.  But in amongst the reams of dross, there lay gems.  For instance, Santer produced a lovely graphic showing the problems with his own models:

The top half is what the models say should have happened in the upper atmosphere over the past 34 years; the bottom half is what has actually happened.  The "fingerprint"of the human-derived carbon dioxide is annoyingly absent - well, annoying to the modellers.  The tropical hotspot between about 500 and 700hPa pressure just isn't there.  Yet the physics underlying the carbon-dioxide-driven global warming hypothesis is clear - it should be! Sceptic and believer agree on that. Why is it missing?  And why, for that matter, has the Arctic air warmed ?

Christy confirmed the problem:

The dots give the data; the squares the average of the data; and the spaghetti lines show the attempts of 25 different models to show what might be happening.  Clearly, they fail - the pattern of the fingerprint is wrong. Christy spent some time castigating the IPCC for ignoring this gap between data and models.  The IPCC claimed that the data in the upper troposphere, as shown here, was somehow deficient yet, as you can see, the spread of four independent sets of measurements is quite small and the model average is a long way from the measurement average.

Christy also had some fascinating things to say about the "average global temperature". The estimation of this starts with measuring the temperature at a whole lot of points around the globe.  At each point, the daily maxima and minima are recorded, and the average temperature at that point for that day is the average of the maximum and minimum.  

The trouble comes when you consider what happens in nature, when very often inversions occur and cool air is trapped near the surface.  Then you put a few buildings around the place, and the turbulence they cause destroys the inversion layer and the night air is warmer than it would otherwise be - regardless of any heat coming from the building.  

The net result is that when you look at data from areas that have become increasingly urbanised, there is little change over time in the day-time maxima, but the nights steadily warm, and this then gets recorded as "global warming." Again, the IPCC claims to have looked at the "urban heat island" effect, and to have taken it into account, but Christy showed that a significant correction was needed - because of the basic atmospheric physics.

The APS Panel was concerned as to how is was possible that the IPCC could claim greater certainty in the latest Assessment Report AR5 than in the previous AR4.  In particular, the human impact had gone from 90 to 95% 'certain'. Lindzen was sniffy:
Do you still believe there is consensus?

Sunday, February 9, 2014

The end of snow?

Today the New York Times ran an extraordinary tale about the end of snow.
"The planet has warmed 1.4 degrees Fahrenheit since the 1800s, and as a result, snow is melting. In the last 47 years, a million square miles of spring snow cover has disappeared from the Northern Hemisphere. Europe has lost half of its Alpine glacial ice since the 1850s, and if climate change is not reined in, two-thirds of European ski resorts will be likely to close by 2100."

"The same could happen in the United States, where in the Northeast, more than half of the 103 ski resorts may no longer be viable in 30 years because of warmer winters. As far for the Western part of the country, it will lose an estimated 25 to 100 percent of its snowpack by 2100 if greenhouse gas emissions are not curtailed — reducing the snowpack in Park City, Utah, to zero and relegating skiing to the top quarter of Ajax Mountain in Aspen."

Now I knew that glaciers had been retreating, but my glaciologist friends have difficulty in accepting that it is purely thermal.  So while Europe may have "lost half its Alpine glacial ice", global warming wasn't necessarily the culprit.

I also knew that, while the globe may have warmed a bit, it was very difficult to say that a particular part of the globe had warmed - warming is patchy.  Just because the average global temperature is a bit up does not mean that the snow line is in retreat.

So I went to look for the facts, and found that Rutgers University has a dataset showing the weekly area of the extent of the snow in the northern hemisphere over the past 40-odd years:

Can you see the end of snow there? Seems to me variable but without any real trend in either the maximum or minimum. The minimum was a bit ragged until about 1972, but it was the start of the satellite era, so some missing data is understandable.

I cannot wait for this climate farce to end, so that I can return to trusting newspapers like the NYT.  Every time they run a piece bleating about climate change I have to check the tale, and invariably find the science is against them.