CC3 -- Why I believe that a third option is needed for climate change

Gaoth Laidir wrote: »

There are lies, damn lies and Akrasia. The IPCC use CO2 and only CO2.

AR5

Nabber wrote: »

Seems like they are hedging their bets.

More summer rain = AGW
Less summer rain = AGW
Colder winter = AGW
Warmer winter = AGW

There are so many conflicting predictions that it’s near impossible for AGW to not hit at least once or twice a year.
When the warming trend ends it’s because there is a lag that “we don’t understand”. Yet confidence in knowing enough to claim human GHG are the sole forcing factor never wanes.

Thargor wrote: »

Likewise if its all just a liberal conspiracy by the worlds scientific community for whatever reasons then why have the 10 hottest years ever recorded all occurred in the last 15 years with last year being the second hottest ever seen? Its generally global heat thats considered a problem not storms hitting our minuscule little patch of the Earths surface.

Thargor wrote: »

Every measurement is an estimate really, have you identified a specific problem with the methodology that the NOAA and NASA and all the rest might have missed? Anyway the US makes up ~6% of the worlds surface, cherrypicking such a small area is pointless (although would you happen to have a source for that out of curiosity?).

What kinds of errors have been made? Well first, let’s understand how these two researchers measure atmospheric temperatures. They are not using thermometers, rather they are using microwave signals from the atmosphere to deduce temperatures. The microwave sensors are on satellites which rapidly circle the planet. 

Some of the problems they have struggled with relate to satellite altitudes (they slowly fall over their lifetimes, and this orbital decay biases the readings); satellite drift (their orbits shift east-west a small amount causing an error); they errantly include stratosphere temperatures in their lower atmosphere readings; and they have incorrect temperature calibration on the satellites. It’s pretty deep stuff, but I have written about the errors multiple times here, and here for people who want a deeper dive into the details.

It’s important to recognize that there are four other groups that make similar measurement estimates, so it’s possible to compare the temperatures of one group against another. The new paper, completed by Eric Swanson and published by the American Meteorological Society compares the results from three different groups. He focused on measurements made over the Arctic region. His comparison found two main differences amongst the three groups that suggests the errors.

To better appreciate the issues, the satellites have instruments called Microwave Sounding Units (MSUs) or more recently, Advanced Microwave Soundings Units (AMSUs). These instruments allow reconstruction of the lower troposphere (TLT), the mid-troposphere temperature (TMT), and the lower stratosphere temperature (TLS). But the measurements are not at a specific location (like a thermometer) - they are smeared out over large spaces. As a consequence, it’s possible to have one layer of the atmosphere contaminate the results of another layer. You wouldn’t for instance, want your measurement of the troposphere (lower atmosphere) to include part of the stratosphere (above the troposphere).

Among the key differences among the research teams are their methods to ensure this contamination is minimized. According to the recent paper, which was published in January 2017:

At present, the UAH v6 (most recent Christy/Spencer data) results are preliminary and a fifth revision has now been released as v6beta5 (Spencer 2016). The release of the UAH version 6 products before publication is unusual, and Spencer recently stated that a manuscript has been submitted for a peer-reviewed publication. While some may find it scientifically inappropriate to utilize UAH v6b6 data before publication, these data have already been presented in testimony during congressional hearings before both the U.S. House and Senate and have also appeared on websites and in public print articles. 

The author compared the Christy/Spencer data (UAH data) with another group (the RSS group) and found that the results diverged during the 1986-1988 time period. This shift “could arise from a step change or bias in either series.” When the author compared UAH with the third group (NOAA), the difference was still evident. However, when he compared RSS to NOAA, there was hardly a difference. 

The author also noted that the timing of this divergence coincided with the merging of a new satellite NOAA-9, and this satellite has previously been identified as a source of error in the UAH results. But the author continued the analysis to more recent times and found another anomaly in 2005 which has since been corrected in NOAA.

Look, measuring temperatures from satellites flying high above Earth is hard. No one doubts that. But let’s not be deluded into thinking these satellites are more accurate than thermometers (as some people suggest). Let’s also not blindly accept low-ball warming information from research teams that have long histories of revising their data. I created the image below a few years ago to show the upward revisions made by the Christy/Spencer team over time in their global troposphere temperatures.