After talking with John Christy, I decided I should further expound upon the points I made in my last post.

The issue is that the two main satellite-based records of global lower tropospheric temperature change have been diverging in the last 10 years, with the RSS version giving cooler anomalies than our (UAH) version in recent years, as shown in the following plot:
(the RSS anomalies have been re-computed to be relative to the 1981-2010 period we use in the UAH dataset)

Ten years ago, this meant that the AGW folks were claiming RSS was right and we (UAH) were wrong, since the RSS global warming trends were greater than ours.

But now the shoe is on the other foot, and the RSS linear trend since January 1998 has actually cooled slightly (-0.03 deg. C per decade) while ours has warmed slightly (almost +0.05 deg. C per decade).

John works hard at making our dataset as good as it can be, and has correctly reminded me that he and others have several peer reviewed and published papers recent years on the subject of the accuracy of the UAH dataset:

Christy, J.R. and Norris, W.B. 2006. Satellite and VIZ-radiosonde intercomparisons for diagnosis of nonclimatic influences. Journal of Atmospheric and Oceanic Technology 23: 1181-1194.

Christy, J.R., Norris, W.B., Spencer, R.W. and Hnilo, J.J. 2007. Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements. Journal of Geophysical Research 112: doi:10.1029/2005JD0068.

Christy, J.R. and Norris, W.B. 2009. Discontinuity issues with radiosondes and satellite temperatures in the Australia region 1979-2006. Journal of Atmospheric and Oceanic Technology 25: OI:10.1175/2008JTECHA1126.1.

Christy, J.; Herman, B.; Pielke, Sr., R.; Klotzbach, P.; McNider, R.; Hnilo, J.; Spencer, R.; Chase, T. et al. (2010). “What Do Observational Datasets Say About Modeled Tropospheric Temperature Trends Since 1979?”. Remote Sensing 2 (9): 2148. doi:10.3390/rs2092148

Douglass, D. and J. R. Christy, 2009: Limits on CO2 climate forcing from recent temperature data of Earth, Energy & Environment, Volume 20, Numbers 1-2, January 2009 , pp. 177-189(13) doi:10.1260/095830509787689277.

Randall, R.M. and Herman, B.M. 2008. Using limited time period trends as a means to determine attribution of discrepancies in microwave sounding unit derived tropospheric temperature time series. Journal of Geophysical Research: doi:10.1029/2007JD008864.

Bengtsson, L. and K.I.Hodges, On the Evaluation of Temperature Trends in the Tropical Troposphere, Clim. Dyn., doi 10.1007/s00382-009-0680-y, 2009.

These papers either directly or indirectly address the quality of the UAH datasets, including comparisons to the RSS datasets.

Based upon the evidence to date, it is pretty clear that (1) the UAH dataset is more accurate than RSS, and that (2) the RSS practice of using a climate model to correct for the effect of diurnal drift of the satellite orbits on the temperature measurements is what is responsible for the spurious behavior noted in the above graph.

Our concerns about the diurnal drift adjustment issue have been repeatedly passed on to RSS in recent years.

What Will the Next IPCC Report Say?

As an aside, it will be interesting to see how the next IPCC report will handle the various global temperature datasets. There have been a few recent papers that have gone through great pains to explain away the lack of long-term warming in the satellite and radiosonde data (the missing “hot spot”) by trying to infer its presence from upper tropospheric wind data (a dubious technique since geostrophic balance is a poor assumption in the tropics), or by using a few outlier radiosonde stations with poor quality control and spurious warming trends.

Call me a cynic, but I think we can expect the IPCC to simply ignore (or at most brush aside) any published evidence that does not fit the AGW template.

…or, OMG! HAS UAH BEEN BOUGHT OFF BY GREENPEACE!?

Over the last ten years or so there has been a growing inconsistency between the UAH and Remote Sensing Systems versions of the global average lower tropospheric temperature anomalies. Since I sometimes get the question why there is this discrepancy, I decided it was time to address it.

If we look at the entire 30+ year record, we see that the UAH and RSS temperature variations look very similar, with a correlation coefficient of 0.963 and linear trends which are both about +0.14 deg. C per decade:

(In the above plot I have re-computed the RSS anomalies so they are relative to the 1981-2010 average annual cycle we use; this does not affect the trends…just makes it more of an apples-to-apples comparison).

But if we examine a time series of the DIFFERENCE between the two temperature records, we see some rather interesting structure:

(Note: I have applied a 3-month smoother to the data to reduce noise).

As can be seen, in the last 10 years or so the RSS temperatures have been cooling relative to the UAH temperatures (or UAH warming relative to RSS…same thing). The discrepancy is pretty substantial…since 1998, the divergence is over 50% of the long-term temperature trends seen in both datasets.

WHY THE DIVERGENCE?

So, why the discrepancy? Well, if it was OUR (UAH) data that was cooling relative to RSS, people would accuse us of being bought off by Exxon-Mobil (I wish!…still waiting for that check..). At least that has been the history of this debate.

But now WE are the ones with “excess” warming. So where are the accusations that RSS is being bought off by Big Oil?

Hmmmm?

(It’s OK, we are used to the hypocrisy. 🙂 )

Anyway, my UAH cohort and boss John Christy, who does the detailed matching between satellites, is pretty convinced that the RSS data is undergoing spurious cooling because RSS is still using the old NOAA-15 satellite which has a decaying orbit, to which they are then applying a diurnal cycle drift correction based upon a climate model, which does not quite match reality. We have not used NOAA-15 for trend information in years…we use the NASA Aqua AMSU, since that satellite carries extra fuel to maintain a precise orbit.

Of course, this explanation is just our speculation at this point, and more work would need to be done to determine whether this is the case. The RSS folks are our friends, and we both are interested in building the best possible datasets.

But, until the discrepancy is resolved to everyone’s satisfaction, those of you who REALLY REALLY need the global temperature record to show as little warming as possible might want to consider jumping ship, and switch from the UAH to RSS dataset.

It’s OK, we’ve developed thick skin over the years. 🙂 You can always come home later.

Gee, I wonder if some of all that green money will start flowing our way now? I’m not going to hold my breath.

Post-La Nina Warming Continues
The global average lower tropospheric temperature anomaly for June, 2011 increased to +0.31 deg. C (click on the image for a LARGE version):

The Northern Hemisphere, Southern Hemisphere, and and Tropics all experienced temperature anomaly increases in June:

YR MON GLOBAL NH SH TROPICS
2011 1 -0.010 -0.055 +0.036 -0.372
2011 2 -0.020 -0.042 +0.002 -0.348
2011 3 -0.101 -0.073 -0.128 -0.342
2011 4 +0.117 +0.195 +0.039 -0.229
2011 5 +0.133 +0.145 +0.121 -0.043
2011 6 +0.314 +0.377 +0.251 +0.235

I would like to remind everyone that month-to-month changes in global-average tropospheric temperature have a large influence from fluctuations in the average rate of heat transfer from the ocean to the atmosphere. In other words, they are not of radiative origin (e.g. not from greenhouse gases). El Nino/La Nina is probably the most dramatic example of this kind of activity, but there are also “intraseasonal oscillations” in the ocean-atmosphere energy exchanges occurring on an irregular basis, too.

YEARLY temperature averages probably provide a better indication of the existence of radiative forcings on the climate system (whether warming or cooling). Nevertheless, we must remember that even DECADAL time scale (or longer) changes in the ocean circulation could also be involved, which can cause long-term climate change independent of any kind of greenhouse gas (or cosmic ray-induced) radiative forcing. (That last sentence has not been approved by the IPCC…but I don’t really care.)

I’m pretty excited that today (Independence Day, 2011) is the release date for my new book, Fundanomics: The Free Market, Simplified.

Our friend, Josh, did the cover art and it perfectly captures one of the book’s main messages: the greatest prosperity for ALL in a society is achieved when people are free to benefit from their good ideas.

In Chapter 1, A Tale of Two Neanderthals, Borgg and Glogg are the tribe’s firestarters, who get the idea to invent firesticks (matches). This leads to a system of trading with a neighboring tribe which has many great hunters, and as a result the inventors’ tribe never goes hungry again.

But the favored treatment the inventors receive from the tribe’s elders later leads to resentment in the tribe, and people forget how much better off they all are than before — even the poorest among them. Technology and prosperity might change, but human nature does not.

Simply put, a successful economy is just people being allowed to provide as much stuff as possible for each other that is needed and wanted. Economics-wise, everything else is details. When we allow politicians and opportunistic economists to fool us into supporting a variety of technical and murky government “fixes” for the economy, we lose sight of the fundamental motivating force which must be preserved for prosperity to exist: Liberty and the pursuit of happiness.

The main role of the government in the economy is help ensure people play fair…and then get out of the way.

I devote each chapter to a common economic myth.

For example, it’s not about money, which has no inherent value and is simply a convenient means of exchange of goods and services that is more efficient than bartering.

It’s not even about “jobs”, because it makes all the difference what is done in those jobs. Many poor countries have a much lower standard of living than ours, yet fuller employment. If we want full employment, just have half the population dig holes in the ground and the other half can fill them up again. The goal is a higher standard of living…not just “jobs”.

And the desire of some for a “more level playing field” and for “spreading the wealth around” is simply pandering to selfishness and laziness. The truth is that most of the wealth has already been spread around, in the form of a higher standard of living. If we do not allow the few talented and risk-taking people among us have at least the hope of personally benefiting in proportion to their good ideas, then economic progress stops.

The good news is that those few talented people need help, which is where most of the rest of us come in. One person with a new idea for a computer cannot design, manufacture, market, distribute, and sell millions of computers to the rest of society. They need our help, and in the process everyone benefits.

I also examine the role of various government economic programs, most of which end up hurting more than helping. A major reason why the government is so prone to failure is the lack of disincentives against failure in government service. In the real marketplace failures are not rewarded, which helps keep us on the right track to prosperity.

Even the truly needy in our country would be better off if we allowed private charitable organizations, rather than inefficient government bureaucracies to compete for the public’s donations.

I’ve been interested in basic economics for the last 25 years, but frustrated by the technical details (marginal costs, money supply, etc.) that too often scare people away from understanding the most basic forces which propel societies to ever high standards of living. Now, with our country facing tough decisions about our financial future, I decided it was time to stop yelling at the idiots on TV (and giving away all my ideas to talk show hosts) and put the material in a short — less than 100 pages — book that would be approachable by anyone.

I’ll be signing the first 500 copies. The price is $12.95 (including free shipping in the U.S.) You can see all of the chapter first pages at Fundanomics.org. I think this book would be especially valuable to homeschoolers.

(NOTE REGARDING COMMENTS, BELOW: In response to a comment that it was ironic for a scientist whose research is 100% funded by the U.S. Government to be against wasteful government spending, my statement that “I view my job a little like a legislator” has caused quite a stir, especially over at ThinkProgress. This was a rather poor analogy…my point was that a federally-funded person like myself can be against excess government spending, just as some federally-funded legislators are, that’s all. I did not mean to imply I wanted to be a de facto legislator. The context of the full comment, below, should have made that clear.

And, once again, ThinkProgress reveals the hypocrisy of those who think its OK for Al Gore to play a climate scientist, or NASA’s James Hansen to actively campaign for Malthusian energy policy changes and for presidential candidates – in violation of the Hatch Act, as NASA employees are told during their annual ethics training classes.)