The Current Wisdom is a series of monthly articles in which Senior Fellow Patrick J. Michaels reviews interesting items on global warming in the scientific literature that may not have received the media attention that they deserved, or have been misinterpreted in the popular press.
Traditionally The Current Wisdom only comments on science appearing in the refereed, peer-reviewed literature, or that has been peer-screened prior to presentation at a scientific congress. This is an exception, in response to a massive pre-peer-review public relations campaign currently in progress from the Berkeley Earth Surface Temperature (BEST) science team.
Prior to April, 2011, issues of this Wisdom, which began in 2010, are available at our blog Cato@Liberty (www.cato-at-liberty.org/).
On October 21, the Berkeley Earth Surface Temperature (BEST) research team sent four manuscripts on surface temperature histories to the peer-reviewed journal Journal of Geophysical Research (JGR). The same day, they issued a press release detailing the research findings contained in those manuscripts.
The most prestigious journals, such as Science and Nature, automatically reject any submission if the results are made public prior to their publication. Other journals can be (but aren't necessarily) a bit more lax. But the sheer scope of the BEST pre-peer-review PR campaign has been very impressive.
The original BEST press release confidently stated that their findings would be incorporated the next comprehensive report of the United Nations' Intergovernmental Panel on Climate Change, which presumes that they will be accepted for publication largely in their current form.
For several reasons, I think this is highly presumptuous.
Consider their paper on urban heat islands (UHI), the well-known warming of towns and cities compared to the surrounding countryside. UHIs can be very impressive. Washington DC and Tokyo's are both in excess of 2°C (3.6°F) for average temperature, but the effect can be much greater — as much as 12°C (21.6°F) on clear, calm nights in the winter.
They are also ubiquitous, having been found systematically at locations in the U.S. with populations of only 1200. And they are positive, meaning that they are in the warm direction. (There are negative UHIs in China, probably a result of extreme urban air pollution that significantly reduces incident sunlight, compared to the countryside.)
At any rate, BEST found a global urban cooling effect, counter to virtually every other study in science history.
Now, this may turn out to be correct and every prior study may have been wrong. But that's doubtful. It is a given that bricks and pavement heat up much more than vegetated ground during the day, and that the roughness of the city impedes the flow of ventilating winds, resulting in warmer nights.
I suspect that the official peer-reviewers are going to relentlessly home in on this result, and I doubt that anyone would recommend publication of the paper without extensive documentation and without the statements, contained in the submitted manuscript, about "urban cooling" and "rural warming". Consequently, the flat-out statement that their manuscripts will be accepted seems a bit overconfident.
Where's the "Pause"?
In their extensive and well-orchestrated press offensive, BEST's director Richard Muller made it quite clear on the BBC that they had not found the "pause" in global warming that begins in the late 1990s in other analyses. Is that really true?
In response to Muller's statement, David Whitehouse, from the Global Warming Policy Foundation in the United Kingdom, excerpted the BEST team's monthly temperature departures from average for the last ten years. The result certainly looks like the familiar "pause." However, there is an obviously bad data point in early 2010 (which is noted on the BEST website).
The response of the green blogs (and the Washington Post) to Whitehouse was that indeed there was a warming — of 0.14°C, if one removed the last two points.
In reality, while that is true, because of the inherent noise in BEST's land-only data, that "trend" does not come close to statistical significance, which means that it cannot be distinguished from zero, or no trend.
(This is a common problem in climate rhetoric, and even the United Nations' Intergovernmental Panel on Climate change and the U.S. National Climatic Data Center often make the egregious error of stating "trends" that in fact are no different than zero.)
Note that Whitehouse's analysis begins in January 2001. In reality, the divergence between the BEST and the rest largely occurs in the late 1990s.
1998 saw one of the largest El Niño events ever measured. These are periodic warmings of the tropical Pacific Ocean that occur when, for reasons currently unknown, easterly trade winds slow or even reverse. When this happens, a normal upwelling of cold water off of South America is suppressed, and the global average temperature suddenly jumps.
When the trades return, the suppressed cold water comes to the surface with a vengeance, and global temperatures drop for a year or so far below where they peaked from the El Niño. This "reverse phase" is called La Niña — something we will visit again later in this Wisdom.
The key words here are Pacific Ocean. The BEST analysis is for land temperatures only (which also does not include islands). Consequently the extreme warmth of 1998 (and the following cold La Niña) does not appear as it does in the global (land and ocean) records. This is why there's no spike in the 1998 data in the chart shown above. On the other hand, it is quite obvious in the land-ocean record:
When fishing for global climate fish, use global data.
Which of the three global records is most reliable during the "pause?" That can be determined by comparison to the completely independent record of temperatures measured by satellites. It turns out that the East Anglia record most accurately captures the 1998 El Niño, and therefore it is the one that should be examined in depth for recent behavior.
How Long Have We Gone Without Warming?
The correspondence between the East Anglia thermometer record and the satellite record, which measures microwave radiation from the lower atmosphere, is reassuring. It is noteworthy that there are two versions of the satellite data, one from the University of Alabama-Huntsville, where it was first developed, and another from Remote Sensing Systems, a California consultancy that processes the data in a slightly different fashion.
Monthly versions of the three records (the East Anglia history and the two versions of the satellite) are pretty close together in how long they say the current lack of warming has gone on. This can be determined by passing trends through records of increasing length and finding when a statistically significant warming emerges. Using this method, there is no significant warming in the last 15.0 years in the CRU thermometer record, 13.9 years in the Alabama version of the satellite data, and 15.6 years in the California analysis.
How Long Will We Go Without Warming?
Obviously, no one really knows. But let's start with the observation that the current era of steady temperatures, according to the figures above, began around 1996.
We are currently experiencing another — for now — moderate La Niña, or the cold phase of El Niño. Satellite temperatures, as of this writing, have dropped below where they were in the previous La Niña of 2008, so 2011 isn't going to be particularly warm compared to the average of the last 15 years.
In addition, the latest forecast from the Department of Commerce's Climate Prediction Center is for the current La Niña to become stronger and persist through at least the first half of 2012:
Consequently, 2012, like 2011, is not likely to be particularly warm when compared to the last 15 years.
Assume that, beginning in 2013, surface temperatures rise at the rate they did from the mid-1970s through the late 1990s. How much time would have to elapse before a statistically significant warming trend was established, post-1995?
Significance would finally be achieved in 2021. That would be after a 24-year stretch with no significant net warming.
So, in summary, BEST really does not tell us much that is new. It, too, contains the "pause," but the big 1998 peak is missed because the study was only for land areas, while most of the 1998 warming was at the surface of the ocean due to the massive El Niño. Satelllite data, not used in the BEST science, tells us that the East Anglia climate record is probably most reliable for global estimates during the "pause." La Niña conditions mean that 2011 and 2012 are not likely to be particularly warm. Even if surface temperatures begin to rise in 2013 at the rate that they rose from the mid 1970s to the late 1990s, a significant warming trend since 1995 will not be established until 2021.
It seems hard to believe that there will be much political will for expensive global warming policies after two-and-a-half decades without a significant rise in temperature.