Initial Notes: This post contains graphs of running trends in global surface temperature anomalies for periods of 12+ and 16 years. They indicate that we have not seen a warming hiatus this long since the 1970s.
Other than the overview and updates, much of the following text is boilerplate. It is intended for those new to the presentation of global surface temperature anomaly data.
The NCDC stirred up a few news articles and some dialogue around the blogosphere yesterday with their State of the Climate Report for May 2013. I’m not going to dwell on their rankings because, as we can see in following graph, the May 2013 value is not exceptional. It’s just another little wiggle in a global temperature record that has been exceptionally flat since 2001.
NCDC Global (Land and Ocean) Surface Temperature Anomalies
In other words, the NCDC is making a big to-do about nothing.
NCDC GLOBAL SURFACE TEMPERATURE ANOMALIES
Introduction: The NOAA Global (Land and Ocean) Surface Temperature Anomaly dataset is a product of the National Climatic Data Center (NCDC). NCDC merges their Extended Reconstructed Sea Surface Temperature version 3b (ERSST.v3b) with the Global Historical Climatology Network-Monthly (GHCN-M) version 3.2.0 for land surface air temperatures. NOAA infills missing data for both land and sea surface temperature datasets using methods presented in Smith et al (2008). Keep in mind, when reading Smith et al (2008), that the NCDC removed the satellite-based sea surface temperature data because it changed the annual global temperature rankings. Since most of Smith et al (2008) was about the satellite-based data and the benefits of incorporating it into the reconstruction, one might consider that the NCDC temperature product is no longer supported by a peer-reviewed paper.
The NCDC data source is here. NCDC uses 1901 to 2000 for the base years for anomalies.
Update: The May 2013 NCDC global land plus sea surface temperature anomaly is +0.66 deg C. It increased +0.14 deg C since April 2013.
149-MONTH RUNNING TRENDS
As noted in my post Open Letter to the Royal Meteorological Society Regarding Dr. Trenberth’s Article “Has Global Warming Stalled?”, Kevin Trenberth of NCAR presented 10-year period-averaged temperatures in his article for the Royal Meteorological Society. He was attempting to show that the recent hiatus in global warming since 2001 was not unusual. Kevin Trenberth conveniently overlooked the fact that, based on his selected start year of 2001, the hiatus has lasted 12+ years, not 10.
The period from January 2001 to May 2013 is now 149-months long. Refer to the following graph of running 149-month trends from January 1880 to May 2013, using the NCDC global temperature anomaly product. The last data point in the graph is the linear trend (in deg C per decade) from January 2001 to the current month. It is slightly negative. That, of course, indicates global surface temperatures have not warmed during the most recent 149-month period. Working back in time, the data point immediately before the last one represents the linear trend for the 149-month period of December 2000 to April 2013, and the data point before it shows the trend in deg C per decade for November 2000 to March 2013, and so on.
149-Month Linear Trends
The highest recent rate of warming based on its linear trend occurred during the 149-month period that ended in late 2003, but warming trends have dropped drastically since then. Also note that the early 1970s was the last time there had been a 149-month period without global warming—before recently.
192-MONTH RUNNING TRENDS
In his RMS article, Kevin Trenberth also conveniently overlooked the fact that the discussions about the warming hiatus are now for a time period of about 16 years, not 10 years—ever since David Rose’s DailyMail article titled “Global warming stopped 16 years ago, reveals Met Office report quietly released… and here is the chart to prove it”. In my response to Trenberth’s article, I updated David Rose’s graph, noting that surface temperatures in April 2013 were basically the same as they were in June 1997. We’ll use June 1997 as the start month for the running 16-year trends. The period is now 192-months long. The following graph is similar to the one above, except that it’s presenting running trends for 192-month periods.
192-Month Linear Trends
The last time global surface temperatures warmed at the minimal rate of 0.03 deg C per decade for a 192-month period was the late 1970s.
The most widely used metric of global warming—global surface temperatures—indicates that the rate of global warming has slowed drastically and that the duration of the hiatus in global warming is unusual during a period when global surface temperatures are allegedly being warmed from the hypothetical impacts of manmade greenhouse gases.
A NOTE ABOUT THE RUNNING-TREND GRAPHS
There is very little difference in the graphs of 149-month and 192-month running trends if GISS or HADCRUT products are used in place of NCDC data. I’ll alternate the data source monthly to show this.
GISS LAND OCEAN TEMPERATURE INDEX (LOTI)
Introduction: The GISS Land Ocean Temperature Index (LOTI) data is a product of the Goddard Institute for Space Studies. Starting with their January 2013 update, it uses NCDC ERSST.v3b sea surface temperature data. The impact of the recent change in sea surface temperature datasets is discussed here. GISS adjusts GHCN and other land surface temperature data via a number of methods and infills missing data using 1200km smoothing. Refer to the GISS description here. Unlike the UK Met Office and NCDC products, GISS masks sea surface temperature data at the poles where seasonal sea ice exists, and they extend land surface temperature data out over the oceans in those locations. Refer to the discussions here and here. GISS uses the base years of 1951-1980 as the reference period for anomalies. The data source is here.
Update: The May 2013 GISS global temperature anomaly is +0.56 deg C. It warmed about +0.05 deg C since April 2013.
UK MET OFFICE HADCRUT4 (LAGS ONE MONTH)
Introduction: The UK Met Office HADCRUT4 dataset merges CRUTEM4 land-surface air temperature dataset and the HadSST3 sea-surface temperature (SST) dataset. CRUTEM4 is the product of the combined efforts of the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia. And HadSST3 is a product of the Hadley Centre. Unlike the GISS and NCDC products, missing data is not infilled in the HADCRUT4 product. That is, if a 5-deg latitude by 5-deg longitude grid does not have a temperature anomaly value in a given month, it is not included in the global average value of HADCRUT4. The HADCRUT4 dataset is described in the Morice et al (2012) paper here. The CRUTEM4 data is described in Jones et al (2012) here. And the HadSST3 data is presented in the 2-part Kennedy et al (2012) paper here and here. The UKMO uses the base years of 1961-1990 for anomalies. The data source is here.
Update (Lags One Month): The April 2013 HADCRUT4 global temperature anomaly is +0.43 deg C. It increased +0.01 deg C since March 2013.
The three datasets are compared in the next two time-series graphs. The first graph compares the GISS, HADCRUT4 and NCDC global surface temperature anomaly products starting in 1979. Again, due to the timing of this post, the HADCRUT4 data lags the GISS and NCDC products by a month. The graph also includes the linear trends. Because the three datasets share common source data, (GISS and NCDC also use the same sea surface temperature data) it should come as no surprise that they are so similar. For those wanting a closer look at the more recent wiggles, the second graph starts with Kevin Trenberth’s chosen year of 2001. Both of the comparisons present the anomalies using the base years of 1981 to 2010. Referring to their discussion under FAQ 9 here, according to NOAA:
This period is used in order to comply with a recommended World Meteorological Organization (WMO) Policy, which suggests using the latest decade for the 30-year average.
Comparison Starting in 1979
Comparison Starting in 2001
The last graph presents the average of the GISS, HADCRUT and NCDC land plus sea surface temperature anomaly products. Because the HADCRUT4 data lags one month in this update, the most current average only includes the GISS and NCDC products. The flatness of the data since 2001 is very obvious, as is the fact that surface temperatures have rarely risen above those created by the 1997/98 El Niño.
Average of Global Land+Sea Surface Temperature Anomaly Products
Given the threat to unleash the EPA on coal fired electricity generation it should be shown that change to the level of atmospheric CO2 has had no significant effect on average global temperature.
This is demonstrated at http://climatechange90.blogspot.com/2013/05/natural-climate-change-has-been.html . This paper presents a simple equation that calculates average global temperatures since they have been accurately measured world wide (about 1895) with an accuracy of 90%, irrespective of whether the influence of CO2 is included or not. The equation uses a single external forcing, a proxy that is the time-integral of sunspot numbers. A graph is included which shows the calculated temperature anomaly trajectory overlaid on measurements.
Bob, Can’t find a personal email address so I am left with asking you a question on your blog. Have not been able to get a satisfactory answer anywhere and you seemed the logical person to ask. It is, “why has there developed a large divergence between the Northern and Southern Hemispheric temperatures in ~ the last ten years”. It is there in both the land and ocean data http://www.woodfortrees.org/plot/hadcrut4nh/from:1945/plot/hadcrut4sh/from:1945 It would seem that the “pause” is in part do to this diversion. Some have suggested this is an effect of the difference in Land Sea ratios, but that difference has always existed. Others have suggested that it is a temporary, perhaps like the pause, Anyway wondered f you find this at all intriguing?
CMS: Thanks for the question. There are a couple of reasons for the additional rate of warming in the Northern Hemisphere that began in the mid-1970s. There’s about twice as much land in the Northern Hemisphere than there is in the Southern Hemisphere and land surface air temperatures warm faster than sea surface temperatures.
The second reason: the sea surface temperatures of the North Atlantic and North Pacific have additional modes of natural variability that are not evident in the sea surface temperatures of the oceans in the Southern Hemisphere. To help emphasize the additional variability in North Atlantic and North Pacific, I’ve detrended their sea surface temperature anomalies and compared them to the detrended sea surface temperature anomalies of the Southern Hemisphere in the following graph:
The graph is from the following post:
Interesting. The land surface ratio would effect two things. 1. As the land warms and cool more than water, one would expect that the land temperature, and hence land rich areas, would tend to be both higher and lower. 2. The rate of change would be different with the higher land areas leading in any common change. That is what I assume I should be looking for.
The question of natural versus unnatural variability is the whole ball of wax isn’t it. I have read your discussions about step change and ENSO, but it looks like I will have to study your other articles as well. Thanks, great food for thought.
Oh one last thing. I have one other chart that I find interesting. I know that it is not in your particular area of interest, but do you have an opinion?
Hi CMS: Yup, another good find. The relationship between ENSO and annual variations in CO2 is discussed in a number of papers. For example:
L\According to the link you provided, It looks more like a question of changes in upwelling of deep layers than change of solubility due to temperature. I graphed it against PDO and seem like a reasonable correlation. I have a question about the step function and ENSO. While ENSO seems to be some kind of equilibrium mechanism, what accounts for the step change itself. It would suggest a non linear reaction, which of course I assume is part of a larger equilibrium process. Do you have a theory why we have a step up at this point rather than a continuation of the previous regime. I guess the question comes down to what was special about 1998. I imagine you have covered this somewhere in your posts, but if you would be kind enough to give me a link…
Anyway kind of you to take the time to respond to my questions.
CMS: The step functions are basically caused by the leftover warm water from strong El Nino events. La Nina and El Nino events act as a chaotic recharge-discharge oscillator, with La Ninas acting as the recharge mode and El Ninos acting as the discharge.
During an El Nino, the warm water from below the surface of the west Pacific Warm Pool sloshes into the eastern tropical Pacific and spreads across the surface. During the decay of the El Nino, the warm water sloshes back to the west where it remains on the surface. That leftover warm water counteracts the effects of the trailing La Nina on remote ocean basins like the North Atlantic, so that it doesn’t cool proportionally during the La Nina–hence the upward shifts in the sea surface temperatures of the Atlantic, Indian and West Pacific oceans.
There’s more info here [42MB]:
Click to access the-manmade-global-warming-challenge.pdf
Would it be incorrect to assume in times when La Niña predominates that the opposite process occurs?
CMS: If your question is related to downward shifts, we haven’t seen those yet.
However, the East Pacific data shows slight cooling if it’s corrected for volcanic aerosols.
Note also that the South Atlantic-Indian-West Pacific also shows cooling between the strong El Ninos–or without the strong El Ninos, that region would have cooled:
That leaves us with the North Atlantic, which has the AMO.
Thanks a lot, I appreciate the time and effort, not only that you have spent answering my questions, but for your substantial contribution to all those who are interested in the question of Global Warming.