One of the most frequent contrarian and denialist myths is that the Earth is now cooling. The commenters usually use 1998, the peak of an unusually powerful El Niño, as the starting point for a trend, asserting that temperatures have not been rising since then. Their myth does not stand up to scrutiny from the evidence. Visit the Temperatures page for detail. This is a quick summary.
It is important to distinguish between short-term natural variability and long-term rise. There are fluctuations in global average temperature, driven in large part by the oceans, and the transition points around 1910, 1940 and 1970 are likely shifts in decadal natural variability; the flattening of temperatures since about 2000 may also be such a transition but it in no way negates the long-term monotonically increasing and accelerating rise in temperatures attributed to human causes, especially the burning of fossil fuels and deforestation. See the PNAS 2009-09-14 article cited below for details about decadal variability.
From Peter Sinclair’s “Climate Denial Crock of the Week”: Party like it’s 1998 – cherry picking temperature statistics and 1998 Revisited
One of the enduring myths of climate denialism is that global warming stopped sometime in the last decade. I see it in the blaring headlines of pseudoscience websites, in comments on my videos, even some of our most distinguished journalists have been taken in.
WASHINGTON — A new analysis of global surface temperatures by NASA scientists finds the past year was tied for the second warmest since 1880. In the Southern Hemisphere, 2009 was the warmest year on record.
Although 2008 was the coolest year of the decade because of a strong La Nina that cooled the tropical Pacific Ocean, 2009 saw a return to a near-record global temperatures as the La Nina diminished, according to the new analysis by NASA’s Goddard Institute for Space Studies (GISS) in New York. The past year was a small fraction of a degree cooler than 2005, the warmest on record, putting 2009 in a virtual tie with a cluster of other years –1998, 2002, 2003, 2006, and 2007 — for the second warmest on record.
“There’s always interest in the annual temperature numbers and a given year’s ranking, but the ranking often misses the point,” said James Hansen, GISS director. “There’s substantial year-to-year variability of global temperature caused by the tropical El Nino-La Nina cycle. When we average temperature over five or ten years to minimize that variability, we find global warming is continuing unabated.“
From “SkepticalScience”, 28 Sep. 2009: How we know global warming is still happening
Skeptics proclaim that global warming stopped in 1998. That we’re now experiencing global cooling. However, these arguments overlook one simple physical reality – the land and atmosphere are only one small fraction of the Earth’s climate (albeit the part we inhabit). Global warming is by definition global. The entire planet is accumulating heat due to an energy imbalance. The atmosphere is warming. Oceans are accumulating energy. Land absorbs energy and ice absorbs heat to melt. To get the full picture on global warming, you need to view the Earth’s entire heat content. …
From “RealClimate”, 18 Jul. 2009: Warming, interrupted: Much ado about natural variability
A guest commentary by Kyle Swanson – University of Wisconsin-Milwaukee
I am quite humbled by the interest that has been generated by our paper “Has the climate recently shifted?” (Swanson and Tsonis, 2009), and would like the thank the RealClimate editors for the opportunity to give my perspective on this piece.
PNAS: Long-term natural variability and 20th century climate change , doi: 10.1073/pnas.0908699106; Swanson, Sugihara and Tsonis
Global mean temperature at the Earth’s surface responds both to externally imposed forcings, such as those arising from anthropogenic greenhouse gases, as well as to natural modes of variability internal to the climate system. Variability associated with these latter processes, generally referred to as natural long-term climate variability, arises primarily from changes in oceanic circulation. Here we present a technique that objectively identifies the component of inter-decadal global mean surface temperature attributable to natural long-term climate variability. Removal of that hidden variability from the actual observed global mean surface temperature record delineates the externally forced climate signal, which is monotonic, accelerating warming during the 20th century.
Supporting Information (pdf)
In the hotly debated arena of global climate change, using short-term trends that show little temperature change or even slight cooling to refute global warming is misleading, write two climate experts in a paper recently published by the American Geophysical Union — especially as the long-term pattern clearly shows human activities are causing the earth’s climate to heat up.
In their paper “Is the climate warming or cooling?” David R. Easterling of the National Oceanographic and Atmospheric Administration’s National Climatic Data Center and Michael Wehner of the Computational Research Division at the Department of Energy’s (DOE) Lawrence Berkeley National Laboratory note that a number of publications, websites and blogs often cite decade-long climate trends, such as that from 1998-2008, in which the earth’s average temperature actually dropped slightly, as evidence that the global climate is actually cooling.
However, Easterling and Wehner write, the reality of the climate system is that, due to natural climate variability, it is entirely possible, even likely, to have a period as long as a decade or two of “cooling” superimposed on the longer-term warming trend. The problem with citing such short-term cooling trends is that it can mislead decision-makers into thinking that climate change does not warrant immediate action. The article was published April 25 in Geophysical Research Letters. …
Journal Reference: David R. Easterling, Michael F. Wehner. Is the climate warming or cooling? Geophys. Res. Lett., 2009; 36: L08706 DOI: 10.1029/2009GL037810
Have you heard that the world is now cooling instead of warming? You may have seen some news reports on the Internet or heard about it from a provocative new book.
Only one problem: It’s not true, according to several independent statisticians who analyzed temperature data for The Associated Press.
The following graphs show the NOAA NCDC Global Temperature Anomalies with a 30-year running average since 1880 (monthly values showing the prior 360 months). Climate is defined by the WMO as fitting into 30-year windows, so this is a reasonable climate summary, filtering out the noise of “weather”. Land, ocean and combined (both) temperatures are shown and it is clear that land mass temperatures show more rapid change, as expected. Click on the graph for a full-sized image.
The following shows NOAA global (land and ocean combined) temperature anomalies. The value shown for each month is the 12-month running average for the prior twelve months, filtering and smoothing annual seasonal variations. There are three linear least square fits to the data for the decades of the 1980’s, 1990’s and 2000’s.
It is very clear, however, that choosing 1998 as the starting point for a trend analysis is a fine example of biased “cherry-picking”; the 1998 El Nino was uncharacteristically strong, a weather phenomenon, not a major indication of climate change. While there does appear to be a leveling off since 2002, it is no more significant than decreases previously seen in 1984, 1989, 1991, 1996 and 1999. The long-term trend is still upward, getting warmer, although the pace has slowed a little recently. There are indications that the recent slowdown may be due to a prolonged La Nina and to increasing aerosols (e.g., the “Atmospheric Brown Clouds” generated from south and east Asia). There is also a weaker hypothesis, without any backing evidence so far, that the current solar sunspot minimum might have an overall cooling effect. Click on the graph for a full-sized image.
From “RealClimate”, 18 Nov. 2008: Mind the Gap!
Confusion has continued regarding trends in global temperatures. The misconception ‘the global warming has stopped’ still lives on in some minds. We have already discussed why this argument is flawed. So why have we failed to convince ;-) ? The confused argument hinges on one data set – the HadCRUT 3V – which is only one of several estimates, and it is the global temperature record that exhibits the least change over the last decade. Other temperature analyses suggest greater change (warming). Thus, one could argue that the HadCRUT 3V represents the lower estimate, if a warming could be defined for such a short interval. …
Another issue is that some of the data – i.e. the data from the Climate Research Unit (CRU) – have incomplete coverage, with large gaps in the Arctic where other data suggest the greatest increases in temperature.
The incentive leading to the creation of this page was to react to disinformation expressed in a Globe and Mail commentary on 12 April 2009. “Eyes Wide Open” and “GlynnMhor of Skywall” had claimed that we are now in a cooling trend. I pointed them to this page and received replies accusing me of slander and asking for an apology, based on an argument from “George Fish” that a recent paper by Swanson and Tsonis supported the view that “Even alarmists are admiting that the earth is now cooling while trying to explain why that still means the end of the world is coming. “Eyes Wide Open” also responded accusing me of presenting just “more of your bull and chicanery” here and stating that I couldn’t “hide the fact that temperatures peaked in 1998 and are now on a significant cooling trend”. He then offered a link to this graph:
I replied to his comment: “Eyes Wide Open, you’ve attempted to make a statement about the entire world by referring us to southern hemisphere sea surface temperatures and global sea surface temperatures, not the global combination of land and sea. You’ll see continued rising temperatures quite clearly from the measurements indicated on my “Temperatures” page, showing a wide range of presentations, including land, ocean, satellite, hemispheric and global temperatures, with varying degrees of temporal focus and trend analysis. The reality is there, available for download and independent verification and analysis.”.
Accused of chicanery by him, I replied “Eyes Wide open, the chicanery is yours – using your same source, here are the global surface and lower tropospheric temperatures and trends since 1980“, pointing him to this graph from his chosen site:
Referring back to the allegation about Swanson and Tsonis, I commented:
No George Fish, there was no slander, there will be no apology since none is justified and the Swanson and Tsonis paper does not refute warming:
With all due respect… The “global warming stopped” meme is particularly lame since it relies on both a feigned ignorance of the statistics of short periods and being careful about which data set you use. It also requires cherry-picking the start year, had the period been “exactly a decade” or 12 years then all the trends are positive. The use of the recent Swanson and Tsonis paper is simply opportunism. Those authors specifically state that their results are not in any way contradictory with the idea of a long term global warming trend. Instead they are attempting to characterise the internal variability that everyone knows exists.
Quoting from the Swanson and Tsonis paper: Of course, it is purely speculative to presume that the global mean temperature will remain near current levels for such an extended period of time. Moreover, we caution that the shifts described here are presumably superimposed upon a long term warming trend due to anthropogenic forcing.
Not surprisingly, George Fish responded with denial, stating “Bottom line: we are cooling get over it.” and pointing to the following graph, contained in an article titled “Tropospheric Temperature Trends for March” at “The Blackboard” calling it a “better analysis”:
Neither he nor the author at The Blackboard seems to understand Uncertainty, noise and the art of model-data comparison, referring to short term weather variability in comparison to long term climate change.
Update: 12 June 2009
“Eyes Wide Open” continues in Globe and Mail commentary to misrepresent temperature data, most recently related to an article titled Reefs collapse across Caribbean, study says , which describes how climate change is devastating coral reefs. He attempts to refute the influence of temperature change by commenting that the average sea surface temperature anomaly for the last six months (up to the end of April 2009) reported by the Hadley Climate Research Unit (CRU) was 0.2545 degrees C; he then goes on to state some past numbers.
“As per Hadley Centre, from 1939 to 1945 64.3% of the time the temperature anomaly was within 0.25 degrees of the figure above. From 1876 to 1877 45.8% of the months were within 0.25 degrees of that figure. Some extreme change!“
I asked for the source of his data, commenting that the numbers didn’t seem to agree with the NOAA data. He provided a link to the data, I downloaded them and have performed some simple analysis which demonstrates his chicanery. The following is taken from the parent page for the data:
Following my own analysis, I responded to him saying:
“Eyes Wide Open, I’ve done a preliminary analysis of the Hadley sea surface temperatures, highlighted in your posting at 6/10/2009 8:57:47 PM, and it is abundantly clear that you have carefully cherry-picked your data points, reaching a very misleading conclusion. I have graphed the data with running 6-month and 12-month averages (the latter to minimize seasonal variation) and it is very clear that there is a continuing long-term rise and that your chosen data point are at previous very unusual high points, most likely periods of uncharacteristic activity. … In short, you have seriously misrepresented the reality; I’m not surprised, given your past record here.“.
Gee Alan, more shonk analysis on your part. You certainly like to try and waste everyone’s time don’t you? You missed the point completely! Here you are ranting on about unprecedented, rapid change blah, blah, blah! The fact is that temperatures go up, temperatures go down and the reefs are still with us (although threatened by REAL threats such as mechanized fishing, underwater tourism, etc.).
Certainly there are other threats to coral reefs than temperature change but his argument misses the mark because it ignores the fact that with a rising average, there will be higher extremes, in this case probably the detrmining factor, and the pace of change is very likely unprecedented, reducing the ability of the corals to adapt to the changing conditions. Later in the commentary (6/11/2009 9:12:29 PM), “E. Baqeiro” identified a paper describing the increasing influence of a parasite of the “Queen conch” correlated to temperature increase. [Baqueiro Cárdenas, E., L. Frenkiel, A. Zetína Zarate and D. Aldana Aranda. 2007. Coccidian (Apicomplexa) parasite infecting Strombus gigas Linné, 1758 Digestive gland. Journal of shellfish research 34 (1); 4-8]. Clearly temperature does have a strong influence in reef biological degradation and “Eyes Wide Open” is continuing his campaign of disinformation.
The following graph, showing a 12-month sliding average from the Hadley SST2 data is from the spreadsheet which I used for my analysis. It’s clear that there is a continuing long-term sea surface temperature rise.
Update: 23 Aug. 2009
“GlynnMhor of Skywall” commented on Aug. 22 2009 at 5:53:36 PM with his usual flair for distortion “When was the last time you saw in any media report an actual graph of how temperatures have behaved over the last few decades? They stopped doing that once the temperatures stopped rising, because the data make the alarmist assertions look bad.“
So I decided to have a look at the actual measurements and the trend of the northern and southern hemisphere sea surface temperatures from 1980 to the present. My new temperature figure 26 (below) shows the annual running average (each month averaged over the preceding 12 months to filter out seasonal variations) for both the northern and southern hemispheres. Over that period, the northern oceans warmed at the rate of 0.0164 Celsius degrees per year (with a statistical “goodness of fit” R^2 = 0.7347) and the southern oceans at 0.0075 Celsius degrees per year (R^2 0.5243).
GlynnMhor has insisted that there has been recent cooling (or at least a levelling off) and that is roughly true for the period from about 2001 to 2008, following the unusually strong El Nino of 1998. However, there’s nothing to indicate that this is an unusual departure from natural variability and it is quite clear that both hemispheres have been experiencing a sharp and continuing rise since approximately the beginning of 2008. Eat your words GlynnMhor.