Arguments
What has global warming done since 1998?
What the science says...
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The planet has continued to accumulate heat since 1998 - global warming is still happening. Nevertheless, surface temperatures show much internal variability due to heat exchange between the ocean and atmosphere. 1998 was an unusually hot year due to a strong El Nino. |
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Climate Myth...
It hasn't warmed since 1998
For the years 1998-2005, temperature did not increase. This period coincides with society's continued pumping of more CO2 into the atmosphere. (Bob Carter)
To claim global warming stopped in 1998 overlooks one simple physical reality - the land and atmosphere are just a small fraction of the Earth's climate (albeit the part we inhabit). 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.
This analysis is performed in An observationally based energy balance for the Earth since 1950 (Murphy et al. 2009) which adds up heat content from the ocean, atmosphere, land and ice. To calculate the Earth's total heat content, the authors used data of ocean heat content from the upper 700 metres. They included heat content from deeper waters down to 3000 metres depth. They computed atmospheric heat content using the surface temperature record and the heat capacity of the troposphere. Land and ice heat content (the energy required to melt ice) were also included.
Figure 1: Total Earth Heat Content anomaly from 1950 (Murphy et al. 2009). Ocean data taken from Domingues et al. 2008. Land + Atmosphere includes the heat absorbed to melt ice.
Nuccitelli et al. (2012) arrived at a similar conclusion with more recent and updated data (Figure 2).
Figure 2: Land, atmosphere, and ice heating (red), 0-700 meter OHC increase (light blue), 700-2,000 meter OHC increase (dark blue). From Nuccitelli et al. (2012).
A look at the Earth's total heat content clearly shows global warming has continued past 1998. The planet is still accumulating heat. So why do surface temperature records show 1998 as the hottest year on record? We see in Figure 1 that the heat capacity of the land and atmosphere is small compared to the ocean. More than 90% of global warming heat goes into warming the oceans, while less than 3% goes into increasing the surface air temperature. Hence, relatively small exchanges of heat between the atmosphere and ocean can cause significant changes in surface temperature.
In 1998, an abnormally strong El Nino caused heat transfer from the Pacific Ocean to the atmosphere. Consequently, we experienced above average surface temperatures. Conversely, the last few years have seen moderate La Nina conditions which had a cooling effect on global temperatures. And the last few months have swung back to warmer El Nino conditions. This has coincided with the warmest June-August sea surface temperatures on record. This internal variation where heat is shuffled around our climate is the reason why surface temperature is such a noisy signal.
Using moving averages to discern the long-term trend
With so much internal variability, scientists employ statistical methods to discern long-term trends in surface temperature. The easiest way to remove short-term variations, revealing any underlying trend, is to plot a moving average, performed in Waiting for Cooling (Fawcett & Jones 2008) . Figure 3 displays the 11-year moving average - an average calculated over the year itself and five years either side. They've used three different data-sets - NCDC, NASA GISS and the British HadCRUT3. In all three data-sets, the moving average shows no sign that the warming trend has reversed.
Figure 3: Globally-averaged annual mean temperature anomalies in degrees Celsius, together with 11-year unweighted moving averages (solid lines). Blue circles from the Hadley Centre (British). Red diamonds from NASA GISS. Green squares from NOAA NCDC. NASA GISS and NOAA NCDC are offset in vertical direction by increments of 0.5°C for visual clarity.
The linear trend since 1997 or 1998
Next, Fawcett and Jones look for a cooling trend in the 10 years since 1998. They find the linear trend over 1998 to 2007 is a warming trend in all three data-sets. Note that HadCRUT3 displays less warming than NASA GISS and NCDC. This is most likely due to the fact that HadCRUT data doesn't cover parts of the Arctic where there has been strong warming in recent years.
Figure 4: Linear trends (solid lines) in the three global annual mean temperature anomaly time series over the decade 1998-2007.
Cowtan & Way (2013) also evaluates global surface warming across the globe by using a statistical method known as 'kriging' andby using satellite data to fill in the gaps where there are no temperature stations. Their study shows that the global surface warming trend for 1997–2012 is approximatley 0.11 to 0.12°C per decade.
Removing the El Niño signal from the temperature record
The reason that 1998 was such an anomalously warm year was due to a strong El Niño that year. Fawcett and Jones remove the El Niño Southern Oscillation (ENSO) signal by calculating a linear regression of global temperatures against the Southern Oscillation Index. A detailed description of the process is found in Fawcett 2007. The result is shown in Figure 5.
Figure 5: Three time series of globally-averaged annual mean temperature anomalies (circles) in degrees Celsius, together with ENSO-adjusted versions (lines), for the period 1910-2007.
All 3 data sets demonstrate that the anomalously hot 1998 was due to the strong El Niño of 1997/98. When ENSO-adjusted, 1998 looks much less remarkable than it does in the original data. In all 3 ENSO-adjusted data-sets, 2006 is the hottest year on record and the trend from 1998 to 2007 is that of warming.
Removing other Exogeneous Factors
In addition to removing the ENSO signlal, Foster and Rahmstorf (2011) used multiple linear regression to remove the effects of solar and volcanic activity from the surface and lower troposphere temperature data. Their results are shown in Figure 6.
Figure 6: Average of all five data sets (GISS, NCDC, HadCRU, UAH, and RSS) with the effects of ENSO, solar irradiance, and volcanic emissions removed (Foster and Rahmstorf 2011)
When removing these short-term effects, the warming trend has barely even slowed since 1998 (0.163°C per decade from 1979 through 2010, vs. 0.155°C per decade from 1998 through 2010, and 0.187°C per decade for 2000 through 2010).
Is 1998 actually the hottest year on record?
Of the three surface temperature records (HadCRUT3, NASA GISS, and NCDC), only HadCRUT3 actually shows 1998 as the hottest year on record. For NASA GISS and NCDC, the hottest year on record is 2005. A new independent analysis of the HadCRUT record sheds light on this discrepancy. The analysis is by the European Centre for Medium-Range Weather Forecasts (ECMWF) who calculated global temperature, utilizing a range of sources including surface temperature measurements, satellites, radiosondes, ships and buoys. They found warming has been higher than that shown by HadCRUT. This is because HadCRUT is sampling regions that have exhibited less change, on average, than the entire globe.
Figure 7 shows the regions that HadCRUT have sampled compared to the regions ECMWF included in their dataset. The ECMWF analysis shows that in data-sparse regions such as Russia, Africa and Canada, there is strong warming over land that is not included in the HadCRUT's sampling data. This leads the ECMWF to infer with high confidence that the HadCRUT record is at the lower end of likely warming.
Figure 7: Increase in mean near-surface temperature (°C) from (1989-98) to (1999-2008). Top figure shows HadCRUT sampling regions, lower figure shows ECMWF analysis (ECMWF 2009).
This result is not unexpected. NASA GISS find a major contributor to the record hot 2005 is the extreme warming in the Arctic (Hansen 2006). As there are few meteorological stations in the Arctic, NASA extrapolated temperature anomalies from the nearest measurement stations. They found the estimated strong Arctic warmth was consistent with infrared satellite measurements and record low sea ice concentrations.
Figure 8: Surface temperature anomaly for the first half-decade of the 21st century (Hansen 2006).
Intermediate rebuttal written by dana1981
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 4 October 2015 by pattimer. View Archives
Further I presume that you used least-squares to fit the line. This assumes that temperature anomalies are normally distributed. Glancing at the graph, this doesn't seem to be the case (several major excursions from the mean trend line), so the outliers will unduly influence the line of best fit. Least squares is extremely non-robust to non-normal data.
The second graph doesn't help your argument much, and might actually hinder it some. If you could send me or point me to the raw data, I'd be happy to do a different analysis on it and see if there is a meaningful trend in the data.
http://tamino.wordpress.com/2007/08/31/garbage-is-forever/
The strong version of Carter's claim that warming stopped in 1998 requires the slope to be zero or negative since then. It isn't, therefore the strong version is proven false (and the 60 individuals who signed that have demonstrated their commitment to ideology over data). Even the weak version ('no significant warming') is shown false.
The data above does not match the data set he is using.
Based on the global surface record compiled by the Hadley Centre and the global UAH satellite record there has been warming over the past decade.
http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3vgl.txt
http://vortex.nsstc.uah.edu/data/msu/t2lt/tltglhmam_5.2
Plotting the two temperature records for the last 10 years shows that:
· The surface record showed a linear increase of 0.062 degrees C per decade
· The satellite record showed a linear increase of 0.059 degrees C per decade
The two warmest years during this period were 1998 (a strong ENSO year) and 2005 (a somewhat weaker ENSO year).
Both of these rates of increase are considerably lower than the average rate of increase over the past 28 years, when satellite readings first became available:
· The surface record showed a linear increase of 0.171 degrees C per decade
· The satellite record showed a linear increase of 0.142 degrees C per decade
Interestingly, both years were predicted to be “record warm” years, with the usual media hype about this being additional proof of alarming global warming caused by man.
Both turned out to be rather normal years, but there was not much media hype, since (as we all know) “good news is no news”.
But as I showed earlier, if we compare the past decade we see that there is still warming, but that the rate has slowed down considerably in comparison with the earlier record.
Sure, there are two ENSO years in the record, 1998 and 2005 (which also turn out to be the two warmest years). But, then again, there will always be ENSO years and scientists have been unable to predict when these will occur or explain exactly why they occur when they do.
The question that this site raised should not have been whether or not it has warmed since 1998 but rather whether or not the rate of warming has decreased since 1998 as compared to earlier decades, and if so, whether or not this indicates a trend of slowdown in temperature increase or just an anomaly caused by individual ENSO years.
From a recent Reuters' piece: "Rajenda Pachauri, the head of the U.N. Panel that shared the 2007 Nobel Peace Prize with former U.S. Vice President Al Gore, said he would look into the apparent temperature plateau so far this century.
"One would really have to see on the basis of some analysis what this really represents," he told Reuters, adding "are there natural factors compensating?" for increases in greenhouse gases from human activities."
Source: http://tinyurl.com/3doxvc
And then the Met office. They recently issued a forecast for 2008, stating this much: "The forecast value for 2008 mean temperature is considered indistinguishable from any of the years 2001-2007, given the uncertainties in the data." Source: http://tinyurl.com/2ezepk
So, the IPCC is looking into "the plateau", and the Met Office says it persists into its' eight year, and who knows, after another eight years it may be very very cold again. Over at Tamino's Open mind there was some discussion about whether we should set 2015 as the year when the science could be declared settled;-). But the details seem to take some time to agree upon. The problem with outliers!
Anyhow we can conclude than since prior to Pinatabu there has been no statistically significant warming trend (its all within error bounds).
Now how much was the upper projection of the IPCC? +6°C to the year 2100. From now on that roughly means at least five times the warming rate we've seen so far since satellite measurements began and more than ten times the warming rate since we started to increase our CO2 emissions (around 1940-45). That anyone can believe this without the IPCC presenting any evidence at all is flabbergasting to be honest.
I'll admit that there is a risk (albeit minor IMHO) for a two degree warming, but such a risk you handle differently and you certainly won't scare children nor keep people in poverty because of it.
Sulphur aerosols from China?
http://jhubert.livejournal.com/181274.html
"A simple mathematical calculation of the temperature change over the latest decade (1998-2007) alone shows a continued warming of 0.1 °C per decade."
http://www.metoffice.gov.uk/corporate/pressoffice/myths/2.html
"A simple mathematical calculation of the temperature change over the latest decade (1998-2007) alone shows a continued warming of 0.1 °C per decade."
http://www.metoffice.gov.uk/corporate/pressoffice/myths/2.html
"A simple mathematical calculation of the temperature change over the latest decade (1998-2007) alone shows a continued warming of 0.1 °C per decade."
http://www.metoffice.gov.uk/corporate/pressoffice/myths/2.html
The average for the first 5 months of 2008 is 0.16°C colder according to Hadley's HADcrut3, and 0.10°C colder according to NOAA while the atmospheric carbon dioxide level continues its rise. Climate history shows that added atmospheric carbon dioxide has not had any significant influence on average global temperature. See graphs of NOAA and other credible data (all with source websites given) at http://www.middlebury.net/op-ed/pangburn.html at four different time scales up to 150,000 ybp.
" they strain out gnats and swallow camels..."
THE current estimated GMT (actual) is 14C.
The anomaly 1970 -2008 is around +0.55C which as a linear trend is +0.18/decade.
If that trend continues in a linear fashion, then by 2108 the GMT will be 15.8C assuming all other things remain equal.
Not impressed.
It is unclear how the calculation at 15 was made. NOAA data is available at LINK and Hadley data at http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt . These both show a trend of about +0.1 degree per decade. Although short term trends can be misleading, like the 22 year run up from 1976 to 1998, the dramatic drop of global average temperature in 2008 may be indicative of a change in character of the climate. The current UAH satellite numerical data (these data consist of the differences of lower atmospheric temperature from the 1979 thru 1998 average) is at http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt . According to these data, the AVERAGE GLOBAL TEMPERATURE for the first 9 months of 2008 is LOWER than the average from 2000 thru 2007 by an amount equal to 43.1% of the total linearized increase (NOAA data) during the 20th century. Since 2000, the CARBON DIOXIDE LEVEL HAS INCREASED by 14.4% of the total increase since the start of the Industrial Revolution.
http://reallyrealclimate.blogspot.com/2008/10/updated-11-year-global-temp-anomoly.html
Double click the chart to enlarge it.
Also, when we correct for ENSO, the temperature trend remains virtually flat. Here is a chart comparing raw HadCrut3 with ENSO corrected HadCrut3.
http://reallyrealclimate.blogspot.com/2008/07/gavin-schmidt-enso-adjustment-for.html
As you can see, there is virtually no difference. The period in question had 7 ENSO event. 4 were El Ninos and 3 were La Ninas. Taken together they had almost no effect on the trend line.
Yes and it's always GISS data used by the alarmists.
1. I am intrigued by the slant, depending on the POV. Ie, if the temp is trending up, it is the result of manmade causes. However, a cold year (2008) is the result of natural causes (La Nina). Hmmm...
2. I'd be interested to see the variation in measuring points over the years, to confirm or reject the notion that some of the warming is due to the removal of Siberian monitoring stations after the USSR disintegration.
3. Looking at the charts for the last 10 or so years, it seems the warming is mostly concentrated in the far northern hemisphere. Would be interesting to see how that is explained.
Also theWags has a valid point I raised some time ago...namely that the number of stations collecting data has declined alarmingly over the last 20 years, so we should be asking whether these graphs are truly representative of the global condition. See
http://www.uoguelph.ca/~rmckitri/research/nvst.html
for a graph of stations vs temperature. It also appears that too many of the remaining stations are in the US for a realistic sampling.
Thanks again for a great site.
I think it is a bit disingenuous to use surface based temperature graphs rather than sattelite based ones. There is a new paper from one Arno Arak who claims that hte sattelites show no warming when measured to Dec 08. Is there anywhere this is refuted.
Shane
S
The far north has a couple of geologoc features that never seem to be talked about. The midatlantic ridge does not stop in the north atlantic but continues on under the Arctic ice pack. A paper last year stated that the activity had increased and that the ridge was spreading faster. The subduction zones are along the northern faces of Greenland to Alaska. So naturally the northernmost zones are showing increased volcanism. With all this increased tectonic activity I would expect major climate change at the north polar region. I truely can't understand why the IPCC has not taken this into account.
who is scaring children, or keeping anyone in poverty?
first of all, the only thing we should be able to agree on, is that virtually nothing has been done so far to actually slow down climate change. for every Prius added to the road (which still runs entirely on fossil fuel), there's another new SUV. we've been talking about this issue, but doing virtually nothing.
where are the scared children? the younger generation is growing up with the same over-consumption habits as the older generations.
and who is "kept in poverty" by climate change science? an analysis of the recent proposed climate bill (going through the US house of reps) is that it would cost the average US family (not person) $175/yr by 2020. how does that amount keep anyone in poverty?
who is going to be "kept in poverty" if we do nothing are the poorest countries in the world, that already struggle to find enough water, and grow enough food, to meet demand. it's those countries that will be hardest hit by higher temperatures, not the cooler, wealthier northern powers. they'll be kept in poverty by those who refuse to act on climate change. not the other way around.
please don't twist the argument to make it seem like the skeptics are the ones standing up for the poor.
As the atmospheric carbon dioxide level continues to increase and the average global temperature doesn’t it is becoming more and more apparent that many Climate Scientists have made an egregious mistake and a whole lot of people have been misled.
" Global temperatures" ) there appears to have been little or no global warming since about 2003.
Observations based on the various graphs show according to my "eyeballed" interpretation :
University of Alabama data - No warming since 2003.
RSS - No warming since 2003
Hadcrut3 - No warming since 2003
NCDC - no warming since 2003
GISS - no warming since 2003
The temperature data on these graphs show a flat or declining trend from 2003 to the present. By "flat" I mean varying within less than say 0.05 of a degree from 2003 to 2007, which I would argue is well within the accuracy with which we can measure the global temperature of the Earth. Also bearing in mind that we are supposedly talking about and looking for the IPCC"s "catastrophic" global warming trend here. After 2007, the global temperatures as shown on these graphs seem to decline more abruptly.
Now my questions are: does anyone disagree with the data and trends shown on these graphs ? Does anyone disagree with my observations - and why ?
I note also that the graph posted above ( figure 2 ) also shows a flat temperature trend since 2002.
I would have expected the gradient to be related to the concentration of GG's and thus increase more in later years??
i guess you refer to fig.1. The paper from which it is taken is an observational study, they measured the actual heat content of the oceans. Consequently the latent heat of evaporation of sea water as well as all the other energy related effects are automatically included.
I am fully on board with the argument that most of the heat is stored in the ocean, and that the atmosphere has a noisy temperature signal. However what I do not understand is the sharp drops in total energy content, for example around 1968 and 1996. Given constant or slowly rising CO2 concentration and the coean heat reservoir with a large time constant, I would have expected (naively perhaps) some monotonously rising function for total heat content.
Have any explanations been proposed?
Ocean temperature has decreased since 2003. See R.A. Pielke, Sr., Physics Today, 94, Nov. (2008). which contains this graph: LINK
Actually, the oceans have been warming since 2003. Observations of upper ocean heat show some short term cooling but measurements to greater depths (down to 2000 metres) show a steady warming trend:
However, the ocean cooling myth does seem to be widespread so I'll shortly update this page to clarify the issue.
Look at this link for information on global warming stagnation since 2002: LINK The site is run by Ole Humlum, Professor of Physical Geography at the Department of Geosciences, University of Oslo. He says that "all five global temperature estimates presently show stagnation, at least since 2002. There has been no increase in global air temperature since 1998, which was affected by the oceanographic El Niño event. This does not exclude the possibility that global temperatures will begin to increase again later. On the other hand, it also remain a possibility that Earth just now is passing a temperature peak, and that global temperatures will begin to decrease within the coming 5-10 years. Only time will show which of these possibilities is the correct."
temperature is not global warming, the trend in temperature is. And, as will be repeated over and over, short term trends has no meaning whatsoever, even just statistically. Look critically at the data shown, ask for the uncertainty in the determination of the trends, look at the determination coefficient (whre shown).
And take care, making hypothesis is easy untill you confront them with the known science. Any claim need to be justified quantitatively, which i can't see in the link you posted. Remember, climate change has (don't know why) a strong emotional impact on people, both "alarmists" and "deniers". The most conservative choice is stick to an expert advice, from climatologists; it's the very same thing we all do in our daily lives.
Climategate U-turn as scientist at centre of row admits: There has been no global warming since 1995 http://tr.im/O7vd
How can it be both?
Try as the Mail did to spin the interview, there's really not much there.
Here's the part I found most shocking:
"Discussing the interview, the BBC’s environmental analyst Roger Harrabin said he had spoken to colleagues of Professor Jones who had told him that his strengths included integrity and doggedness but not record-keeping and office tidying."
Tut-tut. Lots of integrity but he can't keep his office tidy. Surely he must go.
Vince, what say you to the graph in #40, here?
"Question - Do you agree that from 1995 to the present there has been no statistically-significant global warming
Answer - Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods. "
So, once again, at the Daily Mail they showed that they do not understand science but unrelentlessly continue to misguide they readers.
"Did global warming stop in 1998?" Did global warming START in 1998? U.S. Data Since 1895 Fail To Show Warming Trend LINK WASHINGTON, Jan. 25— After examining climate data extending back nearly 100 years, a team of Government scientists has concluded that there has been no significant change in average temperatures or rainfall in the United States over that entire period. While the nation's weather in individual years or even for periods of years has been hotter or cooler and drier or wetter than in other periods, the new study shows that over the last century there has been no trend in one direction or another. The study, made by scientists for the National Oceanic and Atmospheric Administration was published in the current issue of Geophysical Research Letters. It is based on temperature and precipitation readings taken at weather stations around the country from 1895 to 1987. ...
21 years ago that was the latest news. Almost quaint, but for some reason it's finding a lot of currency in the past few weeks. Here's some more of that same article, helping to provide full context:
"Dr. Kirby Hanson, the meteorologist who led the study, said in a telephone interview that the findings concerning the United States do not necessarily ''cast doubt'' on previous findings of a worldwide trend toward warmer temperatures, nor do they have a bearing one way or another on the theory that a buildup of pollutants is acting like a greenhouse and causing global warming. He said that the United States occupies only a small percentage of Earth's surface and that the new findings may be the result of regional variations.
...
Dr. Hanson of NOAA said today that the new study does not in any way contradict the findings reported by the NASA scientists and others. He said that his study, in which he was joined by George A. Maul and Thomas A. Karl, also of NOAA, looked at only the 48 contiguous states.
Dr. Hanson said that global warming caused by the greenhouse effect might have been countered by some cooling phenomenon that has not yet been identified and that the readings in his study recorded the net effect.
''We have to be careful about interpreting things like this,'' he said.
One aspect of the study that Dr. Hanson said was interesting was the finding that the urbanization of the United States has apparently not had a statistically significant effect on average temperature readings. A number of scientists have theorized that the replacement of forests and pastures by asphalt streets and concrete buildings, which retain heat, is an important cause of rising temperatures.
Dr. Hansen of NASA said today that he had ''no quarrel'' with the findings in the new study. He noted that the United States covered only 1.5 percent of Earth. ''If you have only one degree warming on a global average, how much do you get at random'' when taking measurements in such a relatively small area, he asked rhetorically.
''We are just arguing now about whether the global warming effect is large enough to see,'' he added. ''It is not suprising we are not seeing it in a region that covers only 1.5 percent of the globe.''
Actually, the new ocean temperature buoy system (ARGO) does show that it's the sea that is storing up heat. The following is the measurement of ocean heat measured by ARGO down to 2000 metres deep and shows the oceans are steadily accumulating heat (von Schuckmann 2009):
Apologies for repeating the same graph from my response to comment #40 but it seems repetition is required for this particular argument.