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NOAA: North American 2008 Cooling Attributed to Natural Causes

Cooler North American temperatures in 2008 resulted from a strong natural effect, and the overall warming trend that has been observed since 1970 is likely to resume, according to scientists at National Oceanic and Atmospheric Administration (NOAA) and CIRES (Cooperative Institute for Research Environmental Sciences), a cooperative institute of the University of Colorado Boulder and NOAA.

A paper on the study will be published 8 December in the journal Geophysical Research Letters.

Our work shows that there can be cold periods, but that does not mean the end of global warming. The recent coolness was caused by transitory natural factors that temporarily masked the human-caused signal.

—Judith Perlwitz, lead author of the study and a researcher with the Cooperative Institute for Research Environmental Sciences, and NOAA Earth System Research Laboratory

Left side: 1970-2007 trend in annual surface air temperature. Right side: 2008 annual surface air temperature, shown as a departure from the 1971-2000 climatology. Credit: NOAA. Click to enlarge.

Using computer-generated models as well as observations, the team analyzed causes for climate variations in the recent decades. Special emphasis was given to the reasons for North American coolness in 2008. The research is an exercise in climate attribution, a scientific process for identifying the sources of observed climate and weather patterns.

We found that North American coolness resulted from a strong bout of naturally caused cooling in the tropical and northeastern Pacific sea surface temperatures. This illustrates how regional patterns can vary independent of the overall global average. In 2008, global land temperatures were the sixth warmest on record, whereas it was the coldest year in North America since 1996.

—Martin Hoerling, a NOAA meteorologist and co-author

The analysis included historical data and climate model simulations that were conducted in the US and internationally. The science team discerned both natural and human-caused influences for 2008.

North American temperatures would have been considerably colder in 2008 had there been no human-induced warming influence present.

—Judith Perlwitz

The scientists conclude that the North American temperatures are likely to resume increasing again, and do not see the recent coolness as an emerging downward trend.

Our work shows the importance of the role of natural climate variability in temporarily masking or enhancing human-induced climate change. Through diagnosis, we ensure that natural changes, when occurring, are not misunderstood to mean that climate change is either not happening or is happening more intensely than the expected human influence.

—Arun Kumar, a NOAA meteorologist and co-author


  • Perlwitz, J., M. Hoerling, J. Eischeid, T. Xu, and A. Kumar (2009) A strong bout of natural cooling in 2008. Geophys. Res. Lett., in press doi: 10.1029/2009GL041188



Jon Stewart (ie. The Jon Stewart Show) talks about ClimateGate ...very funny!

Aaron Turpen

Since NOAA insists on ignoring satellite-based data and promotes only surface temperature data from, shall we say, questionable locales, I say


I'm really tired of all of these b.s., government-funded "science" experiments using bogus "climate models" based on stuff they don't even understand. Every one of them says "GLOBAL WARMING! AUGHHH! THE SKY IS FALLING! RUN FOR YOUR LIVES! BUY AL GORE'S NEW BOOK!"

Their game is up. I have yet to see ACTUAL data from any of these knobs. According to the satellite data, we stopped warming in 1998 and have been slowly going downward since.

Can we please stop worrying about this boogeyman CO2 crap and start looking at ACTUAL environmental issues now?


I don't give a care how many elite PhD's someone has...if they can't explain something using sound science & the scientific method, why should I blindly trust them to make government policy (tax me and take my freedom away)?


Climate Gate inventors will have a field day.

Who is naive enough to believe that weather-climate changes have to be 100% linear. Large phenomenae like El Nino, La Nina, Sun spots, Volcanos will always have short term effects.

The longer general trend is the important thing to watch. Major worldwide Glaciers are melting down at a much faster rate for the last 30 years and that trend does not reverse with one cooler year in a few areas. That's what the climate gate fabricators should pay attention to.


Ah, so now it's okay to admit that it's cooling naturally. But this doesn't explain the continuing pattern of unethical behavior by the cabal of "climate scientists." ClimateGate has so deeply affected the Earth's biggest nations that China now officially reports it is all a giant hoax:

I'd just like to say this is discouraging for many alarmists who had counted on China as their ally in their war on global warming. Both China and India say fugoffovit!

Harv, here's your answer for the glaciers:


AGW might be happening, but like Jon Stewart said, don't cut corners with the scientific method. Do some real research & experimentation using the scientific more glossing over data, no more fudge factors, no more jumping to conclusions, no more groupthink, no more apocalyptic cult behavior. If you can't use the scientific method for scientific subjects, STFU.


Here's the BBC's report on the Himalayan glaciers:

Search on Climategate for 65M hits. The most viewed story on internet and now (extremely tardy) even the MSM near you.

Chris McCormick

It is a bit odd that Mr. Turpen or Eii, and stating different casses on lack of information/scientific methods etc. There are plenty of peer reviewed science investigations. From satellites (A-train, GRACE, COSMIC, ....) as well as the standard ocean and land and weather balloon data..... If any one of us want to only pick on one summation of one report, then the challenge is neither appropriate nor helpful. It would be better if you read the report, I would contend (hope) that all the peer reviewed/scientific method was followed. Read almost anything, or preferred most of the studies from NCAR and UCAR.


The denialists are relentless.
On my mind are what are their undeclared interests if any.
I was going to add Harvey you don,t mind voicing reason to those who choose to be deaf.
I have heard of people that can reason with a brick.


It is very hard to admit you are wrong. That is the only thing holding back progress on sustainability. The fact that HadCRU Met has admitted failure in their science such that they will now attempt to re-create the temp record for the past 160 years - tells the science story.

It is on this data that ALL three temp records rely and they have acknowledged error. It is on these three records that the theory of AGW CO2 warming exists. Thus the theory is falsified at least until new records can be verified.

If the alarmists wanted to help the poor, form a global government or limit population - they would have done better to be honest and state those goals. Instead they tried to manipulate science to flimflam their agenda on good people. They have been caught and have failed.

It is now up to those who caused these failure to admit their part in the scheme and move on.

Stan Peterson

After all, who wouldn't want us well-meaning, superior human beings and climactic Cassandras to peddle anything but genuine,'natural', 'organic'... Bovine Excrement??


Chris McCormick: Go to the library of any major university and you will find an almost limitless collection of peer-reviewed research articles, on virtually every subject from gonads to quantum physics to the organizational behavior of corporate secretaries. Just because something is peer-reviewed doesn't automatically mean it should be viewed as scientific fact, or that it was even done in accordance with the scientfic method.

Chris McCormick

It is just that people have been claiming that the 'results' are not scientifically based, nor vetted or peer reviewed. I take exception to that; as I am involved in this data/information/knowledge first hand (see for one. I am amazed at the lack of information coming from naysayers with respect to global warming, especially when it is specifically anthropogenic based studies. They often spout some conspiracy, or one world political motivation, or taxes or ...just nonsensical debate style(s). On your comments on 'peer reviewed' vs. scientific facts; it is well understood that science progresses, and, on rare occasions have scientific findings been overturned.

The Goracle



"The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't." - Kevin Trenberth, one of the leading authors of the IPCC report on climate change.

Top "scientists" are claiming that they can't explain what is going on with regard to the ever-changing climate. At the same time we are being told by "scientists" that MASSIVE government programs (loss of freedom and confiscation of income from the people) are needed to "fix" this emergency... Yes, the same emergency that we don't have any proof of and our models/simulations don't fit.

Who, exactly, has the "undeclared interests," as arnold asked about in his/her post?


Chris McCormick

Mr. Goracle- Seems you are only concern of what you would call taxation. Would you assume any environmental regulation bad, if not proved; maybe you were against lead in gasoline, though I do not want to change the subject. I think your information/quote on Dr. Trenberth would be out of context, in that he was referring more to lack of data, and lack of local precisions. The rest of the quote below is below...
"The fact is that we can't account for the lack of warming at the moment and it is a
travesty that we can't. The CERES data published in the August BAMS 09 supplement on
2008 shows there should be even more warming: but the data are surely wrong. Our
observing system is inadequate."
He is not stating that Global warming is not happening, he is looking at a particular CERES data set that he is not content with.



In full context the Doc's statement is no less damning. Why did he not come out and state this in an IPCC report? Or a press release? Or a letter to the editor of any science journal? Or to a convention of "climate scientists?" Or mention it in a talk to his students?? He is stating he's disappointed in his predictions for warming and it is a "travesty."

thanks for the honesty Doc.



Instead of uncritically posting all kinds of links you find on your favourit blogs, you could actually READ some stuff.

The paper is here:"

Vijay Kumar Raina says of his report the following: "This series is meant to serve as a basis for informed ebate and discussion on critical issues related to the environment"

And the conclusion he starts with:
"Glaciers in the Himalayas (India) have been
exhibiting a continuous secular retreat since the
earliest recording began around the middle of the
nineteenth century. Kumdan glaciers, of the Upper
Shyok valley, have been the only exception for their
periodic fluctuations."

Seems he is not really too sure about himself.

And the report jumps from the methodology in chapter 5 right into the conclusion in chapter 6. Where are his data? Where is the program that he used to extract the glacier areas from the satelite images? How did the conclusion follow from the analysis? He talks about the fluctuation of glaciers with an 'Advance phase', 'Quiescent phase' and 'Retreat phase', but never assesses how this affects his research. Could it be that the glaciers which he observed to be stable are actually in their 'Retreat phase' and should be shrinking? We are left guessing.

We are presented with a brief description of the expeditions and a very short description of methodology as the only basis for his conclusions. Conclusions that do not follow from the table in chapter 6, which shows all glaciers LOSING mass over the 1962-2001/2004 period (that's another oddity, the starting year is 1962 and the ending year is 2001-2004. Can I pick one?).

Why don't you go ask *him* to release his data and sources? Oh, I forgot, your skepticism goes only in one direction.

Thomas Lankester

@Aaron Turpen

I think you will find that NOAA use the most accurate and reliable data source. Satellite certainly for sea surface temperatures where the radiance model and the surface type (sea water) are well defined. This is not the case for land surface temperature where the land cover is highly variable. I have been in discussion with Leicester University about the potential for developing monthly composites of land surface temperature (LST) derived from ESA's ENVISAT but issues such as having a global, accurate and up to date land cover map means that on occasions the LST product generates anomalies of up to 6C. Until such LST issues have been resolved, it seem quite prudent for NOAA to stick to ground truth, surface measurements.

Regarding your point that temperatures have declined since 1998, one should point out that as 1998 was the warmest year on record, comparison with any other year (e.g. 1898) would show a drop in temperature. In other words, relative to 1998 any comparison with a later year would show a temperature decrease but comparison with an earlier year would show a tmperature increase. All this proves is that you have correctly identified and carefully selected the warmest year on record. However, it does not shed any light on the effect of the underlying radiative forcing except to illustrate that decadal oscillations of solar intensity and ocean circulation can cause spot temperatures to fluctuate.

I can also add my own non-pertinent observation on short time scale fluctuations:
in comparison to the summer solstice, winter solstice temperatures are lower. Temperatures have actually dropped between summer and winter!

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