AGW: atmospheric physics

[IlarMeilyr]

More braindead clueless nonsense from an idiot. Repeating your cult's myths won't make them real.

Denying reality will not make your cult's bullshit any less dishonest.

Oh, IlieMostly, you're still totally clueless. I don't deny reality, << blather snipped>>.

You just did.

And, you lie incessantly.

You talk about shit you don't even comprehend.

 

[IlarMeilyr]

How much has the globe "warmed" in the past 16 years or so?

 

[MeBelle]

How much has the globe "warmed" in the past 16 years or so?

[ame=http://www.youtube.com/watch?v=pg9YGmmPX6w]Roger Miller "Dang Me" - YouTube[/ame]

 

[RollingThunder]

How much has the globe "warmed" in the past 16 years or so?

Quite a bit, actually. Too bad you're too brainwashed and retarded to comprehend that fact, even when you're shown the data.

Long-Term Global Warming Trend Continues
NASA
January 16, 2013
(NOT UNDER COPYRIGHT - Government publication - free to reproduce)

Scientists at NASA’s Goddard Institute for Space Studies (GISS) say 2012 was the ninth warmest year since 1880, continuing a long-term trend of rising global temperatures. The ten warmest years in the 132-year record have all occurred since 1998. The last year that was cooler than average was 1976.

The map at the top depicts temperature anomalies, or changes, by region in 2012; it does not show absolute temperature. Reds and blues show how much warmer or cooler each area was in 2012 compared to an averaged base period from 1951–1980. For more explanation of how the analysis works, read World of Change: Global Temperatures.

The average temperature in 2012 was about 14.6 degrees Celsius (58.3 degrees Fahrenheit), which is 0.55°C (1.0°F) warmer than the mid-20th century base period. The average global temperature has increased 0.8°C (1.4°F) since 1880, and most of that change has occurred in the past four decades.

The line plot above shows yearly temperature anomalies from 1880 to 2011 as recorded by NASA GISS, the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center, the Japanese Meteorological Agency, and the Met Office Hadley Centre in the United Kingdom. All four institutions tally temperature data from stations around the world and make independent judgments about whether the year was warm or cool compared to other years. Though there are minor variations from year to year, all four records show peaks and valleys in sync with each other. All show rapid warming in the past few decades, and all show the last decade as the warmest.

Scientists emphasize that weather patterns cause fluctuations in average temperatures from year to year, but the continued increase in greenhouse gas levels in the atmosphere assures that there will be a long-term rise in global temperatures. Each individual year will not necessarily be warmer than the previous year, but scientists expect each decade to be warmer than the previous decade.

“One more year of numbers isn’t in itself significant”, GISS climatologist Gavin Schmidt said. “What matters is this decade is warmer than the last decade, and that decade was warmer than the decade before. The planet is warming. The reason it’s warming is because we are pumping increasing amounts of carbon dioxide into the atmosphere.”

Carbon dioxide traps heat and largely controls Earth’s climate. It occurs naturally but is also released by the burning of fossil fuels for energy. The level of carbon dioxide in Earth’s atmosphere has been rising consistently for decades, largely driven by increasing man-made emissions. The carbon dioxide level in the atmosphere was about 285 parts per million in 1880, the first year of the GISS temperature record. By 1960, the atmospheric carbon dioxide concentration, measured at NOAA’s Mauna Loa Observatory, was about 315 parts per million. Today, that measurement exceeds 390 parts per million.

The continental U.S. endured its warmest year on record by far, according to NOAA, the official keeper of U.S. weather records. NOAA also announced that global temperatures were 10th warmeston record by their analysis methods.

“The U.S. temperatures in the summer of 2012 are an example of a new trend of outlying seasonal extremes that are warmer than the hottest seasonal temperatures of the mid-20th century”, NASA GISS director James E. Hansen said. “The climate dice are now loaded. Some seasons still will be cooler than the long-term average, but the perceptive person should notice that the frequency of unusually warm extremes is increasing. It is the extremes that have the most impact on people and other life on the planet”.

 

[SSDD]

Just more of SSooooDDuuuumb's delusions and cultic myths.

20-Year-Old Report Successfully Predicted Warming: Scientists

Like I said, little of what you post is actual science. That post comes from a blog...Do blog entries equal science in your mind?

Here is some published science regarding the accuracy of the models you place so much trust in.

A paper published today in the Journal of Climate finds that ensembles of climate models used by the IPCC to predict future climate change "may lead to overly confident climate predictions." The authors find that many models share the same computer code, have the same limitations, and "tend to be fairly similar," resulting in confirmation bias

An Error Occurred Setting Your User Cookie

A paper published today in the Journal of Geophysical Research in essence reveals climate models are not capable of reproducing the observed climate of the past century, much less the future. According to the paper, "few models reproduce the strong observed warming trend from 1918 to 1940," there are "large differences" in the forcings and feedbacks used in various models and that some of these are "unrealistic."

A balance between radiative forcing and climate feedback in the modeled 20th century temperature response - Crook - 2011 - Journal of Geophysical Research: Atmospheres (1984?2012) - Wiley Online Library

A new paper published in the Journal of Climate finds there has been "little to no improvement" in simulating clouds by state-of-the-art climate models. The authors note the "poor performance of current global climate models in simulating realistic [clouds]," and that the models show "quite large biases...as well as a remarkable degree of variation" with the differences between models remaining "large."

An Error Occurred Setting Your User Cookie

A paper published in the technical newsletter of the Global Energy and Water Cycle Experiment finds that climate models suppress the negative feedback from low clouds, which serve to cool the Earth by reflection of incoming sunlight. The paper notes that cloud feedbacks in computer models are not only uncertain in magnitude, but even in sign (positive or negative).

http://www.gewex.org/images/G.Stephens_Feb2010GNews.pdf

A new paper published in Global and Planetary Change finds that IPCC climate models are unable to reproduce either the El Nino Southern Oscillation [ENSO] or the Indian summer monsoon, the two most influential natural weather patterns on Earth, both of which have large effects upon global climate. The authors therefore caution that, given these large uncertainties of natural variation, current models cannot be relied upon to project future global warming from greenhouse gases.

ScienceDirect.com - Global and Planetary Change - Revisiting the Indian summer monsoon-ENSO links in the IPCC AR4 projections: A cautionary outlook

A paper published today in the Journal of Geophysical Research - Atmospheres admits that state-of-the-art climate models exaggerate alleged warming from greenhouse gases, finding the models "overestimate the observed temperature change" in comparison to historical data since 1850. The authors also find the various models have a "large spread" or widely divergent temperature projections.

Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models - Forster - 2013 - Journal of Geophysical Research: Atmospheres - Wiley Online Library

A new paper published in the the International Meteorological Association journal Tellus finds that state-of-the-art climate models are not able to reproduce atmospheric teleconnections, such as the El Nino Southern Oscillation [ENSO]. According to the authors, "Due to internally generated [natural] climate variability, the models are not able to reproduce the observed temporal behaviour [behavior over time]." Teleconnections such as ENSO and other natural ocean/atmospheric oscillations dominate climate and extreme weather worldwide.

How well do state-of-the-art atmosphere-ocean general circulation models reproduce atmospheric teleconnection patterns? | Handorf | Tellus A

A paper published in Geophysical Research Letters finds climate models "suffer from temperature-dependent biases" which "leads to an overestimation of projections of regional temperatures." According to the authors, "10-20% of projected warming is due to model deficiencies

Temperature dependent climate projection deficiencies in CMIP5 models - Christensen - 2012 - Geophysical Research Letters - Wiley Online Library

So there are 8 peer reviewed published papers stating that models are not to be trusted. And you are relying on blogs.

 

[RollingThunder]

Just more of SSooooDDuuuumb's delusions and cultic myths.

20-Year-Old Report Successfully Predicted Warming: Scientists

Like I said, little of what you post is actual science. That post comes from a blog...Do blog entries equal science in your mind?

LOLOLOLOL....you can still surprise me with how retarded you are. LiveScience is not what most folks would call a "blog". It is a science news website. From their wesite:
"LiveScience, launched in 2004, is the trusted and provocative source for highly accessible science, health and technology news for people who are curious about their minds, bodies, and the world around them. Our team of experienced science reporters, editors and video producers explore the latest discoveries, trends and myths, interviewing expert sources and offering up deep and broad analyses of topics that affect peoples' lives in meaningful ways. LiveScience articles are regularly featured on the web sites of our media partners: MSNBC.com, Yahoo!, the Christian Science Monitor and others. "

I guess you're still so retarded that you don't bother to even read the material others post. From the above referenced article that you claim is not "actual science":
"...in work published online today (Dec. 9) in the journal Nature Climate Change"

Here is some published science regarding the accuracy of the models you place so much trust in.

There is some published science listed there but it doesn't say what you've been duped into thinking it says. None of the papers say that climate models don't work or aren't useful; they do critique and criticize different components of the models as part of the continuing scientific effort to improve the models. You have a little paragraph in a quote box before each citation supposedly describing the main findings of the paper but the stuff in those boxes in not from the paper being cited, they are from some denier cult blog and they are propaganda, not a fair description of the science.

Let's look at some of the citations you presented.

A paper published today in the Journal of Climate finds that ensembles of climate models used by the IPCC to predict future climate change "may lead to overly confident climate predictions." The authors find that many models share the same computer code, have the same limitations, and "tend to be fairly similar," resulting in confirmation bias

An Error Occurred Setting Your User Cookie

Actual paper:

Abstract

Projections of future climate change are increasingly based on the output of many different models. Typically, the mean over all model simulations is considered as the optimal prediction, with the underlying assumption that different models provide statistically independent information evenly distributed around the true state. However, there is reason to believe that this is not the best assumption. Coupled models are of comparable complexity and are constructed in similar ways. Some models share parts of the same code and some models are even developed at the same center. Therefore, the limitations of these models tend to be fairly similar, contributing to the well-known problem of common model biases and possibly to an unrealistically small spread in the outcomes of model predictions.

This study attempts to quantify the extent of this problem by asking how many models there effectively are and how to best determine this number. Quantifying the effective number of models is achieved by evaluating 24 state-of-the-art models and their ability to simulate broad aspects of twentieth-century climate. Using two different approaches, the amount of unique information in the ensemble is calculated and the effective ensemble size is found to be much smaller than the actual number of models. As more models are included in an ensemble, the amount of new information diminishes in proportion. Furthermore, this reduction is found to go beyond the problem of “same center” models and systemic similarities are seen to exist across all models. The results suggest that current methodologies for the interpretation of multimodel ensembles may lead to overly confident climate predictions.

Concludes that "current methodologies for the interpretation" of the models "may lead to overly confident climate predictions". NOT false climate predictions, not too high or too low climate predictions, just maybe "overly confident climate predictions".

A balance between radiative forcing and climate feedback in the modeled 20th century temperature response - Crook - 2011 - Journal of Geophysical Research: Atmospheres (1984?2012) - Wiley Online Library

Abstract

In this paper, we breakdown the temperature response of coupled ocean-atmosphere climate models into components due to radiative forcing, climate feedback, and heat storage and transport to understand how well climate models reproduce the observed 20th century temperature record. Despite large differences between models' feedback strength, they generally reproduce the temperature response well but for different reasons in each model. We show that the differences in forcing and heat storage and transport give rise to a considerable part of the intermodel variability in global, Arctic, and tropical mean temperature responses over the 20th century. Projected future warming trends are much more dependent on a model's feedback strength, suggesting that constraining future climate change by weighting these models on the basis of their 20th century reproductive skill is not possible. We find that tropical 20th century warming is too large and Arctic amplification is unrealistically low in the Geophysical Fluid Dynamics Laboratory CM2.1, Meteorological Research Institute CGCM232a, and MIROC3.2(hires) models because of unrealistic forcing distributions. The Arctic amplification in both National Center for Atmospheric Research models is unrealistically high because of high feedback contributions in the Arctic compared to the tropics. Few models reproduce the strong observed warming trend from 1918 to 1940. The simulated trend is too low, particularly in the tropics, even allowing for internal variability, suggesting there is too little positive forcing or too much negative forcing in the models at this time. Over the whole of the 20th century, the feedback strength is likely to be underestimated by the multimodel mean.

Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models - Forster - 2013 - Journal of Geophysical Research: Atmospheres - Wiley Online Library

Abstract

[1] We utilize energy budget diagnostics from the Coupled Model Intercomparison Project phase 5 (CMIP5) to evaluate the models' climate forcing since preindustrial times employing an established regression technique. The climate forcing evaluated this way, termed the adjusted forcing (AF), includes a rapid adjustment term associated with cloud changes and other tropospheric and land-surface changes. We estimate a 2010 total anthropogenic and natural AF from CMIP5 models of 1.9&#8201;±&#8201;0.9&#8201;W&#8201;m&#8722;2 (5–95% range). The projected AF of the Representative Concentration Pathway simulations are lower than their expected radiative forcing (RF) in 2095 but agree well with efficacy weighted forcings from integrated assessment models. The smaller AF, compared to RF, is likely due to cloud adjustment. Multimodel time series of temperature change and AF from 1850 to 2100 have large intermodel spreads throughout the period. The intermodel spread of temperature change is principally driven by forcing differences in the present day and climate feedback differences in 2095, although forcing differences are still important for model spread at 2095. We find no significant relationship between the equilibrium climate sensitivity (ECS) of a model and its 2003 AF, in contrast to that found in older models where higher ECS models generally had less forcing. Given the large present-day model spread, there is no indication of any tendency by modelling groups to adjust their aerosol forcing in order to produce observed trends. Instead, some CMIP5 models have a relatively large positive forcing and overestimate the observed temperature change.

This is just saying that the models aren't correctly modeling the cooling effect of the aerosols that are somewhat offsetting the CO2 driven warming.

A paper published in Geophysical Research Letters finds climate models "suffer from temperature-dependent biases" which "leads to an overestimation of projections of regional temperatures." According to the authors, "10-20% of projected warming is due to model deficiencies

Temperature dependent climate projection deficiencies in CMIP5 models - Christensen - 2012 - Geophysical Research Letters - Wiley Online Library

Abstract
Monthly mean temperatures for 34 GCMs available from the CMIP5 project are compared with observations from CRU for 26 different land regions covering all major land areas in the world for the period 1961–2000 by means of quantile-quantile (q-q) diagrams. A warm period positive temperature dependent bias is identified for many of the models within many of the chosen climate regions. However, the exact temperature dependence varies considerably between the models. We analyse the role of this difference as a contributing factor for some models to project stronger regional warming than others by looking at the entire ensemble rather than individual models. RCP4.5 temperature projections from all GCMs for two time periods (2021–2050 and 2071–2100) are compared against a linear fit to the 50% warmest months from the respective q-q plot for each model and region. Taken together, we find that in general models with a positive temperature dependent bias tend to have a large projected temperature change, and these tendencies increase with increasing global warming level. We argue that this appears to be linked with the ability of models to capture complex feedbacks accurately. In particular land-surface atmosphere interactions are treated differently and with different degree of realism between models.

So there are 8 peer reviewed published papers stating that models are not to be trusted. And you are relying on blogs.

No, there's 8 more instances of your puppet masters duping and bamboozling you into believing things that just aren't true.

 

[skookerasbil]

Just more of SSooooDDuuuumb's delusions and cultic myths.

20-Year-Old Report Successfully Predicted Warming: Scientists

Like I said, little of what you post is actual science. That post comes from a blog...Do blog entries equal science in your mind?

LOLOLOLOL....you can still surprise me with how retarded you are. LiveScience is not what most folks would call a "blog". It is a science news website. From their wesite:
"LiveScience, launched in 2004, is the trusted and provocative source for highly accessible science, health and technology news for people who are curious about their minds, bodies, and the world around them. Our team of experienced science reporters, editors and video producers explore the latest discoveries, trends and myths, interviewing expert sources and offering up deep and broad analyses of topics that affect peoples' lives in meaningful ways. LiveScience articles are regularly featured on the web sites of our media partners: MSNBC.com, Yahoo!, the Christian Science Monitor and others. "

I guess you're still so retarded that you don't bother to even read the material others post. From the above referenced article that you claim is not "actual science":
"...in work published online today (Dec. 9) in the journal Nature Climate Change"






There is some published science listed there but it doesn't say what you've been duped into thinking it says. None of the papers say that climate models don't work or aren't useful; they do critique and criticize different components of the models as part of the continuing scientific effort to improve the models. You have a little paragraph in a quote box before each citation supposedly describing the main findings of the paper but the stuff in those boxes in not from the paper being cited, they are from some denier cult blog and they are propaganda, not a fair description of the science.

Let's look at some of the citations you presented.








Actual paper:

Abstract

Projections of future climate change are increasingly based on the output of many different models. Typically, the mean over all model simulations is considered as the optimal prediction, with the underlying assumption that different models provide statistically independent information evenly distributed around the true state. However, there is reason to believe that this is not the best assumption. Coupled models are of comparable complexity and are constructed in similar ways. Some models share parts of the same code and some models are even developed at the same center. Therefore, the limitations of these models tend to be fairly similar, contributing to the well-known problem of common model biases and possibly to an unrealistically small spread in the outcomes of model predictions.

This study attempts to quantify the extent of this problem by asking how many models there effectively are and how to best determine this number. Quantifying the effective number of models is achieved by evaluating 24 state-of-the-art models and their ability to simulate broad aspects of twentieth-century climate. Using two different approaches, the amount of unique information in the ensemble is calculated and the effective ensemble size is found to be much smaller than the actual number of models. As more models are included in an ensemble, the amount of new information diminishes in proportion. Furthermore, this reduction is found to go beyond the problem of &#8220;same center&#8221; models and systemic similarities are seen to exist across all models. The results suggest that current methodologies for the interpretation of multimodel ensembles may lead to overly confident climate predictions.

Concludes that "current methodologies for the interpretation" of the models "may lead to overly confident climate predictions". NOT false climate predictions, not too high or too low climate predictions, just maybe "overly confident climate predictions".








Abstract

In this paper, we breakdown the temperature response of coupled ocean-atmosphere climate models into components due to radiative forcing, climate feedback, and heat storage and transport to understand how well climate models reproduce the observed 20th century temperature record. Despite large differences between models' feedback strength, they generally reproduce the temperature response well but for different reasons in each model. We show that the differences in forcing and heat storage and transport give rise to a considerable part of the intermodel variability in global, Arctic, and tropical mean temperature responses over the 20th century. Projected future warming trends are much more dependent on a model's feedback strength, suggesting that constraining future climate change by weighting these models on the basis of their 20th century reproductive skill is not possible. We find that tropical 20th century warming is too large and Arctic amplification is unrealistically low in the Geophysical Fluid Dynamics Laboratory CM2.1, Meteorological Research Institute CGCM232a, and MIROC3.2(hires) models because of unrealistic forcing distributions. The Arctic amplification in both National Center for Atmospheric Research models is unrealistically high because of high feedback contributions in the Arctic compared to the tropics. Few models reproduce the strong observed warming trend from 1918 to 1940. The simulated trend is too low, particularly in the tropics, even allowing for internal variability, suggesting there is too little positive forcing or too much negative forcing in the models at this time. Over the whole of the 20th century, the feedback strength is likely to be underestimated by the multimodel mean.








Abstract

[1] We utilize energy budget diagnostics from the Coupled Model Intercomparison Project phase 5 (CMIP5) to evaluate the models' climate forcing since preindustrial times employing an established regression technique. The climate forcing evaluated this way, termed the adjusted forcing (AF), includes a rapid adjustment term associated with cloud changes and other tropospheric and land-surface changes. We estimate a 2010 total anthropogenic and natural AF from CMIP5 models of 1.9&#8201;±&#8201;0.9&#8201;W&#8201;m&#8722;2 (5&#8211;95% range). The projected AF of the Representative Concentration Pathway simulations are lower than their expected radiative forcing (RF) in 2095 but agree well with efficacy weighted forcings from integrated assessment models. The smaller AF, compared to RF, is likely due to cloud adjustment. Multimodel time series of temperature change and AF from 1850 to 2100 have large intermodel spreads throughout the period. The intermodel spread of temperature change is principally driven by forcing differences in the present day and climate feedback differences in 2095, although forcing differences are still important for model spread at 2095. We find no significant relationship between the equilibrium climate sensitivity (ECS) of a model and its 2003 AF, in contrast to that found in older models where higher ECS models generally had less forcing. Given the large present-day model spread, there is no indication of any tendency by modelling groups to adjust their aerosol forcing in order to produce observed trends. Instead, some CMIP5 models have a relatively large positive forcing and overestimate the observed temperature change.

This is just saying that the models aren't correctly modeling the cooling effect of the aerosols that are somewhat offsetting the CO2 driven warming.

Temperature dependent climate projection deficiencies in CMIP5 models - Christensen - 2012 - Geophysical Research Letters - Wiley Online Library

Abstract
Monthly mean temperatures for 34 GCMs available from the CMIP5 project are compared with observations from CRU for 26 different land regions covering all major land areas in the world for the period 1961&#8211;2000 by means of quantile-quantile (q-q) diagrams. A warm period positive temperature dependent bias is identified for many of the models within many of the chosen climate regions. However, the exact temperature dependence varies considerably between the models. We analyse the role of this difference as a contributing factor for some models to project stronger regional warming than others by looking at the entire ensemble rather than individual models. RCP4.5 temperature projections from all GCMs for two time periods (2021&#8211;2050 and 2071&#8211;2100) are compared against a linear fit to the 50% warmest months from the respective q-q plot for each model and region. Taken together, we find that in general models with a positive temperature dependent bias tend to have a large projected temperature change, and these tendencies increase with increasing global warming level. We argue that this appears to be linked with the ability of models to capture complex feedbacks accurately. In particular land-surface atmosphere interactions are treated differently and with different degree of realism between models.

So there are 8 peer reviewed published papers stating that models are not to be trusted. And you are relying on blogs.

No, there's 8 more instances of your puppet masters duping and bamboozling you into believing things that just aren't true.

not enough info s0n.


But nobody cares anyway.

Green fatigue sets in: the world cools on global warming - Climate Change - Environment - The Independent

 

[IlarMeilyr]

Global warming stopped 16 years ago, reveals Met Office report quietly released... and here is the chart to prove it | Mail Online

 

[RollingThunder]

Global warming stopped 16 years ago, reveals Met Office report quietly released... and here is the chart to prove it | Mail Online

LOLOLOLOLOLOLOLOLOL.....oh lord.....are you still jacking off to that totally debunked denier cult myth???.....you are such a clueless cretin, IlieMostly......

British Met Office refutes "misleading" claim "Global Warming stopped 16 years ago"
MPR News
October 15, 2012
(excerpts)
The Daily Mail piece seems to have "cherry picked" a high point of warming in 1997, and a relative low point in 2012 to get a "level" temperature trend. Here's is the Daily Mail "proof" graph below. As an example of cherry picking, the black lines are my additions selecting other data points along the graph that can be chosen had somebody wanted to misleadingly suggest the strong warming between 2000 and 2012 is the best trend, or the relative cooling between 1997 and 2007.

Source: Daily Mail (My lines in black)

Both of my starting and ending points (black lines) would be misleading and draw inaccurate conclusions for the reader about global temperature trends in the next few years. It's very dangerous, misleading, and scientifically dishonest to pick any one 16 year period and make inferences about where long term climate trends are headed.
*****

Met Office
October 14, 2012
(Government Publication - not under copyright - free to reproduce)

An article by David Rose appears today in the Mail on Sunday under the title: ‘Global warming stopped 16 years ago, reveals Met Office report quietly released… and here is the chart to prove it’

It is the second article Mr Rose has written which contains some misleading information, after he wrote an article earlier this year on the same theme – you see our response to that one here.

To address some of the points in the article published today:

Firstly, the Met Office has not issued a report on this issue. We can only assume the article is referring to the completion of work to update the HadCRUT4 global temperature dataset compiled by ourselves and the University of East Anglia’s Climate Research Unit.

We announced that this work was going on in March and it was finished this week. You can see the HadCRUT4 website here.

Secondly, Mr Rose says the Met Office made no comment about its decadal climate predictions. This is because he did not ask us to make a comment about them.

You can see our full response to all of the questions Mr Rose did ask us below:

Hi David,

Here’s a response to your questions. I’ve kept them as concise as possible but the issues you raise require considerable explanation.

Q.1 “First, please confirm that they do indeed reveal no warming trend since 1997.”

The linear trend from August 1997 (in the middle of an exceptionally strong El Nino) to August 2012 (coming at the tail end of a double-dip La Nina) is about 0.03°C/decade, amounting to a temperature increase of 0.05°C over that period, but equally we could calculate the linear trend from 1999, during the subsequent La Nina, and show a more substantial warming.

As we’ve stressed before, choosing a starting or end point on short-term scales can be very misleading. Climate change can only be detected from multi-decadal timescales due to the inherent variability in the climate system. If you use a longer period from HadCRUT4 the trend looks very different. For example, 1979 to 2011 shows 0.16°C/decade (or 0.15°C/decade in the NCDC dataset, 0.16°C/decade in GISS). Looking at successive decades over this period, each decade was warmer than the previous – so the 1990s were warmer than the 1980s, and the 2000s were warmer than both. Eight of the top ten warmest years have occurred in the last decade.

Over the last 140 years global surface temperatures have risen by about 0.8ºC. However, within this record there have been several periods lasting a decade or more during which temperatures have risen very slowly or cooled. The current period of reduced warming is not unprecedented and 15 year long periods are not unusual.

Q.2 “Second, tell me what this says about the models used by the IPCC and others which have predicted a rise of 0.2 degrees celsius per decade for the 21st century. I accept that there will always be periods when a rising gradient may be interrupted. But this flat period has now gone on for about the same time as the 1980 – 1996 warming.”

The models exhibit large variations in the rate of warming from year to year and over a decade, owing to climate variations such as ENSO, the Atlantic Multi-Decadal Oscillation and Pacific Decadal Oscillation. So in that sense, such a period is not unexpected. It is not uncommon in the simulations for these periods to last up to 15 years, but longer periods are unlikely.

Q.3 “Finally, do these data suggest that factors other than CO2 – such as multi-decadal oceanic cycles – may exert a greater influence on climate than previously realised?”

We have limited observations on multi-decadal oceanic cycles but we have known for some time that they may act to slow down or accelerate the observed warming trend. In addition, we also know that changes in the surface temperature occur not just due to internal variability, but are also influenced by “external forcings”, such as changes in solar activity, volcanic eruptions or aerosol emissions. Combined, several of these factors could account for some or all of the reduced warming trend seen over the last decade – but this is an area of ongoing research.

———–

The below graph which shows years ranked in order of global temperature was not included in the response to Mr Rose, but is useful in this context as it illustrates the point made above that eight of the warmest years on record have occurred in the past decade.

Graph showing years ranked in order of global temperature.

 

[SSDD]

[
LOLOLOLOLOLOLOLOLOL.....oh lord.....are you still jacking off to that totally debunked denier cult myth???.....you are such a clueless cretin, IlieMostly......

Poor damaged inadequate thunder. I am afraid that it is you who is pushing the myth. The warming has stalled in the face of ever increasing atmospheric CO2. Sorry you aren't smart enough, or mature enough to realize that you picked the wrong horse.

 

[westwall]

Global warming stopped 16 years ago, reveals Met Office report quietly released... and here is the chart to prove it | Mail Online

LOLOLOLOLOLOLOLOLOL.....oh lord.....are you still jacking off to that totally debunked denier cult myth???.....you are such a clueless cretin, IlieMostly......

British Met Office refutes "misleading" claim "Global Warming stopped 16 years ago"
MPR News
October 15, 2012
(excerpts)
The Daily Mail piece seems to have "cherry picked" a high point of warming in 1997, and a relative low point in 2012 to get a "level" temperature trend. Here's is the Daily Mail "proof" graph below. As an example of cherry picking, the black lines are my additions selecting other data points along the graph that can be chosen had somebody wanted to misleadingly suggest the strong warming between 2000 and 2012 is the best trend, or the relative cooling between 1997 and 2007.

Source: Daily Mail (My lines in black)

Both of my starting and ending points (black lines) would be misleading and draw inaccurate conclusions for the reader about global temperature trends in the next few years. It's very dangerous, misleading, and scientifically dishonest to pick any one 16 year period and make inferences about where long term climate trends are headed.
*****

Met Office
October 14, 2012
(Government Publication - not under copyright - free to reproduce)

An article by David Rose appears today in the Mail on Sunday under the title: ‘Global warming stopped 16 years ago, reveals Met Office report quietly released… and here is the chart to prove it’

It is the second article Mr Rose has written which contains some misleading information, after he wrote an article earlier this year on the same theme – you see our response to that one here.

To address some of the points in the article published today:

Firstly, the Met Office has not issued a report on this issue. We can only assume the article is referring to the completion of work to update the HadCRUT4 global temperature dataset compiled by ourselves and the University of East Anglia’s Climate Research Unit.

We announced that this work was going on in March and it was finished this week. You can see the HadCRUT4 website here.

Secondly, Mr Rose says the Met Office made no comment about its decadal climate predictions. This is because he did not ask us to make a comment about them.

You can see our full response to all of the questions Mr Rose did ask us below:

Hi David,

Here’s a response to your questions. I’ve kept them as concise as possible but the issues you raise require considerable explanation.

Q.1 “First, please confirm that they do indeed reveal no warming trend since 1997.”

The linear trend from August 1997 (in the middle of an exceptionally strong El Nino) to August 2012 (coming at the tail end of a double-dip La Nina) is about 0.03°C/decade, amounting to a temperature increase of 0.05°C over that period, but equally we could calculate the linear trend from 1999, during the subsequent La Nina, and show a more substantial warming.

As we’ve stressed before, choosing a starting or end point on short-term scales can be very misleading. Climate change can only be detected from multi-decadal timescales due to the inherent variability in the climate system. If you use a longer period from HadCRUT4 the trend looks very different. For example, 1979 to 2011 shows 0.16°C/decade (or 0.15°C/decade in the NCDC dataset, 0.16°C/decade in GISS). Looking at successive decades over this period, each decade was warmer than the previous – so the 1990s were warmer than the 1980s, and the 2000s were warmer than both. Eight of the top ten warmest years have occurred in the last decade.

Over the last 140 years global surface temperatures have risen by about 0.8ºC. However, within this record there have been several periods lasting a decade or more during which temperatures have risen very slowly or cooled. The current period of reduced warming is not unprecedented and 15 year long periods are not unusual.

Q.2 “Second, tell me what this says about the models used by the IPCC and others which have predicted a rise of 0.2 degrees celsius per decade for the 21st century. I accept that there will always be periods when a rising gradient may be interrupted. But this flat period has now gone on for about the same time as the 1980 – 1996 warming.”

The models exhibit large variations in the rate of warming from year to year and over a decade, owing to climate variations such as ENSO, the Atlantic Multi-Decadal Oscillation and Pacific Decadal Oscillation. So in that sense, such a period is not unexpected. It is not uncommon in the simulations for these periods to last up to 15 years, but longer periods are unlikely.

Q.3 “Finally, do these data suggest that factors other than CO2 – such as multi-decadal oceanic cycles – may exert a greater influence on climate than previously realised?”

We have limited observations on multi-decadal oceanic cycles but we have known for some time that they may act to slow down or accelerate the observed warming trend. In addition, we also know that changes in the surface temperature occur not just due to internal variability, but are also influenced by “external forcings”, such as changes in solar activity, volcanic eruptions or aerosol emissions. Combined, several of these factors could account for some or all of the reduced warming trend seen over the last decade – but this is an area of ongoing research.

———–

The below graph which shows years ranked in order of global temperature was not included in the response to Mr Rose, but is useful in this context as it illustrates the point made above that eight of the warmest years on record have occurred in the past decade.

Graph showing years ranked in order of global temperature.

Poor deluded blunder......even the head of the IPCC knows it's a loser now....it's a shame you haven't the brain power to realise it too.....



"THE UN's climate change chief, Rajendra Pachauri, has acknowledged a 17-year pause in global temperature rises, confirmed recently by Britain's Met Office, but said it would need to last "30 to 40 years at least" to break the long-term global warming trend.

Dr Pachauri, the chairman of the UN's Intergovernmental Panel on Climate Change, said that open discussion about controversial science and politically incorrect views was an essential part of tackling climate change."



Cookies must be enabled. | The Australian

 

[IlarMeilyr]

Rolling Fart appears to believe that after 16 years, when the average temperature is at the same point it began at, that is proof of AGW.

 

[polarbear]

Rolling Fart appears to believe that after 16 years, when the average temperature is at the same point it began at, that is proof of AGW.

All of Germany is cracking Global Warming jokes today. Only last week climatologists were jubilant that spring arrived early and did their usual victory laps in the media circus.
Guess what happened today:
Wintereinbruch: Jetzt kommt der Frost-Schock - Seite 3

Wintereinbruch: Jetzt kommt der Frostschock

Temperatures are dropping to -5 and -10C depending on the region.
The news media are bombarded with comments like this one:

Heute 16:41 von
im-wilke


Nur mal so zur Erinnerung: Im Jahr 2000 verkündete der Hamburger Klimaforscher Mojib Latif:

&#8220;Winter mit starkem Frost und viel Schnee wie noch vor zwanzig Jahren wird es in unseren Breiten nicht mehr geben.&#8221; Winter ade: Nie wieder Schnee? - SPIEGEL ONLINE

He is referring to Mojib Latif, the European Climate Guru who predicted on January 4th 2000 "Winters with frost and snow as we had them 20 years ago in Germany and similar latitudes will be a thing of the past"
And every German language news paper in Europe printed it.
Winter ade: Nie wieder Schnee? - SPIEGEL ONLINE
It`s archived and he can`t pretend now, that he never said it. The usual wording definition hair splitting won`t work this time around either because
he and his organization were at it the entire time (tweeting, yelling, ringing the big alarm bells... see we warned you) while Germans enjoyed a pleasant spring

They just can`t stand it when people want to enjoy
themselves...and sent them on a (global warming) guilt trip
It`s an anomaly and it was all predicted correctly
Just short of stating Ya`ll soon fry and you deserve it because you haven`t been listening to us


And this morning most Germans woke up to this:

Germans have been had more than most other countries by CO2 alarmists who pushed through their agenda into legislation.
Many Germans now file mock- compensation claims in the courts.
such as " I bought a property in the Eiffel mountains, because I was assured by the Government that it would soon be beach front property" ..."A promise is a promise!"...and so on.
Last week all week long not a day went by without climatologists pushing their "editorials" on every news paper in Germany when people enjoyed the warm sun a little bit...and as of today day if you wanted to go sunbathing in Germany which looks as if the next ice age had already started you had to do it like this:

Hey for a while I was getting a bit jealous, but now I feel better after I have seen that today Germany does not look much different from Manitoba:



By coincidence I caught anti-oil "auntie" Myrna discarding a bottle of 2 cycle mix- oil not more than 3 yards from the garbage can.
It was still dripping oil when one of my boys picked it up and disposed of it properly.
Myrna is the biggest enviro loudmouth in our community. Every year like clock-work she protests against aerial spraying when we have a mosquito-west-nile-virus problem.
Later when all this snow will melt and her yard is flooded she will be yelling "global warming...the polar ice is melting"
She is a typical enviro-ozone-ass-hole example, voting NDP (New Democratic Party), no matter what, watches David Suzuki (Canada`s Al Gore) on television and quotes him every time to everyone in the grocery store on a hot summer day when she is in there cooling off, because she is too cheap to buy an air conditioner.

 

[RollingThunder]

Rolling Fart appears to believe that after 16 years, when the average temperature is at the same point it began at, that is proof of AGW.

Oh, IlieMostly, you mostly lie. The "average temperature" is not "at the same point it" was 16 years ago, it is appreciably higher, more ice is melting, the Arctic just hit a new record low extent and volume, the oceans are getting warmer and sea levels are rising, the other symptoms of global warming and the accompanying climate changes accumulate faster everywhere.

When you base your posts on a bogus claim like the one you just made, parroting some demented denier cult myth, you just look even more like an idiot than you usually do (actually quite an accomplishment, now that I think of it, considering how low that bar is). Because you're a rather dimwitted denier cultist and a conspiracy theory nutjob, you reject the testimony of the experts, in this case the climate scientists, no matter how many scientists from a number of disciplines concur or how many countries have scientist involved. For those who aren't as brainwashed and bamboozled as you are, here's the facts.

NOAA: Past Decade Warmest on Record According to Scientists in 48 Countries
Earth has been growing warmer for more than fifty years
National Oceanic and Atmospheric Administration - NOAA
July 28, 2010
(GOVERNMENT PUBLICATION - Not Under Copyright - free to reproduce)
The 2009 State of the Climate report released today draws on data for 10 key climate indicators that all point to the same finding: the scientific evidence that our world is warming is unmistakable. More than 300 scientists from 160 research groups in 48 countries contributed to the report, which confirms that the past decade was the warmest on record and that the Earth has been growing warmer over the last 50 years.

Based on comprehensive data from multiple sources, the report defines 10 measurable planet-wide features used to gauge global temperature changes. The relative movement of each of these indicators proves consistent with a warming world. Seven indicators are rising: air temperature over land, sea-surface temperature, air temperature over oceans, sea level, ocean heat, humidity and tropospheric temperature in the “active-weather” layer of the atmosphere closest to the Earth’s surface. Three indicators are declining: Arctic sea ice, glaciers and spring snow cover in the Northern hemisphere.

“For the first time, and in a single compelling comparison, the analysis brings together multiple observational records from the top of the atmosphere to the depths of the ocean,” said Jane Lubchenco, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator. “The records come from many institutions worldwide. They use data collected from diverse sources, including satellites, weather balloons, weather stations, ships, buoys and field surveys. These independently produced lines of evidence all point to the same conclusion: our planet is warming,”

Ten Indicators of a Warming World. (Credit: NOAA)

The report emphasizes that human society has developed for thousands of years under one climatic state, and now a new set of climatic conditions are taking shape. These conditions are consistently warmer, and some areas are likely to see more extreme events like severe drought, torrential rain and violent storms.

“Despite the variability caused by short-term changes, the analysis conducted for this report illustrates why we are so confident the world is warming,” said Peter Stott, Ph.D., contributor to the report and head of Climate Monitoring and Attribution of the United Kingdom Met Office Hadley Centre. “When we look at air temperature and other indicators of climate, we see highs and lows in the data from year to year because of natural variability. Understanding climate change requires looking at the longer-term record. When we follow decade-to-decade trends using multiple data sets and independent analyses from around the world, we see clear and unmistakable signs of a warming world.”

While year-to-year changes in temperature often reflect natural climatic variations such as El Niño/La Niña events, changes in average temperature from decade-to-decade reveal long-term trends such as global warming. Each of the last three decades has been much warmer than the decade before. At the time, the 1980s was the hottest decade on record. In the 1990s, every year was warmer than the average of the previous decade. The 2000s were warmer still.

“The temperature increase of one degree Fahrenheit over the past 50 years may seem small, but it has already altered our planet,” said Deke Arndt, co-editor of the report and chief of the Climate Monitoring Branch of NOAA’s National Climatic Data Center. “Glaciers and sea ice are melting, heavy rainfall is intensifying and heat waves are more common. And, as the new report tells us, there is now evidence that over 90 percent of warming over the past 50 years has gone into our ocean.”

More and more, Americans are witnessing the impacts of climate change in their own backyards, including sea-level rise, longer growing seasons, changes in river flows, increases in heavy downpours, earlier snowmelt and extended ice-free seasons in our waters. People are searching for relevant and timely information about these changes to inform decision-making about virtually all aspects of their lives. To help keep citizens and businesses informed about climate, NOAA created the Climate Portal at NOAA Climate.gov. The portal features a short video that summarizes some of the highlights of the State of the Climate Report.

State of the Climate is published as a special supplement to the Bulletin of the American Meteorological Society and is edited by D.S. Arndt, M.O. Baringer, and M.R. Johnson. The full report and an online media packet with graphics is available online: BAMS State of the Climate.

 

[SSDD]

Since NOAA is known to tamper heavily with their data, the claim doesn't carry much weight thunder.

 

[RollingThunder]

Since NOAA is known to tamper heavily with their data, the claim doesn't carry much weight thunder.

I'm sure it "doesn't carry much weight" with you and the other anti-science, extremely ignorant and very retarded members of your little cult of reality denial. But since your myths about NOAA's supposed "data tampering" are too stupid and unsupportable for anybody with any sense to believe, and because this report I just cited is actually based on the work of a lot of other scientists all around the world ("more than 300 scientists from 160 research groups in 48 countries contributed to the report"), your quibble is, once again, the insane rant of a clueless retard.

 

[SSDD]

[
I'm sure it "doesn't carry much weight" with you and the other anti-science, extremely ignorant and very retarded members of your little cult of reality denial. But since your myths about NOAA's supposed "data tampering" are too stupid and unsupportable for anybody with any sense to believe, and because this report I just cited is actually based on the work of a lot of other scientists all around the world ("more than 300 scientists from 160 research groups in 48 countries contributed to the report"), your quibble is, once again, the insane rant of a clueless retard.

I am still waiting for you to give me a rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

Give me a good, scientifically sound reason for those changes. Or sling some insult, call some names and stand there as stupid as ever wearing your mental issues like some sort of pitiful armor.

 

[RollingThunder]

I'm sure it "doesn't carry much weight" with you and the other anti-science, extremely ignorant and very retarded members of your little cult of reality denial. But since your myths about NOAA's supposed "data tampering" are too stupid and unsupportable for anybody with any sense to believe, and because this report I just cited is actually based on the work of a lot of other scientists all around the world ("more than 300 scientists from 160 research groups in 48 countries contributed to the report"), your quibble is, once again, the insane rant of a clueless retard.

I am still waiting for you to give me a rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

Give me a good, scientifically sound reason for those changes. Or sling some insult, call some names and stand there as stupid as ever wearing your mental issues like some sort of pitiful armor.

I am still waiting for you to give me a rational, scientifically sound reason why you believe that NOAA is making these adjustments for nefarious purposes. Or why "more than 300 scientists from 160 research groups in 48 countries" who "contributed to the report" are all going along with NOAA in furthering this supposed deception. I mean, what have you got other than some some pathetically insane conspiracy theory involving tens of thousands of scientists all around the world who are all "tampering" with the temperature records and other data while they are all keeping the 'code of silence' about the conspiracy better than the Mafia ever could. LOLOLOLOL.

 

[IlarMeilyr]

I'm sure it "doesn't carry much weight" with you and the other anti-science, extremely ignorant and very retarded members of your little cult of reality denial. But since your myths about NOAA's supposed "data tampering" are too stupid and unsupportable for anybody with any sense to believe, and because this report I just cited is actually based on the work of a lot of other scientists all around the world ("more than 300 scientists from 160 research groups in 48 countries contributed to the report"), your quibble is, once again, the insane rant of a clueless retard.

I am still waiting for you to give me a rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

Give me a good, scientifically sound reason for those changes. Or sling some insult, call some names and stand there as stupid as ever wearing your mental issues like some sort of pitiful armor.

I am still waiting for you to give me a rational, scientifically sound reason why you believe that NOAA is making these adjustments for nefarious purposes. Or why "more than 300 scientists from 160 research groups in 48 countries" who "contributed to the report" are all going along with NOAA in furthering this supposed deception. I mean, what have you got other than some some pathetically insane conspiracy theory involving tens of thousands of scientists all around the world who are all "tampering" with the temperature records and other data while they are all keeping the 'code of silence' about the conspiracy better than the Mafia ever could. LOLOLOLOL.

Nefarious or not, it either took place or it didn't.

If it did, nefarious or not, there should be some valid basis for the "adjustments."

Name them.

Or to repeat the question you were asked by SSDD but which you chose to duck, you are asked to provide

rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

 

[RollingThunder]

I am still waiting for you to give me a rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

Give me a good, scientifically sound reason for those changes. Or sling some insult, call some names and stand there as stupid as ever wearing your mental issues like some sort of pitiful armor.

I am still waiting for you to give me a rational, scientifically sound reason why you believe that NOAA is making these adjustments for nefarious purposes. Or why "more than 300 scientists from 160 research groups in 48 countries" who "contributed to the report" are all going along with NOAA in furthering this supposed deception. I mean, what have you got other than some some pathetically insane conspiracy theory involving tens of thousands of scientists all around the world who are all "tampering" with the temperature records and other data while they are all keeping the 'code of silence' about the conspiracy better than the Mafia ever could. LOLOLOLOL.

Nefarious or not, it either took place or it didn't.

If it did, nefarious or not, there should be some valid basis for the "adjustments."

Name them.

Or to repeat the question you were asked by SSDD but which you chose to duck, you are asked to provide

rational, scientifically sound reason why NOAA has cooled 754 months since 2008 with 735 of those months being prior to 1960 and has warmed 793 months since 2008 with 570 of those months being post 1959.

Sure, adjustments to the temperature records took place. There are numerous reasons having to do with making the records more comparable by adjusting for certain known factors that result from the fact that the temperature records were taken with differing and improving instrumentation over time, with widely varying station locations, with changes in station locations over time, with differing time of day of the recorded observations, etc, etc..

The difference between us here is that, while neither one of us has the scientific knowledge to judge the validity of the climate scientists' reasons for making these adjustments, except in the most general way, I have some trust in the scientific integrity of the scientific community and see no reason to doubt that they are doing everything for entirely valid reasons, while you (and the other denier dimwits), on the other hand, imagine that there is a huge world-wide conspiracy by tens of thousands of scientists in over a hundred countries to somehow "fudge" the records and create an illusion of warming. The motives behind this 'conspiracy' are perhaps clear to you dingbat denier cultists but no one who is sane and rational or who knows anything at all about science or scientists sees your conspiracy theory as anything but utterly nuts and without any foundation in reality. The validity of the science involved though is not affected by your ignorance and denial of reality or by my inability to "provide" you with all of the details of the scientific reasoning behind these adjustments. I'm not here to be your tutor; I'm here to debunk your lies, propaganda and misinformation about the reality and dangers of AGW. You're too retarded and filled with misinformation to tutor anyway. If you want to know the fine details, look them up yourself.

For starters, you might read this.

Long-Term Monthly Climate Records from Stations Across the Contiguous United States
United States Historical Climatology Network (USHCN) - Carbon Dioxide Information Analysis Center (CDIAC)
(GOVERNMENT PUBLICATION - not under copyright - free to reproduce)

Time of Observation Bias Adjustments

Next, monthly temperature values were adjusted for the time-of-observation bias (Karl, et al. 1986; Vose et al., 2003). The Time of Observation Bias (TOB) arises when the 24-hour daily summary period at a station begins and ends at an hour other than local midnight. When the summary period ends at an hour other than midnight, monthly mean temperatures exhibit a systematic bias relative to the local midnight standard (Baker, 1975). In the U.S. Cooperative Observer Network, the ending hour of the 24-hour climatological day typically varies from station to station and can change at a given station during its period of record. The TOB-adjustment software uses an empirical model to estimate and adjust the monthly temperature values so that they more closely resemble values based on the local midnight summary period. The metadata archive is used to determine the time of observation for any given period in a station's observational history.

Homogeneity Testing and Adjustment Procedures

Following the TOB adjustments, the homogeneity of the TOB-adjusted temperature series is assessed. In previous releases of the USHCN monthly dataset, homogeneity adjustments were performed using the procedure described in Karl and Williams (1987). This procedure was used to evaluate non-climatic discontinuities (artificial changepoints) in a station's temperature or precipitation series caused by known changes to a station such as equipment relocations and changes. Since knowledge of changes in the status of observations comes from the station history metadata archive maintained at NCDC, the original USHCN homogenization algorithm was known as the Station History Adjustment Program (SHAP).

Unfortunately, station histories are often incomplete so artificial discontinuities in a data series may occur on dates with no associated record in the metadata archive. Undocumented station changes obviously limit the effectiveness of SHAP. To remedy the problem of incomplete station histories, the version 2 homogenization algorithm addresses both documented and undocumented discontinuities.

The potential for undocumented discontinuities adds a layer of complexity to homogeneity testing. Tests for undocumented changepoints, for example, require different sets of test-statistic percentiles than those used in analogous tests for documented discontinuities (Lund and Reeves, 2002). For this reason, tests for undocumented changepoints are inherently less sensitive than their counterparts that are used when changes are documented. Tests for documented changes should, therefore, also be conducted where possible to maximize the power of detection for all artificial discontinuities. In addition, since undocumented changepoints can occur in all series, accurate attribution of any particular discontinuity between two climate series is more challenging (Menne and Williams, 2005).

The USHCN version 2 "pairwise" homogenization algorithm addresses these and other issues according to the following steps, which are described in detail in Menne and Williams (2009). At present, only temperature series are evaluated for artificial changepoints.

1. First, a series of monthly temperature differences is formed between numerous pairs of station series in a region. Specifically, difference series are calculated between each target station series and a number (up to 40) of highly correlated series from nearby stations. In effect, a matrix of difference series is formed for a large fraction of all possible combinations of station series pairs in each localized region. The station pool for this pairwise comparison of series includes USHCN stations as well as other U.S. Cooperative Observer Network stations.

2. Tests for undocumented changepoints are then applied to each paired difference series. A hierarchy of changepoint models is used to distinguish whether the changepoint appears to be a change in mean with no trend (Alexandersson and Moberg, 1997), a change in mean within a general trend (Wang, 2003), or a change in mean coincident with a change in trend (Lund and Reeves, 2002) . Since all difference series are comprised of values from two series, a changepoint date in any one difference series is temporarily attributed to both station series used to calculate the differences. The result is a matrix of potential changepoint dates for each station series.

3. The full matrix of changepoint dates is then "unconfounded" by identifying the series common to multiple paired-difference series that have the same changepoint date. Since each series is paired with a unique set of neighboring series, it is possible to determine whether more than one nearby series share the same changepoint date.

4. The magnitude of each relative changepoint is calculated using the most appropriate two-phase regression model (e.g., a jump in mean with no trend in the series, a jump in mean within a general linear trend, etc.). This magnitude is used to estimate the "window of uncertainty" for each changepoint date since the most probable date of an undocumented changepoint is subject to some sampling uncertainty, the magnitude of which is a function of the size of the changepoint. Any cluster of undocumented changepoint dates that falls within overlapping windows of uncertainty is conflated to a single changepoint date according to

* a known change date as documented in the target station's history archive (meaning the discontinuity does not appear to be undocumented), or

* the most common undocumented changepoint date within the uncertainty window (meaning the discontinuity appears to be truly undocumented)​

5. Finally, multiple pairwise estimates of relative step change magnitude are re-calculated (as a simple difference in mean) at all documented and undocumented discontinuities attributed to the target series. The range of the pairwise estimates for each target step change is used to calculate confidence limits for the magnitude of the discontinuity. Adjustments are made to the target series using the estimates for each shift in the series.

Estimation of Missing Values

Following the homogenization process, estimates for missing data are calculated using a weighted average of values from highly correlated neighboring stations. The weights are determined using a procedure similar to the SHAP routine. This program, called FILNET, uses the results from the TOB and homogenization algorithms to obtain a more accurate estimate of the climatological relationship between stations. The FILNET program also estimates data across intervals in a station record where discontinuities occur in a short time interval, which prevents the reliable estimation of appropriate adjustments.

Urbanization Effects

In the original HCN, the regression-based approach of Karl et al. (1988) was employed to account for urban heat islands. In contrast, no specific urban correction is applied in HCN version 2 because the change-point detection algorithm effectively accounts for any "local" trend at any individual station. In other words, the impact of urbanization and other changes in land use is likely small in HCN version 2. Figure 2 - the minimum temperature time series for Reno, Nevada - provides anecdotal evidence in this regard. In brief, the black line represents unadjusted data, and the blue line represents fully adjusted data. The unadjusted data clearly indicate that the station at Reno experienced both major step changes (e.g., a move from the city to the airport during the 1930s) and trend changes (e.g., a possible growing urban heat island beginning in the 1970s). In contrast, the fully adjusted (homogenized) data indicate that both the step-type changes and the trend changes have been effectively addressed through the change-point detection process used in HCN version 2.

Figure 1. (a) Mean annual unadjusted and fully adjusted minimum temperatures at Reno, Nevada. Error bars indicating the magnitude of uncertainty (±1 standard error) were calculated via 100 Monte Carlo simulations that sampled within the range of the pairwise estimates for the magnitude of each inhomogeneity; (b) difference between minimum temperatures at Reno and the mean from its 10 nearest neighbors.

Station Siting and U.S. Surface Temperature Trends

Recent photographic documentation of poor siting conditions at stations in the USHCN has led to questions regarding the reliability of surface temperature trends over the conterminous U.S. (CONUS).

To evaluate the potential impact of poor siting/instrument exposure on CONUS temperatures, Menne et al. (2010) compared trends derived from poor and well-sited USHCN stations using both unadjusted and bias-adjusted data. Results indicate that there is a mean bias associated with poor exposure sites relative to good exposure sites in the unadjusted USHCN version 2 data; however, this bias is consistent with previously documented changes associated with the widespread conversion to electronic sensors in the USHCN during the last 25 years (see e.g., Menne et al. 2009). Moreover, the sign of the bias is counterintuitive to photographic documentation of poor exposure because associated instrument changes have led to an artificial negative (“cool”) bias in maximum temperatures and only a slight positive (“warm”) bias in minimum temperatures.

Adjustments applied to USHCN Version 2 data largely account for the impact of instrument and siting changes, although a small overall residual negative (“cool”) bias appears to remain in the adjusted USHCN version 2 CONUS average maximum temperature. Nevertheless, the adjusted USHCN CONUS temperatures are well aligned with recent measurements from the U.S. Climate Reference Network (USCRN). This network was designed with the highest standards for climate monitoring and has none of the siting and instrument exposure problems present in USHCN. The close correspondence in nationally averaged temperature from these two networks is further evidence that the adjusted USHCN data provide an accurate measure of the U.S. temperature.

The Menne et al. (2010) results underscore the need to consider all changes in observation practice when determining the impacts of siting irregularities. Further, the influence of non-standard siting on temperature trends can only be quantified through an analysis of the data which do not indicate that the CONUS average temperature trends are inflated due to poor station siting.

Four sets of USCHN stations were used in the Menne et al. (2010) analysis, and these are available via the following direct links to the NCDC web site and will open in a separate browser window. Set 1 includes stations identified as having good siting by the volunteers at surfacestations.org. Set 2 is a subset of set 1 consisting of the set 1 stations whose ratings are in general agreement with an independent assessment by NOAA’s National Weather Service. Set 3 are those stations with moderate to poor siting ratings according to surfacestations.org. Set 4 is a subset of set 3 consisting of the set 3 stations whose ratings are in agreement with an independent assessment by NOAA’s National Weather Service. For further information, please see Menne et al. (2010). The set of Maximum Minimum Temperature Sensor (MMTS) stations and Cotton Region Shelter (Stevenson Screen) sites used in Menne et al. (2010) are also available. Access to the unadjusted, time of observation adjusted, and fully adjusted USHCN version 2 temperature data is described in the DATA ACCESS section below.