Spencer & Christy's model not working again: "A Comparative Analysis of Data Derived from Orbiting MSU/AMSU Instruments" by

Journal of Atmospheric and Oceanic Technology, Vol. 34, No. 1 (2017) 225-232; doi: http://dx.doi.org/10.1175/JTECH-D-16-0121.1

A Comparative Analysis of Data Derived from Orbiting MSU/AMSU Instruments

R. Eric Swanson^a  (Warrensville, NC, U.S.A.)

Received June 14, 2016; final form October 3, 2016; published online January 16, 2017.

Abstract

Spencer and Christy of the University of Alabama in Huntsville (UAH) recently introduced a new method to process MSU/AMSU satellite brightness temperature data with their version 6 (v6) data. A comparison of UAH v6 north polar lower stratospheric (TLS) data with that from Remote Sensing Systems (RSS) is presented, indicating a possible bias between 1986 and 1988. Comparing UAH and NOAA Center for Satellite Applications and Research (NOAA) TLS data produces a similar result. An additional analysis utilizing midtropospheric (TMT) data also found a similar bias. Comparing the NOAA TMT data for the May 2016 release against UAH and RSS TMT evidenced another excursion, dated at the middle of 2005, that was corrected in later releases. These comparisons reinforce the concerns expressed by other analysts regarding the merging procedure for UAH v6, repeating similar concerns regarding the earlier UAH v5 products. Any biases in the UAH, RSS, or STAR products would impact the trends calculated for these products and could explain the differences between these trends. Biases in the UAH series would also impact the UAH TLTv6 lower-troposphere product, which is a linear combination of the UAH TMT, tropopause temperature (TTP), and TLS series.

Key words: Climate records; Satellite observations; Filtering techniques; Pattern detection; Time series

^a Retired.

© 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author e-mail: R. Eric Swanson, e_swanson@skybest.com

http://journals.ametsoc.org/doi/abs/10.1175/JTECH-D-16-0121.1

Joe Romm: Climate Deniers’ Favorite Temperature Dataset Just Confirmed Global Warming

CREDIT: ROY SPENCER, UNIVERSITY OF ALABAMA AT HUNTSVILLE

by Joe Romm, Climate Progress, March 2, 2016

February smashed monthly global temperature records, according to the satellite data analyzed by the University of Alabama at Huntsville (UAH). At the same time, a brand new study concludes that miscalculations explain why the Remote Sensing Systems (RSS) satellite temperature dataset had appeared to show a relatively slow rate of global warming.

So Ted Cruz and his fellow climate science deniers need a new meme to replace their “satellites find no warming since 1998” talking point, which replaced the “there’s been no warming since 1998” talking point after that one fell apart when 2014 became the hottest year on record — and again when 2015 blew away the 2014 record.

In fact, for those who live in reality, as opposed to in denial, satellite data, ground-based weather stations, sea-based buoys, and even weather balloons all reveal a steady long-term warming trend.

Let’s start with the UAH data, which show a stunning 1.5 °F (0.83 °C) warming in February 2016 compared to the historical (1981-2010) average for the lower troposphere (the lowest part of the atmosphere):

The lower tropospheric temperature (LT) anomaly, via UAH scientist Roy Spencer.

How amazing is this temperature jump? First off, remember that the 1981-2010 baseline used by the UAH is itself some 0.8 °F (0.45 °C) hotter than pre-industrial levels — so you can add that to all of the numbers here.

Second, February was more than half a degree Fahrenheit — 0.52 °F (0.29 °C) — warmer than January, which itself was “the warmest January in satellite record.”

Third, it was so hot last month that Dr. Roy Spencer of the UAH reports, “Incredibly, land areas outside the tropics in the Northern Hemisphere were a ‘whopping’ 1.46 degrees C above average, 0.5 degrees above any previous monthly anomaly.” This is a 2.6 °F warming above the 1981-2010 average — topping the previous anomaly by 0.9 °F.

Lower atmospheric warming over land outside of the tropics (vs. the 1981-2020 average) via UAH scientist Roy Spencer.

Fourth, it was so hot last month that Spencer — one of country’s leading climate science deniers — told the Washington Post:

I’ve always cautioned fellow skeptics that it’s dangerous to claim no warming. There has been warming. The question is how much warming there’s been and how does that compare to what’s expected and what’s predicted.

Now we know there has been a lot of warming, it’s consistent with what scientists predicted, and, most worrisome of all, scientists now predict it will keep speeding up! Maybe we should start listening to them.

I’m sure you’ve heard from Ted Cruz and other climate science deniers that there hasn’t been any warming in the satellite record since 1998. What they really meant was there was not as much warming as expected in the lower troposphere in the (questionable) RSS data.

The UAH’s Spencer and Dr. John Christy — both leading deniers — reported just last month that the UAH data shows a “Global climate trend since Nov. 16, 1978 [of] +0.12 C [0.22 F] per decade.”

In fact out of all the temperature datasets — land, sea, weather balloons, and two from satellites (UAH and RSS) — only one dataset had shown unexpectedly slow warming in recent years, the RSS data. Unsurprisingly, that is the dataset deniers like Ted Cruz have glommed on to — despite the fact that it was widely believed the RSS data was being misanalyzed.

Indeed, back in 2011, Spencer himself explained the discrepancy between the UAH data and the RSS data on his website: “my UAH cohort and boss John Christy, who does the detailed matching between satellites, is pretty convinced that the RSS data is undergoing spurious cooling because RSS is still using the old NOAA-15 satellite which has a decaying orbit, to which they are then applying a diurnal cycle drift correction based upon a climate model, which does not quite match reality.”

The drift correction is needed because different parts of the planet are observed by satellites at different times during the day — and because satellites drift from orbit to orbit. Spencer adds that the UAH data is probably better because “We have not used NOAA-15 for trend information in years…we use the NASA Aqua AMSU [advanced microwave sounding unit], since that satellite carries extra fuel to maintain a precise orbit.”

Since Spencer is a leading climate science denier, however, he did not urge his fellow deniers to avoid using the likely flawed RSS data. Quite the reverse:

But, until the discrepancy is resolved to everyone’s satisfaction, those of you who REALLY REALLY need the global temperature record to show as little warming as possible might want to consider jumping ship, and switch from the UAH to RSS dataset.

Seriously! Spencer is such a gung-ho denier of climate science he is telling his fellow deniers who want to minimize the reality of global warming that they should not use his own data set, which he and Christy believes is superior, but instead they should use the RSS data, which they believe had a flawed diurnal cycle drift correction.

So only hard-core climate science deniers should be surprised to learn that the new study in the Journal of Climate by members of the RSS team finds that the … wait for it … the RSS data had been low-balling recent global warming because of a flawed diurnal cycle drift correction. That study, aptly titled, “Sensitivity of satellite-derived tropospheric temperature trends to the diurnal cycle adjustment,” concluded, “Previous versions of the RSS dataset have used a diurnal climatology derived from general circulation model output to remove the effects of drifting local measurement time. In this paper, we present evidence that this previous method is not sufficiently accurate, and present several alternative methods to optimize these adjustments using information from the satellite measurements themselves.”

The researchers then use an improved and optimized adjustments methodology and report:

The new dataset shows substantially increased global-scale warming relative to the previous version of the dataset, particularly after 1998. The new dataset shows more warming than most other middle tropospheric data records constructed from the same set of satellites. We also show that the new dataset is consistent with long-term changes in total column water vapor over the tropical oceans, lending support to its long-term accuracy.

In short, once a long-standing analytical error was fixed, the RSS data showed long-term global warming comparable to UAH. Here is the result:

Comparison between previous, flawed RSS global (80° S to 80° N) anomaly time series (V3.3, black line), with results using a more accurate methodology (V4.0, blue line).

The corrected dataset shows a 0.125 °C [0.225 °F] rate of warming per decade from 1979 to 2014. The corrected trend is 60% higher than the earlier, flawed rate of warming.

For those wondering why the satellite trends are slightly lower than the surface temperature trends, which exceed 0.16 °C (0.29 °F) per decade — and rising: It is always worth remembering that the surface temperature data directly measures the temperature at the surface where we live. The satellites indirectly measure the temperature of the lower atmosphere, where we don’t. Also, given that 2016 is likely to be the hottest year in the satellite record, the satellite trend — like the surface temperature trend — appears to be speeding up.

The phantom slowdown in the last of the big global temperature datasets is gone. The reality is that the globe has warmed and will continue to warm — primarily because of human-caused carbon pollution — as climate scientists have been saying for decades.

No doubt the climate science deniers will find another talking point to urge delay. But it is time for the rest of us to redouble our efforts to preserve a livable climate.

http://thinkprogress.org/climate/2016/03/02/3755715/satellites-hottest-february-global-warming/

Quelle suprise! UAH low-balling satellite temperature data by a factor of three

[Readers, this is something like the 5th time in the past 10 years that UAH (i.e., John Christy and Roy Spencer) has been caught lowballing their satellite temperature data.]  

A new study suggests that the University of Alabama at Huntsville is lowballing the warming of the atmosphere

by John Abraham, "Climate Consensus - The 97%," The Guardian, March 25, 2015

 Satellite orbiting Earth. Photograph: JG Photography / Alamy/Alamy

A very important study was just published in the Journal of Climate a few days ago. This paper, in my mind, makes a major step toward reconciling differences in satellite temperature records of the mid-troposphere region. As before, it is found that the scientists (and politicians) who have cast doubt on global warming in the past are shown to be outliers because of bias in their results.

The publication, authored by Stephen Po-Chedley and colleagues from the University of Washington, discusses some major sources of error in satellite records. For instance, after satellites are launched, they scan the Earth’s atmosphere and calibrate the atmospheric measurements using a warm target onboard the satellite and cold space. The accuracy with which the atmospheric measurements are calibrated can influence the inferred temperature of the atmosphere (called the warm-target bias). Additionally, over the years, multiple satellites have been launched and the selection of which satellite data are used can play a role. Finally, biases can occur because the satellite orbits drift during their lifetime, and the influence of diurnal temperature variation can affect the global temperature trends. 

Of these three errors, the last one (probably the most important one) was the focus of the just-published paper. 

It is known that there is a problem because there are multiple groups that create satellite temperature records, for instance: NOAA, Remote Sensing Systems (RSS), and the University of Alabama Huntsville (UAH). The problem is that their results don’t agree with each other. In particular, the UAH team, led by Dr. John Christy and Dr. Roy Spencer (who have discounted the importance and occurrence of climate change for years), presents results that differ quite a bit from the others. In fact, in the current paper, it is stated that “Despite using the same basic radiometer measurements, tropical TMT trend differences between these groups differ by a factor of three.”

An important aspect to this issue is that, for many reasons, it is expected that the tropospheric temperatures in the tropics will warm more than surface temperatures. This is called “tropospheric amplification.” According to two satellite groups, there is in fact such amplification. According to the UAH team, there is no amplification. The presence or absence of amplification is often used by some skeptics to discount the importance of global warming.

Why are there differences? Well, that’s part of what this paper tries to answer.

Each of the teams tries to deal with and correct for various satellite errors. For example, sometimes the diurnal cycle effect is removed using temperatures from climate models. The RSS and NOAA teams “apply a drift correction based on the diurnal cycle from a GCM (global climate model), whereas UAH produces a microwave-sounding-unit, mid-tropospheric-temperature, diurnal correction based on temperature comparisons between three co-orbiting satellites ... UAH does not yet correct the diurnal drift for satellites carrying Advanced Microwave Sounding Units because they attempt to use these satellites during periods when the diurnal drift is small.”

The present paper presents a calibration scheme that allowed a diurnal correction to be obtained from the satellite measurements themselves, in particular by solving for a common diurnal cycle correction using temperatures from all available satellites.

As the authors state in the paper, their new results agree with the two groups that show more warming. They disagree with UAH. As the authors state,

In general, our trends corrected with a GCM and trends corrected with our observationally derived diurnal cycle correction are similar to trends from NOAA and RSS ... the UAH ocean trend is notably lower than trends from the other datasets.

So, how do the trends compare? Well, the lowest trends (in degrees Celsius heating per decade) are from UAH, and they equal 0.029 °C per decade for the 1979–2012 period for the mid-troposphere region between 20° South and 20° North. The new results are almost 4 times higher at 0.114 °C per decade. The results using a diurnal correction from a climate model are in close agreement with the new findings (0.124 °C per decade). As additional support, the NOAA and RSS values are also close to the corrected results. The simple fact is – UAH is an outlier.

They also discovered that the results from RSS, NOAA, and the new study all show tropical amplification and are in agreement with the expected amplification from climate models. They state, “There is no significant discrepancy between observations and models for lapse rate change between the surface and the full troposphere.”

To summarize the amplification factor, the new study obtains a value of 1.4. If the diurnal cycle is eliminated using climate models, the result is 1.49. According to NOAA and RSS, the values are 1.31 and 1.10, respectively. Again, UAH is the outlier with an amplification factor of 0.56.

I wrote to Stephen Po-Chedley and asked for a summary. He told me,

We developed an observationally based diurnal cycle correction to remove the influence of satellite diurnal sampling drifts on long-term tropospheric temperature trends. This is important because other analyses (RSS and NOAA) used a model-derived diurnal cycle correction and questions have been raised about the validity of this bias correction. Trends from our work are in accord with trends from global circulation models and basic theory. 

We also found that the model-derived diurnal cycle correction used by RSS and NOAA is similar to our bias correction. The tropical tropospheric trend from the present study is 2.5 times that from another group, UAH. While this work shows that it is possible to understand discrepancies between MSU/AMSU datasets, there are still important differences between the datasets that need further scrutiny.

In short, the Earth is warming, the warming is amplified in the troposphere, and those who claim otherwise are unlikely to be correct.

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/mar/25/one-satellite-data-set-is-underestimating-global-warming

John Abraham: Another global warming contrarian paper found to be unrealistic and inaccurate

Abraham et al. show that a paper by ‘sceptics’ Spencer and Braswell is rife with unrealistic assumptions in an overly simple model

by John Abraham, "Climate Consensus - The 97%," The Guardian, October 21, 2014

A woman looks at a globe model in the climate village during the United Nations Framework Convention on Climate Change (COP-16), in Cancun, 2010. Photograph: Ronaldo Schemidt/AFP/Getty Images

It’s hard to find a reputable scientist who denies that human emissions of greenhouse gases are warming the planet and that there will be consequences for human society and the biological health of the planet. There are a few holdouts who, for various reasons, either think humans are not causing warming or that the warming will not have much consequence.

Some members of this vocal minority spend a lot of time trying to convince the public that they are right. They write letters to newspapers, appear in slick movies, give press conferences, promote their views to Congress, and so on. Their high profile gives the public a false sense that there are two relatively equal-sized bodies of experts that cannot agree on climate change; this is not true. 

An even smaller subset also tries to publish their views in the scientific literature – the dueling ground for experts. Sometimes these contributions have been useful, adding some nuance to the discussion, but all too often they have proven to be of very poor quality when other scientists have had a chance to dissect them.

A few months ago, I co-authored an article which charted the different quality in scientific output from the Dwindling Few contrarians compared to the majority of experts. My colleague, Dana Nuccitelli, summarized the article here. What we show is that the Dwindling Few have had a very poor track record – having papers rebutted time after time after time because of errors they have made. The low quality of their research has caused journal editors resign, and they have wasted the time of their colleagues who have had to publish the rebuttals to their work. 

Well, again this year, I’ve wasted my time (and my colleagues’ time) by rebutting a 2014 paper published by the darling of the Dwindling Few, Roy Spencer. Dr. Spencer wrote a paper earlier this year that used a very simple ocean model to suggest that standard climate models overestimate the Earth’s sensitivity to carbon dioxide increases in the atmosphere. You can see his manuscript here although it is behind a paywall so you will have to shell out about $40 to read it.

Dr. Spencer and his colleague Danny Braswell made a number of basic math and physics errors in the article that call into question their conclusions. 

Before we get into the errors, let’s talk about what their model does. They basically treated the ocean like a non-moving fluid and allowed heat to diffuse into the ocean depths. They did allow some mixing in the upper layers through added terms in a one-dimensional equation. The model neglects down-welling or up-welling of waters which occur particularly at the poles. In the end, they end up with a bunch of tunable parameters, which they adjusted so that the model output matches the measured temperature history.

So, what were the errors and poor modeling choices?

1. The model treats the entire Earth as entirely ocean-covered
2. The model assigns an ocean process (El Niño cycle) which covers a limited geographic region in the Pacific Ocean as a global phenomenon
3. The model incorrectly simulates the upper layer of the ocean in the numerical calculation.
4. The model incorrectly insulates the ocean bottom at 2000 meters depth
5. The model leads to diffusivity values that are significantly larger than those reported in the literature
6. The model incorrectly uses an asymmetric diffusivity to calculate heat transfer between adjacent layers
7. The model contains incorrect determination of element interface diffusivity
8. The model neglects advection (water flow) on heat transfer
9. The model neglects latent heat transfer between the atmosphere and the ocean surface.

Now, simple models like this one can still be useful, even though they necessarily gloss over some details. But some of these errors and omissions are pretty obvious, and would have been easy to fix. For instance, by treating the entire Earth as water covered, Spencer and Braswell omit 30% of the surface of the Earth that’s land-covered, and which heats up faster than the oceans. They then compare the CO2sensitivity of their ocean-only model to those obtained from more realistic models — apples and oranges. Furthermore, the application of a very local phenomenon (El Niño) to the entire globe just doesn’t make much sense. 

But, I here want to talk about the numerical errors, in particular items 3, 4, 6, and 7. In order to explain what went wrong, I need to talk about the underlying math.

The diffusion equation Spencer and Braswell used has a second derivative of temperature with respect to depth in the water. To solve this equation, the common approach is to break the ocean into a number of finite slabs of water and approximate the derivatives by finite differences. So far, so good. The problems arise when you apply what are called boundary conditions. That is, conditions at the ocean surface and the bottom of the ocean. At both locations, Spencer and Braswell’s approach fails.

First, at the ocean surface, you are required to make calculations at the exact surface. In fact, the physical phenomenon which Spencer and Braswell introduce require actual surface temperatures. However, in their computer program, no surface temperatures were ever determined. They basically transcribed a temperature 25 meters deep into the ocean onto the surface (and no, they didn’t do this because of ocean mixing). At the ocean bottom, Spencer and Braswell insulated the ocean, and thereby did not allow any energy exchange there.

Finally, Spencer and Braswell incorrectly used upstream element-diffusivity values in their heat transfer term. They were obligated to use mean values representing adjacent elements. When we implemented the corrected numerical scheme, the quality of the results dissolved. Once again, Roy Spencer has failed in his attempt to show the Earth is not very sensitive to climate change.

These errors are the sort of thing that could have been avoided by consulting any elementary textbook on heat transfer, or any number of papers that have published similar ocean diffusion models. My colleague and co-author, Dr. Barry Bickmore from BYU described the situation like this,

What our paper shows is that Spencer and Braswell’s model was flawed on a very basic level, in such a way that it could have predicted wildly low climate sensitivity to greenhouse gases. Whatever sensitivity their model predicts, the true value is probably significantly higher, and therefore probably in the range indicated by the IPCC. 

Spencer and Braswell might object that their paper says ocean temperature measurements “might not provide a very strong constraint on our estimates of climate sensitivity.” Let’s just say that Roy Spencer forgot to include that little detail when he recently told a U.S. Senate committee, “Our most recent peer-reviewed paper on this subject... has arrived at a climate sensitivity of only 1.3 degree C for a doubling of atmospheric carbon dioxide, based upon a variety of global measurements, including warming of the global oceans since the 1950s.”

In a recent blog post, Dr. Spencer challenged well-known and well-respected Dr. Andrew Dessler to a debate. While the peanut gallery was busy chiding Dessler for not taking the bait, it perhaps is important to remember that the place where scientists debate is in the scientific literature. It is a venue that has not been kind to Dr. Spencer in the past decade or so. We published our latest work in an open-source journalhere so that any interested reader can see the results for themselves.

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/oct/21/global-warming-contrarian-paper-unrealistic-inaccurate

Shoot and a miss: Wall Street Journal op-ed attacks 97% climate consensus

by Climate Science Watch, May 27, 2014

A new opinion piece in the Wall Street Journal attacks the 97% scientific consensus on man-made global warming while completely missing the point on what scientists are actually saying about climate change. Joseph Bast of the Heartland Institute and Roy Spencer can try to obscure the consensus by nitpicking over details, but it won’t change the facts: climate change is real, human-caused and dangerous.

The following is a guest post by Climate Nexus:

Shoot and a Miss: WSJ Op-Ed Attacks 97% Climate Consensus

The Heartland Institute’s Joseph Bast and serially corrected Dr. Roy Spencer have a new opinion piece in the Wall Street Journal attacking the 97% scientific consensus on man-made global warming. The bulk of their argument amounts to nitpicking over the meaning of words like “dangerous” and “catastrophic,” completely missing the point on what scientists are actually saying about climate change.

The evidence is solid: 97% of climate scientists agree that warming is real and human-caused. The scientists’ assessment of whether warming is dangerous or urgent is not covered in the 97% surveys, but the dangerous nature of warming is well-documented in other comprehensive sources.

97% of climate scientists agree that warming is real and human-caused. Multiple studies with differing methodologies have reached this conclusion, a few of which are named in the WSJ piece. The surveys do not attempt the task of gauging exactly how dangerous scientists believe warming to be. This would be difficult as it is a much more complicated question and not typically discussed in the abstract section of peer-reviewed papers.

While complaining about the omission of questions about the harmfulness of warming, Bast and Spencer prove just how universal the consensus is. They say that even scientists who are skeptical of “catastrophic” global warming would agree with the surveys’ statements. Scientists who actually dispute the human contribution to climate change are apparently a smaller group of outliers every day.

Bast and Spencer even reference the IPCC, implying that a “key question” remains: humans might have caused some warming, but just how much? Bast and Spencer may have missed it, but the IPCC actually answers that question. The scientists’ best estimate is that humans have caused ALL of the observed warming since 1951. It doesn’t get much clearer than that.

Attempts to refute the consensus have been widely discredited. Bast and Spencer reference one thoroughly debunked “Petition Project” with 31,000 supposed signatures. The project contains numerous false signatories and its organizers have admitted “there’s no way of filtering out a fake.” The project is run by the Oregon Institute of Science and Medicine, which in the past has argued that nuclear weapon dangers have been exaggerated and that the Y2K bug would end the world. Its leader Art Robinson is skeptical of evolution and HIV-AIDS and believes that nuclear waste should be used to “enhance” Oregon’s drinking water.

Widespread consensus also exists that warming is harmful. The 97% surveys do not reference the harmfulness of warming, but plenty of other authoritative and comprehensive sources do. Bast and Spencer directly quote the IPCC as saying climate change “poses risks for human and natural systems.” Risks to human systems are not a good thing. Elsewhere the IPCC details impacts of human-caused climate change that are happening right now, including increased heat waves and extreme precipitation, which are not particularly positive developments either.

The National Climate Assessment further confirmed that climate change is here and now, and that its impacts “are expected to become increasingly disruptive across the nation throughout this century and beyond.” In their climate overview “What We Know,” the American Association for the Advancement of Science stated that climate change impacts will be “highly damaging.”

Bast and Spencer’s tactic of conceding the basic science but disputing its implications is increasingly popular, as evidenced by the rise of the “delayers.” But this just shows that climate contrarians are grasping at straws. They can try to obscure the consensus by nitpicking over details, but it won’t change the facts: climate change is real, human-caused and dangerous.

Earlier CSW posts:

Quantifying, once again, the scientific consensus on human-caused global warming (May 22, 2013)

New study finds striking level of agreement among climate experts on anthropogenic climate change (June 21, 2010)

Interview with Stephen Schneider on climate science expert credibility study (July 2010). Expert credibility matters.

Recent Climate Nexus guest posts:

Lomborg hypes already-debunked Bengtsson story in new Forbes column (May 22, 2014)

Wall Street Journal’s attempts to politicize National Climate Assessment fall flat (May 9, 2014)

Wall Street Journal misquotes IPCC to advocate inaction on climate change (April 7, 2014)

http://www.climatesciencewatch.org/2014/05/27/shoot-and-a-miss-wall-street-journal-op-ed-attacks-97-climate-consensus/

Dana Nuccitelli: Climate imbalance – disparity in the quality of research by contrarian and mainstream climate scientists

Contrarian papers tend to be rebutted quickly in peer-reviewed literature, but receive disproportionate media attention

by Dana Nuccitelli, "Climate Consensus - The 97%," The Guardian, April 11, 2014

Both the quality of mainstream and contrarian climate research and their media coverage have been unbalanced, but in different directions. Photograph: www.alamy.com

A new paper has been published in the journal Cosmopolis entitled "Review of the consensus and asymmetric quality of research on human-induced climate change." The paper was authored by John Abraham, myself, and our colleagues John Cook, John Fasullo, Peter Jacobs, and Scott Mandia. Each of the authors has experience in publishing peer-reviewed responses to flawed contrarian papers.

Despite the 97% expert consensus on human-caused global warmingsupported by peer-reviewed research, expert opinion, the IPCC reports, and National Academies of Science and other scientific organizations from around the world, a large segment of the population remains unconvinced on the issue. A new commentary by Edward Maibach, Teresa Myers and Anthony Leiserowitz in Earth's Future notes that most people don't know there is a scientific consensus about human-caused climate change, which undermines public engagement on the subject.

This 'consensus gap' is in large part due the media giving disproportionate coverage to climate contrarians. In our paper, we sought to evaluate whether that disproportionate media coverage was justified by examining how well contrarian hypotheses have withstood scientific scrutiny and the test of time. The short answer is, not well.

Low climate sensitivity papers by Lindzen and Spencer (open circles) and peer-reviewed rebuttals (closed circles). Created by John Garrett of Wildomar, CA.

The first contrarian argument examined in our paper was the claim that the Earth is not warming. This argument was particularly popular in the late 1990s and early 2000s, when John Christy and Roy Spencer from the University of Alabama at Huntsville published an analysis of satellite data that seemed to indicate the lower atmosphere was cooling. This appeared to contradict surface temperature measurements from thousands of thermometers around the world, which when combined together, indicated substantial global warming. Contrarians were certain that the thermometers were wrong, the satellites were right, and we didn't have to worry about global warming.

However, it turns out that satellite measurements of atmospheric temperatures are very tricky. The satellites are positioned above the atmosphere that they're trying to measure, and have to peer through many different atmospheric layers. Their orbits also drift, and satellites have limited lifespans, forcing scientists to splice together measurements from different instruments.

Gradually, various problems with the satellite temperature measurements were identified, some by the Huntsville group, and several by other groups. Corrections were made to the record, and before long the satellite record showed the warming of the lower atmosphere happening at a similar rate to that estimated from the thermometers around the globe.

Evolution of lower tropospheric temperature trends from satellite observations.

Two decades later, additional possible biases are still being identified in the satellite temperature record. Nevertheless, contrarians continue that the lower atmosphere isn't warming as fast as it should be, or that the surface thermometer measurements are biased hot (recent research has shown they actually have a cool bias). However, Christy and Spencer's claim that the planet isn't warming did not withstand scientific scrutiny or the test of time.

The second contrarian argument we investigated involved the claim that the global climate is not very sensitive to the increased greenhouse effect because the planet has some sort of natural climate response that will offset global warming. One of the first such arguments in the peer-reviewed literature was the 'infrared iris' hypothesis from contrarian darling Richard Lindzen.

The premise of Lindzen's hypothesis was that as the climate warms, the area in the atmosphere covered by high cirrus clouds will contract to allow more heat to escape into outer space, similar to the iris in a human eye contracting to allow less light to pass through the pupil in a brightly lit environment. However, within a year of Lindzen's iris hypothesis paper being published, four scientific groups had published their own studies finding significant flaws in his methods and assumptions, shown in dark blue in the first graphic above.

Several more critiques were published in the ensuing years failing to find evidence supporting the iris concept (red in the first graphic), showing that while the scientific community took this new hypothesis seriously, it simply failed to withstand scientific scrutiny. Although this is the case for most of Lindzen's arguments, he continues to be among the most highly sought contrarians by journalists and policymakers who try to create the perception of significant disagreement amongst climate science experts.

Roy Spencer and his colleague Danny Braswell have similarly published papers arguing that the climate is not as sensitive to the increased greenhouse effect as most climate scientists believe and most of the available evidence indicates. A paper they published in 2008 used a very simple climate model to make this argument, but subsequent research showed that their model was actually too simple, and failed to accurately represent how the global climate operates (green in the first graphic).

Spencer and Lindzen published several other papers making similar arguments in subsequent years, but these again failed to withstand scientific scrutiny (orange, black, and light blue in the first graphic). Various other scientific groups pointed out several flaws in the methods and assumptions in each of their publications, and in fact one editor resigned because he felt his journal had failed its task of conducting rigorous peer-review in publishing a fundamentally flawed 2011 Spencer and Braswell paper (black in the first graphic).

To contrast, human-caused global warming is based on solid fundamental physics that we've understood for over a century. In contrast to the relatively few studies mentioned here, thousands of studies have scrutinized and reaffirmed the basic physics that underlies the theory. It has withstood the test of time.

While there are still some areas of climate science undergoing serious research, like how much we're influencing changes in various types of extreme weather, the central tenets of human-caused global warming are solidly established. While some challenges have been advanced in the scientific literature, these challenges have been found to be incorrect.

In addition to the failure of their alternative hypotheses to withstand scientific scrutiny, research has shown that contrarian scientists have less expertise and fewer publications than mainstream climate scientists, and that as climate expertise increases, so does acceptance of human-caused global warming.

This then raises the question as to why contrarians are given disproportionate attention by the media and policymakers. They represent a small minority of experts with fringe views that have failed to convince the rest scientific community, simply because their ideas haven't withstood scientific scrutiny. On the other side we have human-caused global warming, supported by 97% of peer-reviewed research, expert opinion, fundamental physics, and having withstood the test of time. The fact that these two groups are treated as being on equal scientific footing and the issue continues to be 'debated' in the media has resulted in a misinformed public, and that's a problem.

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/apr/11/climate-change-research-quality-imbalance