Because the pool of climate experts who dispute that humans are the primary cause of global warming is so small, representing just 2 to 4 percent of climate scientists, climate contrarians often reference the same few contrarian scientists. Two such examples are Roy Spencer and John Christy of the University of Alabama at Huntsville (UAH), both of whom have testified before US Congress several times, and are often interviewed and quoted in the conservative media.

And because that pool of contrarian climate experts is so small, their credibility often seems indestructible. For example, Richard Lindzen has been wrong on essentially every position he's taken on major climate science issues over the past quarter century, and yet the conservative media continue to treat him as a foremost climate expert. Therefore, it's important to remind ourselves what these few climate scientist contrarians really believe, and whether their arguments have any scientific validity.

Yesterday, Roy Spencer took to his blog, writing a post entitled "Time to push back against the global warming Nazis". The ensuing Godwinian rant was apparently triggered by somebody calling contrarians like Spencer "deniers." Personally I tend to avoid use of the term, simply because it inevitably causes the ensuing discussion to degenerate into an argument about whether "denier" refers to Holocaust denial. Obviously that misinterpretation of the term is exactly what "pushed [Spencer's] button," as he put it.

However, this misinterpretation has no basis in reality. The term "denier" merely refers to "a person who denies" something, and originated some 600 years ago, long before the Holocaust occurred. Moreover, as the National Center for Science Education and Peter Gleick at Forbes have documented, many climate contrarians (including the aforementioned Richard Lindzen) prefer to be called "deniers."

"I actually like 'denier.' That's closer than skeptic," says MIT's Richard Lindzen, one of the most prominent deniers. Steve Milloy, the operator of the climate change denial website JunkScience.com, told Popular Science, "Me, I just stick with denier ... I'm happy to be a denier." Minnesotans for Global Warming and other major denier groups go so far as to sing, "I'm a Denier!".

Spencer is also on the advisory board of the Cornwall Alliance, a group with 'An Evangelical Declaration on Global Warming' claiming that "Earth and its ecosystems—created by God's intelligent design and infinite power and sustained by His faithful providence —are robust, resilient, self-regulating, and self-correcting, admirably suited for human flourishing, and displaying His glory." The declaration also has a section on "What We Deny," and Spencer recently wrote in The Christian Post,

...we deny "that most [current climate change] is human-caused, and that it is a threat to future generations that must be addressed by the global community."

Thus it's rather hypocritical of Spencer to complain about the use of a word meaning "a person who denies" when he has expressly admitted to denying these climate positions.

In his blog post, Spencer also wrote of those he calls "global warming Nazis,"

"Like the Nazis, they advocate the supreme authority of the state (fascism), which in turn supports their scientific research to support their cause (in the 1930s, it was superiority of the white race)."

Aside from being incredibly offensive, these comments are extremely hypocritical coming from Roy Spencer, who previously described his job as a UAH climate scientist as follows.

"I view my job a little like a legislator, supported by the taxpayer, to protect the interests of the taxpayer and to minimize the role of government."

The day before Spencer's blog post, John Christy along with another UAH colleague Richard McNider, published an opinion piece in the Wall Street Journal. Their piece was in response to comments by US Secretary of State John Kerry, who said,

"We should not allow a tiny minority of shoddy scientists and science and extreme ideologues to compete with scientific fact,"

Christy and McNider believe it's climate contrarians like themselves who 'embrace the facts.' To support this claim, they tried to argue that mainstream climate scientists are in denial about the accuracy of climate models.

"We might forgive these modelers if their forecasts had not been so consistently and spectacularly wrong. From the beginning of climate modeling in the 1980s, these forecasts have, on average, always overstated the degree to which the Earth is warming compared with what we see in the real climate."

First of all, modern climate modeling began in the 1970s. It's also wrong to claim that their forecasts have always overstated global warming. Just as one example, NASA's James Hansen published a paper in 1981 with a model that slightly underestimated the ensuing global warming.

Hansen et al. (1981) global warming projections under a scenario of high energy growth (red) and slow energy growth (blue) vs. observations (black). Actual energy growth has been between the two Hansen scenarios.

Climate model global warming projections have also far outperformed predictions made by climate contrarians, and have performed fairly well overall (including current climate models).

IPCC AR5 Figure 1.4. Solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the UK Hadley Centre (green). The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red).

On the other hand, Christy and Spencer's estimates of the temperature of the Earth's atmosphere have consistently underestimated global warming. In the 1990s, they initially claimed the lower atmosphere was cooling, and had to make several warming adjustments when other groups identified errors and biases in their data set.

Changes in UAH lower atmosphere temperature trend estimates, growing consistently warmer over time as cool biases are removed. Created by John Abraham.

In their opinion piece, Christy and McNider present a graph that's supposed to prove their argument that climate models have overestimated global warming. However, rather than compare models and observations of global surface temperature, which are of the greatest importance for those of us living on the Earth's surface, they instead show temperature data from higher up in the atmosphere, the temperature of the mid-troposphere (TMT).

The figure in the Wall Street Journal piece suffers from several problems. First, it improperly averages the data (also known as "baselining") in a way that results in shifting the observational data downwards with respect to the model data, visually exaggerating the discrepancy. Second, it doesn't show any error bars or uncertainty ranges, and the error bars on the TMT data are large. Third, it simply averages together two satellite TMT data sets (presumably from UAH and Remote Sensing Systems), ignoring the fact that there is a large difference in the estimated warming trends from these two data sets, and that other TMT data sets that Christy and McNider excluded show even greater TMT warming, more in line with model projections.

The other problem is that Christy and McNider assume that the observational data are perfect, and thus that any discrepancy must mean the models are wrong. However, a U.S. Climate Change Science Program report co-authored by Christy concluded that the difference between satellite estimates and model projections of atmospheric warming is probably mostly due to errors in the observations.

"This difference between models and observations may arise from errors that are common to all models, from errors in the observational data sets, or from a combination of these factors. The second explanation is favored, but the issue is still open."

For more details, see Climate Science Watch. Christy and McNider's 'skepticism' now only seems to apply to the models and not to the observations, despite their long history of needing to make large adjustments to correct for cool biases in their own observational data. As climate scientist Andrew Dessler said,

"As far as the data go, I don't really trust the satellite data. While satellites clearly have some advantages over the surface thermometer record, such as better sampling, measuring temperature from a satellite is actually an incredibly difficult problem. That's why, every few years, another big problem in the UAH temperature calculation is discovered."

Spencer, Christy, and McNider offer perfect examples of what John Kerry was criticizing – shoddy, biased science being treated on equal footing with solid mainstream science. In reality, there should be an immense credibility gap between the climate contrarians who have been consistently wrong and who deny the inconvenient data, and the mainstream climate scientists whose positions are supported by the full body of scientific evidence.

When a fringe 2 to 4 percent minority - who consistently produce shoddy analysis and compare those with whom they disagree to Nazis - are given equal credibility by the media and policymakers as the 97 percent of scientific experts, we have a problem.