Roy Spencer is one of the less than 3% of climate scientists whose research suggests that humans are playing a relatively minimal role in global warming. As one of those rare contrarian climate experts, he's often asked to testify before US Congress and interviewed by media outlets that want to present a 'skeptical' or false balance climate narrative. He's also a rather controversial figure, having made remarks about "global warming Nazis" and said,

"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."

In any case, as one of those rare contrarian climate scientists, Spencer is in a good position to present the best arguments against the global warming consensus. Conveniently, he recently did just that on his blog, listing what he considers the "Top Ten Good Skeptical Arguments," throwing in an 11th for good measure. He also conveniently posed each of these arguments as questions; it turns out they're all easy to answer.

1) No Recent Warming. If global warming science is so "settled", why did global warming stop 15 years ago, contrary to all "consensus" predictions?

Quite simply, it hasn't. Even global surface temperatures (which is how Spencer is likely measuring 'global warming', although they only account for about 2% of the Earth's warming), have warmed about 0.2°C over the past 15 years, according to the best available measurements. More importantly, the planet has continued to accumulate heat at a rate equivalent to 4 Hiroshima atomic bomb detonations per second over the past 15 years.

2) Natural or Manmade? If we don't know how much of recent warming is natural, then how can we know how much is manmade?

We do.

The IPCC stated with 95% confidence that most of the global warming since 1950 is human-caused, with a best estimate that 100% is due to humans over the past 60 years. The IPCC was able to draw this conclusion with such high confidence because that's what the scientific evidence and research clearly and consistently concludes.

3) IPCC Politics and Beliefs. Why does it take a political body (the IPCC) to tell us what scientists "believe"? And when did scientists' "beliefs" translate into proof? And when was scientific truth determined by a vote…especially when those allowed to vote are from the Global Warming Believers Party?

The IPCC merely organizes the world's top climate scientists every 5 to 7 years. It's those scientists who summarize the up-to-date status of the scientific research in their respective fields of expertise. The IPCC report and the 97% expert consensus on human-caused global warming are themselves not proof of anything. They summarize and reflect the scientific evidence – that vast body of evidence is the reason the consensus exists.

4) Climate Models Can't Even Hindcast. How did climate modelers, who already knew the answer, still fail to explain the lack of a significant temperature rise over the last 30+ years? In other words, how to you botch a hindcast?

Global surface temperatures have risen more than 0.5°C over the past 30 years. That rise is significant, both in the statistical and figurative sense. Climate models have accurately reproduced that rise.

5) …But We Should Believe Model Forecasts? Why should we believe model predictions of the future, when they can't even explain the past?

Climate models have accurately reproduced the past, but let's put them aside for a moment. We don't need climate models to project future global warming. We know from past climate change events the planet will warm between about 1.5 and 4.5°C from the increased greenhouse effect of a doubling of atmospheric carbon dioxide (the 'climate sensitivity').

In a business-as-usual scenario, atmospheric carbon dioxide levels are expected to surpass 900 ppm by 2100 – that's close to two doublings from the pre-industrial level of 280 ppm. Hence we know that business-as-usual will cause between 2.5 and 7.5°C (most likely 5°C) warming if we stop carbon dioxide levels from rising beyond about 900 ppm. This is based on simple math and what we know about the physics of the climate – no fancy models needed.

6) Modelers Lie About Their "Physics". Why do modelers insist their models are based upon established physics, but then hide the fact that the strong warming their models produce is actually based upon very uncertain "fudge factor" tuning?

Putting aside the accusation that hundreds of climate modelers are all liars – the answer is that their models are indeed based upon well established physics. NASA climate modeler Gavin Schmidt's TED talk on the subject is well worth watching.

Spencer's question likely refers to the uncertain size of the cooling influence of aerosols. However, that is a physical uncertainty. We don't have very good measurements of this effect; unfortunately the rocket carrying NASA's Glory satellite that had instruments to measure the climate effect of aerosols crashed two years ago. Nevertheless, climate models use the available data to account for their influence, and their projections include the associated uncertainties.

7) Is Warming Even Bad? Who decided that a small amount of warming is necessarily a bad thing?

We're headed for about 5°C global surface warming above pre-industrial temperatures by 2100 if we continue on a business-as-usual path. 5°C is the difference between average temperatures now and those during the last ice age. That's not "small" by any stretch of the imagination. As for who decided that amount warming is a bad thing – climate scientists researching the impacts of climate change.

8) Is CO2 Bad? How did carbon dioxide, necessary for life on Earth and only 4 parts in 10,000 of our atmosphere, get rebranded as some sort of dangerous gas?

Carbon dioxide itself is not "bad." Water is also necessary for life. Too much water will kill you. Too much carbon dioxide causes dangerous climate change. Greenhouse gases were determined to be pollutants as defined in the US Clean Air Act . This was a ruling of the (politically conservative) US Supreme Court.

9) Do We Look that Stupid? How do scientists expect to be taken seriously when their "theory" is supported by both floods AND droughts? Too much snow AND too little snow?

This question is a bit like asking, "Do I look fat?". Do you want an honest answer?

The warming of the atmosphere, happening especially at high latitudes, reduces the temperature difference between higher and lower latitudes. This tends to make storms move more slowly. This results in storms dumping more precipitation in localized areas, which causes more flooding in those areas and droughts outside of them. Higher temperatures also increase evaporation, exacerbating droughts and adding more moisture to the air for stronger storms. A climate scientist should understand these concepts.

10) Selective Pseudo-Explanations. How can scientists claim that the Medieval Warm Period (which lasted hundreds of years), was just a regional fluke…yet claim the single-summer (2003) heat wave in Europe had global significance?

There is no contradiction here – a regional event can have global significance, for example via economic impacts. In any case, the Medieval Warm Period was a regional phenomenon and the planet as a whole was cooler than today.

11) (Spinal Tap bonus) Just How Warm is it, Really? Why is it that every subsequent modification/adjustment to the global thermometer data leads to even more warming? What are the chances of that? Either a warmer-still present, or cooling down the past, both of which produce a greater warming trend over time. And none of the adjustments take out a gradual urban heat island (UHI) warming around thermometer sites, which likely exists at virtually all of them — because no one yet knows a good way to do that.

Ironically, most of the adjustments to Spencer's own satellite temperature data set have been in the warming direction, so this question may be an example of psychological projection. Scientists also recently identified a problem in Arctic temperature data analysis that's leading to an incorrect adjustment in the cooling direction, and there have of course been other cooling adjustments in the surface temperature record. The urban heat island effect has also been demonstrated over and over to have no significant influence on the surface temperature record.

Notice a Pattern?

You may have noticed some patterns in these questions. Most are based on false premises and are trivially simple to answer. These 'top ten good skeptic arguments' are frankly not very good or challenging. They also reveal a very one-sided skepticism, although to his credit Spencer did also list 10 'skeptic' arguments that don't hold water. These are glaringly wrong arguments like 'there is no greenhouse effect' and 'CO2 cools the atmosphere,' that some contrarians nevertheless believe. Interestingly, Spencer discusses the science disproving the 10 bad arguments, but there's no scientific discussion supporting his to 'good' arguments.

From reading and answering Spencer's questions, we learn that the basic science behind how we know humans are causing global warming and that it's a problem are quite well-established. There are some remaining uncertainties, like how much warming is being offset by aerosol cooling, but overall we have a very strong understanding of the big picture. For quite a while now we've understood the Earth's climate well enough to know that we can't continue on our current high-risk path.

When will we stop using these trivially wrong contrarian arguments as an excuse for climate inaction? Now that's a tough question to answer. © Guardian News and Media 2014

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