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How to Talk to a Climate Skeptic: Responses to the most common skeptical arguments on global warming

 

‘Position statements hide debate’–True enough, but that is not the whole picture

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: All those institutional position statements are fine, but by their very nature they paper over debate and obscure the variety of individual positions. The real debate is in the scientific journals.

Answer: This is a fair point. Group position statements are designed to present a united front. The best indicator of what individual scientists think is in the current scientific literature, where new and different is the paramount value and scientists are free to express their own ideas, as long as they’re supported by data and logic. What does the literature look like in terms of the climate debate? Sounds like a good topic for research.

- 7 years ago

‘Consensus is collusion’–Is climate science maturing, or should we reach for our tinfoil hats?

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: More and more, climate models share all the same assumptions — so of course they all agree! And every year, fewer scientists dare speak out against the findings of the IPCC, thanks to the pressure to conform.

- 7 years ago

‘Peiser refuted Oreskes’–In a poor piece of work that has been retracted by its author

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Sure, Oreskes found no one bucking the consensus, but her paper was refuted by Benny Peiser, who did the exact same survey and found very different results.

Answer: True, Benny Peiser did attempt a similar study and submitted it as a letter to Science responding to the Oreskes study. But for very good reasons, it was not published.

Peiser claimed to find 34 articles in his “reject or doubt the consensus view” category. That’s 3 percent of the total, so even taken at face value it doesn’t cast much doubt on the consensus. But it is greater than the 0 percent Oreskes found, and serves as ammunition for the “there is no consensus” crowd.

- 7 years ago

‘Models don’t account for clouds’–Clouds are complex and uncertain, but unlikely to stop warming

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Clouds are a large negative feedback that will stop any drastic warming. The climate models don’t even take cloud effects into account.

Answer: All of the atmospheric global climate models used for the kind of climate projections synthesized by the IPCC take the effects of clouds into account. You can read a discussion about cloud processes and feedbacks in the IPCC TAR.

- 7 years ago

‘Climate models are unproven’–Actually, GCM’s have many confirmed successes under their belts

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Why should we trust a bunch of contrived computer models that have never had a prediction confirmed? Talk to me in 100 years.

Answer: Given the absence of a few duplicate planets and some large time machines, we can’t test a 100-year temperature projection. Does that mean the models can’t be validated without waiting 100 years? No.

- 7 years ago

‘Aerosols should mean more warming in the south’–More North. Hemisphere warming is well-understood

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Scientists claim that global warming from greenhouse gases is being countered somewhat by global dimming from aerosol pollution. They even claim that aerosol pollution caused the cooling in the mid-century. But GHGs are evenly mixed around the globe, while aerosols are disproportionately concentrated in the Northern Hemisphere. It follows that warming should be greater in the Southern Hemisphere — but that’s the opposite of what is happening. Clearly climate scientists do not know what is really going on.

- 7 years ago

‘We can’t even predict the weather next week’–But weather is not climate

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Scientists can’t even predict the weather next week, so why should we believe what some climate model tells us about 100 years from now?

Answer: Climate and weather are very different things, and the level of predictability is comparably different.

- 7 years ago

‘Chaotic systems are not predictable’–Sure, but who says climate is chaotic?

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Climate is an inherently chaotic system, and as such its behavior can not be predicted.

Answer: Firstly, let’s make sure we define climate: an average of weather patterns over some meaningful time period. We may thus discount the chaotic annual fluctuations of global mean temperature. That’s weather, and one or two anomalous years does not represent a climate shift.

Quite a few people believe that climate is a chaotic system, and maybe on some large-scale level it is. But it is not chaotic on anything approaching the time scales of which humans need to be mindful.

- 7 years ago

Understanding what is happening right under our noses does not require paleoclimate perfection

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Climate science can’t even fully explain why the climate did what it did in the past. How can they claim to know what is going on today?

Answer: There are two requirements for understanding what happened at a particular point of climate change in geological history. One is an internally consistent theory based on physical principles; the other is sufficient data to determine the physical properties involved.

- 7 years ago

‘They predicted global cooling in the 70s’–But that didn’t even remotely resemble today’s consensus

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: The alarmists were predicting the onset of an ice age in the ’70s. Now it’s too much warming! Why should we believe them this time?

Answer: It is true that there were some predictions of an “imminent ice age” in the 1970s, but a cursory comparison of those warnings and today’s reveals a huge difference.

- 7 years ago

‘Hansen has been wrong before’–Maybe, but not about the climate!

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: In 1988, Hansen predicted dire warming over the next decade — and he was off by 300%. Why in the world should we listen to the same doom and gloom from him today?

Answer: While in some instances it is ignorant repetition of misinformation, at its source this story is a plain lie.

- 7 years ago

‘It was warmer during the Holocene Climatic Optimum’–This period was not global and not like today

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: It was warmer during the Holocene Climatic Optimum than it is today — without any human influence.

 

Answer: Though some temperatures during that period were in the same range as today, they were confined to the northern hemisphere and the summer months.

- 7 years ago

‘The Medieval Warm Period was just as warm as today’–Repeating this point does not make it true

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: It was just as warm in the Medieval Warm Period (MWP) as it is today. In fact, Greenland was green and they were growing grapes in England!

Answer: There is no good evidence that the MWP was a globally warm period comparable to today. Regionally, there may have been places that exhibited notable warmth — Europe, for example — but all global proxy reconstructions agree it is warmer now, and the temperature is rising faster now, than at any time in the last one or even two thousand years.

- 7 years ago

‘Greenland used to be green’–Don’t judge a book by its cover, much less a land by its name

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: When the Vikings settled it, Greenland was a lovely, hospitable island, not the frozen wasteland it is today. It was not until the Little Ice Age that it got so cold they abandoned it.

Answer: First, Greenland is part of a single region. It can not be necessarily taken to represent a global climate shift. See the post on the Medieval Warm Period for a global perspective on this time period. Briefly, the available proxy evidence indicates that global warmth during this period was not particularly pronounced, though some regions may have experienced greater warming than others.

Second, a quick reality check shows that Greenland’s ice cap is hundreds of thousands of years old and covers over 80% of the island. The vast majority of land not under the ice sheet is rock and permafrost in the far north. How different could it have been just 1,000 years ago?

Below is a brief account of the Viking settlement, based on Jared Diamond’s “Collapse“.

- 7 years ago

Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Global warming has been going on for the last 20,000 years.

Answer: It is true that 20,000 years ago the temperature was some 8 to 10° C colder than it is today. But to draw a line from that point to today and say, “look, 20K years of global warming!” is dubious and arbitrary at best.

If you have look at this graph of temperature, starting at a point when we were finishing the climb out of deep glaciation, you can clearly see that rapid warming ceased around 10,000 years ago (rapid relative to natural fluctuations, but not compared to the warming today, which is an order of magnitude faster). After a final little lift 8,000 years ago, temperature trended downward for the entire period of the Holocene. So the post-industrial revolution warming is the reversal of a many-thousand-year trend.

- 7 years ago

‘The hockey stick is broken’–Well, no … but who’s playing hockey anyway?

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: The Hockey Stick graph — the foundation of global warming theory — has been shown to be scientifically invalid, perhaps even a fraud.

Answer: The first order of business here is to correct the mischaracterization of this single paleoclimate study as the “foundation” of global warming theory.

What’s going on today is understood via study of today’s data and today’s best scientific theories. Reconstructions of past temperatures are about, well, the past. Study of the past can be informative for scientists, but it is not explanatory of the present nor is it predictive of the future. The scientific foundation of global warming theory contains much more than a few tree-rings and the temperature during the Medieval Warm Period.

RealClimate has an interesting article about what it would mean for today’s climate theories if the MWP had indeed been warmer than today.

Now, about that pesky bit of sporting equipment …

- 7 years ago

‘Vineland was full of grapes’–Or was it an early advertising campaign?

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Newfoundland was so warm in the Medieval Warm Period that when the Vikings landed they called it Vineland and brought boatloads of grapes back to Europe.

Answer: Once again: you can’t draw conclusions about global climate from an anecdote about a single region, or even a few regions. You need detailed analysis of proxy climate indicators from around the world. These proxy reconstructions have shown that the Medieval Warm Period (around the time the Vikings are said to have discovered North America) was not as pronounced or as warm as today’s warmth. From NOAA’s paleoclimate website comes these quotes:

- 7 years ago

‘Global warming is part of a natural cycle’–This idea is one short step above appealing to magic

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Current warming is just part of a natural cycle.

Answer: While it is undoubtedly true that there are natural cycles and variations in global climate, those who insist that current warming is purely natural — or even mostly natural — have two challenges.

First, they need to identify the mechanism behind this alleged natural cycle. Absent a forcing of some sort, there will be no change in global energy balance. The balance is changing, so natural or otherwise, we need to find this mysterious cause.

Second, they need to come up with an explanation for why a 35% increase in the second most important greenhouse gas does not affect the global temperature. Theory predicts temperature will rise given an enhanced greenhouse effect, so how or why is it not happening?

- 7 years ago

‘Mars and Pluto are warming too’–No they aren’t — and what if they were?

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Global warming is happening on Mars and Pluto as well. Since there are no SUVs on Mars, CO2 can’t be causing global warming.

Answer: Warming on another planet would be an interesting coincidence, but it would not necessarily be driven by the same causes.

The only relevant factor the earth and Mars share is the sun, so if the warming were real and related, that would be the logical place to look. As it happens, the sun is being watched and measured carefully back here on earth, and it is not the primary cause of current climate change.

- 7 years ago

‘Volcanoes emit more CO2 than humans’–Not even close …

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: One decent-sized volcanic eruption puts more CO2 in the atmosphere than a decade of human emissions. It’s ridiculous to think reducing human CO2 emissions will have any effect.

Answer: Not only is this false, it couldn’t possibly be true given the CO2 record from any of the dozens of sampling stations around the globe. If it were true that individual volcanic eruptions dominated human emissions and were causing the rise in CO2 concentrations, then these CO2 records would be full of spikes — one for each eruption. Instead, such records show a smooth and regular trend.


(image from Global Warming Art)

- 7 years ago