What do scientists really say about climate change?

There’s a video making the rounds on social media by Richard Lindzen, who is an emeritus professor of meteorology.

Most of the claims in the video are literally true, but they’re presented in a way that misrepresents the actual facts of climate change science.  I’ve gone through and highlighted the ones that caught my eye, but I’m sure that an actual climate scientist would be able to add to the list.

“For 30 years . . . the climate has changed remarkably little. . . . In fact, it seems that the less the climate changes, the louder the voices of the climate alarmists get.”

The phrase “remarkably little” is vague enough that we can’t mark this claim as strictly false, but it is misleading.  In the past 30 years the global mean temperature has gone up over 1.5 degrees Fahrenheit. This seems small compared to seasonal and day-to-day variation, but the consensus view of scientists is that long-term temperature increase of this magnitude is very dangerous.

There is a graphic labeled “Climate Change over Time” at twenty seconds in, which gives the impression that there has been no global temperature increase for the past two decades. The graph isn’t labeled, so I can’t be sure where it comes from, but it is misleading, and perhaps wrong.

Here’s a graph from NASA of global temperatures over time:

The temperature graph in the video misrepresents the actual global temperatures by showing 1998 as being much warmer than the most recent years. You’ll notice that the NASA graph shows recent peaks as being warmer than 1998, and it also shows the record breaking temperatures of the past few years.

I imagine the graph displayed in the video was drawn from some genuine source (perhaps a temperatures of a single region rather than the globe, or perhaps it’s uncorrected satellite data), but it does not represent the current scientific view of the history of global temperatures. (The graph is also guilty of “cherry picking” by starting near 1998 which was an unusually large upward spike.)

“There are basically three groups of people dealing with this issue. Groups one and two are scientists.”

One can group people however one likes, so true enough. However, the graphic representation of one scientist on the “worried about global warming” or IPCC side and one scientist on the “skeptic” side might be misleading.

If the depiction gave you the impression that the two groups are roughly equal in number, then you were deceived. A more accurate graphic would have at least 20 climate scientists in “Group 1″ and a single scientist in “Group 2.”

It’s also somewhat misleading to suggest that these are the only groups that are relevant to this discussion. For example, there are professional organizations of scientists – such as the AAAS, the American Physical Society, and the American Chemical Society – which have looked at the science of climate change and have agreed with the IPCC that the danger is real.

“Group two is made up of scientists who don’t see this as an especially serious problem. This is the group I belong to. We’re usually referred to as skeptics.”

Again, one can choose groups however, one likes, but if viewers gets the impression that most high-profile climate “skeptics” are scientists, then they have been misled. While there are skeptical climate scientists like Lindzen, the vast majority of “skeptics” that the public hears from are not climate scientists.

“We note that there are many reasons why the climate changes—the sun, clouds, oceans, the orbital variations of the earth, as well as a myriad of other inputs. None of these is fully understood, and there is no evidence that CO2 emissions are the dominant factor.”

It’s true enough that they make this claim, but the claim is misleading or false.

First, the claim that other sources of climate variation are not “fully understood” is a red herring. Nothing is “fully understood.” The relevant question is whether we understand them *enough* to say that we should be concerned about CO2. The consensus view of scientists is that we do.

Saying there is no evidence that CO2 is “the dominant factor” is either misleading or false. It’s true that other factors play a larger role in temperature fluctuations, but the danger of CO2 comes from the fact that it is steadily accumulating, while clouds, for example, develop and then disappear, and solar activity increases then decreases.

Importantly, scientists have studied the impact of all of these factors (solar activity, ocean currents, orbital variations, volcanic activity) and they are able to model their impact on global temperatures. What they find is that most of the variation found in the temperature record can be accounted for in this way, but we have a residual fairly steady rise in global temperatures of about one degree Fahrenheit over the past 30 years. You can see a graphic representation of the warming that’s left over after removing these other factors here:

Our best explanation for the additional warming is the increase in greenhouse gasses.  We know CO2 warms the Earth, and we know we’re increasing the amount of CO2.

Claimed points of agreement:

“1) The climate is always changing.”

Yes, but if this is taken to imply that the current change is natural or nothing to be alarmed about, then no – most scientists reject this claim.

“2) CO2 is a greenhouse gas without which life on earth is not possible, but adding it to the atmosphere should lead to some warming.”

Yes. But it’s worth noting that even this has been denied by many “skeptics” (though few if any with genuine scientific credentials). And one also wonders why the video highlights the phrase “without which life on Earth is not possible.” Life also isn’t possible without water, but I would object if someone wanted to drown the entire globe under a mile of water.

“3) Atmospheric levels of CO2 have been increasing since the end of the Little Ice Age in the 19th century.”

Yes, but another way of phrasing this would be to say that they have been increasing since the Industrial Revolution in the 19th century.

“4) Over this period (the past two centuries), the global mean temperature has increased slightly and erratically by about 1.8 degrees Fahrenheit or one degree Celsius; but only since the 1960’s have man’s greenhouse emissions been sufficient to play a role.”

Yes (depending on what you mean by “slightly”) but if this claim gave you the impression either that (a) pre-1960 anthropogenic CO2 was completely irrelevant, or (b) that nothing changed around 1960 with respect to global temperatures, then you were misled.

Look at the NASA graph of global temperatures again. Notice that right around 1960 we start to see a somewhat steady rise in temperatures. That’s the blade of the infamous “hockey stick.” That’s what the vast majority of scientists are worrying about.

*Most* of the global warming we’ve seen has been since our CO2 has “been sufficient to play a role.” And the “erratic” nature of temperature fluctuations gives us no reason to doubt that our greenhouses gasses are dangerously warming the globe.

“5) Given the complexity of climate, no confident prediction about future global mean temperature or its impact can be made. The IPCC acknowledged in its own 2007 report that “The long-term prediction of future climate states is not possible.”“

This quotation is taken out of context and presented in a misleading way, and Lindzen’s claim is only true if we’re willing to weasel on the meaning of a “confident prediction.”

The above quotation from the IPCC is from a section talking about how scientists need to deal with lots of data and models at different scales, and the next sentence is, “The most we can expect to achieve is the prediction of the probability distribution of the system’s future possible states by the generation of ensembles of model solutions.”

So what they’re saying is that because the global climate is a coupled non-linear dynamical system, it’s impossible (even in principle) to predict exactly what will happen the way we can confidently make predictions about simple mechanical systems such as the orbits of planets. But they’re not saying that we can’t say anything at all. They’re saying that we can use ensembles to make good predictions of how *likely* various scenarios are.

And that’s what the IPCC report does. It tells us how likely it is that global temperatures will increase if CO2 levels increase. And what it tells us is that if we keep pumping out CO2 it is very likely (though not certain) that we will increase the Earth’s temperature dangerously.

“Most importantly, the scenario that the burning of fossil fuel leads to catastrophe isn’t part of what either group asserts.”

This is only true if we take “catastrophe” to mean something like the extinction of humanity, or the collapse of civilization and descent into dystopia.

If we consider it to be a “catastrophe” if sea levels rise to the point where some coastal areas become uninhabitable and other areas need to spend billions of dollars to cope with storm surges, then it isn’t true that “both groups” agree on this.

Similarly, if we consider it to be a “catastrophe” if numerous ecosystems are disrupted (leading to an increase in the already alarming rate of extinction), or if we have an increase in droughts and floods, or if farming gets disrupted as growing zones move towards the poles, then we don’t have agreement.

“So why are so many people worried, indeed, panic stricken about this issue. Here’s where Group Three comes in—the politicians, environmentalists, and media.”

Here Lindzen pretty obviously engages in a bit of unsupported speculation. I, for one, think it’s pretty silly to suppose that politicians think that the best road to money and power is to worry about global warming, or that most environmentalists have a “ near religious devotion to the idea that man is a destructive force acting upon nature.” But you can judge for yourself.

I should point out a few misleading aspects of this section, though.

First, the only non-scientists that Lindzen mentions are those on the pro-IPCC side. It should be noted that most “skepticism” about global warming comes not from climate scientists, but from various “Merchants of Doubt” as Naomi Oreskes has appropriately named them. There’s plenty of money and power for politicians who take the side of the oil companies. There are many “free market” advocates whose “religious devotion” to undermining regulations is comparable to anything the environmentalists have to offer. And there’s an active media market for people who are “skeptical” of climate science.

Also, he speaks of “scientists outside of climate physics” who consider e.g., the possibility that increases in droughts might lead to the displacement of people who rely on farming, and that displacement might then lead to conflict and war, and he dismisses them as “jumping on the band wagon.”

But he ignores the huge number of scientists who have looked at the science and agree that it’s solid. Again, nearly all organizations of professional scientists have assembled panels to look into the science of climate change, and (as far as I have seen) every such panel has concluded that the core assertions of the IPCC are reliable enough to take seriously, and that we face a genuine danger from anthropogenic climate change.

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