The southern summer silly season is here, and newspapers are desperate for copy. That’s about the only good reason I can think of for the nation’s biggest-selling newspaper, Auckland’s NZ Herald, giving Chris “unreliable witness” de Freitas yet more space to re-run some tired old climate sceptic arguments under the headline Emotion clouding underlying science of global warming. Doubt is his product, and he tries very hard to sound reasonable as he spins his tale. It’s a pity then that the Auckland University associate professor not only misrepresents the evidence, but gets it so badly wrong that he’s an embarrassment to his department.
CdF sets out his stall by complaining that the media seldom take the time to explain the science of climate. The “scientific basics”, he says, “are not contentious”, and he proceeds to explain that adding greenhouse gases like carbon dioxide to the atmosphere will cause some warming. He continues:
Debate focuses on climate feedbacks that may or may not suppress, perpetuate or amplify an initial change caused by increasing concentrations of greenhouse gases.
The first misdirection: there is no great debate in this area. There are two sceptic scientists who are desperately trying to argue that there is great uncertainty in this area (Roy Spencer and Richard Lindzen have been trying to find negative feedbacks for years), but their publications are not persuasive to their peers.
A doubling of carbon dioxide, by itself, adds only about one degree Celsius to greenhouse warming.
Nearly. CdF is lowballing the number. The “no feedbacks” warming from a doubling of CO2 above preindustrial levels is usually taken to be about 1.2ÂºC.
Computer climate models project more warming because the modellers build in feedbacks from water vapour and clouds that amplify the initial change. These are the so called positive feedbacks. For example, higher temperature would mean more evaporation globally, which in turn means more heat-trapping water vapour is put into the atmosphere leading to even higher temperatures.
Modellers don’t “build in” positive feedbacks, they emerge from the physics the models are based on. Warming the atmosphere means it will hold more water vapour, which will act to increase warming (as well as add fuel to weather systems and contribute to greater rainfall intensities). The size of this feedback is governed by the Clausius-Clapeyron relation, and is not novel science. This feedback is already observed in action: the atmosphere today contains 4% more water vapour than in 1970.
On the other hand, negative feedbacks might prevail. For example, more water vapour in the atmosphere could lead to greater cloud cover. Clouds reflect the heat from the Sun and cool the Earth, offsetting the initial rise in global temperature.
Another bit of misdirection. Clouds can act to both warm and cool — sometimes both at the same time. The balance between warming and cooling for the atmosphere at large is not clear, but most evidence points to an overall warming effect.
The role of negative feedback processes are played down by global warming alarmists, whereas sceptics point to the four-billion-year-old global climate record that shows runaway global cooling or warming has never occurred because negative feedbacks regulate the global climate system.
This is just nonsense. Positive feedbacks do not have to cause runaway warming (or cooling), but it would be true to say that the balance between natural positive and negative feedbacks over geological time has kept the planet reasonably equitable for hundreds of millions of years (although we got close to trouble several times in the distant past). However, how the climate system behaves under natural (ie non-anthropogenic) forcings and feedbacks isn’t much help to us going forward, because the planet has never had a species come along and increase atmospheric CO2 by 40% in 150 years before. Worse, CO2 acts like a temperature control knob. Over the last 4 million years a change of 100 ppm has been enough to make the difference between cold glacial conditions and warm interglacials, which really ought to suggest to de Freitas that the system is quite sensitive to small changes. To make matters worse, however hard Lindzen and Spencer try, we can’t seem to find a negative feedback (or magic wand) which will save our bacon. And when we add all the forcings and feedbacks together, and consider many lines of evidence, we find that the climate system will warm by around 3ÂºC for a doubling of CO2 (if we’re lucky).
Most people are surprised to hear that no one has uncovered any empirical real-world evidence that humans are causing dangerous global warming. Finding this evidence is crucial, since scientific issues are resolved by observations that support a theory or hypothesis. They are not resolved by ballot.
This is a straightforward lie. There’s plenty of empirical evidence that warming is happening, and that it’s our fault. Here’s a nifty graphic from Skeptical Science that provides an overview of all the lines of evidence that confirm warming is happening:
Perhaps the weasel word here is “dangerous”. Perhaps CdF agrees that all this evidence exists, but fervently believes that continued warming won’t be dangerous. Perhaps he thinks it would be wise to wait until the “dangers” were undeniable even by him. Perhaps he should stop playing chicken with the future of the planet. But then we return to the sweet voice of unreason…
None of this is to say we should simply walk away from considerations of a global warming threat, but prudent consideration of the scientific facts is essential.
Quite so, Chris, quite so. The problem is that the facts are not as you portray them.
No science should have to rely on one group or authority saying, “Just trust us,” particularly when tens of millions of dollars of public policy decisions are on the line.
And finally we get to the point. Unfortunately, Chris has it precisely arse about face. What he means is…
No policy should be delayed because one small group or PR campaign says “don’t trust the science,” particularly when hundreds of millions of lives are on the line.