Previously…chapter by chapter I’m reading a dodgy book in which people try to pretend climate change isn’t really anything to worry about…
Robert M Carter was an Australian geologist and academic. He died earlier this year http://www.smh.com.au/national/climate-change-sceptic-bob-carter-dies-at-74-20160121-gmb2be.html. As is conventional in a review, I’ll talk about him in the present tense when describing the text.
Funded in part by the Heartland Institute, Bob Carter was an early adopter of the ‘global warming has stopped’ argument based on the relatively low level of warming since the 1998 El Nino.
Carter aims for a clearer structure in this chapter by using what he describes as:
“In this chapter, four basic scientific facts are described that provide an essential context for intelligent discussion of the global warming”
“Context 1— error bounds on reconstructing the global average temperature from thermometer data”
Carter starts with a criticism of the HadCRUT temperature data. We encountered HadCRUT in Chapter 2 where it was the preferred choice of Patrick Michaels when discussing climate models. You’ll remember from that chapter Michaels treated the temperature data as a given and indicated no kind of error bars/confidence intervals for the temperature data but only for the models. Ah, but that was a different chapter and a different sceptic. For Carter, the issue is that HadCRUT has error ranges in its data. This is true, there is necessarily error in the data set and the size of that error for any given point can be quite larger – larger (as Carter points out) than the additional warming caused by anthropogenic greenhouse gases.
But this is a statistical shell game he is playing. The error of an individual measurement is not the same as the error in the size of the warming trend. Simply put, aggregating measurement data that has error can reduce the amount of measurement error. It’s why statistics works.
“Context 2— natural temperature variations over geological time”
We haven’t heard much yet in this book about the paleoclimate record but it will loom large later. However, Carter is just knocking down the same straw man we’ve seen before – essentially that past changes in temperature show that temperature can change for reasons other than carbon dioxide levels. This undoubtedly true – other things can cause climate change. However, we know (see Lindzen in Chapter 3 because he agrees) that carbon dioxide CAN cause changes in global temperature and we know that levels of CO2 have increased significantly.
This rather like a defence lawyer saying that their client didn’t commit a murder on the grounds that other murders have happened in the past which their client couldn’t have committed.
Still, Carter perseveres with a graphic Greenland air temperatures for the last 10,000 years. Interestingly for this data set, Carter does not seem to be concerned about any error ranges – I guess measurement error became unfashionable somewhere between the end of the last section he wrote and the start of this one. The data for the graph is from a paper whose abstract and data can be read here https://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.html
One thing to note is the time axis of the graph is in Years Before Present. This is a standard use in collecting data using things such as radiocarbon dating or the techniques used with estimating temperatures using ice-core samples. However, “present” here does not mean 2016 nor does it mean 2000 when the study was published. It means specifically 1950 CE as it is a technical term for a fixed point. The data does not address late-twentieth-century warming. However, the more recent instrument record (which Carter doesn’t trust) is shown as a thin grey line.
In addition, Greenland is far from typical as far as the Earth’s climate goes. In Carter’s first section he expresses scepticism about temperature sets taken from multiple sites world wide and in the next section points to a single indirect set of measurements from one part of the globe. Greenland is not the world.
“Context 3— carbon dioxide variations over geological time”
“It is widely misrepresented in the public domain that Earth’s current levels of atmospheric CO2 are dangerously and atypically high. Such claims are false, because modern CO2 levels lie near to an all-time low as assessed against the geological record.”
At this point, Carter slides from disingenuous to laughable. CO2 levels are atypical for human history. Yes, sure, a civilisation of trilobites might regard current CO2 levels as a tad low but this hardly seems relevant.
“500 million years ago, before land-plant photosynthesis was operating, atmospheric CO2 attained about fifteen times present day levels”
😩! In what way is that sentence reassuring? Never mind the imagined trilobite civilisation, let’s just consider a time when the first multicellular creatures were hanging out. Essentially Carter out-conservatives every other conservative on earth by waxing nostalgically for the good-old-days of the Precambrian, leading to the classic line:
“Utilising coal as an energy resource simply returns the CO2 to the atmosphere from whence it came in the first place,”
i.e. burning coal returns CO2 to the atmosphere bringing Earth close to the atmospheric conditions that prevailed when early plants first colonised the land? Quite what Carter is trying to prove at this point is unclear. Yes, it is a sound argument against a claim that burning coal will destroy all life on Earth (it won’t) but that really wasn’t the issue.
“Context 4— efficacy of warming caused by extra carbon dioxide”
This is the climate sensitivity argument again. However, Lindzen did it better and Carter gets in a muddle.
“Because of this logarithmic relationship, the amount of warming caused by increasing quanta of CO2 depends upon the level of CO2 already in the atmosphere, and diminishes steadily in a ‘less-temperature-bang-for-every-incremental-carbon-dioxide-buck’ pattern. Given the pre-industrial starting point of 280 ppm of atmospheric CO2, only minor additional warming will occur in response to the much-feared doubling of CO2 to 560 ppm.”
Yup, Carter gets logarithms wrong. The logarithmic relationship doesn’t diminish the impact of a DOUBLING of a quantity. A doubling is MULTIPLICATIVE. Seriously Lindzen already explained this back in Chapter 3:
“ Because of the logarithmic dependence of the radiative impact of CO2, it doesn’t matter what the starting value for the doubling is.” Lindzen Chapter 3
Carter closes the chapter with a more general note, essentially that governments should worry about all kinds of possible climate change and not just warming. Quite what governments should do in this regard he doesn’t say but let’s consider the issue of burning fossil fuels. If Carter is right and CO2 from burning fossil fuels has no net warming effect then burning them does not prevent global cooling. If Carter is wrong about CO2 and CO2 does have a warming effect but right about possible global cooling then it would make sense to conserve fossil fuel reserves so that they can be used later to counteract the possible future cooling.
In the meantime credible evidence exists that the anthropogenic global warming is occurring and while the trilobites might be OK with that, those of us from a more recent geological time have cause to be worried.