Last November John Holdren, the science czar of Obama, took questions about climate change in “Open for Questions” via social media and answered some on video. After the subject of last post, I found question number 3 a particularly interesting one:
Are people truly affecting the climate, or is this a natural phenomenon that is part of Earth’s climate cycle? What evidence points to a human role, besides the vague explanation that humans have been polluting the atmosphere?
– Chance Salway via Facebook
This is how it got answered:
We know beyond any reasonable doubt that humans are the main cause of the warming of earth’s climate that has been measured over the past few decades. The warming is unequivocal. It is based on thermometer measurements at thousands of locations across the face of the Earth,
Indeed, there are a couple thousands of locations that form the basis of the global mean surface temperature network (from memory, somewhere around 1,800 are used). But while that number seems impressive, the world is a very, very big place and even a couple thousands locations on land means on average one thermometer for an area of South Carolina.
There are also some biases like convenience sampling (those locations are not determined randomly), missing data, Urban Heat Island Effect, stations that are added, removed or relocated, instrumental changes, and so on. After this they have to statically extracted, which gives it another layer of uncertainty.
as well as measurements from balloons and sounding rockets high in the atmosphere and probes sampling temperatures in the ocean.
The use of “sounding rockets” seems a bit strange here. As far as I can rely on the definition of it, a sounding rocket is not the same as a satellite. Why not even mention satellites that are used to accurately measure global temperatures since the late 1970s? I can’t really imagine that he “forgot” to mention them.
Ocean probes are indeed used for sampling ocean temperatures, but only reliably since 2003. Point is that we started measuring temperatures reliably just since a (couple of) decades ago. These measurements are more detailed and include data from almost the whole Earth, contrary to the surface thermometer measurements from just a couple thousands locations. But for some odd reason it are the less accurate, more biased temperatures measurements that are being used to sound the alarm…
Most importantly, the fingerprint of the warming, its trajectory over time and the way it varies with latitude and altitude, matches what basic physics and climate models alike predict to result from the measured atmospheric buildup of heat trapping gases.
The fact that both temperatures and CO2 emissions increased doesn’t necessarily mean that one is causing the other. Correlation doesn’t necessarily mean causation. As seen in previous post, climate science is an observational science which means that an exact cause can not be determined. Just as in the nurses study in which estrogen intake and the occurrences of heart attacks were analyzed and the results seemed to be that the group who took estrogen showed less heart attacks, while in the experimental studies showed other aspects that were the driving force behind the real effects of estrogen, meaning more heart attacks.
In this case we are measuring CO2 concentrations and temperature, yet we are not taking into account thousands, maybe millions, of other possible parameters. The current temperature trend could be caused by other aspects we didn’t measure. Like for example the recovery from a cold period ending in 1850, ocean cycles,… So I am not really sure about that “beyond any reasonable doubt”.
That trajectory is very interesting in that regard. Yearly CO2 concentrations rise in an almost linear way, but the temperature changes in a very interesting way. Temperatures in the 1930s-1940s were the highest recorded, yet this was in a period with rather low CO2 concentration. However, in the 1950s, when CO2 concentrations started to rise more rapidly, the temperatures went down. Therefor scientists in the media (including Holdren himself!) warned of a new ice age that was coming. It was until the end of the 1970s that temperature started to rise again in sync with CO2 concentration, this until the end of the 1990s. Yet in the last decade and a half there was no increase in temperatures although we emitted 30% of all emitted CO2 during that time. And no, this was not foreseen by the models, nor by basic physics.
Climate scientists in the media were really surprised by this standstill in temperature increase and had to come up with all sort of after-the-fact explanations. After denying the standstill for more than a decade.
And multiple lines of solid evidence show that this measured buildup has resulted mainly from fossil fuel burning and other human activities.
Well, I am very curious what those “multiple lines of solid evidence” really are…
While the climate of the earth has changed over the millennia as a result of natural factors – principally changes in the tilt and orientation of the earth’s axis and rotation, and in the shape of its orbit around the sun – those changes occur far too gradually to have noticeable effects over a period of mere decades. In their current phases, moreover, they would be gradually cooling the earth – taking us to another ice age – if they weren’t being more than offset by human-caused warming.
Well, I’ll be darned. He is going back to his roots and that seemingly is going very well together with the “global warming fits everything” meme.
Concluding, I am not really sure how to understand this answer as a whole. With such a limited framework where something has to be explained in only a couple sentences, one would think that he would show the strongest evidence available. Yet he sticks with some weak arguments, maybe even some logical fallacies and we can only guess what these “multiple lines of solid evidence” are.
To someone that is taking this on base of his authority, this would be a satisfactory answer. But for skeptics this is just a non-answer.