Climate science in a nutshell – Part 2

I ended yesterday’s post by differentiating climate forcings as things that bring about change, from feedback mechanisms that amplify or accelerate change. The other fundamentally important fact to always bear in mind is that the natural climate forcings that have caused Ice Ages in the past are much smaller than the artificial forcing now being caused by humans. This is not propaganda, it is a scientific fact, which can be calculated algebraically and tested in a laboratory. As noted before, the main natural climate forcings are regular wobbles in the Earth’s axis of rotation and less-regular changes in the eccentricity of the Earth’s orbit (both caused by the gravitational effects of the motion of other planets in the solar system). Other natural forcings include the Sun and volcanic activity. However, the overall luminosity of the Sun (i.e. its energy output) has been remarkably constant for a very long time and its short-term sun spot cycle cannot explain palaeoclimatic changes (as does CO2). Conversely, volcanic activity on Earth is not constant and, on occasion, has been extremely violent and persistent. One such period in Earth’s history is now thought to have been responsible for the extinction of the dinosaurs (in combination with a meteorite impact?) 65 million years ago. Therefore, although we can use a variety of techniques to examine rocks and determine temperature and CO2 changes over the whole of the geological record, the most-interesting data are derived for a relatively shorter-timescale from ice core data. Figure 1 from Hansen et al (2008) One of the first things that Hansen points out (in pages 36 to 51 of Storms of my Grandchildren) is that palaeoclimatic data from many places around the world (i.e. not just from ice cores) indicate that the changes recorded were global in their extent. However, fairly rapidly, Hansen then focuses on the last 130,000 years, which is the age of the earliest evidence for anatomically modern humans (Homo sapiens) found in Africa. This coincides (see Figure 1 from Hansen et al 2008, right) with the previous interglacial period (i.e. the Eemian) to that in which we now find ourselves (i.e. the Holocene). Hansen then points out that a gradual descent into glacial conditions would have initially been manageable but, about 70,000 years ago was quite sudden. Thus, it is believed, we almost didn’t make it: Anthropologists believe as few as 1000 breeding pairs of Homo sapiens survived this “bottleneck” to migrate across and re-populate the entire planet when the glaciers finally began to melt 16 or 17 thousand years ago. However, it was not until rapid sea level changes stopped 7,000 years ago that settled agriculture (as opposed to hunter-gatherer subsistence), followed eventually by what we call modern civilisation, would have been possible. Hansen then goes on to present the evidence that shows that the last 7,000 years of relative stability of climate (and therefore sea level) is not only unusual, it may be about to end and, if it does, we will have caused its termination. This is because climate sensitivity to CO2 is itself a function of temperature. That is to say, whereas it may currently appear to be 3 Celsius for a doubling of atmospheric CO2, the palaeoclimatic record also indicates that, if it were to become much colder or much warmer the effect of any CO2 change itself is increased. This is what caused “Snowball Earth” in early Earth history; and it is what has caused the “Runaway Greenhouse” effect on Venus. This is why not doing anything to mitigate AGW is such a bad idea; we just do not know for certain how far we can push the Earth’s climate from its pre-Industrial equilibrium before catastrophic climate change will be unstoppable. What we do know, however, is that, due to feedback mechanisms, the likelihood of inducing accelerating change increases the longer the artificial climate forcing (i.e. burning fossil fuels) is applied. Indeed, this is what we are now starting to see. Therefore it is time for a reality check: AGW is happening, it is significant, and it is bad news for the planet. If we do nothing, population growth will not be a problem – for most mere survival will be the issue; and we will cause the extinction of a significant proportion all life on Earth. Yes indeed, once again, it really is that simple: We are currently playing a game of Russian roulette for our own survival as a species. Indeed, Clint Eastwood’s rogue detective in the classic Dirty Harry film (1971) comes to mind… “You’ve got to ask yourself a question. Do I feel lucky?


About Rick Altman

Possibly just another 'Climate Cassandra' crying 'Wolf' in cyberspace. However, the moral of the old children's story is that the Wolf eventually turned up!
This entry was posted in Anthropocene, Civilisation, Climate Science, Environment, James Hansen, Mass Extinctions, Modernity, Storms of my Grandchildren. Bookmark the permalink.

2 Responses to Climate science in a nutshell – Part 2

  1. Donald says:

    Yes, Global Warming is happening, worse still, I cannot for the life of me understand why some newspapers and other such media are now jumping into the bandwagon that somehow the last ten years have shown some kind of a reversal of the trend when in fact it wasn’t that long ago that they themselves were mentioning how the last few years were the hottest on record. What kind of short minds do they have? You and I have been debating CO2 for yonks now, but so what? only an idiot cannot “feel” the increasing heat each and every summer, only a fool cannot see the causes and effects of the warming trend (which includes colder winters) I’m beginning to think that the news media has become complicit in destroying any chance we might have at saving our world! Sheer stupidity, plain and simple. 😦 A question …. I read this on the “watt’s up” site “For example, how long does it take fluffy snow to be compacted to ice with little bubbles in it? The answers I got ranged from sixty to five-thousand years.” I’ve seen snow, and I’ve seen it turn to ice in a few hours, within days there was ice two feet think, (Mt Buffalo, Victoria) So if Bubbles were to be trapped within the ice, they would be trapped within days, not “centuries or millennia” So that if I were to take the “sixty to five-thousand years” as gospel then this means that each ice cores would hold some five-thousand years worth of CO2. How does it work?, I’m a bit lost here, I tend to think that layers a few feet thick contain only a few years of evidence, the deeper one goes, the further in time one looks; but in years or centuries and so on …. not in thousands of years at a time. Any chance of a blog on this?


    • Rick_Altman says:

      I agree, Donald. The ability of some people to review data (even look at a graph sometimes) and then reach (or at least claim to have reached) completely contrary and indefensible conclusions is absolutely astounding: Indeed, I have cited two examples in response to an item on Climate Denial Crock of the Week today. As for WUWT, as you know, I am now banned (or at least my comment did not appear when I last tried to post one). However, this is all just evidence of the same problem: I think it is called cognitive dissonance or “Thereisnonesoblindism“… 🙂


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