Hansen – where the IPCC went wrong
I could have just called this post “Climate science in a nutshell – Part 3” but that would have been to display a singular lack of imagination (no pun intended); and may not have grabbed your attention. So, yes, I am continuing my review of Storms of my Grandchildren. Hansen says in the Introduction to the book, his intention was to summarise events since his sixtieth birthday in 2001 and, the further you get into the book, the more obvious it becomes that he has spent much of his time since then telling anybody that would listen (and many would not) that the IPCC were seriously underestimating the risks posed by climate change. This has now become a well-established fact that will hopefully be addressed in the forthcoming Assessment Report 5. However, when Hansen started saying this in 2003, it was almost revolutionary…
First of all a brief journey back in time: In Chapter 4, Henson goes on a brief detour to explain why it is that we still don’t have the data to accurately quantify exactly how much pollution in the atmosphere is slowing down the warming that would otherwise be taking place; and why this is now so regrettable. The answers being that special interest groups interfered with decision making 20 years ago to prevent investment in the necessary satellite construction and deployment; and if we understood this “global dimming” effect better we would also have a better idea of how bad things could get (if and when developing countries clean-up their act).
James Hutton is one of the most famous figures in the history of geology who first devised the Principle of Uniformitarianism (which Chrales Lyell later popularised by saying “the the present is the key to the past”). This contends that, for example, by watching the way water can cut a channel through moist sand on a beach when the tide goes out, we can understand how the Grand Canyon was formed; and that the only difference (in this instance) is the time taken to achieve the end result. Hansen’s insight has been to invert this Principle and to realise that the past is the key to the present; in that we can deduce what will now happen by understanding what happened in the past; and why (Chapter 5).
Perhaps the most noticeable thing about the time-series data from the ice core record (reproduced here for convenience) is what Hansen calls the “saw-toothed climate response”: Whereas ice age conditions have generally taken tens of thousands of years to develop; the Earth has typically emerged from them at least ten times faster. This Hansen attributes to the fact that ice melts much faster than it can accumulate (which is dependent on it snowing first). Furthermore, although the pattern of the last 1 million years has been for the Earth to go in and out of ice ages, it has been much warmer in the more distant past. For example, Antarctica first became glaciated when the temperature was 4 Celsius warmer than pre-Industrial times; 35 million years ago when atmospheric CO2 was at 450ppm and falling. This is why Hansen went on record a few years ago saying that humanity needed to avoid allowing such conditions to re-establish themselves because the melting of ice sheets would then be inevitable.
However, what has irritated Hansen for much of the last 10 years is the fact that the IPCC predictions of sea level change in 2001 and 2007 have ignored the melting of ice caps. Furthermore, Hansen is convinced that this is the reason why climate change effects (melting glaciers, permafrost, sea ice, and ice caps in Greenland and West Antarctica) are now accelerating faster than the IPCC predicted: Basically, the IPCC did not allow for amplifying feedback mechanisms. Quite why, I still don’t understand (hopefully I will by the time I finish the book), but I suspect it was because they were relying on climate modelling too much; and not looking out the window enough.
The next factor in the equation (to determine how bad things could get and how quickly they could get there) is the inertia in the climate system: Despite the fact that the Earth can warm-up much quicker than it cools-down (and ice core data do show that air temperatures can change dramatically within just a few years), the oceans take decades to change their overall temperature because of their volume. Although the recent warming (and acidification) of the oceans cannot now be seriously questioned, those that would deny that we have a problem and/or are the cause of the problem will no doubt continue to do so (just as they continue to dispute the veracity of land-based temperature increases). However, what should be remembered is this: Despite all of their limitations, computer modelling did predict the warming of the oceans and the consequential increase in the frequency and intensity of tropical storms, droughts, wildfires, floods, blizzards, etc. Therefore, whilst it may be impossible to prove that any individual extreme weather event is a direct consequence of climate change, in aggregate, it is surely as plain as the nose on your face that this is exactly what we were told would happen. The big question is, what’s next?
Please come back tomorrow to find out! :-)