Saturday, October 31, 2009

Dr Hansen was wrong - let's change the subject

I have pointed out in recent remarks, that if the debate on climate change were being conducted under normal scientific conventions, then the predictions that were made by Dr. Hansen back in 1988 would, by now, be considered to have been proved false, since the predictions that he made on global temperature rise, and the path that temperature would take, have not followed his models. His predictions were based upon:
Scenario A assumes continued exponential trace gas growth, scenario B assumes a reduced linear growth of trace gases, and scenario C assumes a rapid curtailment of trace gas emissions such that the net climate forcing ceases to increase after the year 2000.
The carbon dioxide path has continued to move along the path predicted for scenario A, yet the temperature rise through today has not only failed to accelerate with it, as Dr Hansen predicted, but instead is much closer to following along the temperature curve predicted for scenario C.

Comparison of Dr Hansen’s scenario predictions against actual temperature anomalies (deg C) (prediction here and actual temp from GISS) Baseline 1951-1980 mean.

I took the data from the plot of temperature predictions that Dr Hansen provided, since it allows me to easily read the predicted temperatures, and I then re-plotted the data with the actual temperatures from the GISS website as the black lines, since the original plot only went as far as 2005. I did note that the tabulated data were slightly different from those of the actual temp data plotted in the 2005 curve, and used the more up to date ones for the entire series.

If one looks at the above comparison that Dr Hansen which is extended from the one made in 2005 the difference between the actual temperature and his predictions clearly show that the actual (black) temperatures are falling away from all but the C scenario (blue) a predictive future which was only supposed to occur if we did ameliorate carbon dioxide emissions. There is no accelerated warming, and there was no amelioration of the rising carbon levels, and so his predictions fail.

However, rather than discuss this rather interesting fact, the global “warming” community has managed, yet again, to divert discussion by dragging debate over a different topic of their choosing, so that this primary point can be hidden from public debate. Their topic centers on whether the globe has been warming at all, an issue that depends very much on where your temperature starts. They might have been somewhat embarrassed to begin with 1998 (as some more realistic of the proponents recognize, following their earlier use of that temperature to show how fast the temperature was going up). However the commentators have chosen, very carefully, to attack the suggestion that the temperature might be cooling, rather than the more relevant issue that the global temperature is not following the models. When you can’t argue, then change the subject.

Now, for what it is worth I have made clear that I am more convinced by the hundreds of peer-reviewed publications (such as those referenced by Jean Grove in The Little Ice Age, or by Brian Fagan in his books) that document the Medieval Warming Period and its predecessors and the intervening cold periods, such as those of the Dark Ages and the Little Ice Age. Thus the fact that the present warming period has not reached the extent of the last warming period, let alone those before it, does not unduly disturb me. (That is evidenced by the ground conditions – such as permafrost - in the Arctic inter alia, and the positions of the ecotones in Europe). Yet it is sadly a denigration of true scientific debate to see how vociferously those arguing for AGW change the topic, or readjust the data whenever they seem at the stage of losing a point in the debate.

If one accepts that we are in this cyclic series then arguments about whether by some fraction of a degree or other the temperature was warmer in 1934 than 2005 in the United States become significantly less critical. The question then becomes whether this Warming Period is significantly less warm than the last, or the one before that. The Roman period was apparently warmer than the Medieval one (the evidence coming among other things from the Roman ruins appearing out of the ice in the Alps), and both were warmer than we are now. But we also need to go back to those periods and see what the conditions were that developed in different parts of the globe (such as the extended droughts in what is now California) and learn from that information, and take precautions accordingly, recognizing what we might be facing as the climate changes. For if we do not learn from history, then we are bound to repeat it - as once was said.

The question as to why these periods existed – or whether the intervening cooling periods are the anomalies – is probably a much more worthwhile study, but given the urge that folk have to change the way in which energy is produced, and the vast fortunes that hang on the changes in policy that are being debated, somehow I don’t see much attention being given to those questions soon.


  1. Real Climate says actual is closer to Model B: RealClimate: Hansen’s 1988 projections I don't really have skin in the climate change game. Whenever I read a contrarian position I check out what the AGW crowd have for a repost, generally coming out on their side of the fence, frankly. Damned if we'll ever stop burning coal though.

    Your ref to roots penetrating Icelandic graves in the MWP was intriguing, has any quantitative analysis of that been done? All I could find Googling around was casual references to it.

  2. The RealClimate post used the plot that I derived the predictions from for the 3 scenarios. When I went and downloaded the actual temperature data from GISS (site cited) it did not agree with the black line on the original graph or the one on RealClimate (same line) so I just used the data itself (I had gone to the data because I just wanted to extend the line 4 years). The plots actually speak for themselves, and you can decide which scenario the actual temp lies closest to.

    I got the original comment on the roots from, I believe, Jean Grove's book, which I have on Kindle so it is a little harder to search than for a paperback, but I'll try and chase down a better reference.

  3. That would be Little Ice Age? The Kindle edition is even more expensive than the hardbacks for some reason, hundreds of bucks.

    B+C only diverge around now, still pretty good for 21 years out. I've always been interested in the Global dimming hypothesis so it will be interesting to see if the recession has some counterintuitive effects as well.

  4. There is no accelerated warming, and there was no amelioration of the rising carbon levels, and so his predictions fail.

    Diamond Drill Bits