Guest essay by Eric Worrall
The National Center for Science Education has in my opinion betrayed the scientific principles they claim to defend, by suggesting in its global warming primer that climate models are reliable, and by claiming the serially debunked Mann hockey stick graph is credible.
Q: Still, shouldn’t there be some explanation for the slowing? [the pause]
Yes, there should be, and while scientists are still trying to understand the details, the basic explanation almost certainly goes as follows. The addi- tional heat and energy trapped in the atmosphere by the rising carbon diox- ide concentration can manifest itself in several di erent ways, and the ris- ing surface temperature shown in figures 2.1 and 2.2 is only one of those. In fact, more than 90% of the added heat and energy is expected to warm the water in the oceans (as opposed to warming the land and ocean surface), and data indicate that the ocean waters have continued to warm without any evidence of slowing (figure 2.3).
Scientific models differ from the models you may be familiar with in everyday life, which are typically miniature representations of real objects, such as model cars or airplanes. In contrast, a scientific model is a conceptual representation, often developed with the help of com- puters, that uses known scientific laws, logic, and mathematics in an attempt to describe how some aspect of nature works. The model can be tested by seeing how well it corresponds to reality. Models are important in almost every field of science, but here we’ll focus specifically on models of Earth’s climate.
The principle behind a climate model is relatively simple. Scientists create a computer program that represents the climate as a grid of cubes like those shown in figure 2.6, so that each cube represents one small part of our planet over one range of altitudes in the atmosphere. The “initial conditions” for the model consist of a mathematical represen- tation of the weather or climate within each cube at some moment in time. This representation might incorporate data on such things as the temperature, air pressure, wind speed and direction, and humidity at the time the model begins. The model uses equations of physics (for example, equations that describe how heat flows from one cube to neighboring cubes) to predict how the conditions in each cube will change in some time period, such as the next hour. It then uses the new conditions and the equations to predict the conditions after another hour, and so on. In this way, the model can simulate climate changes over any period of time.
Decades ago, climate models were fairly simple, using grids no more complex than the one in figure 2.6. Over time, however, scientists have in essence used trial and error to make the models better and better. Again, the principle is easy to understand: If your model fails to reproduce the real climate in some important way, then you look to see what might be going wrong. For example, you might have neglected some important law of physics, or the cubes in your grid might need to be smaller to give accurate results. Once you think you know what went wrong, you revise the model, and see if it works better. If it does, then you have at least some reason to think you are on the right track, and if it doesn’t, you go back to the drawing board.
Today’s climate models are fantastically detailed, and they reproduce the actual climate of the past century with remarkable accuracy. Indeed, the modern models work so well that scientists can use them to conduct “experiments” in which they ask what would happen if this or that were different than it is. Figure 2.7 shows an example of the power this approach provides. The red curve shows temperatures over the past century and a half as predicted by the best available climate models, which take into account both natural factors affecting cli- mate, such as changes in the Sun’s output and volcanic eruptions, and human factors, such as the increase in the carbon dioxide concentra- tion from the burning of fossil fuels. Notice that these models provide an excellent match to the general trends in the real data (black curve). In contrast, models that leave out the human factors predict the blue curve, and as you can see, this curve does not agree with the observed warming of the past few decades. The fact that we get a close match between the models and reality only when changes in both natural and human factors are included gives us great confidence that human factors are the cause of the recent warming.
What’s the bottom line for Skeptic Claim 2?
There are no known natural factors that could account for the substantial warming of the past century. We’ve discussed two sets of observations that definitively rule out the Sun as the cause: (1) solar energy input has been falling while the temperature has been rising; and (2) the upper atmosphere has been cooling while the lower atmosphere warms, which is consistent only with greenhouse warming, not warming due to the Sun. Scientists investigate other potential causes with models, and today’s sophisticated models match up extremely well with observations of the actual climate — but only when we include the human contributions to global warming, not natural factors alone. The match makes it highly likely that the models are on the right track, giving us further confidence in the idea that human activity is the cause of most or all recent global warming.
Wait — didn’t I hear that the hockey stick graph has been discredited?
Well, you probably have heard this, since it is frequently repeated in places like the Wall Street Journal’s op-ed pages, but it is not true. The original version of the “hockey stick” was published by climate scientist Michael Mann in 1998, and he used only a single data set. Skeptics jumped on it, claiming all kinds of reasons why the data should be doubted. Scientists took the skeptic concerns seriously, and therefore did what scientists do: They investigated in more detail. Indeed, the reason you see so many data sets — from independent sources including tree rings, corals, stalagmites, ice cores, and more — in figure 2.10 is that the scientific community went to great lengths in trying to either confirm or refute Mann’s original “hockey stick.” Keep in mind that every curve you see in figure 2.10 represents many years of fieldwork and careful research by a substantial group of scientists, who often put their lives on the line to collect the data in remote and dangerous locations. As you can see, these additional studies clearly confirm Mann’s original conclusions. Still not mollified, the skeptics were so adamant in their objections that they convinced Con- gress to ask the National Research Council (NRC) to investigate those conclusions. The NRC report, published in 2006, concluded that the graph and the data were fully valid.
The NCSE document clearly contradicts itself with regard to the reliability of climate models. The suggestion that models are so reliable they can be used to conduct climate experiments is ridiculous in the face of the admission that the reason for the pause is still being investigated, that the models might have to be adjusted. The “modern” models have failed their first serious test.
One third of all the CO2 humans have ever produced was emitted during the pause. If model assumptions were correct, this should have blown global temperatures sky high. The fact surface temperatures stagnated, you can’t simply sweep an anomaly like that under the carpet, or into the ocean. Even if the ocean did swallow the heat, a valid climate model should have predicted this. If a model cannot predict when the ocean will swallow vast amounts of excess heat, then projections of future temperature are utterly unreliable.
As for suggestions Mann’s hockey stick has been upheld by scientific investigation, you could read many excellent analysis of hockey stick methodology issues, but what I find most intriguing is that even the scientists who helped produce the hockey stick had reservations – they just chose not to talk about those concerns in public.
Climategate email 0938018124.txt (CRU Professor Keith Briffa in September 1999, recipients include Michael Mann)
… I know there is pressure to present a nice tidy story as regards ‘apparent unprecedented warming in a thousand years or more in the proxy data’ but in reality the situation is not quite so simple. We don’t have a lot of proxies that come right up to date and those that do (at least a significant number of tree proxies ) some unexpected changes in response that do not match the recent warming. I do not think it wise that this issue be ignored in the chapter.
For the record, I do believe that the proxy data do show unusually warm conditions in recent decades. I am not sure that this unusual warming is so clear in the summer responsive data. I believe that the recent warmth was probably matched about 1000 years ago. …
Climategate email 3759.txt, sent to Keith Briffa in August 2000, discusses substantial evidence that the medieval warm period and little ice age were global, not local variations of limited geographic scope, as was claimed by Michael Mann.
Here is the Oroko Swamp RCS chronology plot in an attached Word 98 file and
actual data values below. It certainly looks pretty spooky to me with
strong “Medieval Warm Period” and “Little Ice Age” signals in it. It’s
based on substantially more replication than the series in the paper you
have to review (hint, hint!). In terms of rbar, sample size, and eps, it is
probably okay back to about AD 980 at this time. I still have 3-4 more
subfossil sections to process, but it is doubtful that the story will
change much. When I come over in October, I am thinking about asking
Jonathan Palmer to come over from Belfast for a visit. What do you think
Cimategate source material available from Wikileaks
Oroko Swamp is in New Zealand, a long way from Northern Europe, where the medieval warm period and little ice age are documented history. The existence of a substantial global medieval warm period and little ice age is a direct contradiction of the flatness of the pre-anthropogenic component of Mann’s hockey stick reconstruction. And its not just the reconstruction from Oroko Swamp in New Zealand – other proxies from Japan, Antarctica and elsewhere have confirmed that the medieval warm period and little ice age were global.
Submitting to pressure to tell a nice tidy story, at least in public, ignoring or discounting evidence which contradicts the alarmist position, trying to sweep aside criticism of a theory by suggesting everything is OK because a major anomaly is being investigated – this isn’t the scientific method I was taught.
In my opinion the NCSE is doing a grave disservice by advancing such a nakedly partisan assessment of climate science, by ignoring or glossing over very real issues with climate alarmist positions. I’m not suggesting the NCSE should necessarily take the skeptic position on every climate issue, but a little more balance would provide a much better teaching resource for their audience. Let us hope the NCSE have the integrity to apologise for and correct their unbalanced assessment, once they realise what they have done.