Monthly Archives: April 2011

Using Models to Create Historical Data

Megan McArdle points to this story about trying to create infant mortality data out of thin air:

Of the 193 countries covered in the study, the researchers were able to use actual, reported data for only 33. To produce the estimates for the other 160 countries, and to project the figures backwards to 1995, the researchers created a sophisticated statistical model. [1]What’s wrong with a model? Well, 1) the credibility of the numbers that emerge from these models must depend on the quality of “real” (that is, actual measured or reported) data, as well as how well these data can be extrapolated to the “modeled” setting ( e.g. it would be bad if the real data is primarily from rich countries, and it is “modeled” for the vastly different poor countries – oops, wait, that’s exactly the situation in this and most other “modeling” exercises) and 2) the number of people who actually understand these statistical techniques well enough to judge whether a certain model has produced a good estimate or a bunch of garbage is very, very small.

Without enough usable data on stillbirths, the researchers look for indicators with a close logical and causal relationship with stillbirths. In this case they chose neonatal mortality as the main predictive indicator. Uh oh. The numbers for neonatal mortality are also based on a model (where the main predictor is mortality of children under the age of 5) rather than actual data.

So that makes the stillbirth estimates numbers based on a model…which is in turn…based on a model.

This sound familiar to anyone?   The only reason it is not a good analog to climate is that the article did not say that they used mortality data from 1200 kilometers away to estimate a country’s historic numbers.

Smart, numerically facile people who glibly say they support the science of anthropogenic global warming would be appalled if they actually looked at it in any depth.   While gender studies grads and journalism majors seem consistently impressed with the IPCC, physicists, economics, geologists, and others more used to a level of statistical rigor generally turn from believers to skeptics once they dig into the details.  I did.

We Are Finally Seeing Healthy Perspectives on CO2 in the Media

The media loves lurid debates.  Which in the climate debate has meant that to the extent skeptics even get mentioned or quoted in media articles, it is often in silly, non-scientific sound bites.  Which is why I liked this editorial in the Financial Post, which is a good presentation of the typical science-based skeptic position – certainly it is close to the one I outlined in this video.  An excerpt:

Let’s be perfectly clear. Carbon dioxide is a greenhouse gas, and other things being equal, the more carbon dioxide in the air, the warmer the planet. Every bit of carbon dioxide that we emit warms the planet. But the issue is not whether carbon dioxide warms the planet, but how much.

Most scientists, on both sides, also agree on how much a given increase in the level of carbon dioxide raises the planet’s temperature, if just the extra carbon dioxide is considered. These calculations come from laboratory experiments; the basic physics have been well known for a century.

The disagreement comes about what happens next.

The planet reacts to that extra carbon dioxide, which changes everything. Most critically, the extra warmth causes more water to evaporate from the oceans. But does the water hang around and increase the height of moist air in the atmosphere, or does it simply create more clouds and rain? Back in 1980, when the carbon dioxide theory started, no one knew. The alarmists guessed that it would increase the height of moist air around the planet, which would warm the planet even further, because the moist air is also a greenhouse gas.

This is the core idea of every official climate model: For each bit of warming due to carbon dioxide, they claim it ends up causing three bits of warming due to the extra moist air. The climate models amplify the carbon dioxide warming by a factor of three — so two-thirds of their projected warming is due to extra moist air (and other factors); only one-third is due to extra carbon dioxide.

That’s the core of the issue. All the disagreements and misunderstandings spring from this. The alarmist case is based on this guess about moisture in the atmosphere, and there is simply no evidence for the amplification that is at the core of their alarmism.

That is just amazingly close to what I wrote in a Forbes column a few months back:

It is important to begin by emphasizing that few skeptics doubt or deny that carbon dioxide (CO2) is a greenhouse gas or that it and other greenhouse gasses (water vapor being the most important) help to warm the surface of the Earth. Further, few skeptics deny that man is probably contributing to higher CO2 levels through his burning of fossil fuels, though remember we are talking about a maximum total change in atmospheric CO2 concentration due to man of about 0.01% over the last 100 years.

What skeptics deny is the catastrophe, the notion that man’s incremental contributions to CO2 levels will create catastrophic warming and wildly adverse climate changes. To understand the skeptic’s position requires understanding something about the alarmists’ case that is seldom discussed in the press: the theory of catastrophic man-made global warming is actually comprised of two separate, linked theories, of which only the first is frequently discussed in the media.

The first theory is that a doubling of atmospheric CO2 levels (approximately what we might see under the more extreme emission assumptions for the next century) will lead to about a degree Celsius of warming. Though some quibble over the number – it might be a half degree, it might be a degree and a half – most skeptics, alarmists and even the UN’s IPCC are roughly in agreement on this fact.

But one degree due to the all the CO2 emissions we might see over the next century is hardly a catastrophe. The catastrophe, then, comes from the second theory, that the climate is dominated by positive feedbacks (basically acceleration factors) that multiply the warming from CO2 many fold. Thus one degree of warming from the greenhouse gas effect of CO2 might be multiplied to five or eight or even more degrees.

This second theory is the source of most of the predicted warming – not greenhouse gas theory per se but the notion that the Earth’s climate (unlike nearly every other natural system) is dominated by positive feedbacks. This is the main proposition that skeptics doubt, and it is by far the weakest part of the alarmist case. One can argue whether the one degree of warming from CO2 is “settled science” (I think that is a crazy term to apply to any science this young), but the three, five, eight degrees from feedback are not at all settled. In fact, they are not even very well supported.