Climate Models

The Kyoto Protocol was an agreement to put a lid on economic development because climate models warn of "global warming". The idea was sold as simply "being sensible" (AKA, the "precautionary principle", see comments at the bottom of this post) because you weighed risk versus cost and made a rational decision. But that characterization of the issue justifies signing up for Kyoto only if the science is solid. But that agreement -- nearly eleven years ago -- is built on a pretty shaky foundation because climate modeling is a "science" only in the sense that it is a technology that attempts to capture known science in computer models. How accurate the models are depends on how well the known science reflects the real world.

People should be queasy when they read new science reports like the following from a news release on PhysOrg about recent research by Peter Crozier and James Anderson at Arizona State University:

So-called brown carbons – a nanoscale atmospheric aerosol species – are largely being ignored in broad-ranging climate computer models, Crozier and Anderson say.

Studies of the greenhouse effect that contribute directly to climate change have focused on carbon dioxide and other greenhouse gases. But there are other components in the atmosphere that can contribute to warming – or cooling – including carbonaceous and sulfate particles from combustion of fossil fuels and biomass, salts from oceans and dust from deserts. Brown carbons from combustion processes are the least understood of these aerosol components.

The parameter typically used to measure degrees of warming is radiative forcing, which is the difference in the incoming energy from sunlight and outgoing energy from heat and reflected sunlight. The variety of gasses and aerosols that compose the atmosphere will, under different conditions, lead to warming (positive radiative forcing) or cooling (negative radiative forcing).

The ASU researchers say the effect of brown carbon is complex because it both cools the Earth's surface and warms the atmosphere.

"Because of the large uncertainty we have in the radiative forcing of aerosols, there is a corresponding large uncertainty in the degree of radiative forcing overall," Crozier says. "This introduces a large uncertainty in the degree of warming predicted by climate change models."

A key to understanding the situation is the light-scattering and light-absorbing properties – called optical properties – of aerosols.

Crozier and Anderson are trying to directly measure the light-absorbing properties of carbonaceous aerosols, which are abundant in the atmosphere.

"If we know the optical properties and distribution of all the aerosols over the entire atmosphere, then we can produce climate change models that provide more accurate prediction," Anderson says.

Most of the techniques used to measure optical properties of aerosols involve shining a laser through columns of air.

"The problem with this approach is that it gives the average properties of all aerosol components, and at only a few wavelengths of light," Anderson says.

He and Crozier have instead used a novel technique based on a specialized type of electron microscope. This technique – monochromated electron energy-loss spectroscopy – can be used to directly determine the optical properties of individual brown carbon nanoparticles over the entire visible light spectrum as well as over the ultraviolet and infrared areas of the spectrum.

"We have used this approach to determine the complete optical properties of individual brown carbon nanoparticles sampled from above the Yellow Sea during a large international climate change experiment," Crozier says.

"This is the first time anyone has determined the complete optical properties of single nanoparticles from the atmosphere," Anderson says.

It's typical for climate modelers to approximate atmospheric carbon aerosols as either non-absorbing or strongly absorbing. "Our measurements show this approximation is too simple," Crozier says. "We show that many of the carbons in our sample have optical properties that are different from those usually assumed in climate models."

Adds Anderson: "When you hear about predictions of future warming or changes in precipitation globally, or in specific regions like the Southwestern United States, the predictions are based on computer model output that is ignoring brown carbon, so they are going to tend to be less accurate."

The precautionary principle: This sounds reasonable on the surface, and in broad outline it is correct, but applying it does not alleviate the need to do a cost-benefit analysis as part of an overall strategy of risk management. Life is full of risks. Avoiding risks is not a solution. Any gain requires taking a risk. The trick is to minimize risks while maximizing benefits. The Kyoto Protocol has lost sight of this. The Chicken Littles of the Global Warming camp tell you fearful stories and try to convince you that we have to forgo economic growth (and even technological advance) because of their fear of the future. I'm reminded of the story of nuclear scientists at Los Alamos fearful that testing the first nuclear weapon might cause the atmosphere to spontaneously combust or the modern day physicists at the CERN that running the Large Hadron Collider will create a black hole that will suck our world into nothingness. These are worries, but they shouldn't stop you. Instead, you do an analysis and make a judgement of risk versus benefit. The fearful few will always opt to "stop! don't take any risks" while the foolhardy few will say "who cares! go for it!". The muddled middle will be swayed either way. The rational few will want to sit down and calculate. To use knowledge to make judgements. What the climate modelers show is that their current models are not as solid a science as they present. So their give themselves over to the fearful few. I'm all for throwing money into developing the science of atmospheric physics and money into climate modeling. But I also think we need to fund those who also talk about the science of remediation or technical fixes. To be fair we need to compare benefit and risk with all options on the table. The Kyoto Protocol was a knee jerk reaction of those fearful few. There is a still a lot of science to be investigated. Even more importantly, there needs to be an intelligent tradeoff between economic development and a risks, not a blanket "precautionary principle" that stops all development. (Notice that it is always the rich and powerful, very satisfied with their current position and status, who advocate this stand down of the precautionary principle.)

I advocate the position taken by Bjorn Lomborg. Here is a summary of his current argument in the latest book, Cool It, as presented in Wikipedia:

The book argues that, while global warming is a genuine concern, the problem needs to be dealt with in a responsible way. He suggests that the solutions currently suggested by Kyoto etc. are both prohibitively expensive, and therefore will not be followed-through, but even if they were fully implemented, they would result in only a minuscule change, perhaps slowing global warming by only 5 years or so, by even the most optimistic predictions.