Monday, September 16, 2013

Does Bjorn Lomborg Understand Physics?

A telling sentence by Bjorn Lomborg makes me wonder if he really understands the science that he's pontificating about. On WUWT he wrote:
Over the past 30 years, they are at least predicting 71% too much heat. Maybe 159%. (see graph)
Without getting into the specific numbers, his use of the word "heat" is inappropriate at best, confusing at least, and and unscientific at worst.

Why? Because the Earth's surface is two-dimensional. As such, it can't hold any heat at all.

Even worse, "heat" isn't a property of a substance. You can't say "this ice cube holds X amount of heat." Heat is a change in energy -- it only makes sense when talking about an energy transfer. So you can say "this ice cube lost X amount of heat."

\frac{\partial u}{\partial t} - \alpha \nabla^2 u=0
heat equation
For this reason, "heat" is only a semi-useful concept and scientists (especially physicists) prefer to stay away from it when they can. Sure, everyone learns about Fourier's heat equation, and thermdynamics is rife with talk of heat, but you'll notice that when talking about, say, radiative transfer in the atmosphere, the ideas are formulated in terms of energy (photons) and not so much heat (energy changes). Heat is for engineers; physicists are about energy and energy changes.

For example, the ocean heat content data is only relative heat content, there is no absolute value of how much heat is in the ocean.

Back to the first point. Conceptionally, the surface is a 2-dimensional (and hence massless) field that (therefore) can't hold any heat at all. Here is what Roger Pielke Sr wrote in Physics Today in 2007:
" colleagues and I have shown that global average surface-temperature changes are not particularly useful for assessing the broad range of human influences on climate."
“Unlike temperature at some specific depth in the ocean or height in the atmosphere, where there is a time lag in the response to radiative forcing, no time lags are associated with heat changes, since the actual amount of heat present at any time is accounted for. Moreover, because the surface temperature is a massless two-dimensional global field while heat content involves mass, the use of surface temperature as a monitor of climate change is not accurate for evaluating heat storage changes. “
On his blog he wrote:
My recommendation is that the next IPCC assessment adopt these definitions for global warming and climate change.
and earlier this year he told me in an interview
“This means this heat is not being sampled by the global average surface temperature trend,” he says. “Since that metric is being used as the icon to report to policymakers on climate change, it illustrates a defect in using the two-dimensional field of surface temperature to diagnose global warming.”
Of course, the thermometer in your back yard is measuring something -- it's the temperature of the small parcel of air that surrounds your thermometer's bulb. More collectively, measurements of the surface temperature are of a very thin skin of air just above (within 2 meters or so) the planet's surface.

Here we have this big huge heat reservoir, the ocean, that is 3-dimensional (so it can hold heat) and relatively uniform (no cities that create urban heat islands), and instead of utilizing it for what it is we're trying to detect a global energy imbalance by measuring the heat in a teeny tiny sliver of gas, just because it's where we eat dinner.

Not very wise.

Of course, we live on the surface, not in the ocean, so we care about the heat content in that little sliver. But naturally it's going to be strongly influenced by whatever the big huge heat reservoir that surrounds us is doing (including its cycles), and it's warming very, very strongly.

There will come a time when the PDO is not it cool phase, and/or when an El Nino leads to a significant boost in surface temperatures, and you can be sure that deniers will be pointing this out as an excuse for temporarily higher temperatures. They will be, as the saying goes, hoist on their own petard.

I suspect then they will go back to claims that the surface record is unreliable, which worked for most of last decade. Suddenly, though, it seems reliable enough. (There will never be an end to denialism, ever, no matter how warm it gets.)

Lomborg's use of the word "heat" in this context is telling, and his (and other's) inability or unwillingness to look at the real metrics of global warming is seriously confusing the world.

If you're going to talk about "heat," then let's talk about all the heat, and not just a sliver of it.

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