Wednesday, April 18, 2007

The Problem With Climate Measurements

I've been reading a lot about climate change lately. One thing that has really become clear is just how poor our historical data is. The Earth's surface is 71% water but there are no weather stations in the ocean even now. Ships have measured SST (sea surface tempuratures) since the 19th century. However they used wooden buckets! Drop the bucket over the side, let it fill with surface water, then pull it back on board (by hand) and measure the tempurature. Holy inaccuracy! When it comes to weather we only care down to about one degree. But climate change is about 0.1 degree per decade! There's no way that measuring water in a bucket will be accurate to even 0.5 degrees. The bucket will either warm up (during the day) or cool (during night or winter) as soon as its pulled back on board. Evaporation in the bucket will cool the water. And in fact a strange jump in temperatures around 1940 caused the climate scientists to add 0.3 degree to all readings before 1940. They surmised that the USA's entry in WWII caused a change from using buckets to using engine intake temperature measurements. Yet a recent study shows that even in 1970 the majority of SST was still done using buckets!

This is crazy. Climate change of 0.6 deg over the 20th century and it turns out that 0.3 was (incorrectly) added to 40 years worth of measurements. Note that if removed, the SST numbers would show more temp change, so this isn't really a climate change denialist argument. It's a data quality argument.

Then there are tree rings. Before we had thermometers, in what's called the "pre-instrument" period, scientists have to use "proxies"; other things that can reveal what temperatures were. Such as ice cores or tree rings. With tree rings the idea is that when temp goes up the rings get larger. Except that there are multiple factors affecting growth: sunlight, humidity, rainfall, soil changes, etc.

The simplest thing for a layman to do here is throw out all measurements except satellite data. The satellite data started in the late 1970s and has shown warming. More importantly the data also shows cooling in the stratosphere and warming in the (near earth) troposphere, which matches a CO2-induced greenhouse effect. Changes in solar activity, for example, wouldn't produce this. However, the CO2 models say that the troposphere should be about 30% warmer than the surface. And the data doesn't show this. So either the satellite data is overly cool or the surface measurements are erroneously warm.

On the Michael Coren show today, two retired profs pointed out that yes temperature is rising, and yes CO2 is a greenhouse effect, but we don't yet have proof that the current rise is because of C02. Climate science is too young a science.


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