365 Days of Climate Awareness 92 – Temperature Change and Variability

All data series from the natural world involve noise—random variation in a system which might cloud a trend. This is not the random systematic error discussed earlier, due to minute changes in the environment or instrument. This is widespread, easily measurable natural variation inherent in any complex system with many inputs, a condition which easily applies to earth’s climate system. Measuring any apparent trend against a system’s natural variability is fundamental to establishing the trend.

The associated plots compare raw temperature changes in the atmosphere to the atmosphere’s natural variability. Variability is measured by the standard deviations of each time series of temperature data from around the world. The world map in the upper left shows six outlined regions whose temperature time series are displayed in temperature-versus-time plots below. In that upper left map plot of raw temperature anomalies, and in the six time series below, obvious raw increases in temperature are obvious.

What is less obvious is the natural variability in the various parts of the world. The upper right plot shows the over-land region of the Arctic to have the highest. (If you recall the discussion on the polar vortex, where north-to-south snakelike swings in the jet stream, known as Rossby waves, have major effects on air temperatures, this huge variation in that part of the world makes sense.) By contrast the tropics are extremely consistent in their temperatures.

So warming over the poles is to a large extent masked by the huge swings in atmospheric temperature there, while smaller increases in the tropics, which have less impact on the ecosystems there, are not so easily noticed. But dividing the temperature anomalies by their standard deviations produces a measure of how extreme the temperature increase is. The middle right map, “Global Warming Level of Emergence” closely resembles the map of standard deviations around the world, showing when an air temperature anomaly would become statistically significant.

Tomorrow: system response times to change.

Be brave, and be well.