Open Mind (Tamino) has again posted an analysis of global temperature data, confirming that global temperatures are accelerating. I analysed his previous post here.
Way back in 2011 I co-authored a paper with Stefan Rahmstorf (Foster & Rahmstorf 2011, hereafter FR11) in which we adjusted global temperature in order to remove (as best we could) the influence of factors we knew were only temporary, and not man-made. Specifically, these are volcanic eruptions (whose aerosols cool the planet), the El Niño Southern Oscillation (ENSO, which warms the world in its positive el Niño phase and cools in its negative la Niña phase), and solar variations (when the sun gets hotter or colder, so does the Earth). These exogenous factors make global temperature fluctuate, but don’t really get anywhere; removing their influence makes the global warming part clearer.
I’ve updated my method for doing so, and extended the time span it covers, so I’d like to share some of the changes to methodology. But before I do I’ll cut right to the chase: doing so removes a lot of the fluctuation in global temperature, so that yearly averages since 1950, which look like this for five prominent global-temperature data sets:
end up looking like this:
He then discusses his analytical technique in depth (read it here). His conclusions are:
Perhaps the main result of FR11 was that the adjusted data showed no sign of acceleration or deceleration, contradicting ideas that global warming had stopped or even slowed; the evidence didn’t support that. But the new adjusted data do not contradict the recent acceleration which the raw data suggest, in fact they confirm it, mainly because the uncertainty in trend estimates is so greatly reduced that the rate change (acceleration) is easier to demonstrate statistically.
Yes, it appears that the rate of global warming has increased.
We face catastrophe. You can clearly see how the slope of the (adjusted) temperature curve is steepening. It looks more like an exponential than a linear slope. In other words, it could easily go on steepening, with the decadal rise in temperature accelerating even further, from 0.3 to 0.4 or 0.5 degrees C over the next two decades. Why aren't we panicking?
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