To begin to answer this question, we need go back to the temperature record. Last week I posted a graph showing the evolution of global temperatures (from the NASA GISS data set, using bimonthly means to coincide with NOAA’s MEI data) since 1950. There is a lot of short-term variation in the data, due largely to the cycle of El Niño and La Niña, but the overall increase is unmistakable. The variation makes evaluating the evolution of the trend in temperature complicated, however, and very highly dependent on where you start and end the analysis. If I were going to calculate a ballpark estimate of how the trend has changed from decade to decade, I would restrict the data to times when the El Niño cycle was mostly neutral, or when the Multivariate ENSO Index (MEI) was between +0.2 and -0.2. I would also rule out points that were influenced by the major volcanic eruptions of El Chichon (1982) and Mt. Pinatubo (1991). This would leave a graph that looks like this:
Figure 1
The trend lines come from a least-squares regression of the best fit, with straight-line relationships over each decade, constrained so that each decadal line segment begins where the previous one ends. What this shows is that the warming looks more like a stepladder than a steadily increasing parabolic curve, with some time periods warming more rapidly than others. Is this a surprising result? Well no, actually. In the 1988 paper “Global Climate Changes as Forecast by the Goddard Institute for Space Studies Three-Dimensional Model,” written by a NASA GISS research team led by Jim Hansen, alternating periods of relatively rapid warming and relatively slow warming (due to natural variations beyond the El Niño cycle) can be clearly seen in the five-year running means in the model’s forecast. (The publication of this paper coincided with Hansen’s trip to Washington to become the first scientist to testify in front of the U. S. Senate that global warming was real and required urgent action.)
So what’s the problem? The trends displayed in Figure 1 are dependent on where I arbitrarily chose the starting and ending points. In my graph, the trend for the decade of the 2000s is approximately 0.05ºC. This is small compared to the 1990s (0.20ºC) and the 2010s (0.32ºC projected for the whole decade, as of the end of 2016), but not zero. However, if you include all the data points and start the trend from the El Niño-enhanced peak in 1998, the trend over the 2000s would naturally be lower, and may even dip below zero if you choose the right endpoint. It should be obvious (if not, see my previous post) that there are objective reasons not to start any trend analysis with the peak of a very strong El Niño, but climate science deniers created a narrative over the last decade that global warming had in fact stopped in 1998, or that at worst there was an extended “pause” or “hiatus” in the warming. These terms were used so aggressively that they frequently appeared in the scientific literature, including the 2014 report of the Intergovernmental Panel on Climate Change (IPCC). (Note: if you are trying to combat false narratives, do not, ever, concede to use the other side’s language.) It was obvious by 2015 that warming had started to accelerate again, boosted partially but not entirely by another strong El Niño. This should have rendered moot any discussion over whether there had been a pause or not. But this is where the Karl et al. paper comes in.
The NOAA research team led by Karl worked with the NOAA temperature record. They found that surface temperature measurements obtained on the ocean were different depending on whether they came from boats or whether they came from buoys. When they corrected for the difference, the trend in their temperature record between 1998 and 2014 increased. This caused an uproar — not in the climate science community, but among the community of climate science deniers, who sensed that their long-running narrative was in jeopardy. Lamar Smith demanded that Karl produce the data and all internal communications regarding this paper. The data were already readily available, but NOAA refused to hand over the emails. Earlier this year, a research team led by Berkely scientist Zeke Hausfather published their results after conducting their own analysis on the NOAA data. Not only did they draw the same conclusions about the NOAA data, but confirmed that the adjustments were consistent with data from other temperature records.
That brings us to last week. John Bates had led a team at NOAA that devised a protocol for publishing results based on NOAA data and archiving the data and the methods of analysis. He felt that Karl had published his results before the quality of the data could be fully confirmed (it eventually was), in order to get the results out in advance of the Paris Conference. Bates also didn’t like the manner in which the data were archived, even though plenty of data from other locations are archived similarly. (The manner in which the data had been first archived was nothing that a researcher looking for data would object to; if anything it's very user-friendly.) Keep in mind also that the delegates to the Paris Conference looked at hundreds of papers, and were already aware of the rapid increase in global temperatures in 2015 that was far more significant than the updated trend in the NOAA data. But Bates recently aired his grievances in the forum for a blog that climate science deniers look at, and soon David Rose had fodder for an article, complete with much hyperbole and a comically misleading graph. Rose repeatedly refers to the Karl et al. paper as the “pausebuster”; I had never heard that one before, but I have to admit that it’s catchy.
To make a painfully long story short, a useful paper was given extremely exaggerated importance by certain people because it messed with their narrative. Accusations of data manipulation ensued. These accusations have now been greatly magnified because another NOAA scientist who designed a protocol for publication decided to publicly complain, in a place where it would do maximum damage to Karl and his research team, that his process wasn’t perfectly followed. In the end, nothing is changed about the science. Temperatures increase more quickly over some time intervals and less quickly over others. We already knew that. But scientists are being accused of dishonesty, even when their analysis has been peer-reviewed and then independently verified in other peer-reviewed publications. The accusations are coming not just from misguided bloggers and journalists, but from powerful people in Congress.
It does not have to be this way. I am confident that most Republicans who take a long, hard look at what is going on will not continue to allow people who promote abject ignorance, to the point of witch-hunting scientists who publish results that contradict their false narratives, to represent them. In other news this week, an older generation of Republican statesmen proposed a plan than includes a carbon tax to fight global warming. This is exactly the kind of debate the two parties should be having: over how to address the very real problem of global warming. Accepting reality should not be ideological.
(If you want to read a good analysis of how the data analysis process works in the context of this past week’s events, Zeke Hausfather wrote this the other day.)
(For updates on new posts, please click the "Follow" button.)
No comments:
Post a Comment