Last week a new estimate of Holocene temperatures was published in the journal Science. This new proxy data reconstruction of temperatures over the last 11,0000 years showed what every sensible person already knows—the recent spike during the Age of Fossil Fuels is unprecedented during the current interglacial (warm period between Ice Ages).
Temperatures rose after 11,000 years ago coming out of the last Ice Age. We started to enter the next Ice Age about 5,400 years ago as temperatures showed a steady decline, but humankind put a stop to that. Note the Huh? spike (dashed line) I put in this graph. I will explain that below. Graph taken from Kevin Drum's Hockey Stick Graph Now Even More Stickish (Mother Jones).
This study got a lot of attention on NPR, in the New York Times, and elsewhere in the mainstream media. But why? What's the big deal? Isn't anthropogenic climate change already very well-established?
It turns out that the new Holocene temperature reconstruction is an extension of the "hockey stick" analysis of Penn State researcher Michael Mann, and shows the same pattern at the end of the stick. To make a long story short, climate "skeptics" took issue with Mann, et. al.'s reconstruction, claiming that there were periods in the Holocene when temperatures were as high (or higher) than they are now. (And there were—look at the graph above.) Somehow, the fact that there have been high average surface temperatures in the (relatively) recent past is supposed to "prove" that there is nothing unusual going on now. Of course, that is a logical non-sequitur, but never mind.
Thus, when this analysis came out, the media jumped all over it because they anticipated a political battle over the new results. And as you regular readers of DOTE already know, politics makes you stupid. And that's exactly what we find in the mainstream reporting.
Now, before I get into the details, which I took from Andy Revkin's Scientists Find an Abrupt Warm Jog After a Very Long Cooling at the New York Times dotearth blog, I want to give you a broad outline of what's going here. Let us imagine, and it's not hard to do, that there are many who think that the Earth is round, but there is a minority who believe the Earth is flat. Revkin's coverage of this new Holocene temperature study took the following form—
We've got a new result demonstrating that the Earth is round, but we've got to be very careful here! We've got to make sure we've dotted our "i"s and crossed our "t"s, because some people (i.e. wingnuts) are sure to dispute this new finding, and continue to claim (without basis) that the Earth is flat, so let's make sure we're well prepared for the political battle to come.
The bone of contention (?) in Revkin's coverage was the resolution of the proxy data used in the study. Simplifying, the new finding uses a resolution of 400 years, which means that the curve in the graph above was drawn at 400-year intervals (covering 11,300 years altogether). At this juncture, the absurd question becomes: couldn't there have been a similar spke in Holocene temperatures within one of those 400 year intervals? That would make it effectively invisible in the graph. That's the Huh? spike I drew in the graph. Here's Revkin—
Besides asking some scientists about the quality of the work, I sought their thoughts on its broader meanings, one of which, I proposed, was this:
While folks have long talked of “abrupt climate change” (as in NRC reports) as a plausible prospect, this paper builds on the idea that we’ve been in the midst of abrupt climate change since the early 20th century.
Builds on the idea that we've been in the midst of abrupt climate change since the early 20th century? Does this New York Times weenie mean to tell us that this "idea" requires further substantiation? Let me show you abrupt climate change.
From Nature's Abrupt Climate Change During the Last Ice Age — "the panel shows the oxygen isotope record (δ18Oice) from the Greenland Ice Sheet Project II (GISP II) ice core over the last 80,000 years (Stuiver & Grootes 2000). Colder air temperatures are indicated by more negative δ18Oice values. Bottom panel shows changes in global sea level over the same time period (Waelbroeck et al. 2002), reflecting the waxing and waning of continental ice sheets during the last ice age. Note the relatively stable, small temperature changes reflected in the ice core δ18O values over the past 10,000 years when continental ice volume has been near modern levels, indicating the modern warm period known as the Holocene. In comparison, climate during the last ice age (between about 18,000 and 80,000 years ago) was much more variable. The abrupt warming and gradual cooling oscillations during this period of Earth’s history are know as Dansgaard-Oeschger cycles, or D-O cycles (Dansgaard 1984)."
The Holocene is that flat, thick portion in the upper left (the "modern warm interval"). You don't get the wild temperature swings which occurred prior to 11,000 years ago (e.g. the Younger Dryas cooling). It has been well-established for nearly 20 years that the Holocene has been a quiet period for the Earth's climate, at least up until 100 years. But mysteriously, Revkin says this new Science study "builds on the idea" that we are experiencing abrupt climate change now.
Jesus wept. Here's Revkin asking Michael Mann a question and part of Mann's response.
Separate from the potential northern bias, are you confident that jogs similar to the one recorded in the last century (a well-instrumented century) could not be hidden in the “smear” of millenniums of proxy [indirect] temperature data? (This is where my ignorance of the strengths/weaknesses of these statistical tools forces me to rely on expert judgment.)
Revkin is referring to the possibility of something like the Huh? spike.
Regarding the resolution issue, this was my main concern initially when I looked at the paper. But I’m less concerned now that I have read the paper over more carefully, because I think that Figure 1a and 1b give a pretty good sense of what features of higher resolution reconstructions (specifically, our ’08 global reconstruction which is shown) are potentially captured. Based on that comparison, I’m relatively convinced that they have the resolution to capture a century-long warming trend in the past were there one comparable to the recent trend.
There are some particularly outrageous quotes from Berkerley physicist Robert Rohde, like this one—
In essence, their reconstruction appears to tell us about past changes in climate with a resolution of about 400 years. That is more than adequate for gathering insights about millennial scale changes during the last 10,000 years, but it will completely obscure any rapid fluctuations having durations less than a few hundred years. The only time such obscuring might not occur is during the very recent period when dating uncertainty is likely to be low and sample spacing may be very tight.
Because the analysis method and sparse data used in this study will tend to blur out most century-scale changes, we can’t use the analysis of Marcott et al. to draw any firm conclusions about how unique the rapid changes of the twentieth century are compared to the previous 10,000 years.
Again, to make a long story short, there is no known natural climate forcing that could cause the Huh? spike I drew in the first graph above. If there were, we would know about it, and it would likely show some weak periodicity like the Dansgaard-Oeschger cycles do in the second graph. I drew that spike as a joke. If such a spike did happen, it would have been an anomaly, a stochastic (random) event of unknown origin during the Holocene. And what is the probability that such a random warm spike occurred? The odds are effectively zero (≅ 0)
But politics makes you stupid. Revkin and Mann (and Rohde) have gotten so defensive about being attacked conservative, global warming-denying wingnuts that they have forgotten that there are numerous lines of evidence pointing to abrupt climate change in the 20th and 21st centuries. They have forgotten that the physics of greenhouse gases in the atmosphere is well-described, that there is no doubt whatsoever that burning fossil fuels emits these gases, and warms the Earth's surface as a result.
In short, they have forgotten that the Earth is indeed round, and not flat. And do you know what the most ironic part of all this is?
Those global warming wingnuts are going to attack this study or basic physics or science in general regardless of what this study's resolution, and regardless of any other reasonable interpretation of what is known about the current climate episode. Because they're crazy! (Crazy implies stupid.) And when you are responding seriously to crazy people, that makes you crazy too, which means the wackos have won.
See my post It Just Doesn't Matter. The climate train has left the station. The time for arguing about whether abrupt anthropogenic climate change is happening now is long gone. The media discussion of this new Science paper is sad, pathetic and embarassing. And the study itself? Well, it's a nice result, but it only provides more confirmation for what we already know.
And now, here's Bill.