My earlier post on global climate change, “We’re All Going to — Die? Warm Up?“, got some interest lately when someone in a forum I participate in challenged me on it in a private message exchange. Since it was a private message exchange I shall not identify my correspondent by screen-name, but I will call him ClimateChanger. As background I will say that ClimateChanger is all on-board with Anthropogenic Global Warming.
The apparent intent of his challenge was to convince me that (1) global warming is happening, and (2) it’s all our fault. I also got a sense from him that (3) this is bad.
Do you ever find yourself trying to convince someone that you agree with them on some issue, but they continue to try to persuade you over to their side of an issue? Does this annoy you, too? I know, right?
Anyway, he wrote:
“In other words, up until just very recently, since the end of the last glacial period, 8,000 years ago when we were at a peak in temperatures, we’ve been trending colder, not hotter”
It was a regional temperature, not a Global Temperature
The The Holocene Climate Optimum was generally warmer than today, but only in summer and only in the northern hemisphere. More over, scientists know the cause of this natural warming, and know without doubt that this proven “astronomical” climate forcing mechanism cannot be responsible for the warming over the last 100 years.
This was in reference to the Holocene Temperature Variations chart I posted.
As to the matter of “regional temperature”, the graph actually consists of several temperature tracks as found in many locations throughout the world, and provides an average of them all (the dark black line). Note that he is right that some regions were colder and some were warmer than the average. But that is characteristic of “average”, and not an argument against the graph. Seeking an average in this case is not to say that everywhere on the globe marched in lockstep to the graph. The average temperature merely identifies the trend. And he is also correct that during the HCO the northern hemisphere experienced warmer temperatures — he left out the fact that the southern hemisphere had lower temperatures. Oh, well.
At risk of repeating myself I shall post this graph again, but with a trendline in RED. The trendline goes from about the midpoint of the graph’s highpoint, about 7,900 years ago, and continues to the midpoint of the beginning of the recent dramatic increase, about 200 years ago:
As you can see, the trend is downwards toward the next period of glaciation. However, when you examine the inset graph continuation it shows a disconcertedly rapid rise in temperature. In my original post I point out that the temperature goes up to 0.5 degrees in a very short time. And then I get the following. My correspondent first takes a quotes from my post and then pulls a Straw Man on it:
He quotes me thus:
we are not yet out of the last Ice Age! We are presently in a period known as the Quaternary Glaciation, which started 2.6 million years ago and hasn’t ended yet. The only reason why you’re not sitting on a huge pile of ice reading this is because we happen to be in what is called an Interglacial Period
And then he responds
Even if true, even if we are still not out of the last ice age, that does not explain the rapid rise of the global temperature since 1980. The global temperature increased more than 0.5 degrees in just 30 years. Why did it accelerate in a few years?
Your own graph shows the Earth was getting colder, but now the Earth is hotter than it has ever been in the last 12,000 years, see your own graph.
First of all, his quotation of me occurs AFTER I wrote this:
…as we move off the chart to the right, the temperature line goes up to near 0.5 degrees.
I said this twice, in fact, but he either ignored or missed it entirely — all the while telling me to look at my own graph!
Yes, my own graph shows an sudden increase to 0.5 degrees, and I mention it twice in one paragraph. Who is he arguing with? I can’t be with me because I wrote what he appears to be trying to claim I didn’t write several months ago.
He wrote “Even if true…” to my statement that we are still in an Ice Age but in the midst of an Interglacial Period, presumably because he disagrees with me about the Ice Age / Interglacial, but he’s generously allowing it for the sake of argument. How kind. I responded:
What do you mean “even if true”? I’m not stating my opinion, I’m stating fact, and fact backed up by climatology. And who says that being still in a current ice age “does not explain the rapid rise of the global temperature since 1980”? That’s a non-sequitor since I did not link the current ice age with any rise in temperature. You’re trying to refute what I haven’t claimed, which is what makes me think you read me very superficially. As to “even if true”, I can back up what I wrote. From a portion of the relevant article in Wikipedia, which is sourced from Science, Nature and ScienceDaily:
“The earth has been in an interglacial period known as the Holocene for more than 11,000 years. It was conventional wisdom that the typical interglacial period lasts about 12,000 years, but this has been called into question recently. For example, an article in Nature argues that the current interglacial might be most analogous to a previous interglacial that lasted 28,000 years. Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now, even in absence of human-made global warming (see Milankovitch cycles). Moreover, anthropogenic forcing from increased greenhouse gases might outweigh orbital forcing for as long as intensive use of fossil fuels continues.”
 – http://www.webcitation.org/5qnO3Fw2p
 – http://www.sciencema…/5585/1287.full (Sorry, it’s a paywall)
 – http://www.scienceda…70829193436.htm
I love it when someone tries to argue with me as if I were a climate change denier, and on top of that, doesn’t have his facts straight about even this basic concept in climatology: we’re in an Ice Age, dude. It’s only looks mild because we’re in a temporary interglacial period. I also love it when I write about how greenhouse gases are apparently providing some forcing of the global temperature, only to have someone turn around to try to convince me that science has shown that CO2 is causing temperatures to rise, as if I said something to the contrary. Now, I will admit that I don’t believe that humans are 100% responsible for all this. So far, anyway. I’m persuadable — in fact I used to believe that there was no anthropogenic global warming, but I’ve come around on that.
There is more to the conversation, but I am not going to extend this post to go on and on about it. I think I have demonstrated my point, which is that people should actually read what they are supposedly responding to before they attempt to respond to it.