Thursday, October 15, 2009

Warming up - Blog Action Day

Today, Blog Action Day, was organized by the appropriately-named as a blogswarm day on climate change. I certainly have posted some on the topic (a check reveals 97 posts tagged with "global warming" although for some reason clicking on the tag only brings up 20 of them), most recently less than two weeks ago. I figured that for my contribution to the effort I would offer some graphs and charts that can be used as resources and/or illustrations.

The first is the chart I expect many of you have seen; it shows the recorded temperatures since 1850. The important thing, the central thing, to note is that except for a temporary dip around 1940-1950, average global temperature has been on a pretty steady climb since 1900. The nanny-nanny naysayers cling desperately to the small drop in the year-to-year average of the past few years, but aside from the fact that this is the result of a natural cooling cycle driven by a change in ocean currents that at most will conceal anthropogenic global warming for a time, it's worth noting that the drop is neither as deep nor as steep as that which occurred in the 1940s - which was followed by another extended period of rapid rise.

In fact, even allowing for expected natural cycles, the warming of the world is dramatic. The following graphic, which comes from the peer-reviewed magazine Science of the American Association for the Advancement of Science (AAAS), shows the likelihood (in percent) of various regions having summer temperatures during the period 2040-2060 that will exceed the highest on record to date.
The nanny-nanny naysayers are forever claiming that it's all natural, nothing to do with us, blah, blah, blah - and often accuse (sometimes openly, sometimes by implication so as to not be held responsible for their words) climatologists of stupidly or - worse - deliberately ignoring some natural trend or another. Unfortunately for them (and, in a philosophical sense, unfortunately for the rest of us as well) that is simply not true. Not only do climatologists take such trends into account, they find that natural cycles simply cannot explain the recent warming, as shown by the following graph. The left graph compares actual recorded temperatures with the results of computer models that try to mimic and predict the real world and which included human influences as well as natural ones. It's a good fit. The right-hand graph, on the other hand, compares those records with computer models that considered only natural influences. In that case, the lines started to diverge in the 1940s and have been getting further apart ever since.

Its not just surface temperature, either: The same applies to global ocean temperatures. Note the right-hand graph below, which compares actual data with models that include human influences and others that do not. The first is an excellent fit; the other, just like with surface temperatures, has increasingly diverged from the hard data.

The conclusion is inescapable: Natural forcings simply cannot explain all of the warming that has occurred over the past several decades. We are screwing with the climate, the nanny-nanny naysayers be damned.

Finally, I wanted to include this:

In case you haven't guessed, this is the classic "hockey stick" graph, done in 1999. It compares the recorded average global temperature for the period 1961-1990 (the solid horizontal line; note the use of a 30-year period in order to smooth out short-term variations) with both recorded temperatures since 1850 (the red line) and with determined temperatures dating back 1000 years, the latter figures calculated from data obtained by the use of various proxies. The graph shows a large number of short-term variations but a relatively constant temperature over the long term - until the industrial age. Then temperatures start to rise pretty steadily until the present day, with current temperatures at levels unprecedented in the previous 1000 years.

The pale blue indicates a type of error bar, that is, a reflection of the range within which the researchers are quite confident the actual figure sits. Note that prior to around 1600, the pale blue area is considerably wider; what that means, in brief, is that the researchers are much less confident in the accuracy of their results for earlier periods. However, even with that in mind, the graph still shows a high degree of confidence that current temperatures are unprecedented in at least 400 years if not more.

The "hockey stick," so-called because of the relatively straight "shaft" in history and the sharply angled "blade" of recent times, has been repeatedly attacked by the nanny-nanny naysayers and questioned by serious researchers. Which leads to my final graph:

This is a collection of nine different attempts to reconstruct temperature records for the last 1000 years. They were done by different teams of researchers (albeit some individuals were involved with more than one team) and used different combinations of proxies. The "shaft" of the hockey stick has gotten twisted and warped, leading to a reasonable conclusion that global temperatures were not as relatively constant as the initial graph indicated.

However, and this is far more important for us, they universally agree that current temperatures are unprecedented in the last 1000 years. The naysayers will nitpick at details and argue technical fine points and yes there are details and fine points to be argued - but especially in an area as complex as climate, where mathematical precision eludes us, and especially in an area with such a huge potential impact on human life and society, it is the weight of the evidence that must guide our choices.

And the weight of the evidence is literally overwhelming: Global warming is real. It is happening. It is already having an impact. And that impact will grow and worsen and the longer we delay action the worse it will be.


Anonymous said...

The original chart goes from 0 - 2000's. All these little snapshots prove nothing and are misleading. Looking at the original chart, the pattern seems to be natural. It's been oscillating up and down, getting stronger/more extreme overall, for the past 2000 years. Any idiot brain can see that pattern when looking at the whole chart.

Larry E said...

Wow. An anonymous comment on a post from six years ago. I'm not sure what to make of that.

I'm also not sure of what to make of the comment itself other than to say that it shows the increasing desperation of the nanny-nanny naysayers, who will resort to any re-interpretation of data, no matter how wild, even if it conflicts with previous re-interpretations.

So now not only is the world warming but has been "overall" doing it for 2000 years? A "natural pattern" of gradually "getting stronger/more extreme" for 20 centuries?

So what is driving this "natural pattern?" Can't be the Sun; the Sun has well-known, well-recognized, cycles of greater and lesser intensity. So what is driving it, anonymous commenter? And why has the rate of increase (which you say has been going on for 2000 years) become so much sharper since the onset of the industrial age and even sharper than that over the past several decades?

Hey, and here's another thing for you to think about: Even if we were to imagine (the word is chosen deliberately) that none of the warming is human-driven, the effects of a given temperature increase remain the same. Which means we are still facing "more extreme" impacts from a changing climate over the next decades. What should we do about that? Or do you just not give a damn as long as you figure it won't affect you, personally?

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