I always like to consider questions of the day from the perspective of deep time. How hot is it these days? Look back 1.35 million years, and you can see it's pretty hot. Here's a chart, published yesterday in the Proceedings of the National Academy of Sciences (free paper here). It combines historical records with geological evidence from the West Pacific to reach back 1.35 million years (kyr= thousands of years ago). The scale is telescoped near the right end, since recent warming has been so fast that it would be hard to make out its details otherwise. Two lines mark some average recent temperatures--the lower line is from 1870 to 1900, when recent global warming was just starting to kick in. The top line is from 2001 to 2005. As the record shows, the temperature has seesawed a lot over time, mainly due to the swing in and out of Ice Ages. The last time the Earth was this hot was about 400,000 years ago, and it will take a couple degree more to put us above anything that the planet has experienced in the past 1.35 million years. As the authors of the new study point out, projections based on "business-as-usual" rates of carbon dioxide emissions indicate that the planet will warm at least 2-3 degrees celsius by 2100. In other words, off the chart.
Comments
It's a razor's edge sometimes between the what and the how things are said. Unfortunately, I think this kind of a graphic does disservice to the global-warming movement. The telescoping emphasizes recent data at the expense of paleoclimate data we cannot represent with equal precision. We do not know how the temperature peaks 100 and 410 kya plateaued, such data is a necessary indicator if we are to make comparisons to the past and draw up predictions for the future. In effect, it gives the other side something to buzz about and pick upon in a given conversation or news cycle, allowing them to ignore the real issues and undermine the concept this graphic is trying to portray - and nobody likes that.
Posted by: Paul | September 26, 2006 12:10 PM
I believe that man-made accentuation of global warming is real, but this graph doesn't support it. As Paul said, the telescoping makes a spike look like a trend. Also, the rise in temperature since the last ice age preceeds human generation of CO2, and the last 140 years may be a statistical wandering about the post-ice age natural warming. One could make a longer term graph dating back to the Hadean Eon 4.5 billion years ago and argue that the long term trend is a definite cooling.
Posted by: joeski | September 26, 2006 3:16 PM
I think many people are puzzled by climate change when they hear us speaking in terms of two or three degrees difference in temperature. To most people, that's just not enough to worry about. This chart could be a useful corrective. In this one measured locale, the difference between the present and a full on ice age was just three degrees.
Posted by: John J McKay | September 26, 2006 3:57 PM
Paul and joeski have a point. However, this record of temperature proxies needs to be compared to the record for atmospheric carbon dioxide. It is the recent, sudden increase in CO2 which drives the recent temperature increase, and that is what is worrisome.
Posted by: David B. Benson | September 26, 2006 8:34 PM
No this is good. I don't support say Professor emeritus Theodore Roszak's humanist attack against Gould, Sagan and other scientists who emphasize the random destructiveness in the universe. My favorite analysis of science is "Doubt and Certainty" by Tony Rothman and Physics Professor Sudarshan (1998 or so). I think that left-brain logic of science goes with right-hand technology that alters our measurements of right-hand racemization -- in otherwords, as Chomsky as even suggested in 2003, science is just a "cycling of the elements." So left-hand carbon-based molecules (ecology as earth) are being replaced with right-hand silica-based molecules (fire as desertification) through "right-hand" technology (metal) with water as the pivot point. Water is a macro quantum molecule that defies the 2nd law of thermodynamics (just read physics professor J.L. Finney's "What's So Special About Water?" article in the Philosophical Transactions of the Royal Society, 2004). As water pressure increases entropy decreases -- due to the Platonic Geometry -- the tetrahedral binding properties of the water molecule with itself.
Tetrahedrons are seen as the key to "saving" Earth -- Buckyfullerenes for "synthetic ecology" and "nanowater," etc., -- silica is supposedly symmetrical but the new silica-DNA biochips will change how humans perceive symmetry! In fact it's been conjectured that silica was right-handed when life formed on earth from the "vital clay" model of Professor A. G. Cairns-Smith -- nonlinear crystallization.
I'm sitting in full-lotus as I type this -- that's how humans can restore brain symmetry, lost at the last major global warming, 2.5 mya, causing permanent bipedalism for hominids. Read "The Lop-sided Ape" by Professor Michael Corballis. Full-lotus yoga restores brain symmetry -- making humans more like peaceful orangutans (and yes I support Professor Jeffrey Schwartz' "Red Ape" argument)through tetrahedron body position and the brain does have silica-molecules that nanotech is reengineering with the silica in soy!!
Highly ironic that the brain of Earth is being replaced with soy farms -- the Amazon.
Posted by: drew hempel | September 27, 2006 10:38 AM
I agree with Joeski. I'd like to know more about that last temperature rise shown before 1870, from 26 to 29 degrees. It would be very useful to know if that big jump was in historic or prehistoric time. Just saw documentary on PBS about a mega-volcano cooling things down 75k years ago - is that part of the drop we see on chart?
I guess I should check the Hansen paper.
Folk should understand that our lives and lifestyles fit within a very narrow subrange of the possible variation, what's natural for the world could be death for us, it may take work to keep things cozy.
Posted by: Bruce | September 27, 2006 1:45 PM
Atmospheric measurements show a different situation than surface temperature measurements:
http://www.john-daly.com/#nasa
Posted by: Larry May | September 27, 2006 3:26 PM
Bruce, the last big temperature increase was from the end of the last glacial maximum, about 20,000 years ago, to the beginning of the Holocene, about 10,000--8,000 years ago.
The volcano super-eruption was Mt. Toba. More about this, and other super-eruptions is available in the June 2006 issue of Scientific American. Having studied this more that most, but only as an amateur, I opine that other than 3--6 years of very cold weather, it had no further global impact. The down spike in temperature about 70,000 years ago is adequately explained entirely by orbital forcing.
Posted by: David B. Benson | September 27, 2006 5:50 PM
Visual communicator extraordinaire Edward Tufte would take great exception to expanding the time scale in the last section of the graph. It gives the illusion that temperatures have moved to a high level and stayed there longer than ever before.
Yes I know this is explained in the text, but it would be better to keep the time scale constant and then use a circle or other device to show a zoomed in view as a breakout graph.
Posted by: sean | September 27, 2006 7:13 PM
For the GW skeptics: Since GW is a biggest problem for us humans, pointing to a time before we even knew how to use tools as evidence of GW's indifference, is dishonest. Yes, the planet will survive. But what good does that do if millions end up suffering or dying?
I think we should compare this graph to fossil record. If we find extinction and rapid evolutionary changes, it would further express the importance of limiting rapid temperature changes. Especially since evolutionary changes seem to require an increase of pre-reproductive death in population.
Posted by: Markus | September 27, 2006 9:19 PM
This graph is pretty interesting about global temperatures through deep time.
This is also useful. It's from Dr Scotese's website. He's well cited.
Posted by: Will Baird | September 28, 2006 1:34 AM
argh. For some reason the comments aren't giving the links from my above posts.
For the deep time temperature graph:
http://www.scotese.com/images/globaltemp.jpg
Page About Paleoclimatology:
http://www.scotese.com/climate.htm
Dr Scotese's General Website:
http://www.scotese.com/
Posted by: Will Baird | September 28, 2006 1:13 PM
John (McKay) the difference between an ice-age and now may be "just" three degrees, but that absolute value tells us nothing about its significance.
Estimating by eye, it seems we are in a period where we are 2 or 3 standard deviations (or more) higher than the long term average for the whole period presented. That certainly seems significant.
Agreed, per other comments, we can't be sure that the picture is not distorted by the frequency of data points in the deep historical period, but even then its hard to imagine a profile that would reduce the significance of the points actually presented.
It's significant.
Posted by: Ian Glendinning | October 1, 2006 3:08 AM
Paul, so "Global warming" is a movement? For a moment, I thought it was a scientific theory. For my part, I won't join the "movement", and stick with good science. This Hansen paper is amenable to quite a bit of serious, scientific criticism. Jim Hansen is not particularly known for scientific objectivity. He does like to make headlines, though.
Also, Markus, yes, it's scary that millions "could" die and suffer from global warming. But millions are dying and suffering today, and what are we doing about it? Why is their suffering and dying not our biggest problem TODAY?
Posted by: Francois Ouellette | October 9, 2006 5:33 PM
One thing that I do wonder about, in a chart like this, is the time-response characteristic of the data. We're comparing modern data with well-defined year-to-year variance against ancient data on a much longer timescale. Is there a lot of spikiness in the ancient data set? I assume we do not have year-to-year data for events kiloyears ago, so really that data is being low-pass filtered, isn't it? What I'm wondering is, how the modern fluctuations on short timescale compare to the year-to-year fluctuations in the kiloyears-ago data. Perhaps the modern incredibly steep rise is not unprecedented, maybe on a longer timescale it just looks like spikiness or isn't even visible at all.
Posted by: dweezil | October 25, 2006 3:05 PM
I second Francois Ouellette's sensible comment above. In particular, I would like to know when the "Global Warming movement" is going to seriously rebut the cost-benefit argument first broached by Lomborg? It seems like perfectly rational argument, is increasingly influential in many policy-making circles (see the website Prometheus for a balanced discussion), so why does the movement fail to address, for example, the points made in Lomborg's recent Op-Ed piece in the Wall St. Journal, in which he criticized the the credibility of the recent well-publicized British estimate of the future costs of global warming?
Intelligent bystanders cannot help but wonder whether the cynics may be correct when they surmise that the climate-modeling profession is more interested in its own future funding than in the future welfare of humanity.
I know that is a terrible thing to suggest, but human nature being what it is -- careerism and peer pressure are no mean things -- what else is one to think?
Luke Lea
Posted by: Luke Lea | November 10, 2006 1:46 PM
With all the dead bodies and decomposing matter; including Cow emissions and dead waste, its not a matter of other chemicals; rather, methane gas polluting our air is out of control.
Posted by: Fermin | April 19, 2007 1:51 PM
Fermin --- Not according to RealClimate. While high, mathane gas concentrations in the atmosphere are not increasing. Unlike carbon dioxide...
Posted by: David B. Benson | April 20, 2007 8:20 PM
Global warming is pure truth, therefore there is no reason for all this discussion and debate. We have now reached a higher level of science where we can manipulate graphs and data to suit the almighty Consensus.
Posted by: Adam | July 5, 2007 8:21 AM