Earth’s past warmth is no get-out clause

CLIMATE scientists have long held that the past 2000 years were almost uniformly cool. Now it seems they were wrong. The 1st century AD looks to have been as warm as today, and the world gradually cooled from then on, right up until the industrial era (see “Tree rings suggest Roman world was warmer than thought”).

Climate change denialists, who have never accepted that we are in unusually warm times, will say “told you so”. They may also claim that scientists are trying to have it both ways – whatever past temperatures were, they are still evidence of global warming today.

Yet once again, they would be misrepresenting the evidence. The new finding confirms the primacy of human-made carbon dioxide emissions in the warming of the past century. A long-term downward trend in temperature makes it even less likely that recent warming could be due to normal variability.

Human activity seemingly snuffed out the natural cooling, caused by orbital wobbles, that was carrying us into the next ice age. We may or may not regard that as good news. But we cannot deny that our hand is still on the thermostat, and is cranking it in the wrong direction.


Issue 2873 of New Scientist magazine


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We Knew It Had Cooled

Thu Jul 12 11:29:18 BST 2012 by John Russell

We always knew natural cooling had been occurring until humans started warming things up c1900. If you look at Michael Mann’s famous 1999 ‘hockey stick’ graph he clearly shows a linear cooling trend prior to 1850 http://www.ncdc.noaa.gov/paleo/pubs/millennium-camera.pdf. OK, now this new paper suggests the cooling trend might have been a bit steeper (0.3C per 100 years) — but the anthropogenic warming trend recorded so far is 23 times greater than that underlying natural cooling trend!

In some quarters this new paper is being hyped beyond belief.

We Knew It Had Cooled

Thu Jul 12 11:53:54 BST 2012 by John Russell

I should have said the proposed new natural cooling trend is 0.3C per 1,000 years. AGW currently stands at +0.7C per 100 years — hence the 23x.

Yet More Spin!

Thu Jul 12 15:45:25 BST 2012 by Mike Smith

Your article makes little sense, against the background of a cooling world there have been a number of rapid warming events the Roman Warm Period and the Medieval Warm Period being just the last two of them. Both of these have been shown to be warmer than now, and therefore the Modern warm period is well within Natural Variation and doesn’t change the overall trend, indeed this current warm period is part of that computed trend – There are no hockey sticks, no flat shafts and no unusually warm blades.

If you vaguely stand by the use of trees as thermometers in the first place, then this well and truly scupers you.

It even gets rid of the long lasting and embarrassing divergence problem – which foils the normal tack of just pretending that the paper didn’t happen or that the scientists involved in the work are not as competent as the rest of us….. or that perhaps the publishing journal is not too picky about what it publishes…. Hoisted by their own petard, as it were….

Trying to spin this as a positive for the CAGW meme is well and truly beyond belief.

There’s no MWP….. Well there was but it was not global….. okay well it might have been global but it wasn’t as warm as today….. to okay it’s a fair cop it’s been there all along and remember that I told you that, oh and by the way it might have been a bit warmer than today….

Obviously, the secret of good comedy is timing……. but it would seem that the secret of “settled science” is also timing 😉

I’ll leave our esteemed readers to draw their own conclusions

Yet More Spin!

Thu Jul 12 20:32:37 BST 2012 by Eric Kvaalen

Yet More Spin!

Thu Jul 12 21:20:14 BST 2012 by Mike Smith

Firstly, it depends what you call rapid, next they’ve only been recently acknowledged as being warm and lastly your depending quite a lot a certain Mr C’s editing if you’re trusting wikipedia in this regard.

Yet More Spin!

Thu Jul 12 21:59:47 BST 2012 by Mike Smith

I simply suggest you study their handy little graph in a bit more detail:

(long URL – click here)

Plus, if you could define what you think is or is not rapid I’d appreciate it – I was going with a period of around 120 years for a 0.8C change, just in case you needed a hint 😉

Yet More Spin!

Fri Jul 13 06:22:56 BST 2012 by Eric Kvaalen

I don’t know why their graph is so different. But look at this graph, from Wikipedia: http://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png There’s no period of 120 years with a 0,8°C rise before the MWP

Yet More Spin!

Fri Jul 13 10:28:11 BST 2012 by John Russell

Mike, you say, “Modern warm period is well within Natural Variation…”.

The point is that the current rapid warming period has none of the hallmarks of natural climatic variations, which — with the exception of those caused by noticeable events like volcanic activity and asteroid strikes — tend to be slow-acting and, for modern science, predictable. So if you’re going to lay the blame for the current warming on natural variation, you’ll need first to explain how the increase in atmospheric CO2 concentrations, from 290 to 395ppm since 1800, with its resultant forcings, is not the cause. After all, the warming effect of green house gasses has been generally understood and accepted by science for over 100 years.

It’s rather like someone saying that the fall of the twin towers was the result of controlled demolition. Before we listen to that theory, first we have to eliminate the likelihood that it was actually the — very noticeable — impact of the ‘planes and the resultant fire that caused the collapse.

Yet More Spin!

Fri Jul 13 12:06:33 BST 2012 by Mike Smith

I’m not saying the C02 has nothing at all to do with the current warm period. Only that as I stated above that the current warm period is wholly within the bounds of the climates natural variability and cycles.

It is not Catastrophic in any way, it will not result in freak weather and neither could it.

“Freak” Weather, is quite simply just Weather, as it was before, so it is now. It’s not warmer than it was, it’s not wetter than it was, it’s not windier than it was…..

The article above simply has no place in a magazine that is supposed to be presenting science to an interested audience.

To extract the signal of CO2 warming one must first get rid of the noise, this has not been done as yet.

I’m happy to ascribe a 0.8 – 1.2 C to a Doubling of CO2, but no more.As without exception all of our direct measurements indicate that climates sensitivity to CO2 is low and once you chuck in our ever so “happy go lucky” clouds into the mix – it’s most firmly going to stay that way.

Not sure what else to tell you mate, you turn up some decent evidence and we can maybe discuss it more, but both myself and the IPCC have been searching for that particular magic bullet for a while now and as yet it remains both enigmatic and elusive.

Yet More Spin!

Fri Jul 13 12:14:30 BST 2012 by Mike Smith

Mea Maxima Culpa, Replying to the right comment, but in the context of the wrong thread – That’ll teach me to have so many windows open 😉

You can ignore my banging on about this article has no place in a science magazine, as a I was in fact referring to the other thread on the article about the supposedly heat induced freaky weather meme.

Oopsies, as they say

Yet More Spin!

Fri Jul 13 20:08:57 BST 2012 by Eric Kvaalen

You meant to put your comment at (long URL – click here) ?

How do you know that our current warm weather, or warm climate rather, is within the bounds of natural variability? How do you know that it will not result in freak weather, and that it can’t? How do you know that the sensitivity is only 0,8 to 1,2 °C?

You’re simply ignoring the graph and map of that other article. (Maybe you should explain under that article why you think the graph and map are wrong.)

Yet More Spin!

Tue Jul 17 14:39:20 BST 2012 by Duncan

“To extract the signal of CO2 warming one must first get rid of the noise, this has not been done as yet.”

Attempts have been done, for instance “Global temperature evolution 1979–2010”

http://iopscience.iop.org/1748-9326/6/4/044022/

“I’m happy to ascribe a 0.8 – 1.2 C to a Doubling of CO2, but no more.”

That would be a mistake, multiple lines of evidence point to a sensitivity around 3C, including the current warming. For instance skeptic love to dish Hansen’s 1988 projection as being too high. It over projected the amount of GHGs released and its sensitivity was 4.2C.

If you account for the actual amount of GHGs in the atmosphere now and change the sensitivity to 3C from 4.2C then you get the temperature raise we have experienced.

The IPCC are doing quite well thankyou. Their projections from 1990 are holding up well.

(long URL – click here)

Yet More Spin!

Fri Jul 13 12:17:05 BST 2012 by adiousir

http://www.wix.com/eipi45/mytheory

That is a very apposite comparison. Those who deny AGW have bought into a worldview that regards all information through a lens of suspicion and cynical doubt. This is in many cases justified; I actually would not be at all surprised if the Twin towers were helped in their fall; governments are not above mass murder to further their ends.

However in the case of Climate Change, this doubt has become embedded and unshakeable by any evidence; even the recent and ongoing wildly unusual weather patterns, a sure sign of the shift in a Chaotic System away from its point of equilibrium, does nothing to persuade those who suspect the whole world is a con arranged to disenfranchise them.

Denialists.

Thu Jul 12 17:21:22 BST 2012 by Martin

“Denialists”? Just the use of such a pejorative term betrays bias on the part of the writer.

Denialists.

Fri Jul 13 03:09:59 BST 2012 by donald penman

I would subscribe to newscientist because much of the things are interesting but your AGW nonsense puts me off.

Denialists.

Sat Jul 14 21:07:17 BST 2012 by Liza

Doesn’t it make you think, that NS doesn’t hesitate to publish “AGW nonsense” among the “interesting things”? Do you think they suddenly drop their quality standards when it comes to climate?

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