From a press release by: National Oceanography Centre, Southampton (NOCS)
Understanding past and future climate
The notion that scientists understand how changes in Earth’s orbit affect climate well enough for estimating long-term natural climate trends that underlie any anthropogenic climate change is challenged by findings published this week. The new research was conducted by a team led by Professor Eelco Rohling of the University of Southampton’s School of Ocean and Earth Science hosted at the National Oceanography Centre, Southampton.
“Understanding how climate has responded to past change should help reveal how human activities may have affected, or will affect, Earth’s climate. One approach for this is to study past interglacials, the warm periods between glacial periods within an ice age,” said Rohling.
He continued: “Note that we have here focused on the long-term natural climate trends that are related to changes in Earth’s orbit around the Sun. Our study is therefore relevant to the long-term climate future, and not so much for the next decades or century.”
The team, which included scientists from the Universities of Tuebingen (Germany) and Bristol, compared the current warm interglacial period with one 400,000 years ago (marine isotope stage 11, or MIS-11).
Many aspects of the Earth-Sun orbital configuration during MIS-11 were similar to those of the current interglacial. For this reason, MIS-11 is often considered as a potential analogue for future climate development in the absence of human influence.
Previous studies had used the analogy to suggest that the current interglacial should have ended 2-2.5 thousand years ago. So why has it remained so warm?
According to the‘anthropogenic hypothesis’, long-term climate impacts of man’s deforestation activities and early methane and carbon dioxide emissions have artificially held us in warm interglacial conditions, which have persisted since the end of the Pleistocene, about 11 400 years ago.
To address this issue, the researchers used a new high-resolution record of sea levels, which reflect ice volume. This record, which is continuous through both interglacials, is based on the ‘Red Sea method’ developed by Rohling.
Water passes between the Red Sea and the open ocean only through the shallow Strait of Bab-el-Mandab, which narrows as sea levels drop, reducing water exchange. Evaporation within the Red Sea increases its salinity, or saltiness, and changes the relative abundance of stable oxygen isotopes.
By analysing oxygen isotope ratios in tiny marine creatures called foraminiferans preserved in sediments that were deposited at the bottom of the Red Sea, the scientists reconstructed past sea levels, which were corroborated by comparison with the fossilised remains of coral reefs.
The researchers found that the current interglacial has indeed lasted some 2.0–2.5 millennia longer than predicted by the currently dominant theory for the way in which orbital changes control the ice-age cycles. This theory is based on the intensity of solar radiation reaching the Earth at latitude 65 degrees North on 21 June, the northern hemisphere Summer solstice.
But the anomaly vanished when the researchers considered a rival theory, which looks at the amount of solar energy reaching the Earth the same latitude during the summer months. Under this theory, sea levels could remain high for another two thousand years or so, even without greenhouse warming.
“Future research should more precisely narrow down the influence of orbital changes on climate,” said Rohling: “This is crucial for a better understanding of underlying natural climate trends over long, millennial timescales. And that is essential for a better understanding of any potential long-term impacts on climate due to man’s activities.”
The study was funded by the United Kingdom’s Natural Environment Council and the German Science Foundation.
Publication:
Rohling, E.J., et al., Comparison between Holocene and Marine Isotope Stage-11 sea-level histories. Earth and Planetary Science Letters (2010). doi:10.1016/j.epsl.2009.12.054
Doubling of the rise since the glacial, around 5 C.
In a couple of millennia if the trend after 1700 continues.
lgl (12:44:35) :
Doubling of the rise since the glacial, around 5 C.
In a couple of millennia if the trend after 1700 continues.
The temperature has been falling for thousands of years.
The temperature has been falling for thousands of years:
http://en.wikipedia.org/wiki/File:Holocene_Temperature_Variations.png
“The temperature has been falling for thousands of years:”
So what, it’s been rising the last 300 years, and if the trend for Armagh were global it would rise 5 C the coming 1000 years, a hugh increase.
lgl (13:44:03) :
So what, it’s been rising the last 300 years, and if the trend for Armagh were global it would rise 5 C the coming 1000 years, a hugh increase.
solar activity has not risen the last three hundred years, and that was the issue.
So the solar activity 1600-1700 was the same as 1900-2000 ?
You know it’s pointless to compare the year 1710 with the year 2010.
http://virakkraft.com/Mann08-solar.png
lgl (14:06:23) :
So the solar activity 1600-1700 was the same as 1900-2000 ?
You know it’s pointless to compare the year 1710 with the year 2010.
It is pointless to compare any single year with any other single year. Solar activity has not increased the last 300 years.
“our reconstruction indicates that solar activity around AD 1150 and 1600 and in the late eighteenth century was probably comparable to the recent satellite-based observations.”
http://www.leif.org/EOS/muscheler05nat_nature04045.pdf
See also: http://wattsupwiththat.com/2010/02/02/solar-cycle-24-update/#comment-317635
lgl (15:17:18) :
http://virakkraft.com/Mann08-solar.png
People keep citing old, obsolete papers.
” Recent 10 Be values are low; however, they do not indicate unusually high recent solar activity compared to the last 600 years.”
http://www.leif.org/EOS/2009GL038004.pdf
The past 10 years or so have seen many studies including our own that show that the myth of steadily increasing solar activity the past 300 years is just that: a myth.
Leif,
I don’t know who is claiming a “steadily increasing solar activity the past 300 years”, I don’t. But all the curves you have linked to is showing a positive trend since 1700. (and since 1500 in Antarctica 10Be)
“they do not indicate unusually high recent solar activity compared to the last 600 years”. Again, we were not discussing back to 1400 AD, and even if true, all the data shows unusually low activity the decades around 1700.
(Even Briffa thinks “the recent warmth was probably matched about 1000 years ago”)
http://virakkraft.com/CET-10Be.png
lgl (06:03:25) :
I don’t know who is claiming a “steadily increasing solar activity the past 300 years”, I don’t.:
lgl (13:44:03) :
So what, it’s been rising the last 300 years
You did. You see a steady trend in temperature over 300 years and claim it is due to a similar steady trend in solar activity.
But all the curves you have linked to is showing a positive trend since 1700.
This is a typical trick: picking the lowest point as a start. And there is no steady ‘positive trend’ in solar activity. There has been three activity ‘episodes’ of about 100 years duration each, with about equal amplitude [max ~1780, ~1840, and ~1950], min ~1800, ~1900, and ~2010]. See, e.g. page 7 of http://www.leif.org/research/Napa%20Solar%20Cycle%2024.pdf
Leif Svalgaard (07:20:47) :
That’s unfair. I never said “steady trend”, but the long term trend since 1700 is up, in both solar activity and temp, CET and most NH temp reconstruction.
(1700 is a logical place to start since that’s the minimum in the temp reconstructions) So all we need is an amplifier for the TSI increase. I’m starting to doubt the idea of using the S-B law and global average values. If TSI increased 0.5 W since 1700 that would mean close to 0.5 W increase at low latitudes where most of the input is. If most of this is then absorbed and much of it transported to higher latitudes, then the simple S-B calculation will be wrong for determining the effect on global temp change.
lgl (09:19:23) :
That’s unfair. I never said “steady trend”, but the long term trend since 1700 is up, in both solar activity
That is your error right there. There is no long-term trend in solar activity since 1700. The Armagh series begin in 1796: http://www.arm.ac.uk/preprints/445.pdf
lgl (09:19:23) :
If TSI increased 0.5 W since 1700 that…
TSI ‘may’ have increased by 0.5 W between 1700 and ~1780, then decreased 0.5 to ~1810, then increased 0.5 to ~1870, then decreased 0.3 to ~1900, then increased 0.5 to ~1990, then decreased 0.3 to ~2010, and so on.
And the CET begins in 1680. Are you unable to see that both 10Be and CET have a positive trend since 1700? (10Be inverted of course) Sorry if the 10Be is wrong, it’s from your link. http://virakkraft.com/CET-10Be.png
lgl (10:20:25) :
And the CET begins in 1680. Are you unable to see that both 10Be and CET have a positive trend since 1700? (10Be inverted of course) Sorry if the 10Be is wrong, it’s from your link. http://virakkraft.com/CET-10Be.png
The issue is that all of this is so uncertain [there is even strong evidence that 1-Be is influenced by the climate itself] that one cannot draw any form conclusions. Different ice cores give different results. CET is not global, etc. Cherry picking from minima is dubious. One of the better reconstructions is by Steinhilber et al. http://www.leif.org/EOS/2009GL040142.pdf
Their Figure 1d is telling. There were a dip in 1700 [although it is not certain what caused that [considering that the Sun was coming out the Maunder minimum – perhaps volcanic activity is partly to blame]]. TSI 1725-1800 was not any different from 1950-2010. Even the Steinhilber graph is disputed for some years, e.g. around 1900. My point is that the EVIDENCE for the myth is weak, if there at all. And even a 0.5 W/m2 change is still 0.04%, corresponding to 0.01% in dT or 0.03K. With a 10x amplifier [much too big, but giving you the benefit of a wild assumption], we are talking about 0.3K, which is not measurable in the data.
One of the better reconstructions is by Steinhilber et al. http://www.leif.org/EOS/2009GL040142.pdf Even the Steinhilber graph is disputed for some years, e.g. around 1900.
There has been a tendency lately to try to deduce the sun’s ‘open flux’ given by the radial component of the heliospheric magnetic field Br. Here is our best reconstruction to date of Br since 1835:
http://www.leif.org/research/Radial%20Component%20of%20HMF%201835-2010.gif
Br varies cyclically between a ceiling and a floor over that time. The trend line in the middle is flat. Its R^2 is 0.0019 [=no trend].
“My point is that the EVIDENCE for the myth is weak”
And my point is that it’s a myth that 0.5 W/m2 (TSI) is insignificant.
“Ocean heat storage has increased by 2 × 10^23 J since the mid-1950s, corresponding to an average heat flux of 0.3 W/m2” (TSI/4)
lgl (10:34:04) :
“Ocean heat storage has increased by 2 × 10^23 J since the mid-1950s, corresponding to an average heat flux of 0.3 W/m2″ (TSI/4)
Which will increase the temperature of the oceans by a very significant 0.03K
lgl (10:34:04) :
And my point is that it’s a myth that 0.5 W/m2 (TSI) is insignificant.
“Ocean heat storage has increased by 2 × 10^23 J since the mid-1950s, corresponding to an average heat flux of 0.3 W/m2″ (TSI/4)
What is the TSI/4 ? if TSI/4 = 0.3 W/m2, then TSI = 4*0.3 = 1.2 W/m2. Perhaps you mean dTSI? but TSI has not increased 1.2 W/m2 since the mid-1950s… Explain.
lgl (10:34:04) :
And my point is that it’s a myth that 0.5 W/m2 (TSI) is insignificant. “Ocean heat storage has increased by 2 × 10^23 J since the mid-1950s
You can make the number look even more impressive by converting it to ergs: 2×10^30 ergs.
Ok, a clumsy way to show that the 0.5 is the dTSI but 0.3 is for the earth surface, which is dTSI/4. Isn’t it?
lgl (12:59:44) :
Ok, a clumsy way to show that the 0.5 is the dTSI but 0.3 is for the earth surface, which is dTSI/4. Isn’t it
It is best to omit all those factors [1/4 for conversion from disk to sphere, 0.33 for albedo] and simply report in terms of [raw] TSI or better in %. If you want input to the surface then it is TSI[raw from sun]/4*0.33 = TSI/12. So the 0.5 W/m2 [beats me where you get that one from, but let it pass], is 0.04 W/m2 at the surface.
No, it’s TSI/4*0.67
The 0.5 W is the increase since 1700 which you can’t see 🙂
lgl (13:44:49) :
No, it’s TSI/4*0.67
The 0.5 W is the increase since 1700 which you can’t see 🙂
My bad with the albedo correction. So you are saying that the heat content since 1955 comes all the way back from 1700?
Solar activity 1725-1800 was higher than 1950-2000, so, indeed I don’t see the stuff coming from 1700. But, AHA: you are claiming that the high solar activity 1725-1800 is the direct cause of the global warming since 1970: 1.7×10^23 J increase in OHC. I see now. Sorry that I was so thick.