From Lund University, a new way to blame modern man. Look for more nuttiness like this as the Durban climate conference approaches. Read the conclusion of the paper below, which is a long winded treatise of speculation.
New study shows no simultaneous warming of northern and southern hemispheres as a result of climate change for 20 000 years
21 October 2011
A common argument against global warming is that the climate has always varied. Temperatures rise sometimes and this is perfectly natural is the usual line.
However, Svante Björck, a climate researcher at Lund University in Sweden, has now shown that global warming, i.e. simultaneous warming events in the northern and southern hemispheres, have not occurred in the past 20 000 years, which is as far back as it is possible to analyse with sufficient precision to compare with modern developments. Svante Björck’s study thus goes 14 000 years further back in time than previous studies have done. “What is happening today is unique from a historical geological perspective”, he says
Svante Björck has gone through the global climate archives, which are presented in a large number of research publications, and looked for evidence that any of the climate events that have occurred since the end of the last Ice Age 20 000 years ago could have generated similar effects on both the northern and southern hemispheres simultaneously. It has not, however, been possible to verify this. Instead, he has found that when, for example, the temperature rises in one hemisphere, it falls or remains unchanged in the other.
“My study shows that, apart from the larger-scale developments, such as the general change into warm periods and ice ages, climate change has previously only produced similar effects on local or regional level”, says Svante Björck.
As an example, let us take the last clear climate change, which took place between the years 1600 and 1900 and which many know as the Little Ice Age. Europe experienced some of its coldest centuries. While the extreme cold had serious consequences for agriculture, state economies and transport in the north, there is no evidence of corresponding simultaneous temperature changes and effects in the southern hemisphere. The climate archives, in the form of core samples taken from marine and lake sediments and glacier ice, serve as a record of how temperature, precipitation and concentration of atmospheric gases and particles have varied over the course of history, and are full of similar examples.
Instead it is during ‘calmer’ climatic periods, when the climate system is influenced by external processes, that the researchers can see that the climate signals in the archives show similar trends in both the northern and southern hemispheres.
“This could be, for example, at the time of a meteorite crash, when an asteroid hits the earth or after a violent volcanic eruption when ash is spread across the globe. In these cases we can see similar effects around the world simultaneously”, says Svante Björck.
Professor Björck draws parallels to today’s situation. The levels of greenhouse gases in the atmosphere are currently changing very rapidly. At the same time, global warming is occurring.
“As long as we don’t find any evidence for earlier climate changes leading to similar simultaneous effects on a global scale, we must see today’s global warming as an exception caused by human influence on the earth’s carbon cycle”, says Svante Björck, continuing: “this is a good example of how geological knowledge can be used to understand our world. It offers perspectives on how the earth functions without our direct influence and thus how and to what extent human activity affects the system.”
Svante Björck’s results were published this summer in the scientific journal Climate Research.
For more information, please contact Professor Svante Björck, Department of Earth and Ecosystem Sciences, Lund University, tel.: +46 46 222 7882, mobile: +46 703 352494, email: Svante.Bjorck@geol.lu.se
- Ulrika Jönsson Belyazid
Current global warming appears anomalous in relation to the climate of the last 20000 years
223 62 Lund, Sweden
ABSTRACT: To distinguish between natural and anthropogenic forcing, the supposedly ongoing global warming needs to be put in a longer, geological perspective. When the last ca. 20000 yr of climate development is reviewed, including the climatically dramatic period when the Last Ice Age ended, the Last Termination, it appears that the last centuries of globally rising temperatures should be regarded as an anomaly. Other, often synchronous climate events are not expressed in a globally consistent way, but rather are the expression of the complexities of the climate system. Due to the often poor precision in the dating of older proxy records, such a statement will obviously be met with some opposition. However, as long as no globally consistent climate event prior to today’s global warming has been clearly documented, and considering that climate trends during the last millennia in different parts of the world have, in the last century or so, changed direction into a globally warming trend, we ought to regard the ongoing changes as anomalies, triggered by anthropogenically forced alterations of the carbon cycle in the general global environment.
I find it fair to conclude that in the perspective of 10 to 20 millennia, the ongoing global warming seems to be an anomaly. Owing to often incomplete chronologies
of the proxy based paleo-archives, especially in relation to the last 150 yr of daily to annual instrumental records, it may, however, be difficult to find clearcut evidence for such a statement. One might also ask the question: What is the likelihood of seeing a global
warming in our proxy records of comparable magnitude to the present warming, and arising only due to natural variations? A statistically reliable answer is of
course difficult to give, but with the gradually in -creased focus on high-resolution records, I would be surprised if it would not have been found in many of
Then again, as geologists we could try to put the ongoing warming into a thought experiment. Firstly, if we use the 8.2 kyr cooling event in the NH (Alley et al.
1997, Hammarlund et al. 2005), which lasted less than 100 yr, as a Holocene analogue of a partly enigmatic climate event, we cannot say for certain what triggered it. How can we try to better understand the underlying processes behind it? Perhaps by climate modeling?
In fact, modeling of available data on early Holo cene cooling events (Renssen et al. 2007) shows that this event was most likely triggered by freshwater outbursts that severely disturbed the thermohaline circulation and meridional heat advection to the north. This
fits well with the geological observations that a large North American glacial lake was drained out into the North Atlantic at that time, i.e. a normal procedure: testing models with data and vice versa. Secondly, if we found a short geologic warming event during, for example, the Holocene, and were able to analyze proxies from that period which disclosed that, for example, aerosols and solar activity had been rather high and that GHGs were >30% higher than during the preceding period, what conclusions would we have drawn? With data in a quantifiable form, modeling attempts would certainly have been carried out to find out the most likely hypothetic mechanisms be hind the warming. After critical analyses of the data and repeated model runs, I think it is likely that geologists and/or geoscientists would find that the high atmospheric GHGs would be the main candidate for the warming, but perhaps with a reservation concerning the effects from increased solar forcing. The type of procedures described above is what the IPCC modelers have performed, by testing dif ferent climate scenarios, such as ones with or without in creased
To summarize, as long as there is no positive and clear evidence for distinct, globally synchronous climate events (since the LGM) with consistent climate signals, we should consider the ongoing global warming as an anomalous climate event, possibly with a global forcing mechanism—increasing atmospheric content of GHGs—altering the energy budget of the Earth. The basis behind and consequences of such a standpoint can obviously be discussed, but the effects of our giant ‘climate experiment’ are undoubtedly difficult to estimate and evaluate since we have no past analogues to a situation with abruptly rising GHGs more than 10 000 yr into an interglacial period. We should therefore be cautious about how and to what degree we contaminate our environment and both directly and indirectly influence natural climate pro – cesses: the dangers of crossing climate thresholds in a greenhouse world have been pointed out by many scientists (e.g. Stocker 1999, Alley et al. 2003, Keller et al. 2008).