No simultaneous warming of northern and southern hemispheres as a result of climate change

New study shows no simultaneous warming of northern and southern hemispheres as a result of climate change for 20 000 years

This image is a comparison of 10 different published reconstructions of mean temperature changes during the last 2000 years. More recent reconstructions are plotted towards the front and in redder colors, older reconstructions appear towards the back and in bluer colors. An instrumental history of temperature is also shown in black. The medieval warm period and little ice age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events. The single, unsmoothed annual value for 2004 is also shown for comparison.

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.

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