Jan 13, 2011
Scientists link bad weather to historical lows
by Clare O'Dea, swissinfo.ch
A Swiss-led team of scientists has used tree rings to detail 2,500 years of European summers, identifying the link between climate and major historical changes.
The findings give fascinating new context to centuries of European history. Results indicate, for example, that wet and warm summers facilitated Roman and medieval prosperity, and that the demise of the Western Roman Empire coincided with a period of increased climate variability.
The wide tranche of temperature and precipitation data is also useful in assessing the magnitude of today’s problems.
Although the extent of recent global warming is unprecedented, the last two millennia did have wet or dry episodes that were more extreme or lasted longer than the warming event that’s now underway, researchers said.
In the paper entitled "2,500 Years of European Climate Variability and Human Susceptibility”, published in Science, lead author Ulf Büngten provides evidence that agrarian wealth and economic growth might be related to climate change that occurs across years or decades.
Büngten of the Oeschger Centre for Climate Change Research at Bern University headed a multi-disciplinary team including climatologists, historians and archeologists from German, American, Austrian and Swiss institutions.
Over time a stable and favourable climate influences food production and human health, with implications for overall prosperity and political stability.
On the negative side pre-industrial societies were vulnerable to famine, disease and war, which were also partly driven by drought, flood, frost and other weather events.
The broader the canvas, the easier it is to identify norms and variations, and what’s new in this research is that it presents palaeoclimatic, or past climate, evidence for a millennium prior to the medieval period.
“All our results are based on tree ring data,” Büngten told swissinfo.ch.
Some 9,000 samples from Central Europe were collected, compiled and analysed, each one containing 100 to 150 annual rings which give a snapshot of vegetation growth and therefore weather conditions for that year.
“There are no missing years. We provide a value for each year, we have no dating uncertainty and it’s a continuous record with annual resolution all the way back. That’s the beauty of the archive”, Büngten said.
2500 Years of European Climate Variability and Human Susceptibility
Climate variations have influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution palaeoclimatic evidence. Here, we present tree ring–based reconstructions of Central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~AD 250 to 600 coincided with the demise of the Western Roman Empire and the turmoil of the Migration Period. Historical circumstances may challenge recent political and fiscal reluctance to mitigate projected climate change
Wenn der Hahn kräht auf dem Mist, dann ändert sich das Wetter, oder es bleibt wie es ist.
(When the rooster crows on the dungheap, then the weather will change, or stay as it is)
Although the extent of recent global warming is unprecedented,