Earth's History: Freeze and Fry

- 6 Jul 2008

By Sam Fowler Page 1 of 3 Today’s rapid climate change is undoubtedly the result ofgreenhouse gases produced by humans. But extraordinary swings in ourplanet’s past climate have been caused by changes in its interior andinfluences from deep space.


In the winter of 1780, New York harbour froze over: people walkedacross the ice from Manhattan to Staten Island. Around the same time,theFrench invaded the Netherlands over frozen rivers, while - on a lighternote - Londoners held Frost Fairs on the iced-up River Thames(pictured). google_protectAndRun("ads_core.google_render_ad", google_handleError, google_render_ad);
This was the period of the Little Ice Age. The world was then aboutone degree cooler than the average for the twentieth century.


The Solar Connection

Meteorologists aren’t the only people to pick out this period asunusual: they’re joined by astronomers who study sunspots(pictured, below).Today, these dark patches – marking magnetic storms on the Sun - comeand go in an 11-year cycle. But there was a complete dearth of darkspots on the Sun from 1645 to 1715, the time that the Earth plungedinto the Little Ice Age. This apparent link between the Sun’s magnetic activity and theEarth’s climate could be coincidence. But German researcher SamiSolanski has confirmed the effect. Based at the Max Planck Institutefor Solar System Research, in Katlenburg-Lindau, Solanski has pushedthe Sun’s magnetic record back to 9000 BC. No-one was observingsunspots then, of course, but the Sun’s activity shows up in certainisotopes - carbon-14 and beryllium-10 - that are preserved in ancientpieces of wood and deep in the ice of Greenland and Antarctica. Solanski hasfound that the Sun’s magnetism and the Earth’stemperature march hand-in-hand over the millennia. When the Sun isviolent, our temperatures go up. When the Sun is dormant (as in theLittle Ice Age), our temperatures drop. He finds, however, that thiscorrelation stops around 1970, when manmade global warming starts tokick in. Solanski reckons that solar activity can account for only 30%,atbest, of the Earth’s warming in the past 40 years.

Volcanic Cool

In 1783, the inhabitants of Iceland were treated to the spectacle ofa wall of fire spouting from the ground. It was accompanied by thegreatest lava outpouring in history, along with lethal gases, such asacidic sulphur dioxide. A quarter of Iceland’s population died. And thefollowing winter, Benjamin Franklin – then in Paris – noted theexceptionally cold conditions, and was astute enough to blame theeruption in Iceland.The great explosions of the Indonesian volcanoes Tambora in 1815 andKrakatoa in 1883 each lowered Earth’s temperature by more than adegree. But in the geological past, eruptions had an even more direeffect. At the Siberian Traps in Russia, some 250 million years ago,the Earth witnessed its largest ever outpouring of lava – enough tocover the entire planet with three metres of molten rock. The ash anddust first cooled the planet to freezing point; then greenhouse gasesheated it up. The toxic gases from the eruption, followed by thefreeze/fry cycle, killed 95% of species on Earth.
Recently - in geological terms - the Ice Ages have repeatedly putour planet in the deep-freeze - but what drives them?Read on to find out more....


<< Start < Previous 1 2 3 Next > End >>