Quote:
Originally Posted by Gwen Morse
These answers are provided my my husband, the geophysicist. His specialty is glaciation and sea-level change. If there are any weird gaps, please forgive me, I'm trying to form neat paragraphs of what he typed in IM from work.
"The longer term ice ages are caused by the Milankovich cycle which is caused by tiny perturbations of the Earth's orbit by Jupiter."
"Things were warm in the northern hemisphere around 1000 AD but not in the southern hemisphere."
"The current cycle is different because the pattern of temperature rise is confined to the lower atmosphere, which is a characteristic of greenhouse-driven temperature increase. The greenhouse gases already in the atmosphere are expected to produce at least 4 degrees Fahrenheit increase on top of any natural warming in the next 50 years. That is as warm as any of the previous interglacials got. If we keep producing greenhouse gases we'll get warmer than any previous period we know about that mammals have lived in. That could be very bad for agriculture. Also currently global average temperature is increasing in both hemispheres, not just the Northern like in 1000 AD."
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May this dumb redneck ask another question?
If the cycles mentioned above are causative, why have there been such large glaciation gaps in the geological record. (there was around 20 millions years without major glaciation before the current glaciation cycle, and around 130 million year during the Cretaceous.)