AgTalk Home
AgTalk Home
Search Forums | Classifieds (5) | Skins | Language
You are logged in as a guest. ( logon | register )

One scientist's opinion on global warming
View previous thread :: View next thread
   Forums List -> AgTalk CafeMessage format
 
dko_scOH
Posted 3/4/2009 01:42 (#631071 - in reply to #630872)
Subject: RE: One scientist's opinion on global warming



39.48, -82.98

The Earth has gone through many cycles driven by orbital changes. [Google "Milankovitch cycles"] These predictable cycles vary the amount of sunlight and where it strikes the Earth. When the cycles allow snow to build up in the northern hemisphere, albedo takes over -- flipping the switch, as it were, to an ice age. Thousands of years later, the process reverses. Orbital changes favor less snow and ice in the NH until bare land and open water suddenly (in geological terms) lower albedo and the switch flips back to interglacial.

At present, we are already in an interglacial period. With humans out of the equation, the next ice age would arrive in about 15,000 to 50,000 years. Owing to the combination of Milankovitch cycles, this should be one of the longer interglacials. Talk of an imminent ice age is due to looking at the length of the last couple interglacials, rather than what caused them.

Until industrial times, the amount of ice and the concentration of atmospheric CO2 had reached the approximate interglacial levels and sea level was steady. Global temperature, though variable, remained in a range of ±¼ °C for the last two thousand years or more.

We are currently on a trajectory to a climate not seen since the PETM 55 million years ago. Only that 6 °C runup in temperature occured over 20,000 years, or 0.03 °C per century. We have now accelerated warming to about 1.6 °C per century and are pushing it at an accelerating rate. We should acknowledge the risk we are taking -- and try to minimize it.

Top of the page Bottom of the page


Jump to forum :
Search this forum
Printer friendly version
E-mail a link to this thread

(Delete cookies)