Global warming compared to what period of Earth's

Started by fblue, 03/24/2008 02:22AM
Posted 03/24/2008 02:22AM Opening Post
If you are going to talk Global Warming, you must state compared to what period of Earth's history?
There has been much greater periods of warming than we see today, as well as much greater cooling. So, do you compare the last 100 years or the last 100,000 years when you decide what constitutes warming.

[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue grin
Amateur Imager
Posted 03/24/2008 03:02AM #1
There was an interesting segment on 60 minutes tonight on the arctic seed bank. Basically, many of the seeds of various grains, fruits and vegetables are being stored in a huge vault or bunker in an area that has 30 degree below zero weather and the bunker itself is being cooled further with air conditioning. The scientists are counting on it to help save humanity when the anticipated lethal effects of global warming hit the planet in a hundred years or so...
Posted 04/01/2008 11:00PM #2
Floyd Blue said:

If you are going to talk Global Warming, you must state compared to what period of Earth's history?
There has been much greater periods of warming than we see today, as well as much greater cooling. So, do you compare the last 100 years or the last 100,000 years when you decide what constitutes warming.

From a paleoclimatic perspective, yes, the time-scale is important, but one must remember that the forcing mechanisms differ at various time-scales. For example, over millions of years, the paleogeography of continents and tectonic forces influence global climate, but these processes are far too slow to account for the current warming. Similarly, on 10^5 to 10^4 yr time-scales, orbital dynamics, particularly the celebrated Milankovitch Cycles, dominate the climate record. Moving to shorter and shorter time-scales, the influence of the sun becomes ever more important with the well-known multidecadal Schwabe, Hale, Gleissberg, etc. cycles of solar variability being well expressed in numerous paleoclimatic records.

Now, with respect to the current warming. When all of the natural forcing mechanisms are summed, the predicted temperature is less than what is observed by the instrumental records of today. By adding the temperature forcing of anthropogenic CO2, the predicted and observed temperatures match within the range of error. This is a key finding of the IPCC report and is consistent with NASAs GISS climate model. So from a mechanistic perspective, the time-scale is important only in determining the relative contribution of forcing mechanisms. Discussion about the Last Glaciation or the Carboniferous has little bearing on cause of the current warming trend except to refine our understanding of the natural forcing mechanisms. Perhaps our understanding will change...Perhaps we do not have a complete list of climatic drivers...Perhaps we have misinterpreted the magnitude of the climatic drivers that we do know....These are all possibilities as science progresses not with proof but the failure to disprove. Given our current knowledge of the climatic system, anthropogenic contributions are consistent with the current warming trend. So, we keep the hypothesis.