December 2, 2012

Detailing climate change from past to present


This is one of many papers that have appeared since 1998, when Michael Mann first published data that shows current temperature levels are higher than anything in the proxy record for this time frame. Many other publications since continue to support this original finding.

One example is a recent paper by Kinnard et al. published in Nature (479, 509-12, 24 Nov.2011) from which the following graph of “Arctic sea ice extent over the last 1,450 years” is taken.

This graph was obtained from a variety of land proxies in the circum-Arctic region. This reconstruction, with high uncertainties in the early centuries noted by the width of the shaded area, shows there is about 2,000,000 square kilometers less ice today than any time in the past. (NOTE: one kilometer is equal to about 0.62 miles.) Clearly, there has been significant climate change, warming, in the past century within that time frame.

Now let’s look at another data set using sediment from salt marshes in North Carolina. But instead of temperature, and sea ice extent, this graph shows sea level changes (meters) off the coast of this state.

This data fits in very well with the earlier data. Note the basically flat portion of the curve starting in 100 B.C.E. to about 1000. The curve then begins to rise, which corresponds to the start of the Medieval Warm Period, levels off at about 1400 during the Little Ice Age, drops some during this cooler spell, and then rises steeply again in the current time. This sea level rise comes from ice melt as well as the expansion that occurs as water warms.

All these data are consistent with the fact that the current warming is without parallel for the past 2,000 years and outside of the normal variability.

And there is still more information — lots more. A final point to be made here is a recent paper in Geology (v. 40; p. 1003-1006; November 2012.) It reports the “reawakening” of the world’s northernmost lake in north Greenland at 83 degrees 37 minutes north latitude that occurred in the last 90 years. Without a biological fingerprint for more than 2,000 years, algae have now returned and a diverse community established there.

The warming today is unlike anything the world has seen for at least two millennia.

It’s unequivocal.

The scientific career of Raymond N. Johnson, Ph.D., spanned 30 years in research and development as an organic/analytical chemist; he is currently founder and director of the Institute of Climate Studies USA ( Climate Science is published the first Sunday of every month.




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