What was done
In a computer-based modeling study that incorporated elements of ocean, atmosphere and ice sheets, the authors searched for an explanation for the cause of the large and abrupt warmings, which - according to climate reconstructions based on data derived from ice and sediment cores taken from various areas of the North Atlantic region - are known to have punctuated the most recent ice age.

What was learned
The authors determined that "reduced calving of icebergs into the North Atlantic after a widespread ice sheet surge constitutes a trigger for the rapid glacial warming events," which typically occur a few hundred years later.  This triggering mechanism is made possible by their model-predicted finding that the stability of the thermohaline circulation during glacial periods is much reduced from that of interglacials, such as the one within which we currently reside.

What it means
What is of even more interest to us about this study than its purported resolution of a specific glacial-climate conundrum is that it demonstrates, via climate-modeling, what has long been known from climate reconstructions based on many types of proxy climate data, i.e., that, as the authors say, "the North Atlantic climate was much more variable during the last glacial period than during the present interglacial."  In addition, whereas they say "the reason for the different variability between glacial and interglacial times" had previously been considered "enigmatic," as they put it, such is no longer the case, if their thinking - and tinkering (climate model-wise) - is indeed correct.

The reason why this finding is of such interest to us is that it demonstrates that global warming should not lead to a more variable climate that is more conducive to abrupt climate changes or more extreme weather events, in direct contradiction of what is routinely claimed by the world's climate alarmists.  As can be readily ascertained by perusing related topics in our Subject Index, more warmth generally always means greater climate stability, as is also demonstrated by another paper (Andrus et al., 2002) that was published in the same issue of Science as the paper of Schmittner et al.

Reference
Andrus, C.F.T., Crowe, D.E., Sandweiss, D.H., Reitz, E.J and Romanek, C.S.  2002.  Otolith ó¹⁸O record of mid-Holocene sea surface temperatures in Peru.  Science 295: 1508-1511.