The term “settled science” gets tossed around in the media a lot these days. Mostly by non-scientists, who know no better, and by some errant scientists, who should. In 2002, the U.S. National Research Council Committee on Abrupt Climate Change published its findings in a book entitled Abrupt Climate Change: Inevitable Surprises. A new report in Science recaps the surprising discoveries made since then, and they are big. So big that ocean circulation models, integral parts of all climate models, do not accurately predict reality. The observed change in AMOC strength was found to lie well outside the range of interannual variability predicted by coupled atmosphere-ocean climate models. Sounds like circulation in the Atlantic Ocean is not so settled.
There has been a wave of triumphal announcements by climate change proponents recently, almost giddy over the summer shrinkage of the Arctic ice sheet. “Lowest level ever!” they proclaim, thought that is not quite true. Nonetheless, The Arctic pack ice has been receding over the last decade or so, but that is only natural. You see, there is a well known, if poorly understood, linkage between the ice at the north pole and the ice in and around Antarctica—and the ice around Antarctica is doing quite well. Satellite radar altimetry measurements indicate that the East Antarctic ice sheet interior increased in mass by 45±7 billion metric tons per year from 1992 to 2003. This trend continues today, reinforcing recent scientific investigations into this millennial scale oscillation between the poles. According to studies, this is how things have been for hundreds of thousands of years.
It is accepted that volcanic eruptions can have a major impact on short term climate. A new study in Nature Geoscience uses instrument records, proxy data and climate modeling to show that multidecadal variability is a dominant feature of North Atlantic sea-surface temperature (SST), which, in turn, impacts regional climate. It turns out that the timing of multidecadal SST fluctuations in the North Atlantic over the past 600 years has, to a large degree, been governed by changes in external solar and volcanic forcings. Solar influence is not surprising but the fact that volcanoes cause climate change lasting decades has some significant implications for those trying to model climate over the next century.
The Atlantic Meridional Overturning Circulation (AMOC), also known as the “Ocean Conveyor Belt,” has been the subject of much study since its discovery. The AMOC is primarily responsible for Europe's temperate climate and some scientists have warned that global warming could cause the ocean's flow to slow down or even stop. This rather counter intuitive result of a warming climate would result in a much colder Europe—perhaps even a new mini-ice age. A new analysis of data from satellites and drifting sensors finds no evidence that the conveyor belt is slowing. In fact, a NASA backed study indicates that the conveyor is far less susceptible to throttling by climate change than some climate change alarmists feared.
Two articles in the July 17 edition of Science describe efforts to model Earth's rapidly changing climate at the end of the last glacial period, between 21 and 11 thousand years years ago (ka). After a year and a half of number crunching on Oak Ridge National Laboratory's Jaguar supercomputer, the first results indicate that climate experienced cooling 17 ka, during the Heinrich Event 1 (H1), followed by an abrupt warming at the onset of the Bølling-Allerød Warming 14.5 ka. These abrupt climate changes were accompanied by large changes in the “ocean conveyor belt”: the Atlantic meridional overturning circulation (AMOC). The results suggest that this transition can be viewed simply as the North Atlantic climate response to rapidly changing glacial meltwater flow. The findings call for a paradigm shift in our understanding of abrupt climate change and weakens the threat of “irreversible tipping points” so popular with climate change extremists.
A recent article in the journal Science has provided a new, detailed climate record for the Medieval Climate Anomaly (MCA), also know as the Medieval Warm Period. It was the most recent pre-industrial warm period, noted in Europe and elsewhere around the globe. The researchers present a 947-year-long multi-decadal North Atlantic Oscillation (NAO) reconstruction and find a persistent positive NAO during the MCA. The interesting thing is that the MCA had basically been removed from the climate record by Michael Mann's infamous “hockey stick” history graph that was adopted by the IPCC a decade ago.