What is natural
Guest contribution by Jim Steele
California and other American coastal cities are arguing about sea level rise. Although observed sea levels have risen less than 8 inches (0.08 inches per year) since 1900, some model makers are predicting much grimmer futures. They predict an increase of 2.4 feet for every 1 ° F increase above pre-industrial temperatures, and then accelerate to nearly 4.5 feet for each additional 1 ° F increase. Why a dramatic increase in sea level? It is based mainly on terrible models, typically presented to coastal planning commissions as "best science," suggesting increasing ice instability and the collapse of the Antarctic ice sheet. "Antarctica has the potential to add more than 3.3 feet to sea level rise by 2100 and more than 49 feet by 2500."
These models have led some citizens to argue that we need to leave the coasts through managed withdrawal. Others argue we should build better walls. But how high? Others rightly ask: "How trustworthy are these models?" Model predictions of a collapsing ice sheet in Antarctica are not based on observations. Models of the catastrophic ice fall in Antarctica are attempts to explain ancient sea levels like the levels 30 feet higher 120,000 years ago.
There are good reasons to question disastrous models. On the one hand, the surface temperatures of the Antarctic outside the coast averaged -70 ° F. The extremely cold surfaces of the Antarctic require multiple global warming before the surface glaciers can ever melt. On the other hand, although the greenhouse theory predicts that increasing CO2 concentrations will increase temperatures, the greenhouse theory also predicts that added CO2 has a cooling effect on the Antarctic (Wijngaarden & Happer 2020, Schmithüsen 2015).
Up to a point, increasing greenhouse gases act like a blanket that warms your body by slowing the loss of body heat. Although CO2 absorbs and then quickly gives off heat in less than a thousandth of a second, it gives off that heat more slowly at colder altitudes. Since warmer bodies give off more heat than colder ones, the higher and colder atmosphere absorbs the heat given off by warmer surfaces faster than it can give off heat to space, which creates the greenhouse effect. In contrast, the surface of Antarctica is much colder and the air miles above it is warmer. Warmer greenhouse gases in the air give heat back to space faster than it can be absorbed by the colder surface. Thus, the atmosphere over the Antarctic cools faster than without greenhouse gases.
Yet researchers are observing regions of receding ice. The Antarctic Peninsula was once named one of the fastest warming regions on earth in the 1980s and 1990s. However, the researchers debated whether the melting was caused by global warming or changing winds. In fact, warmer winds often came from the north. The British Antarctic Survey now reports that the peninsula has cooled rapidly since the 1990s due to frequent southerly winds from the mainland, which can be between 50 ° F and 70 ° F colder. The researchers attribute changing winds to “extreme natural internal variability”.
Strong winds also cause turbulence, which sporadically pulls warmer air from above onto the cold surface, which occasionally leads to "warming peaks". In addition, strong winds moving over mountains can warm the air simply because of the increasing pressure as the winds drop (called foehn storms). Without the addition of heat, the increasing air pressure alone can raise regional temperatures to over 22 ° C, which ultimately leads to dry, ice-free regions or melting ponds that promote the collapse of the ice shelf.
Since air temperatures rarely reach the melting point (except during foehn storms), there is no significant melting of the Antarctic surface ice. However, some glaciers that extend beyond the coast end below sea level and actually lose ice. Antarctic oceans consist of a relatively fresh cold layer of surface water overlying a thick layer of relatively warm salt water known as Circumpolar Deep Water (CDW).
Antarctic winds can push cold surface water towards the coast and then deeper. This also pushes the warmer CDW down and minimizes the melting of the glaciers. At other times, the winds can shift, causing the surface water to move away from the shore while pulling warmer CDW to the surface. The warm CDW then accelerates the melting of submerged glaciers. Natural vibrations like El Nino or the Antarctic Oscillation (also known as SAM) can shift the winds and induce decades of rapidly receding glaciers alternating with decades of stable or growing glaciers.
The Antarctic research community is 50% divided on whether the changes observed are mostly natural or caused by human additions of CO2. However, so far there is no evidence of ice sheet collapse that would accelerate sea level rise, and many researchers trace it back to the extreme claims made by Antarctica's contributions to sea level. Coastal planning commissions should plan the same average sea level rise over the past 100 years, but take into account the changing winds of Antarctica and changing scientific claims.
Jim Steele is Director Emeritus of San Francisco State's Sierra Nevada Field Campus and author of Landscapes and Cycles: An Environmentalist's Journey to Climate Skepticism