If I said my eyes have an optical power of more than 50 dioptres, would you say that is impossible? Or perfectly normal? Or like most people, would you ask, “What in the world is a dioptre?”
Context matters. In today’s often-contentious debates on environmental issues, context is essential. Without understanding the various measurements that are often cited, we cannot know what the statistics mean. Whether we hear problems discussed in terms of square miles, thousands of acres, or millions of tons, we should always ask, “compared to what?”
This week, for instance, there was another new study, now claiming the ice in Antarctica is melting, which threatens rising sea levels and worldwide flooding. It says Antarctica annually loses over 219 billion tons of ice. That sounds horrible, especially considering the perennial warnings of UN scientists that the seas could rise nearly three feet by 2100 if the world does not sharply decrease its energy use.
A loss of that much ice in Antarctica, however, would not cause such a catastrophic rise in sea levels, or anything close to it. We only know that if we ask, “Compared to what?”
Such studies use loaded language. Global warming figures are rarely discussed in terms of “molecules” or “millimeters,” because they sound so small. “Tons” sound bigger, so most studies are about “tons” of greenhouse gases belched into the atmosphere, or “tons” of ice melting. It is estimated that the U.S. produces 5.8 billion metric tons of carbon emissions a year (wow). Such numbers are not out of context – they contain no context at all. They sound awful, but only because we rarely ask, “How big is the sky?” or “How big is the ocean?”
The atmosphere extends some 620 miles above the Earth. Breathable air ends at about 13,000 feet, but the atmosphere doesn’t really end. It just gets thinner as it gets higher. Relative to the size of the Earth it is the thickness of the skin on a peach, but relative to people its magnitude is incomprehensible. Mathematicians calculate that the atmosphere is nearly 143 billion cubic miles. So to understand the context properly, you have to look at emissions by volume, not weight. Mankind adds about 2 molecules of greenhouse gas to a million molecules of atmosphere per year. A scientist friend compares that to spilling a shot glass of whiskey in the swimming pool once a year.
Similarly, melting ice in Antarctica cannot be understood without context. Reports about the Antarctica study point out that melting 360 billion tons of ice could raise sea levels one millimeter. But even this alarming new study shows far less melting than that. Nor does it mention the two trillion tons of snow that falls on Antarctica every year.
An analysis in Science Daily began with a discussion of how large Antarctica is. Its ice sheet is the largest mass of ice on Earth, covering 5.4 million square miles and containing over 7 million cubic miles of ice. Around 90 percent of the fresh water on Earth is frozen there. In East Antarctica, the ice sheet rests on land, sometimes 15,000 feet deep. But in West Antarctica it apparently extends more than 8,000 feet below sea level. So melting virtually all the ice in Western Antarctica would not affect sea levels. That matters because most of the melting observed in Antarctica is in the west, an area said to be the densest region of volcanoes in the world. Many researchers attribute much of the ice loss there to these naturally driven heat sources, not man-made warming.
Whatever the cause, though, it is worth noting that the new study flies in the face of decades of contrary evidence, all of which suggests that the south polar icecap is growing. The National Snow and Ice Data Center has tracked the data from satellites, and shows that the continent has gained 1.8 percent per year since 1970. NASA glaciologist Jay Zwally is often considered the pre-eminent Antarctic ice expert. His study shows the ice loss in Western Antarctica is more than offset by accumulations elsewhere on the continent.
“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” he says. That is less than 1/100th of an inch, so whether it grows or shrinks, the numbers are so small as to be hardly measurable.
So next time you hear alarm over billions of tons of anything, just ask, “Compared to what?”
An edited version of this column appeared in the Grand Junction Daily Sentinel February 1, 2019.
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