The Fate of Greenland: Lessons from Abrupt Climate Change

8. Out of the Ice

8 OUT OF THE ICE The Lessons from Greenland The public debate about climate change has been treated in the press as having two sides—the science showing that our business-as-usual actions will change the climate in ways that on average hurt us, and the opposition arguing that things might end up better than that projection. As noted in the previous chapter, such a two-sided view has always been overly simplistic—there are many more sides; in particular, the possibility that things might end up a lot worse. Our research in Greenland is part of a larger body of emerging science on abrupt climate change, emphasizing the lop-sidedness of the uncertainties . The future could be better than the mainstream scientific projections , but “a little better” is balanced against “a little worse” or “a lot worse,” as reviewed below. Climatic Confirmation If the sun brightens, or Earth reflects less sunlight, or Earth’s greenhouse gases rise, the planet warms. Such changes have come and gone naturally, and they will again. 185 OUT OF THE ICE If we humans continue with business as usual, however, we are likely to cause changes for the whole Earth of a combined size and speed not seen in a very long time, if ever. The CO2 production in the United States is equal to approximately 20 tons per person per year—each of us responsible for roughly 250 times our own weight in CO2 each year, or roughly 20,000 times our own weight over the course of our lifetime at current rates. And, with much of the rest of the world either fairly close to this level of carbon-dioxide production or else trying to get there, that’s a lot of CO2 . Much of that CO2 goes into the ocean, and some goes into trees that grow a bit better with the extra CO2 , but we are still raising the CO2 concentration in the atmosphere, and the atmospheric level will remain elevated centuries and even millennia from now. The mere volume of CO2 doesn’t tell us how important it is—if we released that much water vapor, it would rain out in a week or two, with no one seriously noticing the difference. But if we were to vent even a fraction of that amount of many poisons into our cities, such a release would cause very different results. Burning most of the fossil fuels and leaving the CO2 in Earth’s natural systems will warm the world a lot, with large impacts on ecosystems and economies. Our tour of Greenland has helped provide perspective on this. The ice core records give us many insights into the causes of climate change, and together with moraines and other indicators, the ice in Greenland has revealed how the climate responded to those causes. Understanding these causes and effects allows us to say a lot of common-sense things about the climate, and it allows quantitativetestingoftheclimatemodelsthatareusedtoprojectfuturechanges. Our understanding of greenhouse warming rests primarily on straightforward physics, not on correlations. And the physical understanding of energy transfers and greenhouse gases makes sense of a climate history that is otherwise inexplicable. For example, the globally large and near-synchronous climate changes of the ice-age cycles were caused by features of Earth’s orbit that had almost no effect on the total sunshine reaching the planet. Some places cooled while receiving more sunshine, and ice grew in places where extra summer sunshine favored melting. But as described in chapter 1, CO2 dropped with the ice age and the effects of that CO2 decline successfully explain the size and global reach of the ice age cooling. No other successful explanation has ever been advanced. Figure 8.1 Field team at entrance to Northwest Fjord, Scoresby Sound; from left, Telford Allen, pilot; George Denton, geologist ; Richard Alley, glaciologist; Philip Conkling, writer. (Photo by Gary Comer) Figure 8.2 View northwest toward the late-glacial moraine loop in the Itivdlerssuaq valley. The glacier ended where the bare till meets the tundra at the historical maximum around 1850, but it had turned the corner and extended far out onto the main valley floor during late glacial (probably Younger Dryas) time. This is perhaps the most spectacular late-glacial moraine in southern Greenland, which can help reveal the causes of climate change there. (Figure 3.3 also shows this moraine, but looking in from the left side...