The biggest difference between exploring “what if?” scenarios in fiction and in nonfiction, is the restrictions that the laws of science set on the consequences of making a change in the natural world. Fiction is essentially a continual creation of, and exploration of, “what if?” scenarios. Once I ask a “what if?” question about the natural world, as I do for ten scenarios in What if the Moon Didn’t Exist?, the relevant equations of science immediately come into play and often take me a rollercoaster ride into the unknown.
Consider, for example, the question “what if the ice caps melt?” This is not a purely hypothetical question; it is happening today as a consequence of global warming: The Arctic Ice Cap and the ice sheets on Greenland and Iceland are decreasing significantly.
There are basically two sources of ice that melt during global warming: the sea ice that is already floating in the oceans, such as the Arctic Ice Cap, and the ice resting on the continents and islands. The weight of the floating water is already pushing down on the oceans. In other words, its weight contributes today to the height of the oceans. So, as it melts, the newly liquefied water from the Arctic does not change the height of the oceans
The other sources of melted snow are the ice sheets resting on lands including Antarctica, Greenland, and Siberia. When this ice melts and runs into the oceans, it weight and volume add to the existing water in the oceans and as a result, the oceans rise. This is already beginning to happen, primarily as the ice on Greenland, and to a smaller extent on Iceland, melt.
There are several consequences of adding the newly-melted snow to the oceans besides the change in ocean heights. Frozen water, either floating or on land, is nearly salt-free, which means that as it melts, it becomes salty from the salt already in the oceans, and so the overall salinity (saltiness) of the oceans decreases – more water with the same amount of salt. This will have an effect on life in the oceans, which has adapted to its present salinity.
Second, the white snow on the icecaps has a direct effect on the sunlight striking the Earth’s surface. Some of this light and heat (I will hereafter say light, but I mean both) is absorbed by the Earth’s surface, most notably the solid parts. The darker the surface on Earth, the more sunlight is typically absorbed. The rest of the light is scattered right back into space and the energy associated with that light is lost to us. Snowcaps, being white, scatter much more light back into space than does either bare rock or land covered with other materials, such as sand, soil, or vegetation. So, as the icecaps recede, more of the darker land is exposed, meaning that more sunlight and heat are absorbed by the Earth. This increased energy from the Sun absorbed into the Earth means that the Earth is warming more than it was before the ice began receding.
Warmer land means more heat radiated off the land into the air. This, in turn, means even warmer air. This is what we call a “nonlinear” effect: a change causes even more change.
Third, the heating of the atmosphere, from whatever cause, is intimately connected with weather patterns. For example, when the mid-latitudes of the Pacific Ocean are warmer than usual, the heat that they give off drives humid winds over the western shore of the Americas, creating what is called El Niño http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html . So, changing ice coverage on Earth is changing many things. Can you think of any others?