For my geography course this past semester, I had to read a report from the IPCC, which taught me a couple of things. There are some common misconceptions about ‘global warming’. Global warming does not mean that everyplace on earth gets a couple of degress more balmy. It means the globe on average gets a bit warmer, with potential wild swings in some places, and even local cooling in some areas.
Longer growing seasons may occur in some places. In many other places, though, there’s just barely enough rain, or things are just borderline too hot already, and warming could make these marginal agricultural areas inarable. The IPCC expectation is that most likely global agricultural yield won’t change much, but there will be significant regional variability. Certain parts of the interior plains of North America, and much of sub-Saharan Africa, are at risk from the changing patterns of precipitation.
Changes in temperature and precipitation affect what types of crops can be raised, how pastureland responds to grazing, and whether irrigation is necessary. Hotter means more water and energy need to be used for irrigation.
Changes in temperature and in the temperature-driven ocean currents affect the distribution and size of fish populations: the oceans are a major source of food for an important fraction of the world’s population.
The Inuit people of Canada’s arctic still, to this day, get a big fraction of their diet from the spoils of hunting: hunting for seals, fish, and other animals on the sea ice. The extent and duration of sea ice has already shrunk; even today we’re starting to hear news stories of experienced hunters falling through the ice. Ice that their experience with local geogrpahy told them would be thick enough.
Warmer summers == more energy used to run air conditioners and refrigerators.
Warmer summers == more people die from heat stroke.
In the last couple of years we’ve seen major events in European cities of large numbers of urban elderly people dropping dead from unusual heat waves. If the frequency or intensity of these heat events increases, expect this to happen more often.
Further, the effects of a global warming are sometimes (in IPCC terms) “non-linear”, meaning things don’t just change slightly in a predictable direction. One scenario is of warming causing major melt in eastern and arctic Canada which causes a large amount of snowmelt and receding of land glaciers and sea ice. This large introduction of fresh water into the Hudson Bay and Arctic Ocean makes its way into the Labrador Sea, where it eventually collides with the Gulf Stream; the temperature and salinity differences, it is hypothesized, could tend to deflect the Gulf Stream southward. If this happens, it would no longer be bringing its huge conveyor of heat up to northern Europe, and France, Britain, and Norway would get a lot colder.
And is a little warming good for everyone? What of the Innu and Inuit? Already the permafrost is melting in many places; the coastal town of Tuktoyaktuk, built on permafrost, is subsiding. Buildings collapse, the coast erodes. When the permafrost melts, the half-decomposed organic matter of which it is made can finish decomposing: when it does so, it releases large amounts of the potent greenhouse gases methane and carbon dioxide. The hunting isn’t as good in some places, so communities are now flying in more food from the south. With the change in diet, the ministry of health seems to be finding an increase in diabetes and tooth decay among Inuit.
And what of the political consequences? What of those places where people already fight over water? Will there be more wars between Israel and Syria over the Golan Heights? What if someone decides the waters of the Danube or the Nile must be diverted to meet the needs of increasingly arid agricultrual regions? What if the Americans pull huge quantities of water out of the Great Lakes to serve their big eastern cities or their mid-west agricultural areas? What will that mean for the freshwater fishery that feeds the economy and the mouths of Northeastern Ontario?
Canada’s big worry is of reduced sea ice. In the feared worst-case, the Inuit either abandon their way of life or starve, the delicate Arctic ecosystem is thrown off-kilter, and the usualy ice-locked Arctic Archipelago becomes navigable to ships as a shortcut between Europe and Asia. Ships that bring their cargoes of oil to be spilt in accidents, their filthy bilge water to be dumped in the nutrient-poor arctic waters.
Compared to all that, a little bit of a longer growing season and a marginally milder winter in a few places is simply not worth it.
The report I mentioned at the top was the Third Assessment Report (“Synthesis”).
A cite for Tuktoyaktuk is here.