Sunday, December 19, 2010

Average low temperatures; a global warming hypothesis

If we were to remove the Earth's atmosphere entirely, presumably its surface temperatures would resemble that of its Moon's: Daytime high of 123C(about 253 F) and lows of -233 C (-387 F). The Earth's atmosphere reflects much of that heat energy, so our average daytime temperature rarely exceeds 40 C and that same atmosphere retains the heat that does get through, so the lowest temperatures rarely exceed -40 C.  In fact the average daytime temperature across the surface of the Earth is about 9C (and rising). My hypothesis is that as carbon dioxide increases in the atmosphere, heat will be retained incrementally, while daytime peaks will be somewhat mitigated as the CO2(and other greenhouse gasses) reflect some heat during the day but retain more heat overall, causing among other effects, warmer overall low temperatures.

Currently, Western Europe is suffering from a relatively cold, snowy winter. Many comments suggest that this is because the earth is getting colder. But Europeans, especially brits(I was born in Reading) live in latitudes farther north than much of Canada(Montreal sits roughly at 45 degrees N while London, UK sits at 51 N). The weather there is still currently milder than here in eastern Canada. Meanwhile, our current weather is milder than normal.

Britain, and much of western Europe have benefited from the Atlantic Conveyor, a stream of warm water flowing from the warm south Atlantic up to Europe's west coast. Most models of global warming have predicted this warm water will cease to flow due to the effects of global warming. Europe will get similar mild(for Canadians) winters as northern North America. Eventually, temperatures will all catch up, but for some, the effects will seem more ambiguous.

Since I don't have the raw data, I can only offer anecdote, but it seems to me Montreal's weather has become milder. Evening low temperatures are warmer across seasons, but the high temperatures haven't spiked as high. Winters offer warmer days but Summer days are less likely to be blisteringly hot. This is what inspired my hypothesis. Now perhaps some one can analyse the data and see if this is true.

"If I had to choose between betraying my country and betraying my friend, I hope I should have the guts to betray my country."
-E.M. Forster