[URBAN NOTE] Climate change and Toronto
Jun. 22nd, 2009 07:09 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rfmcdonaldReading The Dragon Tales blog, I recently came across some very disturbing news on climate change as it can affect Canada. Glaciers in the Arctic, it turns out, can melt very very quickly with obvious implications for sea level. (Will earlier noted research suggesting that the northeastern coastline of North America will take a particular hit.)
When I learned about this, I congratulated myself for having had the good sense to move from a low-lying island on the northeastern coastline of North America to a city on the shore of the Great Lakes. Alas, my optimism turns out to have rather badly misplaced. This chart, predicting rainfall patterns in North America in the llast two decades of the 21st century, has some implications for Canada. Climate change will be rather uncomfortable in the United States (much more in some areas than others), and it looks like life in Mexico will be seriously harmed, but Canada seems OK. Oh, there is slated to be much more preciptation in winter (Mont-Tremblant survives?), but things are generally unchanged. Except for summer, when precipitation is projected to fall by between 5 and 10%.
Why is this an issue? For this, see this article abstract, the most relevant sections of which I've reposted below.
A common joke is that although Toronto's located on the shores of Lake Ontario its inhabitants certainly don't have much of a sense of having a waterfront. In a century's time, if the charts referred to above underestimate the situation, might it be that Toronto will be an inland city in faact as well as in sentiment?
When I learned about this, I congratulated myself for having had the good sense to move from a low-lying island on the northeastern coastline of North America to a city on the shore of the Great Lakes. Alas, my optimism turns out to have rather badly misplaced. This chart, predicting rainfall patterns in North America in the llast two decades of the 21st century, has some implications for Canada. Climate change will be rather uncomfortable in the United States (much more in some areas than others), and it looks like life in Mexico will be seriously harmed, but Canada seems OK. Oh, there is slated to be much more preciptation in winter (Mont-Tremblant survives?), but things are generally unchanged. Except for summer, when precipitation is projected to fall by between 5 and 10%.
Why is this an issue? For this, see this article abstract, the most relevant sections of which I've reposted below.
Eos, Vol. 89, No. 52, 23 December 2008
Dry Climate Disconnected the Laurentian Great Lakes
Recent studies have produced a new understanding of the hydrological history of North America’s Great Lakes, showing that water levels fell several meters below lake basin outlets during an early postglacial dry climate in the Holocene (younger than 10,000 radiocarbon years, or about 11,500 calibrated or calendar years before present (B.P.)). Water levels in the Huron basin, for example, fell more than 20 meters below the basin overflow outlet between about 7900 and 7500 radiocarbon (about 8770–8290 calibrated) years B.P. Outlet rivers, including the Niagara River, presently falling 99 meters from Lake Erie to Lake Ontario (and hence Niagara Falls), ran dry This newly recognized phase of low lake levels in a dry climate provides a case study for evaluating the sensitivity of the Great Lakes to current and future climate change.
[. . .]
Lakes without overflow, such as these lowstands in the GLB, can only be explained by a dry climate in which water lost through evaporation exceeded water gained from direct precipitation and catchment runoff. The dry regional climate that forced the lakes into hydrologic closure must have been substantially drier than the present climate. Hydrologic modeling of the present lakes shows that current mean annual precipitation would have to decrease by about 25% in the Superior basin and by about 42% in the Ontario basin, in conjunction with a 5ºC mean temperature increase, to achieve lake closure [Croley and Lewis, 2006]. Paleoclimate simulations and reconstructions using pollen [Bartlein et al., 1998] and stable isotopes [Edwards et al., 1996] indicate that climate in the GLB (Figure 2c) was drier than present at 7900 radiocarbon (8770 calibrated) years B.P. Termination of the lowstand episode about 7500 radiocarbon (8300 calibrated) years B.P. coincides with the onset of a wetter climate as atmospheric circulation adjusted to the rapidly diminishing ice sheet [Dean et al., 2002] and moist air mass incursions from the Gulf of Mexico became more frequent.
The discovery that the Great Lakes entered a low-level phase without having connecting rivers during the early Holocene dry period demonstrates the sensitivity of the lakes to climate change. The closed lakes of this phase occurred when the Great Lakes entered their present nonglacial state. Thus, the closed lakes afford a valuable example of past, high-amplitude, climate-driven hydrologic variation upon which an improved assessment of lake-level sensitivity in response to future climates can be based.
A common joke is that although Toronto's located on the shores of Lake Ontario its inhabitants certainly don't have much of a sense of having a waterfront. In a century's time, if the charts referred to above underestimate the situation, might it be that Toronto will be an inland city in faact as well as in sentiment?
