How a warmer world leads to more severe snowstorms
Thursday, January 29, 2015, 1:29 PM - With the Atlantic provinces and parts of the U.S. Northeast still recovering after the powerful nor'easter that swept through earlier this week, what are these storms going to be like as the world warms?
According to the science - climate science and basic physics - snowstorms may become less frequent, as storms closer to the beginning and end of winter end up producing more rain than snow, but each snowstorm that does develop will potentially unload heavier and heavier loads of snow, possibly over wider areas.
Why is this the case?
As the planet warms, the added heat is going into both the atmosphere and into bodies of water like the oceans and lakes, and this is influencing the two major factors behind the strength of storms and how much snow they're capable of dumping:
- The amount of moisture the atmosphere can hold increases, and
- The temperature difference between the air over land and the water increases, especially in the deepest part of winter.
CLICK BELOW TO WATCH: Extreme Weather 101 highlights the connection between higher temperatures and greater snowfall.
The increase in the amount of water vapour a warmer atmosphere can hold is just basic physics. This results in heavier precipitation from storms, no matter what season it is.
However, when dealing specifically with winter, an overall, global, increase of 2oC or even 4oC - while of great concern for melting glaciers, melting sea ice and climate patterns - will not eliminate below-freezing temperatures, especially across Canada and the northern United States. It will certainly mean generally shorter winters, due to a later start to colder weather and an earlier thaw in the spring, and this will result in less seasonal snowfall overall. However, during the deeper parts of winter, these increases will simply keep temperatures closer to that 'ragged edge' of the freezing point, where snowfall amounts tend to be higher than they are when conditions are colder.
Warmer conditions influence lake effect snowfall as well. While ice amounts on the Great Lakes have been higher the past two winters, there is still a general downward trend in ice coverage with time. With more exposed water during the winter, the chances of lake effect squalls increases, simply because a frozen lake surface cuts off the source of moisture and energy needed to produce these squalls.
This will have a particularly big effect on communities around Lake Erie, which is the shallowest of the Great Lakes, and tends to freeze over more completely in winter now. Less freezing of this lake in the future, and thus more open water, is a situation just waiting for the right winds to blow across, to dump heaps of snow on local residents.
There's the potential for this to affect nor'easters as well, due to waters off the east coast of North America maintaining higher-than-normal temperatures throughout the season, thus heating up the air above the water and providing a stronger contrast with the air temperatures over land during the deeper portions of winter. As mentioned above, this temperature difference is the primary source of strength for nor'easters. Coupled with greater moisture content in the atmosphere, this can push these storms to extreme levels, fueling powerful winds and snowfall amounts that are capable of setting new records, even in places that are used to seeing feet of snow from these events.
Will this mean that, moving forward, each coming snowstorm will be progressively worse than the last?
No. That's just not how weather works. There will still be a mix of weaker and stronger storms. That's just the relatively normal variability of weather coming into play, even with nor'easters and their added dependence on coastal water temperatures.
However, as the world warms and climates shift, the long term trend is expected to reveal a distinct pattern, especially in the US Northeast and in the eastern half of Canada - winter snowfall totals will be on the decline, and rather than the snowfall still being spread out fairly evenly through the season, it will be concentrated into fewer events, more of which will be ramped-up to the extreme.