Good News Bad News With Climate Change
Climate change will cause a drop in heating degree-days but a rise in cooling degree-days
During these spring-like days in mid-February in Vermont, it's hard not to think about climate change. It's been reaching the mid- and upper-40s over the past few weeks in a winter that really isn't. Yes, this particular year might be an anomaly (after all, Europe is experiencing record cold this winter), but increasingly, scientists believe the long-term trend is clearly warming.
The good news with a warmer-than-normal winter in a cold climate is that homeowners save a lot on heating costs and, with a lack of snow, municipalities spend less for snow removal. Sure the ski and tourism industries suffers from winter-deficit, but at least we save some money.
In Vermont, warmer temperatures aren't just a future possibility; the trend has been pretty clearly demonstrated over the past half-century. In the fifty-year span from 1960 to 2010, the average summer temperature in Vermont has risen by 2°F, and the average wintertime temperature has risen by 4.5°F, according to Alan Betts, Ph.D., an atmospheric researcher based in Pittsford, Vermont.
Vermont's climate is heading south
Already, Vermont's summertime climate has "shifted south" since 1960 by about the north-south length of the state — so that the climate of the northern Vermont today is similar to what we had in southern Vermont 50 years ago, and southern Vermont is now more like central Pennsylvania in the '60s. A 2011 paper by Dr. Betts, "Climate Change in Vermont," includes a map showing this effective southern slide of Vermont over this period — and what will likely happen by 2080 under high- and low-emission scenarios for greenhouse gases (click on images).
The long-term projections have wintertime heating loads continuing to drop over the coming decades. If we continue on our present course with a high-emissions scenario, by 2080 Vermont's climate is expected to be like that of northern Georgia today.
The agricultural implications of these changes aren't all bad. Vermont could become a great place to grow peaches, for example, and our growing season will lengthen considerably. The new USDA Hardiness Zone Maps, released in late January, show most of Vermont shifting by about a half-zone since the hardiness zones were last published in 1990 (each zone represents a 10° difference in minimum winter temperature, and a half-zone represents a 5°F shift). Maple syrup production could well disappear from the state, however, while apples may be harder to grow and certain agricultural and forest pests could become far more of a problem.
Dropping heating degree-days
In terms of our energy costs, climate change is expected to result in a significant drop in annual "heating degree-days." (Heating degree days are calculated by measuring the average Fahrenheit temperature for each day — maximum plus minimum divided by 2 — and subtracting that from a "base temperature" of 65°, then adding up the cumulative total of those degrees for the heating season.)
This reduction in heating degree days that is predicted for the future will save us money and reduce greenhouse gas emissions, accordingly. That's good news, especially for folks heating with expensive fuels like heating oil, propane, and electricity.
Increasing cooling degree-days
In the summer, though, cooling energy needs will increase, and that's bad news for most of us. Cooling demand may not increase as quickly as is occurring with the reduction of heating demand, but the impact is greater. For the engineering inclined, annual cooling demand is typically measured as the cumulative Cooling Degree Days. These are typically calculated from a base temperature of 75°F. If the average temperature is above 75°F, that day earns some cooling degree days, and by adding those up for a whole year, we get a cumulative measure of cooling demand.
For most homeowners, a Btu (British Thermal Unit) of cooling is more expensive than a Btu of heating. We almost always use electricity for cooling, while heating may be from natural gas, heating oil, propane, electricity, or a solid fuel such as cordwood or pellets. So, if Vermont's climate really warms to that of northern Georgia's today, we are likely to be impacted significantly with summer energy bills — something many of us don't worry about at all today.
The bottom line is that it's fine to enjoy this warm winter weather and the energy savings it's delivering. But be aware that warmer summers could have a significant energy cost — unless we do what we can to minimize cooling loads and rely more on natural cooling when conditions permit. Fortunately, there's a lot that we can do to reduce those cooling loads, as I covered in this blog a few weeks ago.
- Barbro Hansson
- Alan Betts, Ph.D.
- Alex Wilson
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