Good News Bad News With Climate Change
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Vermont's winter and summer temperatures are both rising. Source: Alan Betts, Ph.D. Click on image to enlarge. 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 u... Vermont's climate heading south Vermont's climate is moving south. This shows the effective shift that's already happened with Vermont's summertime climate and what's expected with high-emission and low-emission scenarios. Source: Alan Betts, Ph.D. Click on image to enlarge. 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. 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. We may not see this house in Vermont anytime soon, but addressing cooling-load avoidance will become more and more important. Photo: Alex Wilson. Click on image to enlarge. 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. Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News . To keep up with his latest articles and musings, you can sign up for his Twitter feed .