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Good News Bad News With Climate Change

Climate change will cause a drop in heating degree-days but a rise in cooling degree-days

Posted on Feb 23 2012 by Alex Wilson

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.


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Image Credits:

  1. Barbro Hansson
  2. Alan Betts, Ph.D.
  3. Alex Wilson
Thu, 02/23/2012 - 10:37

HDD Reduction
by Doug McEvers

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For Minneapolis energy calculations we used to use 8007 heating degree days, in the 2000's we used 7876. The new 30 year average has us at 7581. The 2000's were very warm, enough to move the 30 year average 295 hdd lower.

Thu, 02/23/2012 - 12:04

Edited Sun, 02/26/2012 - 19:06.

Lake George is Open Water
by aj builder, Upstate NY Zone 6a

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Lake George is open water. We normally would have 12-18" of ice. In the 70s and before we built on islands by driving our trucks to work. Boats this year. We have had 4 bad ice years since 1990. Before 1990 an open lake was last recorded back near 1900.

A century is not proof though. We may actually be saving ourselves. Sun activity is said to be a cooling effect at the stage it is in. Who knows....

As to skiing. Skiing is fantastic this year. Get on the slopes and see for yourself. And support your local economy.

Lake George, NY and No Ice, Feb 2012


Thu, 02/23/2012 - 12:30

I seem to be missing ...
by Eric Sandeen

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... the actual "good news" part. :(

Thu, 02/23/2012 - 14:11

Climate change is a wildcard...
by Lucas Durand - 7A

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I'm with you.
I wouldn't be counting my "Vermont peaches" before they fall off the tree...

Thu, 02/23/2012 - 14:37

Yes, but...
by Alex Wilson

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Eric and Lucas,
My town of Dummerston is celebrating how much money it has so far saved in snow plowing this winter, and some residents in our area who wouldn't have been able to afford enough heat to stay warm all winter haven't run out. So there are some near-term economic benefits of a warmer winter, even though the prognosis of climate change, from a big-picture standpoint, is indeed mostly bad.

Thu, 02/23/2012 - 22:08

Europe's Cold & Global Warming
by David McNeely

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Alex, re: your comment, "... after all, Europe is experiencing record cold this winter"

Source: Planetsave (

This was written in 2010. It was the first listing in my Google Search: "Climate Change cooling Europe."

Here in Knoxville, TN we also had no winter. Saw a tree full of cherry blossoms this afternoon, and a Magnolia full of buds about to burst. I see no reason to celebrate, especially when the conservatives continue to label climate change a hoax, and shut down rational discussion of pragmatic alternatives.

Climate change may seem like a vacation from cold winters now, but this bucking bronco is just about to leave the gate: I think we are all in for a hell of a ride.

Fri, 02/24/2012 - 05:36

Peaches in Vermont
by Martin Holladay, GBA Advisor

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If the Vermont climate becomes favorable for peach orchards, it will be disastrous to Vermont's forests. If the climate allows peach cultivation, all of our balsam firs will be dead or dying. Our sugar maples will be in very rough shape, and the maple sugaring industry will be gone.

That's just two species I can think of.

Fri, 02/24/2012 - 10:58

by Doug McEvers

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In the years ahead, superinsulation in Minnesota and Vermont might be a 2x2 wall, think positive.

Fri, 02/24/2012 - 20:04

Cost of a Btu
by James Morgan

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This, while it may be true, may also be misleading for two reasons: first that the Delta-T that the Btu is working to achieve is generally much less in the cooling mode (think 90° external/82° internal vs 20° external/68° internal) and second that the most of that cooling work is done removing humidity rather than cooling the air: in other words it's a false equivalency. The actual net result of a warming climate is that Vermonters are going to be spending a lot less on their annual energy bill in the future.

Sat, 02/25/2012 - 08:39

by James Morgan

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That last sentence should read: "The actual net result of a warming climate is that as long as their homes are properly air-sealed to control the humidity issues, Vermonters are going to be spending a lot less on their annual energy bill in the future.

Sat, 02/25/2012 - 09:07

Edited Sat, 02/25/2012 - 09:08.

re: Martin
by 5C8rvfuWev

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You have to look at the bright side -- Kudzu will have a new slogan ... "The Vine that Ate Vermont"

kudzu lg.jpg

Tue, 02/28/2012 - 12:45

You could grow figs & bananss in Vermont right now
by William Rau

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Martin, You could grow figs, bananas, papayas, etc, in your backyard right now with a "climate battery" or phase change greenhouse: very small energy draw. Your solar system could run the small fans in a climate battery operation. See:

Tue, 02/28/2012 - 13:08

Response to William Rau
by Martin Holladay, GBA Advisor

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Sorry, but the northeast corner of Vermont is not Colorado. Colorado gets far more sun during the winter than Vermont.

Here's a map that tells the story:

Typical winter peak sun hours in Colorado are between 4.5 hours and 5 hours. Where I live, I get 1.6 hours. Big difference.

It's fairly common to get no sun at all for three weeks straight in November -- so, no, I don't have any extra PV-generated electricity to help me grow bananas in Vermont.

Marc Rosenbaum and Amory Lovins had a long e-mail exchange on this issue years ago, with Amory assuming that it's possible to build a house that needs no heating fuel in northern New England, and with Marc patiently explaining to Amory why he was wrong.

Hey, if I lived in Colorado, I could do all kinds of amazing tricks, too.

Tue, 02/28/2012 - 13:21

Thanks for the map. I see the off-grid problem.
by William Rau

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Was the Lovins-Rosenbaum exchange concerning annualized geo-solar design or passive annual heat storage? These techniques store heat from the summer sun in dry soil to be used to heat homes in the winter. Is there some flaw in these technologies, or some geographical constraint that limits their use in the Northeast or elsewhere?

Tue, 02/28/2012 - 13:27

Response to William Rau
by Martin Holladay, GBA Advisor

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The exchange concerned the question of whether it was possible to design a building with a big solar thermal system that could store enough heat to allow the building to do without any source of space heating other than passive solar gain and the active solar thermal system (presumably a system with a very large hot water tank).

Here's a link to the discussion:

Tue, 03/13/2012 - 22:11

climate chang
by david aronson

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How did the Norsemen survive on Greenland with their annimals for more than 100 years? After time the group was frozen out.

Wed, 03/14/2012 - 04:53

Response to David Aronson
by Martin Holladay, GBA Advisor

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The Norse settlers on Greenland arrived during a warm period, and they just barely managed to keep their flocks and herds alive through the long winters for several decades. Then an extended cold snap, called the Little Ice Age, gripped Greenland beginning in the 1400s. The Norse settlers either died or left. For more information, see Climate helped drive Vikings from Greenland.

The fact that there was a "Little Ice Age" in Greenland in the 1400s doesn't mean that late 20th century global warming is not a reality. Here's the real takeaway from the story of the Norse in Greenland: established patterns of agriculture don't always survive periods of climate change; nor do some human populations.

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