The E-mail Commentary from Eco-Justice Ministries
Wacky Weather and Climate
Most of the United States saw an unprecedented "summer in March" heat wave. From the Rocky Mountains to the East coast, temperatures were absurdly above normal, making it the hottest March in the US since record keeping began in 1895. (Meteorologist Jeff Masters has some wonderful descriptions of how hot it got in his Wunderground blog. For example, there were 21 cases where the low temperature for the day beat the previous high temperature for the day.)
Denver was part of that unusual pattern. We had 16 days where the high temperature was 70 or above. In a normal year, we get 2 or 3 of those days.
I admit to a strong temptation to look at the wacky warm weather of March, and scream, "GLOBAL WARMING! GLOBAL WARMING!" But I won't.
After reading some calm and reasoned analysis by a NOAA scientist, I'm forced to admit that such screaming is not warranted. Dr. Martin Hoerling says that "Our current estimate of the impact of GHG [greenhouse gas] forcing is that it likely contributed on the order of 5% to 10% of the magnitude of the heat wave during 12-23 March." He concludes his paper by saying, "And the probability of heatwaves is growing as GHG-induced warming continues to progress. But there is always the randomness. "
So it would be much more appropriate for me to say, "My, what an unusual month that was! (Global warming? Global warming?)" That's not an effective rallying cry for political activism, but it is well-grounded and responsible. Sigh.
Still, last month's remarkable temperatures provide "a teachable moment" that is irresistible. Let me share a few reflections about weather and climate that may deepen our understanding of why global warming is an important and complex topic.
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There is a difference between weather and climate -- a distinction which needs to be repeated often. This spring's odd heat was a weather event. Climate shows up in long-term statistical trends.
The climate in the US -- and around the world -- is definitely warming. Gardeners may see an indication of that trend if you look at the map of "planting zones" on the back of a seed packet, or in your favorite gardening catalogue. A few months ago, the US Department of Agriculture revised that map to show that, statistically, winters are quite a bit milder than they used to be. The bitter cold that can damage trees and veggies is shifting farther north.
A nice little interactive map lets you explore the changes between the 1990 and 2012 versions of the map. Almost all of some states -- Ohio, Nebraska and Texas -- have shifted into warmer zones. Drag the "slider" around to see the changes where you live.
The planting zones are a helpful bit of information for somebody who wants to plant the right kind of tree in their back yard. (One report says that you can now grow figs in Boston!) The climate information contained in the map of planting zones is critical to those who make a living from the land.
Maple syrup production, for example, is highly dependant on a balance between freezing and thawing weather. A Cornell University study predicts that the prime times for tapping trees in New England will shift by about a month through the course of this century, and that the amount of syrup gathered will decline. A friend of mine who produces syrup in northern Minnesota worries that it may not be possible to keep his business going as the climate warms.
Such changes have effects on regional economies and cultures, as well as on individual farmers. Global warming is taking place, and it does have real impacts.
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The planting map and the Cornell study point to a gradual shift in probable conditions, with average temperatures shifting a little bit over a long period of time. Those averages, though, are assembled from the sorts of variability and randomness that cropped up in the hot weather of March. Wild swings in weather bring a different sort of risk that hits the agricultural world hard.
A couple of days ago, Jeff Masters had another blog post that discusses a follow-up to the record temperatures in March. On the morning of April 12, large areas across the Midwest -- down to Tennessee and North Carolina -- had a hard freeze. Morning temperatures dropped below 28 degrees. He wrote:
Though the cold temperatures were not unusual for this time of year, they likely caused widespread damage to flowering plants fooled into blooming by last month's unprecedented "Summer in March" heat wave. ... While freezing temperatures for an extended period will not kill the trees, they will destroy the flowers and fragile buds that are needed to produce fruit later in the year. Temperatures of approximately 28°F will kill about 10% of fruit tree buds and flowers, while temperatures of 25°F will produce a 90% kill rate. ... I expect that this morning's freeze was severe and widespread enough to cause tens of millions of dollars in damage to the fruit industry.
The prudent staff of my local greenhouse know that it isn't safe to put out most of the flowers and veggies yet. When I was there a few weeks ago, the tables that will soon hold acres of flats and seedlings were empty. But the trees don't know that, and given a string of warm days, they'll act like spring has arrived. Then, when "seasonable" conditions come back, the frost is damaging.
Increased variability in the weather -- more extreme weather events and more odd spring heat waves -- present a serious danger that is not reflected in the gradual trends that show up across decades.
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In the Bible, one of the signs of God's power to order creation is seen in the structuring of seasons. The creation story in Genesis 1 says that the stars are placed in the sky as signs of the seasons and the years. God promises Noah and the whole creation that there will be continuity in the natural order: "As long as the earth endures, seedtime and harvest, cold and heat, summer and winter, day and night, shall not cease." (Genesis 8:22) Jeremiah speaks of "the LORD our God, who gives the rain in its season, the autumn rain and the spring rain, and keeps for us the weeks appointed for the harvest." (5:24)
Human impacts on the global climate are shaking up that orderliness. Seedtime and harvest are moving around and are less predictable. That makes some difference to a home gardener. It makes a huge difference to farmers and farm communities, and to the other-than-human parts of creation that also depend on orderly seasons.
This year's warm weather does not call for an alarmist cry of "GLOBAL WARMING", but it does provide an opportunity to look at the changes that we are causing within the delicate balances of God's creation. It is an opportunity to increase our concern, and to be mobilized for long term action.
In a few weeks -- on the weekend of May 4-6 -- your congregation can help "connect the dots" about climate change. Interfaith Power & Light is joining with 350.org in promoting "Climate Impacts Day" to religious communities. Think about what your church can do that weekend to demonstrate the reality of global warming. Maybe that map of planting zones could be a good starting place?
Eco-Justice Ministries * 400 S Williams St, Denver, CO 80209 * 303.715.3873
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