Signs of Change: Reflections from a Winter Landscape
(from the 24 December 2009 edition of the Columbia Paper)
by Anna Duhon
Winter is settling upon the land. Perhaps more than any other season, winter entices, even requires us to read the signs of its mercurial nature closely. Are the roads clear? Is the ice thick enough to walk on? You can’t get out of the way of winter, or at least it must be respectfully accommodated.
While many who work closely with the land have this attunement in every season, what I love about winter is that it reaches straight into the most comfortably insulated aspects of our lives and commands our attention. And so it is winter when we most often peer into whatever blanket of weather is upon us and try to interpret, understand, and predict what it might mean for our lives, whether the evening commute or something more global.
“So much for global warming,” I often hear when the thermometer dips particularly low, or the wind is especially biting. “I’m worried,” is what my friend said on a particularly balmy day last week. Though the recent climate talks in Copenhagen are far removed from life in Columbia County, the specter of climate change is more and more peppering our conversations about the weather.
Interpreting our experiences of the weather against the backdrop of memory, many of us have the sense that the climate, as seen in our little corner of the world, is somehow changing; that things aren’t as they used to be. Yet it is hard to be sure. As weather buff Benjamin Watson once said about the Northeast, “Rarely will you hear a native describe a season or year as being typical.”
There are, however, local signs of a changing climate that transcend our individual senses, and can only be understood in the context of trends over time; it is these signs I have been recently trying to read. When are the first and last frosts each year? How long is each growing season? How intense are the rainstorms? How warm is each winter? Such are the markers that scientists around the world are using to gauge changes in climate, but they can also be the measures of far more locally felt changes.
In Columbia County and the Hudson Valley, the results are clear: the recent trend lines are heading up (longer trends are more ambiguous). Any given year, mind you, may be atypically warm or cold, rainy or dry – such frequent oscillations, in fact, seem to be the norm. But beneath the yearly variability is a steady recent trend towards warmer, wetter weather, more intense storms, shorter winters and longer growing seasons. [See graphs of these trends]
Take the past half-century in Hudson, for instance. The last frost is coming an average of 11 days earlier in spring, while the first frost is coming 9 days later. In other words, winter is shortening and the growing season is getting longer. Indeed, it has extended by nearly three weeks.
One of the predictions for the Northeast that I read with particular interest is that our local climate will get wetter, with more frequent and intense rainstorms and flooding. In Hudson, the average yearly amount of rain has increased by 15 inches over the last 50 years, mostly in summer and fall. Meanwhile the annual number of days with intense, pounding rainfalls, the kind that overflow drainage systems and flood creek beds, has also increased: by 5.7 days over the last six decades.
And then there is the local warming, most clearly pronounced in the winter season we are now in. As I write this, it is convincingly cold outside. But looking at the local trends in winter temperature – a warming of around 3 degrees in Albany over the last 115 years, for instance – I worry that winter in the Hudson Valley may come to mean something very different than its cold and snowy associations.
Therein lies the question we are left with: what do the signs point towards? And then, what can we do about it? That the local climate is trending towards warmer, wetter weather is evident. That these changes are part of global-scale, human-induced climate change is the scientific consensus that has been building for decades. These are signs in which we are deeply implied, both as the recipients of such changes, and their proximate cause. Our culture and livelihoods are woven deeply into the seasons, and perhaps just as deeply into the carbon-dependence that may change them indefinitely.
We are left to reflect, in this cold, quiet season, on the signs that encircle our lives, and our own ability to respond.
Global Context of Climate Change
Regional Contributions to Climate Change
Climate Change in the Northeast and New York State
Local Climate Change Trends in Hudson and Albany
Implications of Local Climate Change for Farmers
The climate is always changing, but observations undeniably show that the global climate is getting warmer. The map below shows changes in global temperature (in degrees Celsius) over the period 1881-2009.
Source: GISS Surface Temperature Analysis Tool, http://data.giss.nasa.gov/gistemp/maps/
The scientific consensus (see sources cited below) attributes the recent warming trend primarily to human-induced emissions of "greenhouse gasses," (GHG) such as carbon dioxide, methane and nitrous oxide, that have occurred since the industrial revolution. GHG emissions predominantly come from the burning of fossil fuels, industrial-scale agricultural practices, and land use changes such as forest clearing. The first two graphs below indicate the relationship between temperature changes over the last 1000 years, and carbon dioxide concentrations. The third graph shows the change in type and amount of carbon emissions.
Source: Climate Change Impacts on the United States, 2000
Climate change does not only refer to warming, but also changes in precipitation patterns, the frequency and intensity of storms, sea level rise, and other related aspects. The following graph depicts the annual global precipitation trends from 1900-2000. Note the increase of precipitation in the Northeast US.
Source: IPCC TAR 2001, SYR Figure 2-6a
Sources: For more information on climate change science, causes, impacts, mitigation and adaptation, see the Intergovernmental Panel on Climate Change Fourth Assessment Report released in 2007. For information more specific to the impacts of climate change in the United States, see the U.S. Global Change Research Program's 2009 report Global Climate Change Impacts in the United States.
While many are aware that the United States and China are the largest GHG emitters, the significant role that regions within the US play in GHG emissions is less well-known. New York State, for example, is responsible for 1% of global GHG emissions (while having .3% of the world's population). A 2001 graph shows that if the Northeast was a country, it would be ranked 7th in the world for greatest annual GHG emissions:
Source: Climate Change in the US Northeast: A Report of the Northeast Climate Impacts Assessment, October 2006
Looking at the weather records and observations in the Northeast United States, it is clear that climactic changes are afoot. The 2006 report, Climate Change in the US Northeast, details many of these changes, including rising temperatures and sea levels, reduced snowfall, increased amount, frequency and intensity of rain events, a longer growing season (by 2.5 days each decade), earlier spring bloom dates by 4-8 days, and earlier ice out dates and spring snow melt leading to earlier peak river flows. In New York State, for example, average annual temperatures have increased by 2.3 degrees since 1970, and winter temperatures have increased by over 5 degrees in that same period. The sea level is 15 inches higher in New York harbor now, than it was in 1850 (NY DEC Climate Change in the Hudson Valley). Below is a map illustrating the increased amounts and frequency of very heavy rainfall events in the Northeast, as compared to the rest of the country.
Source: Climate Change in the US Northeast: A Report of the Northeast Climate Impacts Assessment, October 2006
In general, the Northeast has gotten warmer and wetter, as these graphs of average annual temperature and precipitation over the 20th century show.
While the regional picture of recent climate change is useful, it is also interesting to see what climate trends exist at a very local level. In Columbia County, Hudson has the longest and most consistent weather record, though it mostly extends from the mid-20th century. A little further north, Albany has a far longer weather record that reaches back into the 19th century, and is therefore a good local indicator of longer-scale trends. Below are graphs of the precipitation trends in Hudson over the last 52 years. This trend represents an increase of 15 inches in annual average precipitation over this period.
Though there are few 19th century weather records for Hudson, there are some early published records that give a small window into Hudson precipitation in the 1820s-1840s. This graph includes precipitation data beginning in 1827.
The evident increase in precipitation over the last half century has not occurred evenly across the seasons. By tracking the precipitation in each season, one can see that the greatest increases in precipitation are in summer and fall, while the average annual precipitation has in fact declined slightly in winter. This reflects the regional climate trends observed in the Northeast, as well as the predictions for future precipitation trends in the region.
The intensity of rainfall has also been changing. One way to measure this is by calculating the number of days with extreme precipitation events, defined as days in which more than 1 inch of rain fell within a 24 hour period. The graph below shows an increase of 5.7 days per year with extreme precipitation events from 1947-2008.
The Albany average annual precipitation from 1947-2008 follows a similar trend as in Hudson, though less pronounced. The trend below shows an increase of 6 inches in average annual precipitation during this period.
The precipitation trend in Albany looks very different, however, when the full timeline of weather records are taken into account. Below is a graph of annual average precipitation in Albany from 1826 to the present. Notice how the climate in the 19th century also had periods of high precipitation comparable to the present. There are many factors that have influenced changing precipitation patterns over time; human-induced greenhouse gas emissions are only the most recent.
The annual average temperature has also changed over the course of weather records in Hudson and Albany, though in both cases it has trended up. In Albany, where there is a consistent record from 1889 to the present, there has been a 2.3 degree Fahrenheit increase in the mean average temperature.
One consequence of increasing temperatures has been a shift in seasonal markers. The last frost in spring has on average occurred earlier over time, while the last frost in the fall has occurred later. Below are graphs of the first and last frost dates in Hudson. The last frost date in spring has occurred an average of 11 days earlier over the last 57 years of consistent records, while the first frost date in fall has occured an average of 9 days later.
Such shifts have profound implications for the growing season. Below, graphs show the increase in the average length of the growing season in both Hudson and Albany.
While a longer growing season may seem like a positive trend for farmers, there are many potentially adverse implications. The timing of agricultural activity and natural cycles is extremely important, and this is alreadly being affected. Earlier blossoming plants could easily be damaged by one fluke frost, or crop pests and diseases may be able to overwinter, move north earlier, or find better conditions to flourish. Flooding during important stages of crop production is also an increased concern with earlier snow melt and greater precipitation. Finally, increased temperatures, especially more high degree days, could have an adverse affect on the ability to produce cold-adapted crops crops (i.e. apples, potatoes, blueberries), and greatly reduce dairy yields, which depend on an optimatl temperature range. Overall, the tremendous year-to-year variation in temperature and precipitation make it hard to plan for and adapt to a trend playing out over decades.
David Burg, President of Wild Metro, sent us this comment on 16 January 2010:
I appreciate recieving your recent columns. I have a question about the recent graphs showing rising average temperatures. A great deal depends on where the temperature is measured. Since your data are from Hudson and Albany, could some of rise be due to urban heat island effects? It is well known that an increase in buildings and pavement raises local temperatures in cities. How much would this have affected the measurements you report? Is there any comparable data for local forests during the same time?