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:

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.

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.

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.

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.  

Local Climate Change Trends in Hudson and Albany

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.